At the end of March, a vacuum aluminum brazing furnace was shipped to a manufacturer that serves the aerospace industry. The North America company produces complex heat exchangers, cold plates, and avionic enclosures.
The furnace, from PVT, Inc., has an AMS 2750 qualified work zone of 36” x 30” x 90” with type B instrumentation and Class 1 temperature uniformity. In addition to this furnace, PVT delivered two furnaces in Q4 and one furnace in Q3 2022 to companies manufacturing components for avionics, MRO (maintenance, repair, and overhaul), and electromechanical assemblies.
Maciej Korecki Vice President of Business of the Vacuum Furnace Segment SECO/WARWICK
A manufacturer of a wide variety of vacuum circuit breakers ordered vacuum furnaces for metal heat treatment. The circuit breakers must be brazed with high vacuum.
In 2017, the first furnaces provided were two SECO/WARWICK furnaces. The most recent expansion is three Vector vacuum furnaces that provide high vacuum level and temperature uniformity within the entire load.
"[T]he specificity of this electric power control production requires incredible precision. Circuit breakers need a high level of vacuum and temperature uniformity. They are brazed in vacuum furnaces in a very high vacuum; therefore, it was necessary to use an efficient pumping system consisting of a turbomolecular pump and a dry pump." Maciej Korecki, vice president of the Vacuum Products Segment at SECO/WARWICK Group, a manufacturer with North American locations.
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A heat treat furnace was recently shipped and installed at commercial heat treat facility in Eastern PA. The equipment will expand the company's vacuum heat treat and gas quench capabilities.
Solar Manufacturing recently delivered a Mentor® vacuum furnace. The furnace has stainless steel chamber, a work zone of 12” x 12” x 18” deep, and a maximum operating temperature of 2400°F with a workload capacity of 250 pounds. The furnace includes a VHS 6” diffusion pump for vacuum performance in the 10-6 Torr range, a 7.5HP fan motor for internal gas quenching up to 15PSIG (2-bar), and the SolarVac® fully automated and programmable controls package with a Eurotherm digital recorder.
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A Swiss commercial heat treater ordered a vacuum furnace. A system will increase the production capacity of their nickel and silver brazing processes.
Maciej Korecki Vice President of Business of the Vacuum Furnace Segment SECO/WARWICK
The SECO/WARWICK vacuum furnace helps with hardening larger size parts and significantly increases the efficiency of the current hardening plant. The furnace increases production. In the version ordered by the Swiss, a large working zone (36"X36"X48") with the potential to adjust to an oversized load utilizes the advantages of a round heating chamber.
“[With a] cooling capacity of 15 bar, it is possible to process parts that require very fast cooling . . . . Vector also allows the system to perform more difficult brazing processes with either nickel or silver," explains Maciej Korecki, vice president of the Vacuum Furnace Segment, at SECO/WARWICK Group. "This is our second installation with this partner. Previously, we delivered a solution from the SECO/WARWICK furnace family of a similar size, in a non-pressurized version."
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When heat treat and St. Patrick’s Day collide, Heat TreatToday editors have a little fun. Today’s post is inspired by furnaces and Ireland. Happy St. Patrick’s Day, and enjoy the hot topics!
| The Irish Turf Fire |
Have you heard of this heat treating solution? The fuel for this furnace is turf. “Turf is dried-peat and was a primary fuel source for Irish people for thousands of years[…] In the past, Irish people used turf to heat their homes and cook their food. Turf was harvested from a bog. Cutting turf by hand is a laborious task.” Not sure your general manager will let this one by... (Mairead Geary, “Smell of an open fire in Ireland is intoxicating but what is Irish turf?” IrishCentral)
| Irish Terms |
Here are some Irish and Gaelic terms that a heat treater may want to use instead of the same ol’ same ol’. Just for today. Search more options for yourself here.
Cóir teasa: heat treatment
miotaleolaíocht: metallurgy
foirnéis: furnace
prásáil: brazing
gaibhnithe: forging
ainnéalta: annealing
| Heat Treatment in Ireland |
Content at Heat TreatToday is focused on the North American heat treat industry, however, we would be remiss if we didn’t highlight heat treatment going on in Ireland.
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For a featured in-house heat treater, “medtech” company Stryker has heat treat processes going on at their Ireland R&D base in Cork. After a commitment to invest in three facilities in Cork, Stryker’s Spencer Stiles said, “Our team in Ireland has built considerable research and development and new product development capabilities through the partnership of multiple divisions over the past 20 years in an effort to serve multiple market segments.”
