A656 weldability using GTAW process..

[Nor'Easter]

I am looking to see if anyone on here has experience with the weldability of A656 hot roll steel, specifically using GTAW process (TIG). It is a high tensile steel mainly used in truck frames, heavy equipment, etc.

My attachments will include everything from basic plumbing/wiring bracketry to load bearing scenarios like suspension bracketry and receiver hitches made of A36, with the A656 being cold formed straight frame truck rails.

Many thanks!

 

[kkroger]

ER70S2, The Joint will be just average Mild Steel, the 656 probably just has more moly than the 36... Both are HRS, so it really doesn't make much diff... Basically just like using A36 ....

high Strength Low Alloy HSLA will make a difference. but only when joining HSLA/HSLA You have to pay a little more attention then.

 

[welder4956]

No previous experience with this steel, but it appears to be available in grades 50, 60, 70 or 80. The numbers refer to minimum yield strength, e.g. Grade 50 has 50 ksi minimum yield strength. If you need the weld to develop full strength, ER70S or E7018 will only have 58 ksi minimum yield strength. You could use it to weld grades 50 or 60, or any of the 4 grades to A36. If you are welding grades 70 or 80 to themselves or each other, you will need an electrode with higher yield strength.

 

[oldironfarmer]

Yeah, what he said

You really should know which grade A656 you are welding. If you have grade 80 you probably need to be using a filler with some nickle, and the higher grades are underbead cracking susceptible.

My reason for comments, however, is that if you are welding on the frame of highway equipment you need to assure yourself you don't create a stress riser which causes a crack to start and propagate during use. A few rules:

1 Always weld only to the web of the frame. Never weld across the flanges. As the frame twists in use a small strap welded between the top and bottom flanges will initiate a crack in the frame. Not in the strap. A large strap is worse.

2 Holes are better than welds. You are better off making small attachments to flanges by drilling and bolting instead of welding. Attachment welds are fine to the web away from the high stress bend area. Remember when steel is cold formed the bend is left with lots of high stresses resulting from the steel being forced past it's yield point. Welding in those areas will stress relieve the local weld area, and maybe diminish it's strength. But the sudden change of stress level in the area of the weld can in itself initiate a crack. It may take years, but if the frame cracks in two at 80 mph...

3 Look at the manufacturer's attachments and copy them, if you are welding to existing frames. If what you are putting on looks easier, it probably is, and there is a reason the manufacturer did not do it the easy way. Even though manufacturers use lots of engineers, some of them know what they are doing. Receiver hitches are a good case in point. If you elect to make a rigid connection across two frame members which are supposed to twist under load, something has to give, and it will be the metal, you won't succeed in making the frame rigid unless you add a LOT of steel. Notice when you twist a frame, the opposite sides move opposite to each other, not together.

4 If you weld on frames and then sell your work you need to be doubly concerned about frame failure and potential loss of life resulting from the failure.

5 Drill and bolt is usually the manufacturer's recommendation. It is always nice to seek the recommendation of the manufacturer. It is negligent to not seek their recommendation. That's an important legal word, negligent. It is worth looking up if you are not familiar with the full ramifications of making negligent modifications to highway equipment.