Composition design and heat treatment process research of ZG28CrMn2VB steel
1. Composition Design
ZG28CrMn2VB steel is a typical bearing steel, which is widely known for its high-medium carbon, chromium-molybdenum vanadium steel, and its composition has strict requirements. The main chemical components of ZG28CrMn2VB steel are shown below.
Table 1: Chemical properties of ZG28CrMn2VB steel
| Element | Component Rate(%) |
|--------|-------------------|
| C | 0.26-0.32 |
| Si | ≤0.40 |
| Mn | 1.50-1.90 |
| Cr | 1.60-2.00 |
| Mo | 0.25-0.45 |
| V | 0.15-0.25 |
In addition, the alloy elements of ZG28CrMn2VB steel can promote the transformation of pearlite structure, increase the strength and wear resistance of steel, and reduce the brittle transition temperature. In order to obtain a better performance, ZG28CrMn2VB steel usually contain 0.15-0.25% Ti, 0.20-0.45% Ni, 0.005-0.015% Nb and other elements.
2. Heat Treatment Process
In order to obtain excellent mechanical properties and good surface quality of ZG28CrMn2VB steel, a heat treatment process must be performed. The heat treatment process usually includes four steps: Annealing, Quenching, Tempering and Inertia Cutting.
(1) Annealing
Annealing is carried out at 790-830 ℃ and the cooling speed is less than 5 ℃ /h to obtain a uniform structure, which can reduce the hardness, improve the toughness and elongation of the steel, or even eliminate the internal stress of the steel.
(2) Quenching
After quenching and tempering, the hardness and plasticity of ZG28CrMn2VB steel can be further improved. The quenching temperature is usually 850-920 ℃, and the cooling rate is relatively high, usually more than 5 ℃ /h.
(3) Tempering
After quenching, the hardness of ZG28CrMn2VB steel is too high and the plasticity is reduced. In order to reduce the hardness and improve the comprehensive mechanical properties and comprehensive performance of the steel, tempering is required. The tempering temperature of ZG28CrMn2VB steel is 550-690 ℃ and the holding time is 1-2h.
(4) Inertia Cutting
Inertia cutting is used to eliminate the easy cutting of ZG28CrMn2VB steel due to cooling too fast during quenching. The inertia cutting is usually carried out at 450-550F or 260-345 ℃, and the holding time is 1h.
Based on the above introduction, the composition design and heat treatment process of ZG28CrMn2VB steel have been discussed. The composition design is complex and strict, and the heat treatment process is also more stringent. It is a high-medium carbon, chromium-molybdenum vanadium steel, which is used to make high-load and high-speed working bearings, with high strength and strong wear resistance. In order to obtain the best performance of ZG28CrMn2VB steel, it should be strictly controlled during the process of composition design and heat treatment.
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