MANUFACTURING HEAT TREAT

Don’t Be Unique! 10 Temperature Uniformity Tips

/ MANUFACTURING HEAT TREAT, MANUFACTURING HEAT TREAT NEWS

We’ve assembled some of the top 101 Heat Treat Tips that heat treating professionals submitted over the last three years into todays original content. If you want more, search for “101 heat treat tips” on the website! Today’s tips are all things temperature: thermocouples, how to keep temperatures in check, TUS, and more.

By the way, Heat Treat Today introduced Heat Treat Resources this year; this is a feature you can use when you’re at the plant or on the road. Check out the digital edition of the September Tradeshow magazine to check it out yourself!

Temperature Monitoring When the Pressure is On!

Increasing in popularity in the carburizing market is the use of batch or semi-continuous batch low pressure carburizing furnaces. Following the diffusion, the product is transferred to a high-pressure gas quench chamber where the product is rapidly gas cooled using typically N2 or Helium at up to 20 bar pressure.

In such processes, the technical challenge for thru-process temperature monitoring is twofold. The thermal barrier must be capable of protecting against not only heat during the carburizing, but also very rapid pressure and temperature changes inflicted by the gas quench. From a data collection perspective, to efficiently perform temperature uniformity surveys at different temperature levels in the furnace it is important that temperature readings can be reviewed live from the process but without need for trailing thermocouples.

During the gas quench, the barrier needs to be protected from Nitrogen N2(g) or Helium He(g) gas pressures up to 20 bar. Such pressures on the flat top of the barrier would create excessive stress to the metal work and internal insulation / logger. To protect the barrier therefore a separate gas quench deflector is used. The tapered top plate deflects the gas away from the barrier. The unique Phoenix design means the plate is supported on either four or six support legs. As it is not in contact with the barrier no force is applied directly to the barrier and the force is shared between the support legs. The quench shield in addition to protecting against pressure, also acts as an additional reflective IR shield reducing the rate if IR absorption by the barrier in the vacuum heating chamber.

(PhoenixTM)

3 Tips to Meet Temperature Uniformity Surveys

  1. Adjust the burners with some excess air to improve convection.
  2. Make sure that the low fire adjustment is as small as possible. Since low fire will provide very little energy, it will make the furnace pulse more frequently and this will improve heat transfer by convection and radiation.
  3. Increase internal pressure. This will “push” heat to dead zones allowing you to increase your coldest thermocouples (typically near the floor and in the corners of the furnace).

(Nutec Bickley)

Ways to Increase Temperature Uniformity in Heat Treat Furnaces

  1. A (sometimes) simple way to increase uniformity in a furnace is to add a circulation fan. Circulation fans can be a quick way to add an additional 5°F tighter uniformity on a batch furnace application.
  2. Be sure that the furnace is tuned optimally to reduce/eliminate any overshoot and oscillation around setpoint.
  3. Eliminate any thermal lag by making sure that the control thermocouple and TUS thermocouples have similar sensitivity. If not, the control thermocouples can fall behind and cause the TUS thermocouples to overshoot and fail.

(L & L Special Furnace Co., Inc.)

Pack Your Thermocouples

When a thermocouple is used with an open-ended protection tube, pack rope or fiber between the thermocouple and the protection tube to prevent cold air infiltration from influencing the reading.

(Super Systems, Inc.)

A Good Fit

If a thermocouple fits loosely in a protection tube, avoid errors by ensuring that the tip maintains good contact with the tube.

(Super Systems, Inc.)

Introducing Your Common Thermocouple Types

What are the common thermocouple types?

Thermocouple material is available in types K, J, E, N, T, R, S, and B. These thermocouple types can be separated into two categories: Base and Noble Metals.

Types K, J, E, N, and T are Base Metals. They are made from common materials such as Nickel, Copper, Iron, Chromium, and Aluminum. Each base metal thermocouple has preferred usage conditions.

Types S, R, and B thermocouples are Noble Metals because they are made of one or more of the noble metals, such as Ruthenium, Rhodium, Palladium, Silver, Osmium, Iridium, Platinum, and Gold. Noble metals resist oxidation and corrosion in moist air. Noble metals are not easily attacked by acids. Some Noble metal thermocouples can be used as high as 3100°F.

(Pelican Wire)

Culprits of a Stable Thermocouple

Factors affecting the stability of a thermocouple:

The EMF output of any thermocouple will change slightly with time in service and at elevated temperatures. The rate and change are influenced by metallurgical and environmental factors. The four factors that can induce EMF drift are: Evaporation, Diffusion, Oxidation, and Contamination.

(Pelican Wire)

Does Length Matter?

Does the length of a thermocouple wire matter?

In a word, “Yes.” There are several factors when considering the maximum length of a thermocouple assembly. Total loop resistance and electrical noise. Total loop resistance should be kept under 100 ohms for any given thermocouple assembly. Remember, the total loop resistance would include any extension wire used to complete the circuit. Motors and power wires can create noise that could affect the EMF output.

(Pelican Wire)

Type N Thermocouple (Nicrosil/Nisil)

Type N Thermocouple (Nicrosil/Nisil): The Type N shares the same accuracy and temperature limits as the Type K. Type N is slightly more expensive and has better repeatability between 572°F to 932°F (300°C to 500°C) compared to type K.

(Pelican Wire)

Know Your Thermocouple Wire Insulations

Know your thermocouple wire insulations. When is Teflon® not Teflon®? Teflon® is a brand name for PTFE or Polytetrafluoroethylene owned by Chemours, a spin-off from Dupont. FEP is Fluorinated Ethylene Propylene. PFA is Perfluoroalkoxy Polymer. All three are part of the Fluoropolymer family but have different properties. Of the three compounds, PTFE has the highest heat resistance, PFA second highest and FEP third. The higher the heat resistance the more expensive the insulation. Keep that in mind when specifying the insulation and only pay for what you need.

