30Mn2, alloy structural steel. Standard: GB / T 3077-1988 Chemical Composition: C: 0.27 ~ 0.34 Si Si: 0.17 ~ 0.37 Manganese Mn: 1.40 ~ 1.80 S S: to allow the residual phosphorus content of ≤ 0.35 P: ≤ 0.35 to allow the residual content of chromium Cr: to allow the residual content ≤ 0.30 Ni: to allow the residual copper content of ≤ 0.30 Cu: ≤ 0.30 to allow the residual content 

 30mn2 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. Case [(OD - Wall Thickness) * Thickness] * 0.02466 = kg / m (weight per meter) 
 Mechanical Properties 
 Sample blank size (mm): 25 Heat treatment: first quenching temperature (℃): 840; coolant: water, a second quenching temperature (℃): - tempering heating temperature (℃): 500; coolant: Water tensile strength σb (MPa): ≥ 785 (80) yield strength σs (MPa): ≥ 635 (65) Elongation δ5 (%): ≥ 12 Reduction of ψ (%): ≥ 45 Impact energy Akv ( J): ≥ 63 impact toughness αkv (J/cm2): ≥ 78 (8) Brinell hardness (HBS100/3000) (annealing or tempering state): ≦ 207 Delivery status: to heat treatment (normalizing, annealing or high-temperature tempering) or heat treatment delivery, delivery status should be indicated in the contract. 
 Application examples 
 Most of the steel used in the quenched state, in cars, tractors and general machinery manufacturing, and more for Stamping (4 ~ 11 mm plate) make the car beam, beams, and transmission gear, shaft, bolt cold heading, large cross-section of the quenched parts. In addition, the steel can be used as case-hardened steel, used to make the heart of the Department of carburized parts require a higher intensity, such as mining crane and the rear axle journal and so on. 30Mn2 grades were: China GB, YB, JIS German DIN (W-Nr.) American ASTM, AISI, SAE BS, NF France, the former Soviet Union ГОСТ 20Mn2 SMn420 (SMn21) - 1024,1024,1524 (1024) 150M19 - 20 Г 2 30Mn2 SMn433 (SMn1) 28Mn6 (1.5065), 30Mn5 (1.5066) 1330,1330,1330 150M28 - 30 Г 2 35Mn2 SMn438 (SMn2) 36Mn5 (1.5067) 1335,1335,1335 150M36 - 35 Г 2 
 Chemical composition 
 Grade Chemical Composition% C Si Mn PS Cr Ni Cu 20Mn2 0.17-0.24 0.17-0.37 1.40-1.80 ≤ 0.035 ≤ 0.035 ≤ 0.30 ≤ 0.30 ≤ 0.30 30Mn2 0.27-0.34 0.17-0.37 1.40-1.80 ≤ 0.035 ≤ 0.035 ≤ 0.30 ≤ 0.30 ≤ 0.30 35Mn2 0.32-0.39 0.17-0.37 1.40-1.80 ≤ 0.035 ≤ 0.035 ≤ 0.30 ≤ 0.30 ≤ 0.30 
 Characteristics and Uses 
 20Mn2 
 Section for the production of small (diameter less than 50MM) parts, can replace 20Cr steel. Commonly used in the production of carburized pinion, small shaft; less demanding of the piston pin, ten pin seed heads, diesel engine sleeve, valve push rod, etc.; also be used as quenched and tempered steel, such as the production of cold heading bolts. 
 35Mn2 
 Used as a connecting rod, spindle, crank, axle, lever, fan accessories, 15MM diameter less than the cold-heading variety of important bolts and other mechanical components to withstand high stress. In the production of small cross section (diameter less than 20MM) parts, can replace 40Cr steel.