As a long shear blade used in the shearing process, after the cutting edge comes into contact with the steel plate during service, it will bear the effects of friction, extrusion and shearing force between the steel plate and the steel plate. The cutting edge should be kept sharp during the working process. It is required to have high hardness and good wear resistance after heat treatment, with small deformation. The surface after grinding should be free of oxidation and decarburization. Many manufacturers use medium frequency induction heating machines to complete the heat treatment process, and the results are very good and meet their working requirements. Next, let’s take a look at the medium-frequency heat treatment process of long shear blades.
1. Heat treatment process. The hardness of the cutting edge after heat treatment is 58-62HRC, the hardness of the middle part is 40-45HRC, the deformation of the cutting edge is less than 0.25mm, and there is no serious oxidation and decarburization on the surface.
The long scissors are made of low alloy tool steel CrWMn and 9SiCr steel. Considering its length and shape, a medium frequency induction heating machine is used for preheating and quenching heating. Due to its long size, there are major problems in the heating and cooling process. It's deformation. CrWMn and 9SiCr steel have good hardenability, and the required hardness can be obtained by oil-cooling quenching. It should be noted that the use of overall quenching will bring extraordinary difficulties to the final straightening, and the deformation of the long scissors will be distorted.
Considering that the cutting edge requires high hardness and good wear resistance to meet the needs of its service conditions, a low-temperature tempering of (160-200)℃×(3-4)h should be performed after quenching using a medium-frequency induction heating machine. Fire treatment. The deformation after quenching is generally within 1.5mm, which can be straightened during the tempering process by using a clamp. Place the deformed concave surfaces opposite each other, add washers to both ends and tighten the bolts until the deformation is slightly in the opposite direction. At this time, put it into the tempering furnace. Medium heating, the deformation after loosening is within 0.2mm. The cutting edge hardness is 58-62HRC, and the middle part is 40-45HRC.
2. Key points of heat treatment process analysis and implementation
a. According to the working conditions and technical requirements of the cutting edge, the required hardness can be obtained by partially quenching the cutting edge. The hole in the middle does not require high hardness. The middle part of the blade must be covered with refractory soil mixed with water glass. , which can effectively avoid serious deformation caused by overall quenching, and also facilitates alignment and reduces the workload after heat treatment.
b. Filling or blocking the middle of the blade with refractory soil can help the mass effect caused by the irregular shape, which is equivalent to increasing the thickness of the middle part, so the hardness after quenching is lower than the edge part. This measure is relatively effective. In addition, long scissors are subject to shear force and impact force during use, so they should have sufficient toughness. The hardness of the middle part is 40-5OHRC to ensure that it has the required toughness and strength.
The quality of the heat treatment process directly affects the heat treatment quality of the workpiece. Therefore, it is very important to master the heat treatment process of the workpiece. This article briefly introduces the medium-frequency heat treatment process of long shear blades. After many manufacturers adopt the above process, the large shear blades produced are of good quality and meet their working requirements.
en 
cn 
jp 
ko 
de 
es 
it 
ru 
pt 
vi 
th 
pl 
GS-ZP-1200
