BRAZING

High-Temp Differential-Expansion Problem and How to Solve It

 

 

Source: Vac Aero International Inc.

 

 

 

 

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.

Read the entire article from Vac Aero International,  An Old High-Temp Differential-Expansion Problem

Image source: Vac Aero International Inc.

High-Temp Differential-Expansion Problem and How to Solve It Read More »

Vacuum Brazing for Automotive Applications

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.

Vacuum Brazing for Automotive Applications Read More »

A Braze New World: Sending Non-precious Braze Alloys into Space

The space industry is growing fast and is predicted to be worth over a trillion dollars by 2040.

Keith Ferguson, Senior Business Development Manager at Morgan Advanced Materials’ Braze Alloys Business, explains how braze alloys play their part in safe, reliable and sustainable space exploration. 


A Braze New World

The saying goes, “one small step for man, one giant leap for mankind.” This famous phrase uttered by Neil Armstrong is the perfect advertisement for space exploration and its importance to the future.

Less than a century old, space exploration has come on leaps and bounds since the first artificial satellite, Sputnik 1, was propelled into space in 1957. Since then, the world has witnessed marvels such as landing on the moon, the space shuttle program of the 1970s, and the launch of the International Space Station.

The importance of these missions and their subsequent value is immeasurable. Many might not realize on a day-to-day basis how space exploration has improved lives and the global economy to no end. This includes simple weather forecasting, broadcasting TV and radio, predicting natural disasters, monitoring for fertile land, forecasting sea level patterns, and even aiding research in muscular atrophy.

It’s little wonder then that this industry has significant value. The space industry was reportedly worth $384 million USD in 2017, growing at a rate of 7.4 percent. According to Morgan Stanley, it sees the industry growing to be worth $1.1 trillion USD by 2040.

However, there are challenges. Many believe that the millions of dollars and resources used to explore space could be better used on immediate threats to society like clean water, famine, poverty and more. Outside of external opinion though, there are internal operational challenges. Namely, space exploration needs to become safer and more sustainable.

A huge part of solving this challenge is in brazing alloys.

A Brief History on Brazing in Space

In simple terms, brazing joins two metals by heating and melting a filler (alloy) that bonds to the two pieces of metal and joins them. The filler must have a melting temperature below that of the metal pieces.

The use of braze alloys in space equipment is mission critical, as they allow sensors to be mounted as close as possible to engines to measure and monitor output and feed data back to operators. Indeed, they’ve already aided successful missions. Two of Morgan Advanced Materials’ braze alloys, RI-46 and RI-49, were specifically engineered and used by NASA on the Space Shuttle Main Engine, also known as the RS25.

Braze Alloys (Morgan in Space)

RI-46 specifically was developed as a replacement for the existing Nioro braze alloy, which is comprised of 82/18 Au/Ni (gold/nickel). RI-46 contains much less gold, adding in copper and manganese instead. This helped make the braze alloy significantly less dense and provided crucial weight savings, but also still operable from a wide range of temperatures, between -400°F to 1292°F (-240°C to 700°C).

These alloys have not only been critical for past space missions, but also for future missions. RI-46 and RI-49 have been adopted for NASA’s Space Launch System (SLS), a vehicle that is planned to take a crewed mission to Mars.

As alluded to already, developing new braze alloys is as much about performance as well as sustainability.

The Need for Non-Precious Alloys

It needs no mention that space exploration is a costly exercise. According to NASA, the average cost to launch a Space Shuttle is $450 million per mission. The Space Shuttle Endeavour, the orbiter built to replace the Space Shuttle Challenger, cost an eye-watering $1.7 billion USD.

Wire Form Braze Alloys (Morgan in Space)

Bringing costs down is clearly required to keep space missions feasible. One key part of cost reduction is in reducing the use of precious metal braze alloys.

Precious metals like gold and palladium are becoming increasingly scarce. Of course, the cost of producing alloys from these precious metals is also increasing as a result.

However, there can be a reluctance to come away from using precious metal alloys. Years of research, development, and data mean these alloys are tested and reliable. When dealing with missions and equipment that run into the hundreds of millions of dollars and, more importantly, the lives of crew members, reliability becomes an overarching objective, and failures must be prevented.

To solve this issue, Morgan’s Braze Alloys business has been researching and developing non-precious metal alloys over many years. As seen from the RI-46 and RI-49 alloys, these solutions are just as strong as their equivalent high precious-metal counterparts, but at a fraction of the cost.

Non-precious metal alloys can be made from metals like nickel, chromium, and cobalt. Their success has already been seen in the aerospace sector, and now research is being pioneered into making them fit for going into orbit and beyond.

Space, for All to Enjoy

Space travel is not just for highly trained astronauts and public benefit; there is also a growing commercial aspect. Satellite TV and radio have already been mentioned, but billionaire entrepreneurs such as Richard Branson and Elon Musk have also been pioneering private space travel. The hope is that civilians might one day be able to enjoy outer space as well, albeit at potentially high prices.