Screen Capture of Stryker’s Landing Page
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BOC is a provider of industrial, medical and special gases in Ireland and has been producing atmospheric gases, including oxygen, nitrogen and argon in Ireland for over 70 years.
Source: About BOC, a member of Linde Group
While you may not have heard of these heat treater providers, they are a member of the international Linde Group.
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A heat treatment service provider, Hi-Life tools has been providing heat treatment service for a wide range of Irish based tool making, engineering and medical device companies for more than 20 years.
Source: PTG webpage
The company, part of Precision Tool Group, has built up a vast amount of experience of heat treating a wide range of metals from tool steels, stainless steels, and exotic metals. These can be treated using the standard processes or a custom made process can be developed to suit the customer requirements.
| Irish Voices: Winter, Fire, and Snow |
Thankfully, winter and snow are melting away, but fire remains! Listen to this beautiful ballad sung by Irish Tenor, Emmet Cahill. If you want to listen to a full playlist of Irish folk music, check out The High Kings.
If you’ve ever tried to braze together materials that have widely different Coefficients of Thermal Expansion (COE’s), you know that the material with the higher expansion rate will grow faster than the other when heated and contract faster when cooled down. You also know that once the two different materials have been brazed together and cooling begins, the shrinkage-rate differences between those two materials can produce significant shear stresses at the brazed interface between them and be so strong that the thin brazed joint may be torn apart at either interface. Other similar weaknesses and damage can result as well.
In this HTT Best of the Web Technical Tuesday feature, Dan Kay of Kay and Associates, a vacuum and atmosphere brazing consultant, explains the details of this problem and the solution.
Dan Kay Brazing Engineer Kay and Associates
An excerpt: “Today’s brazing technology is based on a strong foundation of the brazing experiences of many people around the world over a period of many decades (even centuries). I’ve now been very active in the brazing world for almost 50 years and, like my predecessors in the world of brazing, I’ve learned a lot about this fascinating joining process (and I’m still learning). In the article, I’d like to share with you one of my brazing experiences from many years back, one that involved high-temperature differential-expansion between an 18″ (45 cm) diameter tool steel die and a thin carbide plate (round disc) that needed to be brazed to the die’s front surface for wear-protection.”
In this article, Dan, who is also a HTT consultant, helps readers understand the high-temp differential-expansion problem, explore what steps can be taken to prevent it, and ties it all together so that readers can clearly understand what to do.
Alessandro Fiorese, R&D Chief Engineer with TAV Vacuum Furnaces SPA
Alessandro Fiorese, R&D Chief Engineer with TAV Vacuum Furnaces SPA, introduces the vacuum brazing process for automotive applications. For more articles, tips, and news related to heat treatment for automotive applications, keep an eye out for Heat Treat Today’s special print/digital issue Automotive Heat Treating, due in June 2019.
Introduction
Brazing is a heat treatment process in which metallic parts are joined together through a metallic filler with a melting temperature lower than the melting point of the joined parts. The filler metal can be used as a wire, a thin plate, or a paste depending upon the final application we are considering.
To obtain a good welding in terms of mechanical properties and corrosion resistance, it’s necessary to minimize contamination and impurities in the joined zone. Vacuum brazing processing provides a way to reach a high cleaning level of atmosphere during the brazing heat treatment.
The brazing treatment is particularly useful to produce complex shape parts with a lot of joining points per unit of area. Typical brazing applications are oil or water heat exchangers in the civil and automotive fields such as the ones represented below.
The high-performance aluminum heat exchangers manufacturing is growing particularly in the automotive field. In this context, AA 3xxx and 4xxx are commonly used materials for parts and filler material respectively because these materials have a very low specific weight and a very high thermal conductivity level.
As indicated before, one of the cleanest brazing atmospheres is vacuum. For this reason, in the following discussion, we will analyze in detail the complete characteristics of a semi-automatic TAV vacuum brazing furnace for automotive applications.
Vacuum Brazing Furnace
The entire furnace is composed of three different stations:
the heating furnace;
the loading station;
the cooling station.
Heating Furnace
heating furnace
Furnace Vessel
The vessel separates the inner part of the furnace where the hot chamber is placed from the outside environment. The vessel develops along a horizontal axis, it has an elliptical design and it is provided with two flat doors (front and rear). Both doors are hinged and can be opened manually. The front door has an automatically sliding entrance for loading-unloading the furnace.
