Timken-LaTrobe of LaTrobe Pennsylvania invented/formulated Bg-42 in 1946 as a stainless steel ball bearing steel for jet engines.
They wanted a stainless or corrosion resistant steel that could take a beating.
No one made a knife out of it until 1957 and it performed better than anyone could imagine.
BG-42 has two things working against it that make it very expensive, and perhaps too expensive for knives in the Spyderco price range.
First, BG-42 requires a double vacuum melt during the manufacturing process.
In the first melt, the makers assemble all the ingredients in a vacuum and then they melt them together using an electric arc.
They allow it to harden, all the while in vacuum, and then they melt it again with an electric arc and pour it into ingots, still in a vacuum.
Did I mention the vacuum?
Secondly, BG-42 has a long, complex heat treatment, with various steps in temperature for prescribed times.
It will not tolerate the presence of oxygen and so requires either another vacuum, an inert gas environment, or molten salt.
I know of only two people who will heat treat BG-42: Paul Bos of Buck Knife reknown; and Thomas Haslinger, an international chef and knife-maker possessing remarkable talent and skill.
http://www.haslinger-knives.com/
Thomas has heat-treated two BG-42 knives for me.
I chose Thomas because he has a vertical molten salt bath and because of his knives.
Gene Osborn of
Centercross Metal Works has heat-treated one BG-42 knife for me in his argon atmosphere oven.
BG-42 resembles 154-CM and ATS-34 in composition, with the addition of vanadium.
Hitachi, the maker of ATS-34, smelts their steel in a vacuum at least once.
I don't know anything about the manufacture of 154-CM.
BG-42 resembles S30V in that it combines Chrome, Molybdenum and Vanadium in large percentages.
I think the manufacture of S30V also involves a vacuum and I think S30V has a very complex heat treatment.
That said, if Spyderco can produce a cost-effective S30V knife then a BG-42 knife seems reasonable.
I must say that my S30V Chinook II lives in a very sweaty environment, receiving one or two salty sweat baths a day in the waist band of my bike riding clothes.
I ride a lot and hard, and my Chinook gets totally wet with sweat.
As a result, I have three little spots of rust that periodically emerge on the Chinook's blade in the same place, which makes me wonder about the manufacturing process.
In contrast, I have never seen rust or corrosion on my BG-42 blades; but then, I don't carry them next to my skin while riding, as I do my Chinook.
I think S30V and BG-42 have a lot of similarities.
I have had my BG-42 knives hardened to 62.
I don't know how hard one can safely make S30V in a knife blade, but I'd like to know.
I suspect Sal knows much more about these two steels than do I, and I'd like to hear his take on them.
A link to Admiral Steel for price comparisons:
http://www.admiralsteel.com/products/blades.html