50cr Introduction 
 50cr pipe production standards and representation 50Cr [1], alloy structural steel. Uniform digital code: A20502 Standard: GB / T 3077 - 
 Chemical composition 
 [Chemical composition] (wt) (%) Carbon C: 0.47 ~ 0.54 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 
 [Mechanical Properties] sample blank size (mm): 25 Heat treatment: first quenching temperature (℃): 830; Coolant: Oil second quenching temperature (℃): - tempering heating temperature (℃): 520 ; coolant: water, oil tensile strength σb (MPa): ≥ 1080 (110) yield strength σs (MPa): ≥ 930 (95) 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): ≦ 229 Delivery status: heat treatment (normalizing, annealing, or tempering) or heat treatment delivery, delivery status should be indicated in the contract. 
 50cr Introduction 
 [Main Features] good hardenability of this steel, quenching in oil the critical diameter of 14 ~ 49mm, the critical quenching diameter in water up to 28 ~ 77mm, quenched in oil and tempering to obtain a high strength and hardness However, the formation of cracks when the water quenching tendency; in the range 500 ~ 650 ℃ tempered when there is a second category tend to temper brittleness; thermal processing of the sensitivity of white spots. This normalizing or quenching and tempering of steel after cutting was good, after annealing can be cut is also good; steel low in cold plastic deformation, welding is bad, there is a tendency to form cracks, so to be preheated before welding to about 200 ℃, and after welding to eliminate stress to deal with. 
 [Application examples] This steel is usually quenched and tempered or quenched state to use for the manufacture of parts subject to heavy loads and friction, such as hot-rolled with a diameter of 600mm below the roller, gear shaft, gear, transmission shaft, thrust ring, roller bearing spindles, clutch gear tractor, diesel engine connecting rod, bolts, tappet and heavy mining machinery requiring high strength and wear of gears, oil film bearing covers. In some cases, required to create a high surface hardness and wear resistance of high-frequency surface hardened parts. In addition, this steel is also used as a medium elastic springs. [ 
 50cr pipe production standards and 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, 50Cr 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. Alloy seamless pipe and the existing relationship and differences between the two, can not be confused. Alloy steel pipe is produced in accordance with the material (ie material) to define the name suggests is made of alloy tube; and seamless steel pipe according to the production process (with seamless sewing) to the definition, is different from the seamless seamed tube, including the Longitudinal and spiral pipe