(Pelican Wire)

Don’t Be Unique! 10 Temperature Uniformity Tips Read More »

Don’t Be Unique! 10 Temperature Uniformity Tips

/ FEATURED NEWS, INSTRUMENTATION TECHNICAL CONTENT, MANUFACTURING HEAT TREAT, THERMOCOUPLES TECHNICAL CONTENT

OCWe’ve assembled some of the top 101 Heat Treat Tips that heat treating professionals submitted over the last three years into todays original content. If you want more, search for “101 heat treat tips” on the website! Today’s tips are all things temperature: thermocouples, how to keep temperatures in check, TUS, and more.

By the way, Heat Treat Today introduced Heat Treat Resources this year; this is a feature you can use when you’re at the plant or on the road. Check out the digital edition of the September Tradeshow magazine to check it out yourself!

Temperature Monitoring When the Pressure is On!

Increasing in popularity in the carburizing market is the use of batch or semi-continuous batch low pressure carburizing furnaces. Following the diffusion, the product is transferred to a high-pressure gas quench chamber where the product is rapidly gas cooled using typically N2 or Helium at up to 20 bar pressure.

In such processes, the technical challenge for thru-process temperature monitoring is twofold. The thermal barrier must be capable of protecting against not only heat during the carburizing, but also very rapid pressure and temperature changes inflicted by the gas quench. From a data collection perspective, to efficiently perform temperature uniformity surveys at different temperature levels in the furnace it is important that temperature readings can be reviewed live from the process but without need for trailing thermocouples.

During the gas quench, the barrier needs to be protected from Nitrogen N2(g) or Helium He(g) gas pressures up to 20 bar. Such pressures on the flat top of the barrier would create excessive stress to the metal work and internal insulation / logger. To protect the barrier therefore a separate gas quench deflector is used. The tapered top plate deflects the gas away from the barrier. The unique Phoenix design means the plate is supported on either four or six support legs. As it is not in contact with the barrier no force is applied directly to the barrier and the force is shared between the support legs. The quench shield in addition to protecting against pressure, also acts as an additional reflective IR shield reducing the rate if IR absorption by the barrier in the vacuum heating chamber.

(PhoenixTM)

3 Tips to Meet Temperature Uniformity Surveys

  1. Adjust the burners with some excess air to improve convection.
  2. Make sure that the low fire adjustment is as small as possible. Since low fire will provide very little energy, it will make the furnace pulse more frequently and this will improve heat transfer by convection and radiation.
  3. Increase internal pressure. This will “push” heat to dead zones allowing you to increase your coldest thermocouples (typically near the floor and in the corners of the furnace).

(Nutec Bickley)

Ways to Increase Temperature Uniformity in Heat Treat Furnaces

  1. A (sometimes) simple way to increase uniformity in a furnace is to add a circulation fan. Circulation fans can be a quick way to add an additional 5°F tighter uniformity on a batch furnace application.
  2. Be sure that the furnace is tuned optimally to reduce/eliminate any overshoot and oscillation around setpoint.
  3. Eliminate any thermal lag by making sure that the control thermocouple and TUS thermocouples have similar sensitivity. If not, the control thermocouples can fall behind and cause the TUS thermocouples to overshoot and fail.

(L & L Special Furnace Co., Inc.)

Pack Your Thermocouples

When a thermocouple is used with an open-ended protection tube, pack rope or fiber between the thermocouple and the protection tube to prevent cold air infiltration from influencing the reading.

(Super Systems, Inc.)

A Good Fit

If a thermocouple fits loosely in a protection tube, avoid errors by ensuring that the tip maintains good contact with the tube.

(Super Systems, Inc.)

Introducing Your Common Thermocouple Types

What are the common thermocouple types?

Thermocouple material is available in types K, J, E, N, T, R, S, and B. These thermocouple types can be separated into two categories: Base and Noble Metals.

Types K, J, E, N, and T are Base Metals. They are made from common materials such as Nickel, Copper, Iron, Chromium, and Aluminum. Each base metal thermocouple has preferred usage conditions.

Types S, R, and B thermocouples are Noble Metals because they are made of one or more of the noble metals, such as Ruthenium, Rhodium, Palladium, Silver, Osmium, Iridium, Platinum, and Gold. Noble metals resist oxidation and corrosion in moist air. Noble metals are not easily attacked by acids. Some Noble metal thermocouples can be used as high as 3100°F.

(Pelican Wire)

Culprits of a Stable Thermocouple

Factors affecting the stability of a thermocouple:

The EMF output of any thermocouple will change slightly with time in service and at elevated temperatures. The rate and change are influenced by metallurgical and environmental factors. The four factors that can induce EMF drift are: Evaporation, Diffusion, Oxidation, and Contamination.

(Pelican Wire)

Does Length Matter?

Does the length of a thermocouple wire matter?

In a word, “Yes.” There are several factors when considering the maximum length of a thermocouple assembly. Total loop resistance and electrical noise. Total loop resistance should be kept under 100 ohms for any given thermocouple assembly. Remember, the total loop resistance would include any extension wire used to complete the circuit. Motors and power wires can create noise that could affect the EMF output.

(Pelican Wire)

Type N Thermocouple (Nicrosil/Nisil)

Type N Thermocouple (Nicrosil/Nisil): The Type N shares the same accuracy and temperature limits as the Type K. Type N is slightly more expensive and has better repeatability between 572°F to 932°F (300°C to 500°C) compared to type K.

