Steel Application - High Strength Weldment

[mewhg]

Hello all,

I would like to asks the groups assistance on a design problem/material specification.

We are designing a railroad track hand tool where part of the tool will be fabricated from 1.25" steel plate that will be flame cut into a specific profile. Onto this piece will be welded a mild steel tube (about 1" dia) that will act as a pivot point.

Working stress is about 40ksi.

I would like to use A36 plate but modifing the tool profile to lower stress will add undesirable weight.

I would like to find a steel with an Sy in the range of 80ksi that does not need to be heat treated after welding or preheated during welding.

I have looked at HSLA A656 grade 80 but the max plate thickness it is available is 3/4"

Has anyone ever worked with HSLA-100 as used in shipbuilding?

Any other ideas?

TIA
Bill

 

[GRoberts]

I don't know the exact difference between HY-80/100 and HSLA-80/100, but for the HY-80/100, the Navy (for submarines at least) prohibits PWHT.

 

[metman]

Yes I have worked with HSLA-100 and there have been some pretty nasty lawsuits (not in our instances) associated wth weld cracking and consequent catastrophic failure which can be avoided but you have already precluded the avoidance criteria with you stipulations.

17-4 PH Stainless Solution annealed has 110ksi Yield strength. I will be interested to hear comments on the viability of as-welded metallurgy and choice of filler metal.

Jesus is THE life,
Leonard

 

[mewhg]

GRoberts: forgive my ignorance but what does PWHT mean?

Leonard: I'm clueless, how does my stipulations avoid weld cracking??

Why did the catastrophic failure occur?

Bill

 

[metman]

I will answer for GRoberts. PWHT is abbreviation for Post Weld Heat Treatment. His answer triggered my memory. It is the PWHT that is the culprit for embrittling these alloys. The PWHT is typically applied for stress relief but since it is disallowd here you can only vibratory stress relieve.

So I was incorrect in what I first said.

Jesus is THE life,
Leonard

 

[NickE]

Whoa hold on; vibratory stress relief? what is this, we use a vibro polish on our production part to reduce surface defects and introduce a compressive skin. Does the vibro polishing method alos stress relieve?



Nick
I love materials science!

 

[mewhg]

Is it necessary to stress relief at all after welding the HSLA steels? Thats something I want to avoid if its difficult to do.

Bill

 

[metman]

Vibratory stress relief is mechanical vibration at a frequency and amplitude chosen to match the harmonic frequency of the part. This does nothing to the surface finish. It is only to mechanically reduce internal and surface residual stresses induced from welding. This technique is used where thermal stress relief is disallowed as in the case stated by GRoberts, "the Navy (for submarines at least) prohibits PWHT." If I remember correctly, the ASTM spec for some HSLA steels prohibits thermal stress relief.

Bill,
An example of where you need to stress relieve: You have a welded assembly and when you machine it, some of the residual stresses from welding are relieved and the geometry distorts so that tolerances cannot be held like for a bearing fit. Another example is where the applied service stress superimposed on residual welding stress exceed the yield strength or fatigue strength.

Jesus is THE life,
Leonard

 

[metman]

geissele,Look at thread330-54850 and read Linstrum's reply.

4130 might work for you.

Jesus is THE life,
Leonard

 

[GRoberts]

Check out the US steel website at

http://www.ussteel.com.

They have a section on welding T1 type steels (similar to the HY grades) and do not recommend PWHT also.