20CrNiMo, is a Chinese national standard alloy structural steel grades. Uniform digital code: A50202 

 20CrNiMo for containing molybdenum in addition to good overall performance capability is also a certain temperature outside. Manufacture gear for the whole rotor turbine engine forgings, rod valve section. 

 Chemical composition 
 Mass fraction (%): 

 Carbon C: 0.17 ~ 0.23 

 Si Si: 0.17 ~ 0.37 

 Manganese Mn: 0.60 ~ 0.95 

 S S: to allow the residual content ≤ 0.035 

 Phosphorus P: allow the residual content ≤ 0.035 

 Chromium Cr: 0.40 ~ 0.70 

 Ni-Ni: 0.35 ~ 0.75 

 Copper Cu: ≤ 0.30 to allow the residual content 

 Mo Mo: 0.20 ~ 0.30 [1] 

 Mechanical Properties 
 Sample size [blank] 

 15mm 

 [Heat treatment] 

 Quenching temperature (℃): 850; Coolant: Oil 

 Tempering heating temperature (℃): 200; Coolant: air 

 [Mechanical Properties] 

 Tensile strength σb (MPa): ≥ 980 (100) 

 Yield strength σs (MPa): ≥ 785 (80) 

 Elongation δ5 (%): ≥ 9 

 Reduction of area ψ (%): ≥ 40 

 Impact energy Akv (J): ≥ 47 

 Impact toughness αkv (J/cm2): ≥ 59 (6) Brinell hardness (HBS100/3000) (annealing or tempering state): ≦ 197 

 Delivery status: to heat treatment (normalizing, annealing, or tempering) or heat treatment delivery, delivery status should be indicated in the contract [2]. 

 Key Features 
 20CrNiMo formerly U.S. Steel AISI, SAE standard steel No. 8720. Hardenability steel performance 20CrNi similar. Although the Ni content 20CrNi steel steel half, but a small amount of Mo element, the isothermal transformation of austenite to the right upper part of the curve; because an appropriate increase in Mn content, resulting in the hardenability of this steel is still very good strength than 20CrNi steel. Commonly used in the manufacture of small cars, tractor engine and transmission in gear; can replace the 12CrNi3 steel high performance requirements of the Department of heart carburized parts, pieces of cyanide, such as oil drilling and metallurgical open pit with the rock bit claws and teeth cone body. 20CrNiMo for containing molybdenum in addition to good overall performance capability is also a certain temperature outside. Manufacture gear for the whole rotor turbine engine forgings, rod valve section. 

 Application examples 
 Commonly used in the manufacture of small cars, tractor engine and transmission in gear, but also can replace 12CrNi3 steel high performance requirements of the Ministry of carburizing heart pieces, pieces of cyanide, such as oil drilling and metallurgical pit with teeth and claws cone body. 


 20CRNIMO 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 symbolic use of steel