(Pelican Wire)

Know Your Thermocouple Wire Insulations

Know your thermocouple wire insulations. When is Teflon® not Teflon®? Teflon® is a brand name for PTFE or Polytetrafluoroethylene owned by Chemours, a spin-off from Dupont. FEP is Fluorinated Ethylene Propylene. PFA is Perfluoroalkoxy Polymer. All three are part of the Fluoropolymer family but have different properties. Of the three compounds, PTFE has the highest heat resistance, PFA second highest and FEP third. The higher the heat resistance the more expensive the insulation. Keep that in mind when specifying the insulation and only pay for what you need.

(Pelican Wire)

Check out these magazines to see where these tips were first featured:

 

 

 

 

 

 

 

 

Don’t Be Unique! 10 Temperature Uniformity Tips Read More »

A Guide to Selecting Heat Treating Equipment

/ BURNERS & COMBUSTION SYSTEMS TECHNICAL CONTENT, CONTROLS TECHNICAL CONTENT, FEATURED NEWS, MANUFACTURING HEAT TREAT, VACUUM FURNACES TECHNICAL CONTENT, VACUUM PUMPS GAUGES VALVES TECHNICAL CONTENT

OCDo you always feel confident when selecting heat treating equipment? ¿Se siente siempre seguro cuando selecciona equipos de tratamiento térmico?

There are many factors involved when making a purchase. Often, key considerations may be missed. Read this guide on how to select and buy new equipment by Carlos Carrasco, founder of Carrasco Hornos Industriales.

This original content article was originally published in Heat Treat Today’s November 2021 Vacuum Furnace print edition in English and Spanish.

Carlos Carrasco
Founder
Carrasco Hornos Industriales

Why Is This Guide Helpful?

There are many reasons to select industrial furnaces carefully. One is the cost of the furnace. Another is realizing heat treating will affect the product and the bottom line. There is more specialized engineering in heat treating equipment than is apparent from the outside.

The purpose of this guide is to help engineers make the best equipment selection. The decision will affect not only the project, its budget, and results, but will also reflect the buyer’s knowledge. After the heat treating equipment is selected, the realization may occur that perhaps insufficient thought was given to potential maintenance problems or the work required to keep it in top working condition.

The following steps, gathered from more than 50 years of experience in the fields of manufacturing, sales, and maintenance, will be a useful guide to selecting heat treating equipment that will please both management and operators.

Vacuum high-pressure hardening furnace

Step One: Quote Request

When requesting a quote, management knows the exact requirements the heat treated products must have. A reliable supplier should be able to understand all requirements for a quote. Requests must be clear, concise, and contain at least the following information:

  • Heat treating processes that will be carried out on the equipment
  • Shape, general dimensions, and weights of the product(s) to be heat treated
  • Production volumes per hour, day, or month
  • Number of hours available for heat treating
  • Part material
  • Fuel type, or if the heating will be done with electricity
  • Voltage available in the plant
  • Space available for installation of equipment
  • Special considerations for handling loading and unloading

Furnace manufacturers need the above information to begin to create a series of options for the equipment that will be most suitable for the required processes. For example, hourly production defines: the dimensions of the space to heat the load, the type of furnace (continuous or batch), the amount of heat to be released in the furnace, the loading and unloading method, and the devices for accommodating or transporting the load such as trays, baskets, or conveyor belts. All these considerations influence both the initial cost and the operating cost, because in the end, the cost of the proposed equipment and its functionality are directly related to the specifications of the request for a quote.

It is difficult to attempt to use one furnace for all heat treating processes or to attempt to take into account future production needs that may not be necessary. It is impractical to carry out several processes that require different temperatures or have different production volumes. Trying to do so leads to oversized and over-budget equipment.

Vacuum low-pressure carburizing furnace

Step Two: Supplier Selection

Quote requests should only be submitted to manufacturers with the technical capacity and experience to prepare an offer that satisfies the request. Always use references from previous installations with similar quote requirements.

Considering the potential for financial gain, the cost of heat treating equipment can be appealing. The design and construction of heat treating equipment involves a considerable amount of engineering resulting from expensive investments in research and development. This research and development is influenced by user feedback detailing equipment failure. This feedback creates opportunities for manufacturers to fix equipment issues. Without the added benefit of other heat treater’s feedback, equipment failure is more likely. Finding a manufacturer with experience is crucial.

Only suppliers with experience and solid technical capacity will be able to guarantee results from the start. The goal is to receive equipment that requires no corrections after the first load leaves the furnace and to not have to rework the design.

Step Three: Study and Evaluation of Offers

A failed project is too much to risk, and so the responsible supplier will invest time and money in the study and preparation of the offer.

Every responsible supplier has been disappointed by an offer read backwards — when the potential customer reads the price first. Is the overriding need to stay within a certain budget or for heat treating equipment that is capable of processing parts to meet specifications? A careful reading of the offer may justify the cost of the furnace in relation to production needs. If there is a confusing section of the offer, it is important to clarify with the supplier. Investment in production equipment is very important, but it is even more important that the investment be profitable.

The heat treating equipment must satisfy a production need and certain metallographic specifications. Consequently, the dimensions of the space where the parts will be placed may be the main factor in the design of the furnace. This is because metals are only capable of heating up to a certain temperature at a rate that is determined by the heating method, geometry, and load arrangement. Only experienced vendors can make the correct calculations to meet the production needs of the project. Be sure to understand the calculations that lead to the sizing of the proposed system.

How are the parts supported and/or transported within the furnace? This is a point of great importance for the initial cost of these components and for the costs of future maintenance. Keep in mind that any mechanism that works at high temperatures will always be problematic for maintenance and replacement. Cast link belts, for example, have a higher initial cost, but they withstand heavy loads longer than metal mesh belts. However, there is a notable difference in the cost of components made of chromium-nickel alloy and those of carbon steel. Since chromium-nickel materials are able to withstand higher temperatures, their use is recommended and almost essential.

