Back Alley Customs

Bob Capudean

Contributing Writer
Back Alley Customs
Waterford, MI
He is a welding instructor at Oakland Community College, Auburn Hills, MI.

Metals/Materials | Articles

Metallurgy Matters: Thermal cycles, the HAZ, and the strength of martensite

January 18, 2016 | By Bob Capudean

Last time we looked at how welding heat influences the heat-affected zone (HAZ) of metals strengthened by three typical hardening processes: solid-solution hardening, cold working, and precipitation hardening. That leaves one critical strengthening process to consider: transformation (martensite)...

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Metals/Materials | Articles

Metallurgy Matters: Influencing weld strength

April 24, 2015 | By Bob Capudean

Weld metal strength: It’s a subject that’s often discussed, and just as often misunderstood. To fully consider how strong weld metal will be or how you can strengthen it, you have to think about not only the preweld decisions that influence weld strength, but also the postweld reactions and...

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Metals/Materials | Articles

Metallurgy Matters: Reactions speak louder than words

April 6, 2015 | By Bob Capudean

Before we get into nonferrous gas-metal reactions, let’s look at one of the ways you can identify potential cold-cracking problems in steel. In the May/June 2004 issue, we looked at cold cracking—also known as hydrogen cracking, delayed cracking, and under-bead cracking—as it relates to...

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Metals/Materials | Articles

Metallurgy Matters: From one extreme to the other

March 19, 2015 | By Bob Capudean

In terms of temperatures, the heat-affected zone (HAZ) has it all—from near liquidus to near ambient and everything in between—a fact that makes the HAZ a tricky piece of real estate to understand the predict. Why? Remember, a number of metallurgical changes can take place in hot metal, and...

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Metals/Materials | Articles

Metallurgy Matters: Unlike oil and water, gas and metal can really mix it up

March 17, 2015 | By Bob Capudean

Gas-metal reactions take place every time you weld. They happen quickly, especially at temperatures above 3,000 degrees F, and can cause serious problems. Of course, not all gas-metal reactions are bad; some are designed in, while others simply take place with no ill effects. But some prove quite...

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Metals/Materials | Articles

Metallurgy Matters: Solidification—It’s more than meets the eye

March 16, 2015 | By Bob Capudean

There’s a lot going on as your weld puddle solidifies. Grains are trying to grow in a variety of directions, and the entire process can get quite competitive, because some grains grow faster and block the growth of others. Which grains grow faster depends on their orientation at the point where...

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Metals/Materials | Articles

Metallurgy Matters: The tricky subject of weldability

March 9, 2015 | By Bob Capudean

Welding metallurgy is a science, but it’s far from perfect. I mention this here because my January/February column elicited a number of critical, if not scathing, e-mails concerning everything from a typo in Figure 3 to my generalizing the precise and exacting science of metallurgy. The...

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Metals/Materials | Articles

Metallurgy Matters: Welding’s effect on strengthened steel

March 9, 2015 | By Bob Capudean

As I mentioned in the September/October issue, welding can severely influence strengthened or hardened metals, depending on the hardening technique used. Hardening Techniques and Welding Effects Work- or strain-hardened metals exposed to the intense localized head of welding tend to recrystallize...

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Metals/Materials | Articles

Metallurgy Matters: The science of welding metallurgy

March 9, 2015 | By Bob Capudean

It’s time to narrow our focus and look at the science of welding metallurgy, a branch of metallurgy that addresses the behavior of a metal during welding and, just as important, the effects of welding on a metal’s properties. Think about what happens when you weld together two pieces of...

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Metals/Materials | Articles

Metallurgy Matters: Making steels stronger

October 9, 2003 | By Bob Capudean

When it comes to modifying a steel's strength and hardness, it's important to not confuse hardness with hardenability and remember that hardenability characteristics are important because they help identify how much a specific steel will harden during welding.

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Metals/Materials | Articles

Metallurgy Matters: Carbon content, steel classifications, and alloy steels

August 28, 2003 | By Bob Capudean

Steel classification is important in understanding what types are used in certain applications and which are used for others. For example, most commercial steels are classified into one of three groups: plain carbon, low-alloy, and high-alloy. Steel classification systems are set up and updated frequently for this type of information.

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Metals/Materials | Articles

Metallurgy Matters: Phases, structures, and the influences of temperature

June 26, 2003 | By Bob Capudean

When you heat or cool a piece of metal to a specific temperature, that metal goes through what's called a phase change, in which its crystal structure changes. Sometimes the change is obvious. For example, when a piece of metal melts, it goes through a phase change when the crystal structure breaks down and the metal goes from solid to liquid. When it solidifies it's also a phase change, as the structure re-forms from liquid to solid.

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Metals/Materials | Articles

Metallurgy Matters: The structure of metal

April 24, 2003 | By Bob Capudean

Let's start with the obvious: Molten metals have no particular structure. The atoms that make up that metal are just whipping around helter-skelter—at a high rate of speed—with no real orderly, defined pattern.

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Metals/Materials | Articles

Metallurgy Matters: It's all about why

February 27, 2003 | By Bob Capudean

Talk about a can of worms ... From crystalline structures to phase diagrams and interstitial solutions, from microstructures to allotropic transformations, it sometimes seems that for every question metallurgy can answer, for every problem it can solve, it creates two more.

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