I use 1045 but it’s treated similarly to 4140. Forge to shape, normalize, anneal, rough grind, harden in water then temper to a straw color. I use a heated drift to do my tempering. I’ve also read that some people have problems with 4140 cracking when quenching in water.
4140 should always be quenched in oil. It has alloys that make it more hardenable than 1045, meaning it hardens deeper, but that's not required in a hammer. Neither steel is great for hammers. They can attain sufficient hardness, but have poor wear resistance. Plain high carbon steels like 1095 or W1 at around 1% C will harden 1/4 " deep with a tough core that is twice the strength of the core of 1045. with a wear resistant case. Anvil faces, which are essentially hammers, have always been made from high carbon steel because of it's abrasion resistance. I don't where the recent trend to using medium carbon steel for hammers came from, but they don't make a quality hammer.
Hammer hardening/tempering?
in Hand Hammers
Posted
4140 should always be quenched in oil. It has alloys that make it more hardenable than 1045, meaning it hardens deeper, but that's not required in a hammer. Neither steel is great for hammers. They can attain sufficient hardness, but have poor wear resistance. Plain high carbon steels like 1095 or W1 at around 1% C will harden 1/4 " deep with a tough core that is twice the strength of the core of 1045. with a wear resistant case. Anvil faces, which are essentially hammers, have always been made from high carbon steel because of it's abrasion resistance. I don't where the recent trend to using medium carbon steel for hammers came from, but they don't make a quality hammer.