astm a193 grade b7 chemical composition

astm a193 grade b7 is a medium-carbon alloy structural steel. Internationally accepted designations include American AISI 4140/4142 and German DIN 42CrMo4. Its primary chemical composition is carbon (0.38-0.45%), chromium (0.90-1.20%), and molybdenum (0.15-0.25%). It also contains elements such as manganese and silicon, with low sulfur and phosphorus contents. This material exhibits high strength, toughness, and good hardenability, with a tensile strength ≥1080 MPa and a hardness ≤217 HB. It is suitable for structural parts and key components in fields such as construction, mechanical engineering, automotive manufacturing, and aerospace.

Performance optimization can be achieved through quenching and tempering treatments and salt-bath vanadiumization, achieving a post-quench hardness of 50-52 HRC. Vanadization enhances surface wear and impact resistance. Its hot working specifications include heating at 1150-1200°C and multi-stage forging. It is suitable for manufacturing large and medium-sized plastic molds, gears, and drive shafts, which are subject to heavy loads, impact, or low temperatures. Compared with the similar steel grade 40Cr, its comprehensive mechanical properties are better.

astm a193 grade b7 is an ultra-high-strength steel with high strength and toughness, good hardenability, and no significant temper brittleness. After quenching and tempering, it has a high fatigue limit and resistance to multiple impacts, and good low-temperature impact toughness. astm a193 grade b7 is suitable for manufacturing large and medium-sized plastic molds that require a certain level of strength and toughness.

Chemical Composition

Carbon (C): 0.38-0.45%

Silicon (Si): 0.17-0.37%

Manganese (Mn): 0.50-0.80%

Sulfur (S): Residual content allowed ≤ 0.035%

Phosphorus (P): Residual content allowed ≤ 0.035%

Chromium (Cr): 0.90-1.20%

Nickel (Ni): Residual content allowed ≤ 0.30%

Copper (Cu): Residual content allowed ≤ 0.30%

Molybdenum (Mo): 0.15-0.25%

Mechanical properties

Hardness: Annealing, 147~241HB

42CrMo mechanical properties:

Tensile strength σb (MPa): ≥1080(110)

Yield strength σs (MPa): ≥930(95)

Elongation δ5 (%): ≥12

Slice reduction ψ (%): ≥45

Impact energy Akv (J): ≥63

Impact toughness αkv (J/cm2): ≥78(8)

Hardness: ≤217HB

In order to increase the mold life to more than 800,000 mold cycles, the pre-hardened steel can be hardened by quenching and low-temperature tempering. When quenching, preheat at 500-600℃ for 2-4 hours, then keep warm at 850-880℃ for a certain period of time (at least 2 hours), put it in oil and cool it to 50-100℃, then remove it from the oil and air cool it. The hardness can reach 50-52HRC after quenching. To prevent cracking, low-temperature tempering treatment at 200℃ should be carried out immediately. After tempering, the hardness can be maintained above 48HRC.

Physical properties

(1) Critical point temperature (approximate value): Ac1=730°C, Ac3=800°C, Ms=310°C.

(2) Linear expansion coefficient: Temperature 20~100°C/20~200°C/20~300°C/20~400°C/20~500°C/20~600°C,

Linear expansion coefficient: 11.1×10K/12.1×10K/12.9×10K/13.5×10K/13.9×10K14.1×10K.

(3) Elastic modulus: Temperature 20°C/300°C/400°C/500°C/600°C,

Elastic modulus 210000MPa/185000MPa/175000MPa/165000MPa/15500MPa