Furnaces tend to deteriorate rapidly where the heat is being lost. Make sure the door design is the best possible to avoid heat loss. Be sure that all doors included in the design are necessary. Doing so will save maintenance costs.

When it comes to quenching, oil or water circulation systems are extremely important, as is tank capacity. Otherwise, the quenching medium may overheat, causing unsatisfactory results.

In an oven intended for low temperature operations 356°F–1,112°F (180°C–600°C), for example tempering processes, it is necessary to have a fan to recirculate the hot air from the furnace. The uniformity of the temperature in the parts and the speed at which they heat up depends on the speed of recirculation, the weight of the air, and the design of the furnace, which must force the passage of air optimally through the load with the use of deflectors, screens, or distribution plenums. In high temperature furnaces, 1,292°F–2,192°F (700°C–1200°C), the heat transfer depends on the radiation toward the load and its exposed surface, so a recirculation fan is not necessary. Heat treatment is a critical process and temperature pyrometers must have the necessary precision.

List any doubts about the offer and ask the supplier to clarify at length in writing. The answers will make it easier to do a second analysis of the offer and compare it with other offers. In addition, the written clarifications will be a record for review by other collaborators on the project. Ask for feedback and observations on the proposals to get a second opinion.

Ask suppliers to provide a list of similar installations. Industry colleagues are generally unbiased in their comments about their experience with a particular supplier.

Finally, make a comparison chart in the most objective way possible. Keep in mind the fact that offers often do not include some subjective issues that may be important for a final selection. For example, some vendors are likely to have greater knowledge and experience in certain processes, simply because they have invested time and money to fi nd the best solutions to the process and those experiences could be beneficial.

Step Four: The Price

Understanding the scope of the received proposals that meet production and quality requirements is not all that goes into selecting heat treating equipment. After all this, there are still significant differences between various suppliers. Price is one of these differences. At this stage, the industrial furnace manufacturer will need to justify costs. It will be easy to tell if the manufacturer is thinking of the buyer as a future satisfied customer, or only of the economic benefits the sale will bring.

Conclusion

There are innumerable cases in which the equipment was poorly selected: “The substation and/or the cooling tower did not have the capacity;” or “The equipment is not what we expected;” or “They never told us that the furnace needed gas in those capabilities.” These are just a few of the possible comments everyone has heard.

Selecting heat treating equipment should be done slowly, analyzing all the options,  weighing the differences between providers, and seeking clarification. Ask the supplier for multiple equipment options like requesting spare parts for the first year of operation.

Ultimately, time will tell if the furnace selected was the right choice. These recommendations provide a guide to making that decision. We sincerely hope that these recommendations will guide you in the selection of industrial furnaces for heat treating.

About the Author:

In addition to being the founder of Carrasco Hornos Industriales — furnace experts, consultants, and independent sales representatives for various furnace companies and spare parts — Carlos Carrasco is the founder and former president of ASM International, Mexico Chapter with more than 50 years of experience in the heat treat industry.

For more information:

Contact Carlos at contacto@carrasco.com.mx or at www.furnacexpert.com

A Guide to Selecting Heat Treating Equipment Read More »

New Vacuum Furnace for Expanding Cutting Tool Manufacturing Facility

/ FEATURED NEWS, MANUFACTURING HEAT TREAT, VACUUM FURNACES NEWS

Piotr Zawistowski
Managing Director
SECO/VACUUM TECHNOLOGIES, USA
Source: secowarwick.com

HTD Size-PR LogoAn international cutting tool manufacturer will augment the capacity of its heat treat vacuum temper furnaces with two more at their North Carolina manufacturing facility.

This expansion to the company's heat treat capabilities comes two months after ordering their fourth Vector®  from SECO/VACUUM. The two single chamber, horizontal, front-loading furnaces are designed with an all-metal hot zone for clean vacuum processing. This style will be able to keep up with most standard hardening, tempering, annealing, solution heat treating, brazing and sintering applications, as well as low pressure carburizing.

"We are thrilled to be an ongoing partner in this [client's] growth," said Piotr Zawistowski, managing director of SECO/VACUUM. "We know they have multiple competitive options for their vacuum heat treat equipment, so we take nothing for granted, and work hard to earn their business every step of the way."

New Vacuum Furnace for Expanding Cutting Tool Manufacturing Facility Read More »

ELLWOOD Aluminum Acquires 200,000-Lb. Batch Homogenizing Furnace

/ ALUMINUM PROCESSING NEWS, FEATURED NEWS, MANUFACTURING HEAT TREAT

HTD Size-PR Logo

ELLWOOD Aluminum, an Ohio-based manufacturer of aluminum products, recently acquired a 200,000-lb. batch homogenizing furnace to complete the Phase 2 expansion of their plant in Hubbard, OH.

Gillespie & Powers, Inc., a family-owned supplier based in St. Louis, MO, will deliver the furnace to be operational in July 2022. The furnace, the second of its kind at ELLWOOD Aluminum, will be used for manufacturing large diameter aluminum ingots and billets, as well as rectangular slabs and cast plates.

ELLWOOD Aluminum Acquires 200,000-Lb. Batch Homogenizing Furnace Read More »

Ovako Adds 20MW Alkaline Water Electrolyzer for Hydrogen Production

/ BULK GASES & SYSTEMS NEWS, FEATURED NEWS, MANUFACTURING HEAT TREAT

HTD Size-PR LogoOvako, a European manufacturer of engineering steel with a North American presence, will receive a 20MW alkaline water electrolyzer by the end of 2022. The electrolyzer will be used at their plant in Hofors, Sweden for hydrogen heating of steel prior to rolling and hot forming.

