willbird wrote:Some of the textbooks written on steel back in the 1930's 40's and 50's are a really good read. They used to take slices off the end of a steel billet to ensure that there were no flaws in it, they acid etched these samples. The billet was poured from one end and it had what was called a "hot top" on one end, a smaller section that was similar to our sprue on a cast bullet, it was supposed to fill shrinkage and any slag or other imperfections would stay in the "hot top". Well they kept slicing the billet until they did not find any more flaws.
When the billet is rolled out to say 1.2" dia. steel for rifle barrels any flaw in the billet will pretty much run the whole length of the resulting steel bars. It was not uncommon in the shop I worked at in Toledo to get 4140 steel that had flaws in it that caused cracks in the finished parts, or nearly finished parts, time to start over . In one case the part was 30" in dia and 18" tall, and had about 40 hours of machining done on it when the crack was discovered.
We also made some parts from inconel 100, aeromet 100 is a close equivalent, In it's annealed state it is roughly as strong as heat treated alloy steel....but it is a lot more difficult to machine, with cnc and carbide tooling it just takes longer . It also retains pretty much these same mechanical properties at 1000 degrees F. The benefit to us from making the clamps from that material was that no heat treating was required.
Mr. Glock wrote:And, did steel progression over time move up the chart? ie blackpowder was low-carbon, then nickel steel, then x, then y and the top of chart was most recent?
...................Yippy, I can hardly wait .Morne wrote:I intentionally omitted the tool steels (AKA expensive steels) since they don't really pertain much to firearms anyhow.
You could teach a whole college course on tool steels.
S-7 is a general purpose, air hardening, tool steel with a high resistance to impact and shock. It is moderately "red-hard" which makes it one of those rare steels that does very well as either a hot work or a cold work steel. The breakdown is as follows:
TYPE ANALYSIS Element Percentage
The critical temperature for S-7 is 1700 degrees to 1750 degrees F. A heat soak of 20 minutes plus 5 minutes per additional inch of thickness is recommended for a complete hardening (shorter times may be used for smaller pieces, for example chisels Ed.). Pieces up to 2" thick can be air cooled but at thicknesses greater than that an oil quench to 150 F is recommended. Tempering should be done as quickly as possible following the hardening process. The factory specification for cold work is an Rc hardness of 55-57, for hot work a Rc of 50-53 is suggested.
TEMPERING TABLE Temperatures
As Hardened 59-61
S-7 is one of those hot work/cold work steels that many smiths "forge and forget" It can be difficult to find scrap sources of S-7, but it is readily available from steel suppliers and well worth the cost.
References for this article are from, but not limited to, the material specification sheets from Carpenter Technology Corporation, Steel Division and lecture material from Robb Gunter's 1994 ABANA conference demonstration on scrap tool steels.
haspelbein wrote:There have been some discussions regarding the quality of the steel or the treatment of US-made barrels in popular rifles in Europa, such as the Remington 700.
Many claim that the lifetime of the US-made barrels is lower, and that their effective use for long-range shooting is therefore lower and limited to 5000 rounds, and this would not be the case with some higher-priced European manufacturers.
My understanding has always been that there are very limited options regarding the barrel steel, and that the main factors were mainly the form of rifling as well as surface treatments, such as lining the barrel.
So, any input regarding the type of steel used vs. the longevity of the barrel?
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