By Marty Baker 

An opportunity to assist with training in welding of stainless steel took Hobart Institute Instructor Ed Limbert to Tiantai in eastern China, in March. 

“Our week began on Monday as I observed the production, including welding, of the units in the factory,” explained Ed. 

Before instruction could begin, it was necessary to understand what was currently taking place.  Three major areas of concern were identified to include part alignment or fit-up, shielding gas coverage, and distortion.

Training sessions began on Tuesday and focused on improving the knowledge of welding stainless steel and demonstrating to the engineering staff the causes of some of the problems associated with welding of stainless steel.  This was followed by work with the assembly personnel to improve fit-up of the units. 

“Consistency was part of the fit-up problem,” says Ed.  “They were experiencing a variety of issues and each assembly was slightly different from the next.  Some of the units had tight-fitted butt joints, open gap butt joints, misaligned butt joints, and open gaps on lap joints.  I explained that these fit-up variations lead to leaks, lack of good penetration, and large gaps that required large welds, which lead to additional distortion.” 

The parts were sufficiently cleaned before assembly of the units including removal of oil, grease, dust, and oxides.  However, shielding gas coverage was inconsistent.

“Both the surface and purge were incomplete or nonexistent,” Ed continues.  “On the surface, too great of a torch angle was used.  Also, too small of a torch cup opening was used, not allowing sufficient gas coverage on the training side of the weld bead.  On the purge for the inside of the tank, there was none.”

Ed provided a welding demonstration to show the desired affect of a good purge chamber and discussed carbide precipitation and its effects and prevention methods. 

Stresses from forming, poor fit-up and over-welding were the cause of distortion in this case. 

“Once they realized the problem,” says Ed, “they made changes to resolve it.  The engineering staff and the welder understood how to get a quality weld, but before training, did not understand the importance of shielding and its effect on stainless steel.”

Within one week, Ed was able to provide the necessary consultation and training that will save the company a considerable amount of money and time related to quality issues.

 Ed is an American Welding Society (AWS) Certified Welding Inspector (CWI) and a Testing Specialist in the Certification Department at the Hobart Institute.  It was his first trip to China in this capacity and Ed shares a bit of information about the countryside surrounding the city of Tiantai.  Located in the green rolling mountains, the main crops of the region are tea and rice, along with other garden vegetables and fruits.  These products are grown in small fields and gardens, as space permits within the mountainous terrain.  The area is a contrast of modern highways and narrow back roads; of new cement interstate bridges and ancient stone footbridges over streams and rivers; and of modern automobiles on the streets alongside of bicycles, motorbikes, and pedestrians.  Ed’s drink of choice during his visit was hot tea. 

“The temperature while I was there was in the 40’s and 50’s,” said Ed, “but none of the buildings were heated and the climate was damp this time of the year.  So I wore my jacket, indoors and out, and drank hot tea with my meals!”