45Cr [1], alloy structural steel. Uniform digital code: A20452 Standard: GB / T 3077-1988 
 Chemical composition 
 [Chemical composition] (wt) (%) Carbon C: 0.42 ~ 0.49 Si Si: 0.17 ~ 0.37 Manganese Mn: 0.50 ~ 0.80 S S: to allow the residual content ≤ 0.035 
 Phosphorus P: to allow the residual chromium content ≤ 0.035 Cr: 0.80 ~ 1.10 Ni: to allow the residual content ≤ 0.030 Copper Cu: ≤ 0.030 to allow the residual content 
 [Mechanical Properties] sample blank size (mm): 25 Heat treatment: first quenching temperature (℃): 840; Coolant: Oil second quenching temperature (℃): - tempering heating temperature (℃): 520 ; coolant: water, oil tensile strength σb (MPa): ≥ 1030 (105) yield strength σs (MPa): ≥ 835 (85) Elongation δ5 (%): ≥ 9 
 Reduction of area ψ (%): ≥ 40 Impact energy Akv (J): ≥ 39 impact toughness αkv (J/cm2): ≥ 49 (5) Brinell hardness (HBS100/3000) (annealing or tempering state) : ≦ 217 Delivery status: to heat treatment (normalizing, annealing, or tempering) or heat treatment delivery, delivery status should be indicated in the contract. 
 [Main Features] This steel and 40Cr steel compared to steel strength, wear resistance and hardenability were higher in the hardenability of the oil in the critical diameter of 12 ~ 45mm, the critical quenching in water up to 26 ~ 71mm in diameter , but the toughness is lower; modulation in carbon steel, cold heading die steel. The steel affordable, easy to process, after appropriate heat treatment after the availability of a certain toughness, ductility and wear resistance. Normalizing the ball of the organization can promote and improve the hardness is less than 160HBS rough cutting. Temperature 550 ~ 570 ℃ for tempering, the steel has the best mechanical properties. Hardenability of the steel is higher than 45 steel, suitable for high-frequency hardening, flame hardening and other surface hardening treatment 
 [Application Example Usage is similar to 40Cr steel, mainly used to manufacture the more important parts, but also by high-frequency surface hardening and wear resistance require a higher load was made after a variety of parts such as gears, sleeves, shafts, pins son, etc. 
 45cr temperature critical point 
 [Critical temperature] (approximate) Acm = 780 ℃ 
 [Specification] normalizing temperature 850 ~ 870 ℃, hardness 179 ~ 229HBS. [Cold] rough handling practices softening temperature 740 ~ 760 ℃, holding time 4 ~ 6h, then 5 ~ 10 ℃ / h of cooling rate, cooling to ≤ 600 ℃, baked cooled. Treatment before the hardness ≤ 217HBS, soften the hardness ≤ 163HBS. 
 [Health protection of iron swing tempering specification] (670 ± 10) ℃ × 2h, with the furnace temperature, (710 ± 10) ℃ × 2h, with the furnace cooling, (670 ± 10) ℃ × 2h, with the furnace temperature, (710 ± 10) ℃ × 2h, then with the furnace cooling, (670 ± 10) ℃ × 2h, with the furnace temperature, (710 ± 10) ℃ × 2h, with the furnace cooling, a total of three cycles, and then cooled to 550 ℃, baked air-cooled. Treatment hardness 153HBS. [Specification] quenched quenching temperature 850 ℃ ± 10 ℃, oil-cooling; tempering temperature 520 ℃ ± 10 ℃, water, oil cooled.