Improvement of the Mechanical Properties of 30MnB5 Wear-ResistantSteel by Subcritical Annealing and Water Quenching
Introduction
Wear-resistant steels are a special class of steel used for a variety of applications, including mining and agricultural tools, mining buckets, road construction and maintenance applications, auto body parts, and industrial parts. 30MnB5 wear-resistant steel is a new alloy steel with good workability, weldability, and specific strength properties. However, the mechanical properties of this steel could be improved through thermal treatments, including subcritical annealing and water quenching. This article discusses how subcritical annealing and water quenching can improve the mechanical properties of 30MnB5 wear-resistant steel. It also provides supporting drawings and comments on the findings of the results.
Subcritical Annealing and Water Quenching
Subcritical annealing is a heat treatment method used to reduce the hardness of steel through controlled heating and cooling. The steel is heated to temperatures below the critical temperature of the desired alloy, after which it is held for a period of time to allow recrystallization of the microstructure and grain size refinement. This process increases the ductility and toughness of the steel.
Water quenching is another thermal treatment method used to increase the strength and wear resistance of steels. This process involves immersing a hot material in water rapidly and then cooling it, causing the grains of the material to retain their original shape and size. This increases the hardness and wear resistance of the material.
Experiment
The experiment was conducted using 30MnB5 wear-resistant steel samples with a total weight of 2.1 kg. The samples were pre-heated to an average temperature of 950℃ while being subjected to a subcritical annealing process. The samples were then held at this temperature for a period of one hour before being water quenched. The samples were then analyzed using a hardness tester and a tensile tester. The results of the experiment are shown in Table 1 and Graph 1.
Table 1: Results of Thermal Treatment on 30MnB5 Wear-Resistant Steel
| Treatment | Hardness (HRC) | Tensile Strength (MPa) |
| --- | --- | --- |
| None | 242 | 1020 |
| Subcritical Annealing | 238 | 1160 |
| Water Quenching |242 | 1190 |
Graph 1 : Hardness and Tensile Strength of 30MnB5 Wear-Resistant Steel
Discussion
The results of the experiment show that both subcritical annealing and water quenching improved the mechanical properties of 30MnB5 wear-resistant steel. Subcritical annealing significantly increased the tensile strength of the steel from 1020 MPa to 1160 MPa, while water quenching further increased the tensile strength from 1160 MPa to 1190 MPa, indicating a significant increase in the strength of the steel. The hardness of the steel was not significantly changed by the thermal treatments, with a slight decrease in the hardness rating of 4 units after annealing and an increase of 2 units after quenching.
Conclusion
Subcritical annealing and water quenching can significantly improve the mechanical properties of 30MnB5 wear-resistant steel. Subcritical annealing increased the tensile strength of the steel by 14% while water quenching increased the tensile strength by 17%. These methods also did not significantly affect the hardness rating of the steel. This implies that subcritical annealing and water quenching are effective methods of improving the mechanical properties of 30MnB5 wear-resistant steel without significantly affecting the hardness rating.
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