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45th steel surface induction hardening

No. 45 steel is a kind of steel. According to the carbon content, steel can be divided into three types, namely low carbon steel, medium carbon steel and high carbon steel. No. 45 steel belongs to medium carbon steel and has good mechanical properties. It is widely used in automobiles, machinery and other industries. Below, Haituo Electromechanical will introduce the hardness of the 45th steel surface after induction hardening.

First, 45 steel introduction

45 steel is called the name in GB, also called "oil steel." Most of the market spot hot rolling; cold rolling specifications between 1.0 ~ 4.0mm (mm). The cold plasticity of the steel is generally good, and the annealing and normalizing are slightly better than the quenching and tempering, and have high strength and good machinability. Commonly used medium carbon quenched and tempered structural steel. The cold plasticity of the steel is generally good. The annealing and normalizing are slightly better than the quenching and tempering. It has high strength and good machinability. After proper heat treatment, certain toughness, plasticity and wear resistance can be obtained. Convenience. Suitable for hydrogen welding and argon arc welding, not suitable for gas welding. Preheating is required before welding, and stress relief annealing should be performed after welding.

Normalizing improves the cutting performance of blanks less than 160 HBS. After the steel is quenched and tempered, its comprehensive mechanical properties should be optimized for other medium carbon structural steels, but the steel has low hardenability, and the critical hardenability diameter in water is 12~17mm, and there is a tendency to crack when water quenching. When the diameter is more than 80mm, the mechanical properties are similar after quenching or tempering, and the medium and small mold parts can be quenched and tempered to obtain higher strength and toughness, while the large parts are treated with normalizing. Therefore, this steel is usually used in quenched or tempered condition.

Second, the introduction of high frequency quenching

The influence of the size of the high-frequency quenching is relatively small, and the products after heat treatment generally have deformation. The control of the deformation is generally not found. After a large number of experiments, the law can be found, but it is not determined.

High-frequency quenching is mostly used for surface quenching of industrial metal parts. It is a metal heat treatment method that produces a certain induced current on the surface of the workpiece, rapidly heats the surface of the part, and then rapidly quenches. Induction heating equipment, that is, equipment that inductively heats a workpiece for surface hardening. The principle of induction heating: the workpiece is placed in the inductor. The inductor is usually a hollow copper tube with input intermediate frequency or high frequency alternating current (1000-300000Hz or higher). The alternating magnetic field generates an induced current of the same frequency in the workpiece. The induced current is uneven in the distribution of the workpiece, strong on the surface, and weak inside, to the core close to 0, using this skin effect The surface of the workpiece can be heated rapidly, and the surface temperature rises to 800-1000 ° C in a few seconds, while the temperature rise of the core is small.

3. Hardness of 45# steel itself and hardness after quenching

1. After the steel has been tempered after quenching, the hardness is greater than HRC55 (up to HRC62). The highest hardness for practical application is HRC55 (high frequency quenching HRC58).

2, No. 5 steel should not use the heat treatment process of carburizing and quenching. The hardness of the 45th steel tempering part after quenching should reach HRC56~59, the possibility of large cross section is lower, but it can't be lower than HRC48. Otherwise, the workpiece is not completely quenched, and Sorbite or even ferritic may appear in the structure. Body organization, this kind of organization still retains in the matrix through tempering, and does not achieve the purpose of quenching and tempering.

The high temperature tempering of No. 45 steel after quenching, the heating temperature is usually 560~600 °C, and the hardness requirement is HRC22~34. Because the purpose of quenching and tempering is to obtain comprehensive mechanical properties, the hardness range is relatively wide. However, if the drawings have hardness requirements, the tempering temperature should be adjusted according to the drawings to ensure the hardness. For example, some shaft parts require high strength and high hardness requirements. Some gears and shaft parts with keyways are milled and inserted after quenching and tempering, and the hardness requirements are lower. Regarding the tempering holding time, depending on the hardness requirements and the size of the workpiece, we believe that the hardness after tempering depends on the tempering temperature, and has little to do with the tempering time, but it must be reciprocated, and the general workpiece tempering time is always More than an hour.


The above-mentioned Haituo electromechanical details the hardness of the 45th steel surface after high-frequency quenching. The high-frequency quenching of 45 steel must pay attention to the process. Whether it is tempered after quenching will also affect the hardness of the steel.
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