4340 (EN24 / 817M40 / 40CrNi2Mo) is a high-strength, low-alloy steel containing nickel, chromium, and molybdenum. It is known for its excellent toughness, fatigue resistance, and high tensile strength in both normalized and heat-treated conditions. Dette stålet er mye brukt i romfart, bilindustrien og tunge maskiner der det kreves kritisk ytelse under høy belastning.