20CrMnMo 

 20crmnmo representation 20CrMnMo, the Chinese national standard [1] of an alloy structural steel grades. Uniform digital code: A34202. Chemical composition 
 Mass fraction (%): C C: 0.17 ~ 0.23 Si Si: 0.17 ~ 0.37 Manganese Mn: 0.90 ~ 1.20 S S: to allow the residual content ≤ 0.035 
 Phosphorus P: to allow the residual chromium content ≤ 0.035 Cr: 1.10 ~ 1.40 Ni: to allow the residual content ≤ 0.030 Copper Cu: Mo to allow the residual content ≤ 0.030 Mo: 0.20 ~ 0.30 
 Mechanical Properties 
 【Size】 15mm blank sample 
 [Heat] quenching temperature (℃): 850; Coolant: Oil-tempered heating temperature (℃): 200; coolant: water, air 
 [Mechanical Properties] Tensile strength (σb / MPa): ≧ 1180 
 Yield point (σs / MPa): ≧ 885 Elongation (δ5 /%): ≧ 10 section shrinkage (ψ /%): ≧ 45 impact absorbed energy (Aku2 / J): ≧ 55 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. 
 Key Features 
 Advanced high-strength case-hardened steel. Intensity is higher than 15CrMnMo, lower plasticity and toughness, hardenability and mechanical properties than 20CrMnTi high, quenching and tempering has good mechanical properties and low temperature impact toughness. After carburizing with high bending strength and wear resistance, but the grinding easy to crack. Good weldability, suitable for resistance welding, preheating before welding required, be tempering after welding. Machinability and good thermal processing [2]. 
 Application examples 
 Commonly used in the manufacture of high hardness, high strength, high toughness of the larger pieces of important cementite (the requirements are higher than 15CrMnMo), such as crankshaft, camshaft, connecting rods, gear shafts, gears, pin, can be used instead of 12Cr2Ni4 [ 2]. 
 20crmnmo representation 
 ① steel beginning of the two numbers indicate the carbon content of steel, the average carbon content of the very few that, as 40Cr, 25Cr2MoVA alloy steel pipe ② main alloying elements, in addition to individual micro-alloying elements, in general, to a few percent said. When the average alloy content of <1.5%, the steel elements are generally marked only symbols, not marked content, but prone to cause confusion in those special circumstances, after the element symbol can also be marked with the number "1", such as steel "12CrMoV" and "12Cr1MoV", the former chromium content of 0.4-0.6%, 0.9-1.2% for the latter, all the remaining ingredients the same. When the average content of alloying elements ≥ 1.5%, ≥ 2.5%, ≥ 3.5% ... ..., the symbol of the element content should be marked on the back, can be expressed as the corresponding 2,3,4 ... etc. For example 18Cr2Ni4WA. ③ steel vanadium V, Ti Ti, Al AL, boron B, RE alloys of rare earth elements are micro-alloying elements, although very low levels, should bid out in steel. For example 20MnVB steel. To 0.07-0.12% vanadium, boron 0.001-0.005%. ④ High quality steel in the steel should be added the last "A", as distinct from the general high quality steel. ⑤ special purpose alloy steel, steel, known (or suffix) on behalf of the steel uses symbols. For example Lo dedicated 30CrMnSi riveting steel, steel, said to ML30CrMnSi.