What are the differences between 20Cr steel and 40Cr steel

1. Different definitions

20Cr steel is a grade of steel, low hardenability carburizing steel.

40Cr steel is the standard steel grade of China's GB, and 40Cr steel is one of the most widely used steels in the manufacturing industry. After quenching and tempering, it has good comprehensive mechanical properties, good low-temperature impact toughness and low notch sensitivity.

40Cr steel has good hardenability and good cutting performance. When the hardness is 174～229HB, the relative machinability is 60%. The steel is suitable for making medium-sized plastic molds.

2. Different uses

20Cr steel is mostly used to manufacture carburized parts (oil quenching) with high core strength requirements, surface wear, cross-section below 30mm, or complex shapes and low load, such as: machine tool gearbox gears, gear shafts, cams, worm, piston pin, claw clutch, etc.;

After quenching and tempering, 40Cr steel is used to manufacture mechanical parts under medium load and medium speed, such as car steering knuckles, rear half shafts and gears, shafts, worms, spline shafts, top sleeves on machine tools, etc.

3. Different characteristics

Compared with 15Cr steel, 20Cr steel has higher strength and hardenability. The critical hardenable diameter in oil reaches 4-22mm, and the critical hardenable diameter in water reaches 11-40mm, but its toughness is poor. 20Cr steel has high cold strain plasticity and can be drawn in cold state. The machinability of 20Cr steel is good in high temperature normalizing or quenching and tempering state, but it is poor after annealing. 20Cr steel has good weldability and generally does not require heat treatment after welding, but parts with a thickness greater than 15mm need to be preheated to 100-150°C before welding, and tempering heat treatment is not required after welding.

40Cr steel is medium carbon quenched and tempered steel, cold heading die steel. The steel is moderately priced and easy to process. After proper heat treatment, a certain degree of toughness, plasticity and wear resistance can be obtained. Normalizing can promote the refinement of the structure, close to the equilibrium state, and can improve the cutting performance of the blank.

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