Proper Material Selection for Welded Assembly & Heat Treat
Proper Material Selection for Welded Assembly & Heat Treat
(OP)
I have a weldment that we are working on bringing to market. Customers are asking for a more durable welded assembly for longevity. I am trying to achieve a 50-60 Rc Hardness throughout the part. I initially was suggested a 1045 material to machine to size, weld, and heat treat (stress relief of the assemblies prior to case hardening). The price of machining bar stock is driving up the cost tremendously going this route.
I have link showing the picture of the subject weldment sample I just received from my customer.

I have tested the hardness on it and results were Rc 55. Customer has no idea of material other than carbon steel. I have had a PMI done and have attached the snapshot I took from the analyzer.

I have measured its size and material seems to be of standard pipe size, but I have not ruled out tubing either. The larger section has a barely visible seam (seamless pipe or tube) and smaller seam has a visible weld seam. All ends are tapped to there respective pipe sizes of 2 NPT & 1-1/4 NPT
I have had a heat-treat facility tell me to stay away from Alloy Steels?? A machine shop is telling me to staying away from structural pipe?? I am confused at this point of what direction to take on material selection and was looking to some pro's to give some advice.
Thanks in advance.
Ben
I have link showing the picture of the subject weldment sample I just received from my customer.

I have tested the hardness on it and results were Rc 55. Customer has no idea of material other than carbon steel. I have had a PMI done and have attached the snapshot I took from the analyzer.

I have measured its size and material seems to be of standard pipe size, but I have not ruled out tubing either. The larger section has a barely visible seam (seamless pipe or tube) and smaller seam has a visible weld seam. All ends are tapped to there respective pipe sizes of 2 NPT & 1-1/4 NPT
I have had a heat-treat facility tell me to stay away from Alloy Steels?? A machine shop is telling me to staying away from structural pipe?? I am confused at this point of what direction to take on material selection and was looking to some pro's to give some advice.
Thanks in advance.
Ben





RE: Proper Material Selection for Welded Assembly & Heat Treat
What is the application?
These pieces are both welded pipe. Common welded pipe is very poor quality (alloy variations, welds, and size control) but you can get material made to pipe sizes that is to higher quality.
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P.E. Metallurgy, Plymouth Tube
RE: Proper Material Selection for Welded Assembly & Heat Treat
Would pressure vessel quality pipe SA106GrB/C Seamless pipe be a viable option to fabricate this weldment from? Would it be receptive to the case hardening heat treatment process?
RE: Proper Material Selection for Welded Assembly & Heat Treat
Low carbon steel tubing or pipe (like SA106) can be surface hardened via case carburizing.
RE: Proper Material Selection for Welded Assembly & Heat Treat
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Proper Material Selection for Welded Assembly & Heat Treat
All hoses and accessories connected to this weldment and cost our customers time and money disassemble and reassemble. Some have (8) weldments on (1) large blasting unit. I sure would cuss and spit fire if this part didn't last. Some customers know they can get through a season and automatically schedule PM's to replace them.
RE: Proper Material Selection for Welded Assembly & Heat Treat
Through discussions with our welder, I have found the process of preheat and slow cooling for the 1045 material to be more costly also.
As far as the embrittlement of the threads, our heat treat facility has advised a suggestion to mask the threads before case hardening to prevent them from becoming unduly brittle. They seemed quite confident about this. There is no extreme tension on either threaded connection.
The case depth would be specified as .060” minimum total case depth. The case will penetrate the walls of the pipe from both the O.D. and I.D. This will ensure that .120” of the wall thickness will be RC 50+ minimum.
RE: Proper Material Selection for Welded Assembly & Heat Treat
RE: Proper Material Selection for Welded Assembly & Heat Treat
RE: Proper Material Selection for Welded Assembly & Heat Treat
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Proper Material Selection for Welded Assembly & Heat Treat
We are looking to bring this to market as extreme duty solution. Our anticipated 1st year usage is 100-200 after product release.
RE: Proper Material Selection for Welded Assembly & Heat Treat
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Proper Material Selection for Welded Assembly & Heat Treat
The combination of a very hard, corrosion resistant flow surface with smooth, rounded edges would likely last longer than the welded pipe manifold with sharp corners.