Rickard Qvarfort
President of Business
Ovako Hofors

"In June," says Rickard Qvarfort, president of the business unit at Ovako Hofors, "we announced our collaboration with the Volvo Group, Hitachi Energy, H2 Green Steel and Nel Hydrogen with the purpose to invest in fossil-free hydrogen in Hofors[. . .] We are now very pleased to have reached this important milestone of the project. The electrolyzer technology will enable us to eliminate CO2 for heating steel before rolling."

Jon André Løkke
CEO
Nel Hydrogen

Nel Hydrogen Electrolyser AS, a division of Nel ASA, is scheduled to deliver the electrolyzer in 2022 for first hydrogen production in 2023. The electrolyzer will produce oxygen and hydrogen for Ovako's steel-heating processes and will decrease CO2 emissions by 50%.

"We are very excited to announce the delivery of electrolyzer equipment to Ovako, and this groundbreaking project," Jon André Løkke, CEO at Nel Hydrogen explains. "There is huge potential in reducing CO2-emissions from steel-heating processes through the use of green hydrogen, there are numerous similar sites with equally large potential for decarbonization across Europe and the rest of the world."

Learn more about Ovako here.

Ovako Adds 20MW Alkaline Water Electrolyzer for Hydrogen Production Read More »

Guía para la Selección de Equipos para Tratamiento Térmico

/ BURNERS & COMBUSTION SYSTEMS TECHNICAL CONTENT, CONTROLS TECHNICAL CONTENT, FEATURED NEWS, MANUFACTURING HEAT TREAT, VACUUM FURNACES TECHNICAL CONTENT, VACUUM PUMPS GAUGES VALVES TECHNICAL CONTENT

OC¿Se siente siempre seguro cuando selecciona equipos de tratamiento térmico? Do you always feel confident when selecting heat treating equipment?

There are many factors involved when making a purchase. Read this guide on how to select and buy new equipment by Carlos Carrasco, founder of Carrasco Hornos Industriales. The Spanish version is below, or you can check out both the Spanish and the English translation of the article where it was originally published: Heat Treat Today's November 2021 Vacuum Furnace print edition.

¿Se siente siempre seguro cuando selecciona equipos de tratamiento térmico? Hay muchos factores involucrados cuando se hace una compra. Consulte este artículo para conocer los pautas que lo ayudarán en el proceso de selección y compra. Autor: Carlos Carrasco, fundador de Carrasco Hornos Industriales.

Carlos Carrasco
Fundador
Carrasco Hornos Industriales

¿Por qué es conveniente esta guía?

Este artículo ayuda a los ingenieros a comprar equipos de tratamiento térmico. Hay muchas razones para seleccionar cuidadosamente los hornos industriales. Uno, es el costo del horno en sí y otro, es que el producto que se está tratando térmicamente afectará los resultados de su empresa.

En un equipo para tratamiento térmico, hay más ingeniería especializada de lo que parece en el exterior. Hay varias y muy sólidas razones, para hacer una cuidadosa selección de estos equipos, pues sus componentes son inherentemente de alto precio y en la mayoría de los casos, los resultados del tratamiento térmico tienen un importante efecto en la economía de su empresa.

El objetivo de esta guía es el de tratar de ayudarle a hacer la mejor selección del equipo; porque su decisión afectará no sólo al proyecto, su presupuesto y resultados, sino también a su capacidad como ejecutivo. No será la primera vez que escuche usted comentarios respecto a equipos adquiridos por la empresa en etapas anteriores a la suya o en la misma, y es común en la industria, tanto nacional como internacional, que los operadores o el personal de mantenimiento, comenten: “Cuando adquirieron este horno, nadie pensó en los problemas de mantenimiento [. . .] Como ellos no son los que lo usan día con día, no se dieron cuenta de cuánto trabajo se requiere para mantenerlo o bien para trabajar confi ablemente con él”.

Déjese ayudar, pues como ingenieros consultores en hornos y experiencia de más de 50 años en este ramo; tanto en la fabricación, venta y mantenimiento, con buenos resultados, los comentarios siguientes seguramente pensamos le serán útiles.

Horno de temple al vacío

Primer paso: solicitud de la cotizacion

Al solicitar una cotización, nadie mejor que Ud. puede conocer los requisitos que deben tener sus productos tratados térmicamente. Un proveedor confiable, debe ser capaz de entender todas sus necesidades de tratamiento térmico a partir de la solicitud de cotización que le presente. Consecuentemente, su solicitud deberá ser clara, concisa y tendrá como mínimo los siguientes datos:

  • Proceso de tratamiento térmico a efectuarse en el equipo.
  • Forma, dimensiones generales y pesos del (los) producto(s) a tratar térmicamente.
  • Volúmenes de producción por hora, día o mes.
  • Número de horas disponibles para el trabajo de tratamiento térmico.
  • Material del que están construidas las partes.
  • Combustible disponible o en su caso, si la calefacción será por medio de electricidad.
  • Tensión eléctrica disponible en la planta.
  • Espacio disponible para la instalación del equipo.
  • Consideraciones especiales del manejo de la carga y la descarga.

Es conveniente que Ud. sepa que los fabricantes de hornos necesitan la información anterior para empezar a definir una serie de opciones del equipo que podría ser el más adecuado para sus procesos. Por ejemplo, la producción horaria define: Las dimensiones del espacio para calentar la carga, el tipo de horno, continuo o por lotes, la cantidad de calor a ser liberada en el horno, así como el método de carga y descarga y los dispositivos para acomodar o transportar la carga como charolas, canastillas o bandas transportadoras. Todo lo anterior influye, tanto en el costo inicial como en el de operación, porqué, a fin de cuentas, el costo del equipo propuesto y su funcionalidad, están en relación directa a las especificaciones de su solicitud de cotización.

