40Cr according to standard GB / T 3077-1999 corresponding foreign standards: JIS G4053 ASTM A29 / ISO 683-18:1996 
 Chemical composition 
 Grades of C, Si Mn Cr of Ni the PS the CU 
 40Cr 0.37 ~ 0.44 0.17 ~ 0.37 0.50 ~ 0.80 0.80 ~ 1.10 ≤ 0.030 ≤ 0.035 ≤ 0.035 ≤ 0.030 
 Mechanical properties 
 Blank sample size (mm): 25 Heat treatment: the first quenching temperature (° C): 850; coolant: Oil quenching temperature (° C): - tempering the heating temperature (° C): 520; coolant: water, oil 
 40CR roundwood 
 Tensile strength (σb / MPa): ≧ 980 yield point (σs / MPa): ≧ 785 Elongation (δ5 /%): ≧ 9 section shrinkage rate (ψ /%): ≧ 45 impact absorption Gong (Aku2 / J): ≧ 47 Brinell hardness (HBS100/3000) (annealing or high temperature tempered condition): ≦ 207 
 40cr introduced 
 [Reference to the corresponding steel] China GB Standard steel, 40Cr, the German DIN standard material number 1.17035/1.7045 German DIN standard steel 41Cr4/42Gr4 the EN standard steel No. 18, British BS standard steel 41Cr4, the French AFNOR standard Steel 42C4, the French NF standard steel 38Cr4/41Cr4 Italian UNI standard steel, 41Cr4, Belgium NBN standard steel 42Cr4, Sweden SS Standard Steel No. 2245, the U.S. steel AISI / SAE / ASTM standard steel 5140, Japan's JIS standard steel SCr440 (H) / SCr440, U.S. steel AISI / SAE / ASTM standard steel No. 5140, the International Organization for Standardization ISO standard steel 41Cr4. [Critical temperature (approximate) Acm = 780 ° C [normalizing norms] temperature of 850 ~ 870 ° C, the hardness of 179 ~ 229HBS. [Cold press rough softening specification] temperature of 740 ~ 760 ℃, 4 ~ 6h, of the holding time and cooling rate of 5 ~ 10 ° C / h, cooling to ≤ 600 ° C, cooled baked. Before it is processed the hardness the ≤ 217HBS, soften the hardness ≤ 163HBS. [Health protection of iron swing tempering specification (670 ± 10) ℃ × 2h, with the furnace temperature (710 ± 10) ℃ × 2h, followed by furnace cooling, (670 ± 10) ℃ × 2h, with the furnace temperature (710 ± 10) ℃ × 2h, and then followed by furnace cooling, (670 ± 10) ℃ × 2h, with the furnace temperature (710 ± 10) ℃ × 2h, with furnace cooling, a total of three cycles, and then cooling to 550 ° C, baked air-cooled. Treated hardness 153HBS. [Quenched and processing specifications] quenching temperature of 850 ℃ ± 10 ℃, oil cooling; tempering temperature of 520 ° C ± 10 ° C, water, oil, air-cooled. 
 The 40cr characteristics and uses of 
 Feature 
 Modulation of carbon steel, cold heading die steel. The steel affordable, easy processing, after appropriate heat treatment to get a certain toughness, ductility and wear resistance. The normalizing Organization for the Advancement of globalization to improve the hardness of less than 160HBS rough cutting performance. 550 ~ 570 ℃ temperature tempering, the steel has the best mechanical properties. Hardenability of the steel is higher than 45 steel, suitable for frequency hardening, flame hardening, surface hardening treatment. 
 Use 
 Steel after quenching and tempering for manufacturing mechanical parts of the work under medium load and medium speed gear on the car steering knuckles, rear axle and the machine shaft, worm, spline shaft, the top sets, etc.; quenched under high load, impact and medium speed parts such as gears, spindles, pump rotor, the slider rings used in the manufacture and tempering; by quenching and tempering for the manufacture of heavy duty, low impact and abrasion resistance, the cross section on the part of the entity thickness less than 25mm, such as the worm shaft, spindle, ring, etc.; used in the manufacture of high surface hardness and wear resistance after quenching and tempering and high-frequency surface hardening and no great impact on the parts such as gears, sleeves, shaft, spindle, crank, mandrels, pins, connecting rods, screws, nuts, intake valve and so on. In addition, this steel is suitable for the manufacture of carbonitriding processing, transmission parts, such as large diameter and low-temperature toughness, good gear and shaft. Delivery status and hardness] annealed hardness ≤ 207HBS. The 40cr shaft parts shaft parts is the one often encountered in typical parts in the machine. It is mainly used to support the transmission parts, transmission torque and load bearing. Shaft parts are parts of the rotating body, and its length is greater than the diameter of generally concentric axis of the outer cylinder, a conical surface, the inner hole and thread, and the corresponding end. Depending on the structure and shape, the shaft parts can be divided into the optical axis, stepped shaft, hollow shaft and crankshaft and so on. Axis length to diameter ratio less than 5 known as the short axis greater than 20 known as the slender shaft, and most of the shaft in between. Shaft bearings bearing, journal bearing with the shaft section is called. The journal is the axis of the assembly benchmark, their accuracy and surface quality are generally higher, and its technical requirements are generally formulated according to the axis function and working conditions, usually the following: (a) the dimensional accuracy of the supporting role from the journal In order to determine the position of the axis, usually its size require a higher precision (IT5 ~ IT7 and). Assembly drive journal dimensional accuracy is generally lower (IT6 ~ IT9) the (B) the geometry of the accuracy of the geometry of the precision shaft parts mainly refers to the journal, the outer cone, Morse taper hole such as roundness, cylindricity, generally should be tolerance limit in the range of dimensional tolerances. High internal and external circular surface accuracy requirements should be marked on the drawing tolerances. (C) the location accuracy requirements of the mutual positional accuracy of shaft parts is determined by the axis in the mechanical position and function. Assembly drive journal should normally ensure that the concentricity of the bearing journal requirements, otherwise it will affect the transmission accuracy of the transmission (gear), and generate noise. Ordinary precision axis with the axis of segment bearing journal runout is generally 0.01 ~ 0.03mm, precision axis (spindle) is usually 0.001 ~ 0.005mm. (D) surface roughness is generally associated with the drive to match the shaft diameter surface roughness Ra2.5 ~ 0.63μm, and the surface roughness of the bearing to match the bearing shaft diameter Ra0.63 Ra0.63 ~ 0.16. 40Cr elastic modulus: the elastic modulus E (20 ° C) / MPa 200 000 ~ 211.7 thousand, the shear modulus G (20 ° C) 80.8 thousand 
 Heat treatment process 
 Quenching process 
 40Cr quenched 850 ° C, cold oil; tempering 520 ° C, water-cooled, oil cooled. 40Cr surface quenching hardness is HRC52-60, flame hardening can reach HRC48-55. 
 Nitrogen treatment 
 40Cr belong nitride steel, which contains the elements conducive to nitride. 40Cr get a higher surface hardness after nitriding treatment 40Cr quenched and nitrogen treatment hardness of the maximum can reach HRA72 78, namely HRC43 ~ 55. Nitride workpiece process line: Forging - Annealing - roughing - quenched and tempered - finishing - in addition to stress - coarse grinding - nitride - grinding or lapping. Nitride thin, and more brittle, thus requiring higher strength of heart organized by the Ministry, it is necessary to conduct the transfer of heat treatment for tempering sorbite heart, mechanical properties and the quality of the nitrided layer. The soft-nitride active nitride, now more commonly used in gas nitriding.