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

According to standard GB/T 3077-2008, the chemical composition of 40Cr seamless steel pipes 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 steel pipes have 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 ≥47 J, and a Brinell hardness (HBS100/3000) of ≤207 in the annealed or high-temperature tempered state.

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

Second, regarding the heat treatment of 40Cr seamless steel pipes: The first quenching heating temperature for 40Cr seamless steel pipes is 850°C, using oil as the coolant; the tempering heating temperature is 520°C, using water or oil as the coolant. The critical point temperature (approximate value) 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, 40Cr Seamless Steel Pipe Quenching and Tempering Specifications

40Cr seamless steel pipes adopt strict process specifications: a quenching temperature of 850°C ±10°C with oil cooling, and a tempering temperature of 520°C ±10°C with water, oil, and air cooling, ensuring product quality stability and reliability.

Fourth, Characteristics of 40Cr Seamless Steel Pipe

40Cr seamless steel pipe 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 the machinability of blanks with a hardness less than 160 HBS. Tempering at 550-570°C achieves optimal overall mechanical properties. This steel exhibits higher hardenability than 45 steel, making it suitable for surface hardening treatments such as high-frequency quenching and flame quenching.

Fourth, Applications of 40Cr Seamless Steel Pipe: After quenching and tempering, 40Cr seamless steel pipe 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 with a cross-sectional thickness of less than 25mm that require heavy loads, low impact, and wear resistance, 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.