Welding induced deformation: Any technique against? 4

[IJR]

We often have to specify thin flanges and thin webs(about 1/4 of an inch or roughly 6mm) in built up I sections.

Complaint is when you weld up the parts together at the shop, ugly deformations result as is well known

I wonder if there is a way against this, because these thin plates tend to be very useful in most of our work.

respects. And additional thanx to all pals who helped out in my last post.
IJR

 

[JAE]

IJR -
My handy book: "The Procedure Handbook of Arc Welding", by the Lincoln Electric Co. lists the following to control distortion:

1. High-deposition electrodes, automatic welding, and high welding currents tend to reduce the possibility of distortion.

2. The least amount of weld metal, deposited with as few passes as possible, is desirable.

3. Welding should progress toward the unrestrained portion of the member, but backstepping may be practical as welding progresses.

4. Welds should be balanced about the neutral axis of the member.

5. On multipass double-V joints, it may be advisable to weld alternately on both sides of the plate.

6. Avoid excessive prestressing members by forcing alignment to get better fitup of the parts.

7. Joints that may have the greatest contraction on cooling should be welded first.

 

[Ron]

IJR..JAE has given an excellent reference. Mine has dog-ears all throughout. One additional comment...try to counteract distortion with opposing distortion, rather than mechanical restraint. Mechanical restraint introduces some rather significant residual stresses that can give problems in many applications.

Low heat input processes such as Gas Metal Arc Welding (GMAW) or Gas Tungsten Arc Welding (GTAW)...MIG and TIG, respectively, offer lower distortion than Shielded Metal Arc Welding (SMAW) process.

 

[ajh1]

We regularly weld flanges and webs in a similar methodology. While I don't have any hard and fast rules at the moment, there appears to be a direct correlation between the total area of the web and the total area of the flanges. When the web area gets large in relation to the flange area, weld cooling will tend to buckle both the webs and the flanges into distorted shapes that don't look pretty. Heavier flanges will tend to resist the web shrinkage during cooling and keep the part looking better.

Al...

 

[Rowland33]

What about pre-heating the material?

 

[ajh1]

Preheating is not a requirement for the grades and sizes of steel we work with. Our web stock generally runs from 0.120" to 0.375" thick with flanges starting at 0.188" up through 1.00" typical. Material is equivalent to ASTM A572 Grade 55 and A1011 Grade 55.

Al...