![]() The mil-spec process uses a nickel acetate sealant, and the dark color results from the dye used (the natural color left after anodizing is still "aluminum"). The oxides are porous, so it is common to use a sealant. The result is an accelerated formation of natural oxides that harden the surface. They dunk the aluminum parts in a tank of an acidic solution and pump electricity through it. To harden its surface, manufacturers use a process known as anodizing. ![]() 7075 just shrugs it off.Īluminum is too soft to be used bare. Early testing in Southeast Asia showed that human sweat, combined with the high temperatures and humidity of the jungle, would simply eat away at 6061 alloy. Some firms still make them as one piece, but many manufacturers have figured a way to make strong bolts of two pieces that are welded together.Įither are strong enough for the tasks we ask of them, but the big reason for 7075 over 6061 in the production of AR receivers, for instance, is corrosion resistance. Forged bolts are really, really strong, And tough to machine. 7075 is a much stronger alloy and has markedly larger amounts of copper, manganese, chromium and zinc. 6061 is commonly referred to as "aircraft" aluminum and has trace amounts of silicon, copper, manganese, molybdenum and zinc. Army wants the extra wearability that 4150 offers and is willing to pay for it.Īluminum is used in firearms in two alloys: 70. That extra 0.1 percent makes the 4150 alloy so much harder that it becomes a lot more difficult to work with, but the U.S. The "big" difference between 41? The 4150 has 0.5 percent carbon in it. Mild steel, easy to machine and relatively inexpensive, works just fine. Something like a trigger guard doesn't have to be made of high-strength alloy steel. ![]() That leaves most of it, 94.25 percent, iron. It has about 1 percent chromium, 0.25 percent molybdenum, 0.4 percent carbon, 1 percent manganese, around 0.2 percent silicon and no more than 0.035 percent phosphorus and no more than 0.04 percent sulphur. Let's take as an example the steels in the classic barrel argument amongst AR owners: 4140 steel versus 4150 steel.Ĥ140, also known as ordnance steel, was one of the early high-alloy steels, used in 1920s' aircraft frames and automotive axles in addition to rifle barrels. The next three numbers tell you how much of what is in them. The first number is what class-carbon, nickel, chromium and so forth. Numbers such as 1060, 4140 or 5150 all designate how much of what is in them. The Society of Automotive Engineers uses a simple designating system, the four numbers you see bandied about in gun articles. Those alloying agents add useful things to the mix, such as easy machineability, corrosion resistance, abrasion resistance or tensile strength without brittleness to the steel grade in question. Steel can be alloyed with other metals such as nickel, chromium and tungsten-as well as non-metallic elements as molybdenum, sulfur and silicon. The crystals of steel are described by their sizes and shapes, and they have actual names such as austenite and martensite, cementite and ferrite. (Brief rant: Had I any hair left, I'd be pulling it out every time I heard of yet another lubricant that "gets into the pores of the steel.") The shape, size and alignment of those crystals determine the mechanical properties of the steel in question. Steel does not have pores it consists of crystals. What is steel? And why is it so important in gun building? Simply put, steel is iron with enough carbon in it to allow hardening-but not too much because that makes the resulting alloy brittle. If you're in the dark about what it all means, read on. Gun metal terms get bandied about in product literature and the firearms press as if everybody knew just what the hell they were talking about. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |