Introduction to the Mechanical Properties and Chemical Composition of 40Cr Seamless Steel Pipe

According to standard GB/T 3077-2008, the chemical composition of 40Cr seamless steel pipe includes C 0.37-0.44%, Si 0.17-0.37%, Mn 0.50-0.80%, Cr 0.80-1.10%, and Ni ≤ 0.30%. In terms of mechanical properties, 40Cr seamless steel pipe has a tensile strength of ≥ 980 MPa, a yield point of ≥ 785 MPa, an elongation of ≥ 9%, a reduction of area of ≥ 45%, an impact energy absorption of ≥ 47J, and a Brinell hardness (HBS100/3000) of ≤ 207 in the annealed or high-temperature tempered state.

First, the standards for 40Cr seamless steel pipes.

40Cr seamless steel pipes correspond to steel grades including my country's GB standard 40Cr, German DIN standard material numbers 1.17035/1.7045, German DIN standard grades 41Cr4/42Gr4, British EN standard grade 18, British BS standard grade 41Cr4, French AFNOR standard grade 42C4, French NF standard grades 38Cr4/41Cr4, Italian UNI standard grade 41Cr4, Belgian NBN standard grade 42Cr4, Swedish SS standard grade 2245, American AISI/SAE/ASTM standard grade 5140, Japanese JIS standard grades SCr440(H)/SCr440, and the International Organization for Standardization ISO standard grade 41Cr4.

Second, the process for producing 40Cr seamless steel pipes.

Regarding heat treatment, the initial quenching temperature for 40Cr seamless steel pipes is 850°C with oil as the coolant; the tempering temperature is 520°C with water or oil as the coolant. The critical point temperature (approximately) is Acm = 780°C. The standard normalizing temperature is 850-870°C, with a hardness of 179-229 HBS. The standard softening temperature for cold-pressed blanks is 740-760°C, with a holding time of 4-6 hours. The temperature is then lowered to ≤600°C at a cooling rate of 5-10°C/h, and air-cooled after removal from the furnace. The hardness before treatment is ≤217 HBS, and the hardness after softening is ≤163 HBS.

Third, the quenching and tempering treatment specifications for 40Cr seamless steel pipes.

This product utilizes strict process specifications: a quenching temperature of 850°C ±10°C with oil cooling; a tempering temperature of 520°C ±10°C with water, oil, or air cooling, ensuring consistent and reliable product quality.

Fourth, Characteristics of 40Cr Seamless Steel Pipe.

This product is a medium-carbon tempered steel and cold heading die steel. It is moderately priced and easy to process. Appropriate heat treatment imparts a certain degree of toughness, ductility, and wear resistance. Normalizing promotes microstructure spheroidization and improves machinability for blanks with a hardness less than 160 HBS. Tempering at 550-570°C achieves optimal overall mechanical properties. This steel has a higher hardenability than 45 steel and is suitable for surface hardening treatments such as high-frequency quenching and flame hardening.

Fifth, Applications of 40Cr Seamless Steel Pipe.

After quenching and tempering, this product is suitable for manufacturing mechanical parts subject to medium loads and medium speeds, such as automotive steering knuckles and rear axles, as well as gears, shafts, worm gears, spline shafts, and center sleeves on machine tools. After quenching and medium-temperature tempering, it is suitable for manufacturing parts subject to high loads, impact, and medium speeds, such as gears, spindles, oil pump rotors, sliders, and collars. After quenching and low-temperature tempering, it is suitable for manufacturing parts subject to heavy loads, low impact, and wear resistance, with a cross-sectional thickness of less than 25mm, such as worm gears, spindles, shafts, and collars. After quenching, tempering, and high-frequency surface quenching, it is suitable for manufacturing parts with high surface hardness and wear resistance without significant impact, such as gears, sleeves, shafts, spindles, crankshafts, and pins.