Ah, y por favor, no trate de llevar a cabo todos los procesos de tratamiento térmico habidos y por haber en un único horno, ni tampoco quiera tomar precauciones de futuras necesidades de producción, de las cuales no tiene ahora ninguna certeza, ya que es difícil llevar a cabo en un solo horno varios procesos que involucran diferentes temperaturas, volúmenes de producción, etc. Un enfoque en este sentido conduce a equipos sobredimensionados y posiblemente fuera de su presupuesto.

Horno de vacío para carburizado a baja presión

Segundo paso: selección de proveedores

Presente su solicitud de cotización, solamente a quien tenga la capacidad técnica y experiencia para preparar una oferta, que satisfaga dicha solicitud. Utilice siempre referencias de instalaciones previas, y de preferencia similares, o mejor aún, iguales a la que usted requiere.

El costo de los equipos para tratamiento térmico es elevado y representa un atractivo a empresas e individuos que consideran la posibilidad de obtener beneficios económicos. La verdad, es que el diseño y construcción de estos equipos involucra una considerable cantidad de ingeniería, resultado de costosas inversiones en investigación y desarrollo con retroalimentación de casos prácticos (los fracasos enseñan) que han sido aprovechados en beneficio de los clientes potenciales. En suma, no permita que sus necesidades sean el método de aprendizaje de un proveedor. Aquí es donde no hay sustituto a la experiencia.

De hecho, el proveedor con experiencia y sólida capacidad técnica es el único que estará en posibilidad de garantizar resultados desde el principio. Desde luego, a Ud. le interesa obtener resultados dentro de especificaciones, desde la primera carga que sale del horno, y no comprar excusas, promesas y retrabajos para corregir lo que de inicio está mal hecho. Quizá, con buenas intenciones, pero poca y en algunos casos, nula experiencia.

Tercer paso: estudio y evaluación de las ofertas

El proveedor responsable invertirá tiempo y dinero en el estudio y preparación de la oferta, porque no puede correr el riesgo de que su proyecto no cumpla su cometido. Ahora la responsabilidad de evaluar las propuestas recae sólo en Ud.

No hay proveedor responsable, que no haya sufrido la decepción de que su oferta sea leída de atrás para adelante. Nos referimos a que el precio es la primera línea que lee el cliente potencial. Hágase una pregunta: ¿Su necesidad primordial es, un precio o un equipo de tratamiento térmico que sea capaz de procesar las piezas para que cumplan sus especificaciones de su tratamiento térmico? La lectura cuidadosa de la oferta, le dará la respuesta a sus necesidades de producción y a la justificación del costo del horno. Si hubiese alguna sección que no sea de su completa comprensión, no dude en llamar al proveedor para que haga las aclaraciones correspondientes. Por favor, no malentienda. La inversión en equipos de producción es muy importante, pero más importante será que la inversión sea rentable.

El equipo para tratamiento térmico debe satisfacer una necesidad de producción y de ciertas especificaciones metalográficas. Consecuentemente, las dimensiones del espacio en donde serán colocadas las partes, quizá sea el factor principal en el diseño del horno. Esto se debe, a que los metales sólo son capaces de calentarse hasta una cierta temperatura, a una razón que está determinada por el método de calefacción, la geometría y acomodo de la carga. Sólo los proveedores experimentados, pueden hacer los cálculos correctos para que su propuesta satisfaga las necesidades de producción del proyecto, del que Ud. es responsable. Solicite al proveedor le muestre y explique la memoria de cálculo que conduce al dimensionamiento del sistema propuesto.

¿Cómo se soportan y/o transportan las partes dentro del horno? Éste es un punto de gran importancia, por el costo inicial de estos componentes y también por los costos del mantenimiento futuro. Conviene tener en cuenta que, cualquier mecanismo que trabaje a alta temperatura, siempre será problemático su mantenimiento y reposición. Las bandas de eslabones fundidos, por ejemplo, (de mayor costo inicial) soportan mejor y durante mayor tiempo, cargas pesadas en comparación con las bandas de malla metálica. Sin embargo, hay notable diferencia en los costos de componentes de aleación Cromo-Níquel, comparados con los de acero al carbón, pero su uso es prácticamente imperativo.

Los hornos tienden a deteriorarse rápidamente en cualquier lugar en donde haya fuga del calor. Asegúrese de que el diseño de las puertas sea el mejor posible para evitar esta fuga de calor y también de que su horno no tenga puertas que no necesita. Esto le ahorrará costos de mantenimiento.

Por lo que respecta al temple, los sistemas de circulación de agua o aceite son de extrema importancia, lo mismo que la capacidad del tanque. De lo contrario, el medio de temple puede sobrecalentarse y los resultados de su proceso, podrían no ser satisfactorios.

En un horno destinado a operaciones de baja temperatura (180 a 600° C), por ejemplo, procesos de revenido, es necesario disponer de un ventilador para la recirculación del aire caliente del horno. La uniformidad de la temperatura en las partes y la rapidez a la que se calientan las mismas, depende de la velocidad de la recirculación, del peso del aire y del diseño del horno que debe forzar el paso del aire en forma óptima, a través de la carga, con la utilización de mamparas deflectoras o plenos de distribución. En los hornos de alta temperatura (700 a 1200° C), la transferencia de calor depende de la radiación de éste hacia la carga y su superficie expuesta, por lo que un ventilador de recirculación no es necesario. El tratamiento térmico, es un proceso crítico en lo que se refiere a temperatura. Los pirómetros reguladores de temperatura deben tener la precisión necesaria.

