Repair welds on unknown materials?Here are some tips to help you identify what you are soldering.Getty Images
Q: My job involves on-site machine shop welding and repairing machinery and structures.I’m almost never told what type of metal I’m soldering.Can you give me some guidance on how I can determine the type and grade of metal I’m using?
A: The best advice I can give is don’t try to solder it if you don’t know what it is.This is especially true for critical components where failure could result in injury or death.
Welding on certain metals using inappropriate welding procedures may result in defects in the base metal, the weld, or both.
When you are asked to weld an unknown material, how do you determine what it is?First, you should be able to use basic evaluation to narrow down the possibilities.Look at the surface of the material and see how heavy it is.This should allow you to divide materials into broad categories such as carbon or low alloy iron materials, stainless steel or nickel alloys or aluminum alloys.Evaluating the area where you need to weld can also give you important clues.Is there evidence that the part was welded during the original manufacturing process?If so, this is a good indicator of the material’s weldability.Is there any evidence that weld repair has been attempted?If a previous solder fix failed, that’s a red flag telling you to be pretty sure what you’re using before trying a new fix.
If you are servicing a piece of equipment, you can call the original manufacturer to ask what material was used.Some items are usually made of a certain material.For example, aluminum handrails are typically manufactured using grade 6061.Doing some research on the materials typically used to make items to be welded can help you narrow down your options.
Since you work in a machine shop, you should be able to get some really good information about materials from a mechanic.If they’re machining a new material, a machinist might know exactly what it is.They can give you some good information about the material based on its processing characteristics.You should be able to estimate the hardness of the steel based on the feed rates and speeds used during machining.How the machining chips are formed also provides useful information.You should avoid welding steels that produce small chips, as these are likely to be a free-cutting grade that is prone to hot cracking when welded.
Spark testing of steel and cast iron can give you a rough idea of ​​how much carbon the material contains.Chemical spot testing can also determine the presence of specific alloying elements.
Chemical analysis will provide some of the best information to help identify material grades.In many cases, you can submit machining chips from a material for analysis.If there is no machining debris, if possible, remove a small piece of material for analysis – about 1 inch.square.Most testing labs offer metal chemical analysis for less than $200 in many cases.
Most importantly, if you want to make safe and long-lasting repairs, it’s important to spend some time and a little money to get a good idea of ​​what materials you’ll be welding.
WELDER, formerly Practical Welding Today, showcases the real people who make the products we use and work with every day.This magazine has served the welding community in North America for over 20 years.
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