40CrNi 

 40crni representation 40CrNi, is a Chinese national standard alloy structural steel grades. Uniform digital code: A40402. 
 Chemical composition 
 Mass fraction (%): C: 0.37 ~ 0.44 Si: 0.17 ~ 0.37 Mn: 0.50 ~ 0.80 Cr: 0.45 ~ 0.75 
 Ni: 1.00 ~ 1.40 
 Gravitational properties of 
 【Size】 25mm 【sample blank] quenching heat treatment temperature (℃): 820; Coolant: Oil-tempered heating temperature (℃): 500; coolant: water, oil and mechanical properties] [tensile strength (σb / MPa ): ≧ 980 Yield point (σs / MPa): ≧ 785 Elongation (δ5 /%): ≧ 10 section shrinkage (ψ /%): ≧ 45 
 Impact absorbed energy (Aku2 / J): ≧ 55 Brinell hardness (HBS100/3000) (annealing or tempering state): ≦ 241 Edit the main characteristics of this paragraph 
 Carbon alloy quenched and tempered steel. High strength, high toughness and high hardenability. In the quenched state, good mechanical properties, good low temperature impact toughness. A tendency to temper brittleness, water easy to crack. Machinability is good, but poor weldability. Used in the quenched state. Edit this paragraph Application example 
 For the manufacture of forging and cold pressing and important section of a larger size of the quenched parts, such as connecting rod, disc, crankshaft, gears, shafts, screws, etc. 
 40crni 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.