Questions on welding heat treated 4130 tube to stainlesss plate 2

[dwx]

Hi all,

I'm looking into welding a 4130 heat treated steel tube (Renolds 725) With a 22.2mm O.D., and a 1.0mm wall thicckness (

http://www.reynolds-cycle.com/internet/english/prodrange/steel/steel.htm)

to a stainless steel plate, about 0.1875 thick. I am going to search for a hard plate, I would like something about equivalent to 4140N in terms of strength and hardness, but I would be happier with elevated mechanical properties. Normally I would build this part from 4140 heat treated to about RC34-36. Ideally I would use 4340 plate heat treated to RC44, buit I am looking to leave the plate unpainted. The tubing and welds will be sealed and painted.

The assembly will be welded with a full low pressure argon purge, and there will be no post-weld heat treatment.

I just completed a movce to a new house and ALL of my books and manuals are in storage for another 2-weeks, and I am very curious about this.

My questions are:

1) Is it feasable for me to weld a stainless plate to this Reynolds 725 tubing.

2) What cost-effective alloys are available to me in plate form (it will be laser or waterjet cut at a quantity of about 200-600 pcs per order)

3) what welding rod would you all recommend for a good resistance to fully reversed stress.

Thanks for anything that you can offer.

Dave

The joint will look like the picture linked here

 

[unclesyd]

Yes it is possible to weld S/S to 4130 steel tubing.

The problem comes in getting a stainless with anything approaching your requirements to hardness without a heat treat. The initial response would be to use 17/4 PH, but this would require a low heat treatment after welding to give a hardness of Rc 36-40.

A good possibility would be to use Nitronic 60 which offers very good galling and wear resistance and is readily weldable.

Is wear and galling resistance what you are after in the area where the nut goes?

Are you using TIG or MIG as the welding process.

Nice to have a drawing.

 

[Metalguy]

As you're probably aware, when you weld HT 4130 and leave it, the HAZ's are likely to be softer/weaker than the rest of the tube, or possibly harder and somewhat brittle. It all depends on the cooling rate after welding, esp. around 1,200 deg F.

You're probably also aware that that is why the better steel bicycle frames are brazed using lugs, rather than welded.

Now, when you weld any SS to something like 4130, you are going to end up with a lot of Cr and C along the fusion line, and it will probably be brittle w/o PWHT.

You will have a much better product if you weld some SS tube sockets to the SS plates and then heat treat them, and THEN use low-temp. brazing to join the parts.

 

[dwx]

Hi guys,

thanks for the insight. To answer your questions:

Unclesyd-

17-4PH was one of my first thoughts as well. It is expensive, but readily available in plate.

The assembly will be welded with a TIG process, and furthermore, it will be welded using a full purge (so there will be argon surrounding the entire weld, even inside the tube)

I would most likely heat treat the 17-4PH plate before wleding the assembly. The tubing is butted, and the palte is overly thick in the weld area. This is to compensate for the decrease in strength in the HAZ.

I am looking for wear resistance where the nut goes. There is actually a bolt with a serrated belleville washer that clamps through each of the slots to provide a sliding adjustment for the assembly. I would like to leave the metal bare around these slots, because the assembly will be used outdoors, and will most likely rust.

I do not want to spend the money to have this assembly coated for corrosion resistance unless I can use a high wear, spray-on coating that will be resistant to the serrated belleville washer being forced into it. Low cost is paramount here.

I have never use nitronic 50 or 60, I will look into them further.

Metalguy-

It is unfortunate, but Lugged construction is not an option for me here. This is a low volume bicycle frame, and lugs are a costly endeavor.

The front triangle of this frame will be welded form custom Reynolds 853 Air hardening tubing.

My hope was to find a steel with the weld properties of 304L, but with the cpabilty of heat treatment and high hardness.

That is a neat idea with the SS tubes and brazed socket. I will have to put some more thought into that. If I can somehow make it cheap, that would be a nice option.

Thanks guys

Dave

http://www.dw-link.com

 

[Metalguy]

Keep in mind that serrated washers probably won't dig into any hardened steel, so I don't think you'll increase the sliding resistance using them.

If you go with the welded sockets, you can get both plate and sockets in 410 stainless. It will cost more to HT it, and it may "rust/stain" a little, but nothing like bare carbon steel.

It will be cheaper than 17-4 but you'll have to look at both material cost and HT.

My old Gitane TdF only has Reynolds 531!