Welding 101: The Root Causes of Weld Defects

28 January 2020

Weld defects are a common occurrence in the welding industry due to numerous factors. For one, air exposure may lead to a porous outcome for all the welded units. Wrong amount of heat, will possibly cause cracking while bad welding techniques will cause undercuts or incomplete penetration of one kind or another. These are just few of the many factors that contribute to weld defects that are interconnected in one way or another due to poor workmanship and poor weld design.

Poor Workmanship

A welder may produce poor work for many reasons, including poor instruction. This can be a result of bad or incomplete advice from a welding teacher or experienced welder, either from a technical school or in a company training program. But often it’s the result of an incomplete, unspecific welding procedure specification (WPS). A lot of defects could be prevented from the get-go if the WPS delved into specifics. In a way, a good WPS should help a welder become better at his craft with every job. The more detail a WPS gives, the less chance there is for error at the welding station.

Unclear WPS

Many students go through welding training programs without extensive knowledge about how to read and write a good WPS, but it’s a vital part of becoming a good welder. What good grammar is to a writer, a clear WPS is to a welder. An experienced welder should make a list of all the important variables, factors he himself might take for granted after years of welding—depth of passes, any peening necessary, weld sequence, and many more—to make sure the WPS includes these details when needed.

Defective Design

Sometimes weld defects occur more because of welder error or poor instruction and more because the design itself makes the welder’s job difficult. Designers experienced in structural welding know to avoid certain elements when they can, but problems can arise from less experienced design engineers.

Design mishaps include process selection. Some companies, even the largest ones, use welding procedures first written years ago, and because of that they often specify less-than-optimal processes. A procedure may require shielded metal arc welding (SMAW), otherwise known as stick, when the welder could do a much better job using another process. SMAW has its place for certain applications, but it does produce slag, which can get trapped in the weld and cause defects.

Overwelding

Another common problem involves overwelding. For instance, inexperienced designers may see a T joint with a three-centimetre plate so to maintain tensile strength for the assembly they call for a three-centimetre deep fillet weld on either side. This creates various problems because if the fillet weld is more than one centimetre it will require multiple passes. This can waste both time and welded metal, which can cost a company dearly in the long run. It also exerts unnecessary stress, which can lead to weld cracking. Aside from that, using so much weld metal can cause overlap as well. At worst, defects can even cause the vertical member of the T to pull away from the base plate.

By contacting our welding maintenance and repair experts at Sureweld Engineering located in Hastings, Victoria, we can guarantee that you obtain prompt and highly efficient professional onsite repair services for your trucks or heavy machinery, thus reducing the possibility of weld defects.