Hot Chamber
The thermal chamber has a rectangular section 71 (H) x 18 (W) x 144 (L) inches (180 x 45x 365 cm), and it is constituted by steel panels with nickel-chrome resistors. There are 23 independent hot zones that make the chamber temperature very well-controlled. The temperature uniformity requested for this vacuum furnace is ± 37°F (± 3°C) from the set temperature. In the following picture, the ± 37°F Temperature Uniformity Survey (TUS) chart is shown.
Figure 1. TUS example at a specific temperature with 12 TLC
Vacuum System
The vacuum system has three pumping groups, two with a rotary piston pump, a roots pump, and an oil diffusion pump. The third pumping group has a mechanical pump, a roots pump, and a cryo-trap in order to condensate humidity and impurities released during the entire process. The ultimate reachable vacuum without the load is 10-6 mbar (range).
Loading Station
loading station
Loading Baskets
To carry out the brazing heat treatment in a correct way, a specific steel shelved fixtures hold the heat exchangers parts all together with the filler material. For each brazing process, a load from 1984 up to 4850lbs (900 up to 2200kg) can be heat treated at the same time. For gaining a semi-automatic heat treatment process, there is a parking station that can be used as a buffer for the heating furnace.
cooling station
Cooling Station
At the end of the brazing heat treatment, the load is automatically transferred into a separate cooling chamber where the brazed parts are cooled down by forced recirculation of air.
Heat Treatment
Before reaching the brazing temperature, the load is maintained at a lower temperature for a period of time to remove the working oil plate from the heat exchangers. During this maintenance time, a variation between high vacuum and partial pressure of N2 is observed.
Figure 2. Typical brazing cycle. Line yellow is the setpoint, line orange is the temperature TC, line blue is the high vacuum level and purple line is the partial pressure in mbar detected.
After the brazing step, the furnace reaches high nitrogen static partial pressure, starting the cooling phase. This step is considered complete when the furnace injects air up to reach the atmospheric pressure as total pressure. At this time, the front door opens automatically, and the loading track extracts the charge from the furnace.
The demand in aerospace manufacturing for brazing technology is likely to increase as the alloys developed and manufactured through the process are used for more applications — from turbine blades to rocket nozzles to hydraulic assemblies.
“Brazing is used just about everywhere—it’s difficult to classify.” ~ Ed Arata, brazing engineer, Morgan Advanced Materials
Brazing may be difficult to classify, but the process can be explained, and its subsequent value to aerospace design and manufacturing groups is explored in this Best of the Web article from MRO-Network.com
We look now at the third of the seven important criteria that should be followed in order to insure good brazing, namely, the importance of good gap clearance (joint fit-up). We’ll see how reasonably tight joint clearances can significantly improve overall joint quality, whereas poor fit-up often yields poor brazing results (which could then hurt the reputation of the company doing the brazing.)
Slovenia commercial heat treater, MIHEU, is expanding their production capacity with the addition of a new Vector™ High Pressure Gas Quench vacuum furnace. Delivered in February 2016, the new installation will enable MIHEU to increase production capacity and expand their markets by offering a wide variety of processes with the installation of a single system.
According to Aleš Prikeržnik, Managing Director, „ We wanted to partner with a company with expertise in both emerging technologies as well as reliable standard solutions to expand our market base and continue to deliver a high quality product to our customers into the future. The SECO/WARWICK team provides more than good equipment, they have the technical and service support that we demand to keep our operation running smoothly.” Family owned for three generations, learn more about MIHEU at www.miheu.si/en/abous-us.html
Maciej Korecki, SECO/WARWICK Vacuum VP commented, „The VECTOR Universal High Pressure Quench is our signature technology in use by commercial heat treaters worldwide for over 20 years. We are pleased to work with MIHEU as a supplier-partner to provide them with the world’s best technology and technical services. ”
VECTOR™ Universal High Pressure Quench Vacuum Furnaces
The standard Universal VECTOR vacuum furnace is used for wide range of industrial heat treatment applications including gas quench hardening & tempering, degassing, annealing, solution heat treatment and brazing. Equipped with Data Portal™, the control system can connect to a configurable website that gives the user access to archive data using a web browser. This application can use an internal data recorder or it can work with other software. Recorded data is displayed in the form of web pages. Access, depending on the customer’s choice, can be through a local area network or via the Internet from anywhere.
The MIHEU Furnace main parameters include:
Useful dimensions: 600 x 600 x 900 mm (24” X 24” X 36”)
Maximum load gross weight: 600kgs (1,300 lbs.)
temperature: 1300°C (2400°F)
Quenching pressure: up to 10,0 bar abs.
The system was delivered complete with a water cooling system, load fixture, DataPortal™ software package, installation, start up and training.
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