Repro frame alloy?

[Chuck Heald]

Was the Reproduction frame alloy ever revealed?

[Grantham Forester]

If so, since 1948, all the Japanese steel mills use the electric melt furnace process, same as Allegheny Ludlum, Crucibe and Carpenter Technology use here in America. Best way to produce quality alloyed and tool steels. My employer in the tool and die business is not hesitant to use Japanese steels, but the founder, Dick Beecher, was strictly a Carpenter steel man- T-K was a shop standard in his day.

[Autumn Daze]

Chuck, I seem to remember reading somewhere that 8620 HT was used.

[Chuck Heald]

Dave,
I was hoping Richard Skeuse would know for sure. I know the custom rifle guys like the 8620 because it has a high enough carbon content to core harden to a perfect hardness when it is casehardened. This leaves a super hard case and a strong core, like 2 - 2 1/2 times the tensile strength of low carbon steel if I recall.

But the Repro looks like it was never case hardened. So, I was suspicious it was a 4xxx steel that was martensitically (thru) hardened.

[Grantham Forester]

A friend has a Parker 20 gauge Repro- sweet handling gun, but after two seasons in the grouse coverts, the case coloring is almost worn off the receiver. Were these later production Parkers case colored in a different manner than those made in Meridian Conn.??

[Chuck Heald]

Grant,
I believe the answer is yes. The coloring you see on the Repro's appears to be chemical colors, possible applied with a mix of chemicals and low heat. I really don't know the method, but it doesn't appear to be carbon infused by pack method or cyanide method. Nitriding would produce similar results to pack case hardening methods, but can be essentially colorless.

[edgarspencer]

Originally Posted by Chuck Heald

like 2 - 2 1/2 times the tensile strength of low carbon steel if I recall.

not 2-2 1/2 times.
Plain carbon steel (1010) will have a tensile strength, when normalized and tempered, in the 65-70K range, yield in the 35-40K range. Typical 1018 (Approximates WCB will be 70-36.
8620 (.20C, Ni Cr Mo) will be in the 90K tensile, 60K yield range. 8635 (.35C) will be minimum 105K Tensile, 85K yield.

[Chuck Heald]

Edgar,
When the casehardening process of heating and quenching is done, 8620 will core harden. I can't recall the reference I found on this at the moment. The core came up to about twice the strength of normalized.

[edgarspencer]

Any carbon steel will have a higher hardness (Brinell), and, logically, UTS will be higher, when quenched and tempered than when Normalized and tempered, however ductility will suffer dramatically. Quenching will give you a higher surface, or near surface hardness, but the core will be less so. Air quenching after normalizing will give a more uniform cross sectional hardness.

[Parkerman]

Edgar
Thanks for your note. Would you please comment re your thoughts of what treatments would produce the best receiver?
Thank you

Linn