Introduction of 40Cr grade of Wuyang Iron and Steel Production
Wuyang Iron & Steel 40Cr grade introduction 1, introduction
40Cr is China's GB standard steel grade, 40Cr steel is one of the most widely used steel in the machinery manufacturing industry. After quenching and tempering treatment, it has good comprehensive mechanical properties, good low-temperature impact toughness and low notch sensitivity. The hardenability of steel is good, it can be hardened to Ф28~60mm when water quenching, and Ф15~40mm when oil quenching. In addition to quenching and tempering, this steel is also suitable for cyanide and high-frequency quenching. The cutting performance is good, when the hardness is 174~229HB, the relative machinability is 60%. The steel is suitable for medium-sized plastic molds. 2. Characteristics of medium carbon quenched and tempered steel, cold heading die steel. The steel is moderately priced, easy to process, and can obtain certain toughness, plasticity and wear resistance after proper heat treatment. Normalizing can promote the refinement of the structure, close to the equilibrium state, and can improve the cutting performance of the blank. Tempered at a temperature of 550~570 °C, the steel has the best comprehensive mechanical properties. The hardenability of the steel is higher than that of 45 steel, and it is suitable for high-frequency quenching, flame quenching and other surface hardening treatments.
| Chemical composition |
| Tabulation: Depu Steel Date: 2024-01-22 |
| C |
Si |
Mn |
Cr |
Ni |
P |
S |
Cu |
| 0.37-0.44 |
0.17-0.37 |
0.50-0.80 |
0.80~1.10 |
≤0.30 |
≤0.035 |
≤0.035 |
≤0.30 |
Note:
(1): In order to improve the properties of steel, other trace alloying elements other than the above table can be added, and the data comes from the network and is for reference only.
(2): The allowable deviation of the chemical composition of the finished steel plate should be in accordance with the provisions of
GB/T222 40Cr before welding, so as to prevent the internal quenching and quenching of the weld due to the heat dissipation of the matrix. It is best to add normalizing before quenching and tempering after welding.
Weldability of 40Cr:
easy to segregate during crystallization, sensitive to crystallization cracks (a kind of hot cracking), and easy to crack in the concave part of the arc pit and weld during welding. The carbon content is high, and it is easy to obtain a hardened structure (martensitic structure) that is sensitive to cold cracks when it is cooled quickly. When the cooling rate of the superheating zone is large, it is easy to form a hard and brittle high-carbon martensite and make the superheating zone embrittle. Key points of
welding process 1, generally welded in the annealed (normalized) state.
2. The welding method is not limited
3. The preheating temperature is appropriately increased with a large line energy, and the general preheating temperature and interlayer temperature can be controlled between 250~300 °C.
4. The welding material should ensure that the composition of the deposited metal is basically the same as that of the base metal, such as J107-Cr
5, and the quenching and tempering heat treatment should be carried out in time after welding. If it is difficult to quench and temper in time, intermediate annealing or holding at a temperature higher than preheating for a period of time can be performed to exclude diffused hydrogen and soften the tissue. For products with complex structure and many welds, an intermediate annealing can be carried out after a certain number of welds have been welded.
6. Delivery status 40Cr delivery status is delivered in heat treated (normalized, annealed or high temperature tempered) or not heat treated, and the delivery status
should be indicated in the contract.
7. Use:
This steel is used to manufacture mechanical parts that bear medium load and medium speed after quenching and tempering, such as steering knuckles, rear half shafts of automobiles, and gears, shafts, worms, spline shafts, and center sleeves on machine tools;
After quenching and medium temperature tempering, it is used to manufacture parts that bear high load, impact and medium speed work, such as gears, spindles, oil pump rotors, sliders, collars, etc.;
After quenching and low-temperature tempering, it is used to manufacture parts that bear heavy load, low impact and wear resistance, and the solid thickness of the cross-section is less than 25mm, such as worms, spindles, shafts, collars, etc.;
After quenching and tempering and high-frequency surface quenching, it is used to manufacture parts with high surface hardness and wear resistance without great impact, such as gears, sleeves, shafts, spindles, crankshafts, mandrels, pins, connecting rods, screws, nuts, intake valves, etc.
In addition, the steel is suitable for the manufacture of various transmission parts that are carbonitriding, such as gears and shafts with large diameters and good low-temperature toughness.