Achieving this dream is of course hinged on safety and reliability, given that lives will be at stake. The key to improving these factors is being able to place sensors as close as possible to the spacecraft’s engine.

By enabling sensors to be placed near the spacecraft’s engine, mission control and crew can then accurately read and measure data and output. This includes fuel efficiency, temperature, gas flow and monitoring for fire detection or abnormalities. If these sensors are placed too far away from the engines, then data readings become inaccurate and missions can be compromised.

Recent news highlights why sensor technologies are critical, as a two-man space crew had to abort their flight to the ISS after a post-rocket launch failure. The Soyuz spacecraft started to experience failure 119 seconds into the flight, and seemingly, problems were reported by the crew first, not by mission control. The crew described feelings of weightlessness, an indication of a problem during that stage of the flight. Luckily, they aborted, ejected their capsule from the rocket, and returned safely to Earth.

While the cause of the failure is still to be identified at the time of writing, clearly, such a situation should not be happening. Any problems should be picked up by mission control, and not be reliant on crew judgment.

Active Alloys join ceramic sensors to engines. (Morgan in Space)

The challenge though is that some sensors are made from ceramic due to the need to resist corrosion and high temperatures, typically up to 1742°F (950°C ). However, these ceramic sensors then need to be joined to metallic parts of the engine.

This is where “active alloys” come in. Unlike regular braze alloys that join metal to metal, these alloys can join metal to ceramic, or even ceramic to ceramic. Industry standard active alloys like Incusil®-ABA and Ticusil® from Morgan’s range were developed up to 40 years ago but are still in use today. New alloys are also currently in development to withstand much higher temperatures.

A Never-Ending Journey

Morgan Metals and Joining Center of Excellence in Hayward, California (Morgan in Space)

Much like how there is still so much to learn and explore about space, so too is Morgan’s journey with braze alloys. Morgan Advanced Materials is not just committed to making the space industry more sustainable and safer, but it is helping with applications across all industries.

A key pillar of this is through Morgan’s highly specialized Metals and Joining Centre of Excellence (CoE), based in Hayward, California, as well as Morgan’s Brazing Department.

With highly trained researchers and scientists, Morgan’s Braze Alloys business can custom cater alloys to specific applications, run trials to test materials, braze cycles and fixturing. The whole operation, from powder atomization, to preform fabrication and brazing trials, can be looked after from start to finish.

Flexicore® (Morgan in Space)

One of the latest developments being pioneered at the Metals and Joining CoE is Flexicore®. This new technology transforms traditionally brittle alloys (such as AMS4777) into a flexible wire form. In many cases, this will be far superior to pastes in terms of repeatability and ease of use. Along with the operational benefits, Flexicore® will also allow for the use of nickel-based alloys to replace precious-metal alloys. Again, this will help to bring costs down for operators and manufacturers.

Watch This Space

Space travel, as Richard Branson predicts for his own Virgin Galactic programme, is only two or three flights away. We’re truly not far away from entering a new world, and brazing alloys will have their say on how the space industry turns out.

Morgan’s Braze Alloy solutions, like RI-46 and RI-49, as well as others like Palniro-1 and Palniro-7, can already be found across the various programmes and spacecraft. Through more research and development, who knows where this important industry could lead us to.


Morgan Advanced Materials plc is a global engineering company headquartered in Windsor, UK , and is a world leader in advanced materials science and engineering of ceramics, carbon, and composites, engineering high-specification materials, components, and sub-assembly parts to solve challenging technical problems. Markets that Morgan work in include healthcare, petrochemicals, transport, electronics, energy, defense, security and industrial.

A Braze New World: Sending Non-precious Braze Alloys into Space Read More »

Brazing Demands on the Rise for Aerospace Applications

 

Source: MRO-Network.com

 

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

 

Read more: “Applications of Brazing in Aerospace Likely To Increase”

And keep an eye out for more on aerospace heat treating in the upcoming special aerospace manufacturing edition of Heat Treat Today.

 

Photo credit: MRO-Network.com

Brazing Demands on the Rise for Aerospace Applications Read More »

Heat Treat Tips: Burn Out vs. Bake Out

During the day-to-day operation of heat treat departments, many habits are formed and procedures followed that sometimes are done simply because that’s the way they’ve always been done. One of the great benefits of having a community of heat treaters is to challenge those habits and look at new ways of doing things. Heat Treat Today101 Heat Treat Tips, tips and tricks that come from some of the industry’s foremost experts, were initially published in the FNA 2018 Special Print Edition, as a way to make the benefits of that community available to as many people as possible. This special edition is available in a digital format here.

Today we offer one of the 101 tips, which was provided by AeroSPC and originally published under Miscellaneous Tips. 


Heat Treat Tip #42

Burn Out vs. Bake Out: What’s the Diff?

Many organizations use the term burn out and bake out to be the same event. Others have burn out understood to be 50°F above prior maximum temperature after the braze process for a short period. Bake out then is a “close to max” temperature of the oven maintained for over an hour. If your organization is using these terms, ensure that they are internally defined and in alignment with the terms used in your customer specifications.

This tip was submitted by AeroSPC.