Escriba sus dudas sobre la oferta y pida al proveedor que las aclare en forma extensa y por escrito. Las respuestas le facilitarán el hacer un segundo análisis de la oferta y compararla con otras ofertas; además, tendrá un registro para revisión por parte de otros colaboradores en el proyecto. Pida opinión sobre sus observaciones a las propuestas, pues uno tiende a pensar en círculos.

Solicite a los proveedores, le entreguen una lista de instalaciones similares a la suya en las que hayan intervenido. Generalmente, los colegas industriales se muestran imparciales en sus comentarios sobre la experiencia que hayan tenido con un determinado proveedor.

Finalmente, haga un cuadro comparativo, en la forma más objetiva posible. No pierda de vista que, frecuentemente las ofertas no incluyen algunas cuestiones subjetivas, que pueden ser importantes para una selección final. Por ejemplo, es probable que algunos proveedores tengan mayores conocimientos y experiencia en ciertos procesos, sencillamente porque han invertido tiempo y dinero para encontrar las mejores soluciones al proceso y Ud. podría verse beneficiado con esas experiencias.

Cuarto paso: el precio

Seguramente, ahora que ha comprendido el alcance de las propuestas que ha recibido y que cumplen con sus necesidades de producción y calidad, se dará cuenta que aún así habrá diferencias entre sus distintos proveedores que podrían llegar a ser significativas.

Este es el momento en que un fabricante de hornos industriales podrá justificar sus costos. Y usted sabrá si ha realizado su oferta pensando en Ud. como un futuro cliente satisfecho o únicamente en los beneficios económicos que la venta le reportará.

Conclusiones

Son innumerables los casos en que los equipos fueron mal seleccionados: “La sub-estación y/o la torre de enfriamiento no tuvieron capacidad”, “El equipo no es lo que esperábamos”, “Nunca nos dijeron que el horno necesitaba gas en esas capacidades”. Estos son sólo algunos de los comentarios que todos hemos escuchado.

Tómese todo el tiempo que requiera para analizar sus opciones, piense el porqué hay diferencias de un proveedor a otro y solicite que le sean aclaradas. Pida a sus proveedores las opciones a las que puede acceder con el equipo que está solicitando y que éstas sean cotizadas como eso: opciones. No se olvide de solicitar las refacciones que pudieran ser utilizadas durante el primer año de operación de su horno.

Para finalizar, sólo el tiempo dirá si al seleccionar sus hornos, éstos funcionaron como se esperaba.

Sinceramente, esperamos que estas recomendaciones le orienten en la selección de hornos industriales para tratamiento térmico y estamos seguros, que así será. Seguro que debe haber más preguntas relacionadas con este tema, no dude en contactarnos para obtener ayuda.

Sobre el autor:

Expertos en hornos. Representantes de diversas compañías fabricantes de hornos industriales, partes de refacción y equipo de combustión. Con más de 55 años de experiencia en la industria y consultores. Carlos Carrasco es fundador y expresidente del capítulo México de la ASM International.

Contacto Carlos: contacto@carrasco.com.mx

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ELVIAL Increases Heat Treat Capabilities for Aluminum Products

/ ALUMINUM PROCESSING NEWS, FEATURED NEWS, MANUFACTURING HEAT TREAT

Marcin Stokłosa
Project Manager
Nitrex Poland
LinkedIn.com

HTD Size-PR LogoELVIAL S.A.,a large aluminum extrusion company in Greece, has purchased an aluminum extruder furnace to meet needs created by their plant's expansion and increasing manufacturing capacity.

"This additional NX-815 E furnace [. . .] will help increase the production of building materials by the company," says Marcin Stokłosa, project manager at Nitrex. "The first furnace has been operational since 2016."

The NX-815 E is a retort furnace used for extrusion. It operates with NX connect software, and uses the NITREG-C (nitrocarburizing) and NITREG (gas nitriding) technologies for dies extrusion. The order also included a lifting device. All processes for this furnace are compliant to AMS 2759/10.

An ELVIAL representative cited good equipment, technology and service to explain why ELVIAL chose to do business with the supplier this second time.

 

heat treat buyers guideLooking for Endothermic generators? See listings for equipment and services in the Heat Treat Buyers Guide

 

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Innovative Quenching Process from New PEER Energy and Schwing Technologies Partnership

/ FEATURED NEWS, MANUFACTURING HEAT TREAT

HTD Size-PR LogoTwo German companies, with international reach and North American locations, signed a long-term cooperation agreement to further technical development and marketing of fluidized bed technology for the heat treatment of metal components. The partnership between the two companies focuses on combining innovative quenching processes with fluidized bed technology.

Ralf Giebmanns (PEER Energy) and Andreas Guderjahn (Schwing Technologies) want to further advance heat treatment processes and develop new resource-saving and cost-cutting processes with the new G4Q® bath medium

Specifically, PEER Energy GmbH and Schwing Technologies GmbH will research results and developments of heat transfer rates. The application focus is on faster and more uniform heating and cooling processes for metal parts with the aim of conserving resources and further reducing unit costs.

"We are pleased to cooperate with Schwing Technologies. Together with the proven technology leader for fluidized bed heat treatment and with our latest approaches, we want to open up opportunities in new heat treatment markets," emphasizes Ralf Giebmanns, managing director of PEER Energy. Andreas Guderjahn, heat treatment expert at Schwing Technologies, adds: "We will make use of the extensive knowledge and vast experience of the PEER Energy team for the analysis and design of heat treatment lines and jointly develop innovative processes."

