Alloy makeup of MS21250 bolt
Alloy makeup of MS21250 bolt
(OP)
I want to know how to find the specific percentages of alloying properties in a bolt......specifically MS21250. Can this be accomplished with only a P/N? Do I need to know the manufacturer, lot#, batch#, etc.? I am helping research whether any of a group of particular bolts have been negitivly affected by hydrgen embrittlement due to a neglected step in a cadmium plate process.





RE: Alloy makeup of MS21250 bolt
http://www.techstreet.com/aiagate.html
The basic composition specified in the governing document will determine whether a part is susceptible to Hydrogen Embrittlement or not. The lot, batch, etc. will help in identifying how many parts did not receive the appropriate treatment(s).
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Alloy makeup of MS21250 bolt
1. Material: Steel Alloy, MIL-S-5626 (AISI 4140), MIL-S-5000 (AISI 4340), MIL-S-6049 (AISI 8740), MIL-S-8503 (AISI 6150)
So, your % of alloy will depend on which of the materials this Spec. Bolt was made from.
You are probably correct about needing the MFG & Lot/batch# to determine % alloy.
RE: Alloy makeup of MS21250 bolt
RE: Alloy makeup of MS21250 bolt
a) As pointed out by israelkk, quench response is not the same for the different steels authorized by the standard, and many manufacturers switch grades somewhere up the diameter scale.
b) One of the preponderant factors in the NASM8831 requirements is the double shear strength requirement - there is a lot less spare strength here than in tensile, which is another reason to switch grades with varying diameter (really a special case of a)
c) By far the greatest influence upon hydrogen embrittlement in my view would be the variation in the cad. plate process. Some proprietary mixes of cad. plate chemicals contain brightening agents which can have a significant effect upon embrittlement
d) MS21250 is a very widely used bolt in the aerospace field, and is a perfect candidate for sale by distributors. Some odd diameters and lengths may have been on their shelves for some time, and it should be noted that the embrittlement relief treatment duration has been changed a few times over the life of the QQ-P-416 cad plate standard.
e) Last but not least, how do you intend quantifying hydrogen embrittlement ? Often times, without any noticeable difference in structure under an electron microscope, fatigue testing will give better results before cad. plate than after.