If you have any questions, feel free to contact the expert who submitted the Tip or contact Heat Treat Today directly. If you have a heat treat tip that you’d like to share, please send to the editor, and we’ll put it in the queue for our next Heat Treat Tips issue. 

Heat Treat Tips: Burn Out vs. Bake Out Read More »

Brazing Seminars Announced for Fall 2018

Three-day brazing training seminars have been announced for the fall of 2018, one taking place in Spartanburg, South Carolina, September 25-27, and the other in Simsbury, Connecticut, November 13-15.

A Dan Kay Brazing Seminar in Maryland

These identical hands-on 3-day brazing-training programs sponsored by Kay & Associates and taught by Dan Kay will provide intensive training for both the novice and the veteran in all aspects of brazing, including correct brazing of aluminum, titanium, steels, super-alloys, as well as metals-to-ceramics, and will cover furnace, torch, induction, and dip brazing, and all BFMs (nickel, gold, silver, aluminum, titanium, and copper-based).

The 8 a.m. to 5 p.m. programs provide over twenty hours of intensive training and the opportunity for one-on-one applications support. Many samples are investigated in the hands-on training seminar, actual brazing demos are done in which each person can participate, and case-studies are presented and solved via group-interaction.

The seminars are targeted for anyone who impacts brazing operations, such as designers, owners and managers, engineers and supervisors, and production personnel.

Dan Kay (BMetEng, MBA), operates his own brazing consulting/training company and has been involved full-time in brazing for 45-years. He regularly consults in areas of vacuum and atmosphere brazing, as well as in torch (flame) and induction brazing.

To read more or to register, go here: www.kaybrazing.com.

Brazing Seminars Announced for Fall 2018 Read More »

Essential Criteria for Brazing: Proper Joint Fit-up

Source:  Vac Aero International, Inc.

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.)

Read More: Essential Criteria for Brazing:  Proper Joint Fit-up by Dan Kay

Essential Criteria for Brazing: Proper Joint Fit-up Read More »

Majority of Heat Treatment Done In-House at SKF — New Equipment Purchased

Ipsen recently installed both atmosphere and vacuum heat-treating systems at SKF’s state-of-the-art manufacturing facility in St. Louis, Missouri. With the relocation of their existing facility to a new location, SKF continues to focus on enhancing the quality, efficiency and overall effectiveness of their heat-treating equipment. Among this new Ipsen equipment was a complete ATLAS atmosphere heat-treating system, including two ATLAS integral quench batch furnaces and ancillary equipment – washer, temper, endo generator, loader/unloader and a feed-in/feed-out station. SKF also purchased a TITAN® vacuum heat-treating system to round out their production capabilities.

Heat-treating is considered a core competency at SKF, and this new equipment will allow them to bring the majority of heat treatment in-house and efficiently handle the increase they’ve seen in production demands and volume of parts. Reflecting on the equipment purchased and what appealed to SKF, Bryan Stanford said, “Initially, I would say it was the general purposefulness of these Ipsen products that appealed to us. We run a very large variety of parts and batch quantities here. A custom solution designed to run tens of thousands of the same parts was not going to work for us. We wanted a low-cost, off-the-shelf-type solution that would allow us the flexibility we required – which is what the ATLAS and TITAN delivered. Now after having performed some pre-training, I would say what stands out the most is the ease of use and control of the equipment.”

The ATLAS batch furnaces feature a 24″ W x 36″ D x 30″ H (610 mm x 910 mm x 760 mm) load size with an 1,100-pound (500 kg) load capacity. They also operate at temperatures of 1,400 °F to 1,800 °F (750 °C to 980 °C) and have a quench oil capacity of 1,030 gallons (3,900 L). The TITAN vacuum furnace features an 18″ W x 24″ D x 18″ H (455 mm x 610 mm x 455 mm) load size with a 1,000-pound (454 kg) load capacity. It operates at temperatures of 1,000 °F to 2,400 °F (538 °C to 1,316 °C). Overall, this Ipsen equipment will be used for carburizing, carbonitriding, brazing and annealing and will process a wide variety of parts that support SKF’s Lubrication Business Unit.

Majority of Heat Treatment Done In-House at SKF — New Equipment Purchased Read More »

Bodycote Greenville Open for Business

Bodycote, the world’s largest thermal processing services provider, is pleased to announce that its new plant in Greenville, South Carolina is open for business. The facility is now ready to process metal and alloy parts that require brazing or vacuum heat treating services.

The new Greenville facility primarily serves the Southeast region’s manufacturers and their supply chains in the aerospace, defence, energy and medical industries. The plant is expected to receive Nadcap accreditation by the end of 2016, offering quality assurance based on stringent auditing standards for the aerospace and defence industries. Bodycote intends to offer additional services from the facility in the future in response to customer demand.

This investment is part of Bodycote’s further expansion in the Southeast USA. Bodycote is committed to offering world-class heat treating and specialist technology services and is investing in improvements as part of an ongoing strategy to provide the best possible capabilities, mix and geographical network to better serve customers.

Bodycote Greenville Open for Business Read More »