doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Invisible sleeve joints and damascus

Craig: I'm only impersonating a metallurgist on DoubleGun but the gen-u-wine Metallurgical Engineer said this

"The Energy Dispersive X-ray Spectroscopy (EDX) study suggests that element migration between the metals occurred during the manufacturing process; the pressure rolling, twisting, and hammer welding of iron and steel laminates produced essentially a mono-metal."

Drew,
The statement by the metallurgical Engineer is a good indication that all would be well.
I'm guessing that it would usually be the better guns that get sleeved rather than a "clunker" with questionable barrel quality .
Saying that, it's often a bad idea to take things for granted.

I believe, generically, it takes time and temperature for carbon to flow from higher to lower concentration areas. Could be there wasn't enough heat or time for that to happen between the steel and wrought, but chances are at and near welds, the carbon has 'evened out'. Maybe, when some barrels color welds bright, and others color dark, the cause of the coloring is some element or elements that are not able to, or slow to migrate, rather than just the difference of being an iron or steel. Maybe.

I have to believe that the gen-u-ine Metallurgical Engineer would retract or reconsider that statement if he took a moment to think about his choice of words. If the process of rolling, twisting, hammering, and welding of iron and steel resulted in "essentially a mono-metal", then we would expect to see a mono-coloration after blueing and etching, i.e., no difference. There is still a significant enough difference between the layers that we can see, and sometimes even feel, the difference between the iron and steel. It is the contrast which we so frequently discuss and admire. Certainly, there is amalgamation and fusion within the weld joints.

In response to the OP's original question It is my belief that no detrimental change will occur on the damascus monobloc side of the weld BUT I can assure you you will have problems in the HAZ (Heat affected zone) immediately at the root of the weld pool on the tube side
unless treated.Typical modern sleeving tubes are SAE4140/UM8 material Chrome Molybdenum alloys which will crack/fracture unless heat relieved above there upper critical limit and lowered through lower critical limit slowly and evenly.
Regarding the failed Parker it looks to me as if someone followed the std monobloc cut point of 3&1/4" . This works great for 2&1/2" Chambers but it should more accurately be expressed as 3/4" ahead of the chamber/forcing cone intersection point. Thus for a 3" chamber a cut and finished length of 3&3/4" should be used.
I would hope John Foster or Gunman would review and comment.

What Hugh Lomas says about post-annealing of the TIG welded HAZ of the sleeving joint is very interesting and raises several new questions. Foremost would be my assumption that heat relieving or post annealing above the upper critical limit would be at a temperature that might also melt the brazing used to join the barrel breech sections and underlugs of the monobloc. In that event, any post annealing would have to be very localized to prevent melting the braze joints.

While there are @ 200 degrees difference its still a risk. In the past I've used localized flame heat on the HAZ working in from the tube side then reduced T by reducing temp of flame and moving flame away and down tube from HAZ. This way high temp area is kept well away from any brazed joint which seldom get above 250f. I certainly would not want to subject whole monobloc to 1450-1500 F.

Hugh,

If I am aundestanding this right, there would be no HAZ problem with simple soldering of the tubes, ie no welding of the joint, and having the joint line visible. Is this correct?

Yes,absolutely,Lead/Tin soldering is achieved a temperatures significantly below lower critical limits.Additionally the whole monobloc is heated and cools gradually.

Hugh, thanks so much for the enlightenment. In case anyone failed to understand, good welders can work in small areas with the temperatures needed by the alloy steels. There is no need to heat the whole assembly to welding/heat treat temps - only the small HAZ.

I don't think the Met Eng meant that the steel and iron were homogenized, rather they have become more joined than "just stuck together."

DDA