By means of heat treatment, the mechanical properties of conventionally or additively manufactured components are adapted to their static or dynamic application requirements. In this context, the proven and established fluidized bed technology is known for its superior temperature uniformity, robustness and flexibility. It scores particularly well when it comes to high throughput with consistently high quality.

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The Use of Graphite for Vacuum Furnace Fixturing

/ FEATURED NEWS, MANUFACTURING HEAT TREAT, VACUUM FURNACES TECHNICAL CONTENT

OC Carbon/carbon composite. What is it? Why is the vacuum furnace industry excited about its use in graphite vacuum furnace fixtures, grids, and leveling components?

In this Technical Tuesday, originally published in Heat Treat Today’s November 2021 Vacuum Furnace print edition, explore this new material game changer and learn about its versatility in this informative article by Real J. Fradette, senior technical consultant, Solar Atmospheres, Inc., and Roger A. Jones, FASM, CEO emeritus, Solar Atmospheres, Inc.

Roger Jones, FASM, CEO Emeritus, Solar Atmospheres, Inc.
Additionally, Real J. Fradette, Senior Technical Consultant at Solar Atmospheres, Inc.

Introduction

The vacuum furnace industry has searched for many years for the ideal material to be used in fixtures and grids for processing workloads at elevated temperatures. The support structures should be lightweight to achieve desired metallurgical results during the cooling phase of the process cycle. These lighter-weight supporting members will also result in overall lower processing costs due to shorter heating and cooling portions of the overall furnace cycle.

The latest and most successful material used in graphite vacuum furnace fixtures, grids, and leveling components is a carbon/carbon composite (C/C) structure. Graphite is an allotrope and a stable form of carbon.

Carbon/Carbon Composite Material

Carbon fiber reinforced carbon matrix composites (C/C composites) have become one of the most advanced and promising engineering materials in use today. These C/C composites consist of two primary components: carbon fibers and a carbon matrix (or binder). They are among the strongest and lightest high temperature engineered materials in the world compared to other materials such as basic graphite, ceramics, metal, or plastic. C/C composites are lightweight, strong, and can withstand temperatures of over 3632°F (2000°C) without any loss in performance.

Ingots processed with graphite support members

Typical Carbon/Carbon Composite Two-Tier Fixture

Properties of Carbon/Carbon Composites

C/C composites are a two-phase composite material where both the matrix and reinforced fiber are carbon. C/C composites can be tailored to provide a wide variety of products by controlling the choice of fiber type, fiber presentation, and the matrix carbon/carbon composite. They are primarily used for extreme high temperature and friction applications.

C/C composites combine the desirable properties of the two-constituent carbon materials. The carbon matrix (heat resistance, chemical resistance, low-thermal expansion coefficient, high-thermal conductivity, low-electric resistance, low-specific gravity) and the carbon fiber (high-strength, high elastic modulus) are molded together to form a better combined material. The reinforcing fiber is typically either a continuous (long-fiber) or discontinuous (short-fiber) carbon fiber type.

CFC design fixturing for medical implants

Summarizing Properties of Carbon/Carbon Composites

  • Excellent thermal shock resistance
  • Low coefficient of thermal expansion
  • Excellent thermal shock resistance
  • High modulus of elasticity
  • High thermal conductivity
  • Low density (about 114 lb/ft³)
  • High strength
  • Low coefficient of friction (in the fiber direction)
  • Excellent heat resistance in nonoxidizing atmosphere. C/C composites retain their mechanical properties up to 4982°F (2750°C)
  • High abrasion resistance
  • High electrical conductivity
  • Non-brittle failure

Benefits of C/C composites

The carbon fiber matrix can be used to create racks, plates, grids, and fixtures for vacuum heat treating applications.

Various Configurations of C/C Used as Fixtures and Grids

Below are several examples showing different applications of how C/C component graphite materials are used in typical vacuum furnace applications:

347 screens: 347 screens that were annealed at 1875°F in partial pressure nitrogen. The screens were too wide for our normal furnace grid, so we used graphite fixturing to get the screens into the center of the furnace to accommodate the width. The graphite also allows for the screens to settle flat during the heat treating.

Titanium aerospace components: Very intricate and precise graphite fixturing designed to minimize warpage during the solution age heat treatment of these 5-5-5-3 titanium aerospace components. The fixturing was manufactured by 5-axis machining equipment and it allows the part to move during the heat treatment and then settle back into the exact contour of the fixture.

Steel aerospace components: 4340M aerospace components hardened and tempered in partial pressure nitrogen. Graphite fixturing was used to minimize distortion and holes were machined into the graphite plates to help with the cooling phase of the cycle.

Titanium ingots: 10-2-3 titanium ingots homogenized at 2350°F for 24 hours in high vacuum, 10-5 Torr. Each ingot weighs about 10,000 pounds. The fixturing serves two purposes: it keep the ingots from rolling during the heat treatment process, and it also contours to the shape of the ingot so there are no flat spots after the homogenization.

Titanium strips: Titanium strips annealed at 1450°F and aged in high vacuum, 10-5 Torr. Strips were placed on a laser leveled graphite plate to maintain flatness during the run.

Ingot fixtures: These are graphite support members that are used to process the ingots on the first page of the article. They maintain the shape of the ingots while providing support.

The above images are just a small sample of the many supporting graphite designs that have become so critical in vacuum furnace processing. C/C component graphite material can be readily machined for special shapes and applications. We look forward to finding many more ways to successfully use these graphite components.

About the Authors:

Real J. Fradette is the senior technical consultant at Solar Atmospheres, Inc.

Roger Jones is the FASM and CEO Emeritus at Solar Atmospheres, Inc.

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