KCB stainless steel gear pump cold working and heat treatmen

Here are some technical requirements for cold processing and heat treatment of oil pumps:

Main technical requirements for cold working

1. Because the shaft depends on the friction force of the two cones to transfer the torque, in order to ensure that the gear pump gear has enough contact area to transfer the torque, the process requires that after grinding, the joint area of the two cones should not be less than 800

2. There is a semicircular keyway on the cone at both ends of the shaft. Stress concentration is easy to occur at the keyway gap.

3. Smooth transition is required at the junction of cone and cylinder.

Technical requirements for heat treatment

material

According to the service condition of the front gear shaft, the force of the CAM part and the cone part of the shaft are different, so the hardness requirements of the stainless steel gear pump are different after heat treatment.

Cam parts require very high wear resistance, so the part requires very high hardness, and in the cone parts are subjected to the action of cyclic torque and bending moment, so the part requires a good combination of strength and toughness, so the requirements of middle hardness.

In order to meet the requirements of a variety of different parts of the same parts hardness, in mechanical design, often choose low carbon steel by surface treatment to meet the requirements, the camshaft is so material to 20 cr steel, the chemical composition of concrete meet the camshaft GB3077-880 with 20 cr steel can well satisfy the manufacturability, heat treatment, heat treatment after cold working technology to achieve the performance requirements.

This is because 20Cr steel is on the basis of 20 steel, in order to improve the performance of the heat preservation gear pump, add 0. 7-1. 00} Cr and become.

The 20Cr steel has excellent process performance, good machinability after forging normalizing, and the hardness after underfiring is (156-207) HB.

Good cutting performance, high surface finish.

Due to the addition of chromium, improve the hardenability of steel, and chromium is an element to strengthen ferrite, dissolve in ferrite can also play a strengthening role, so improve the core strength of camshaft carburizing.

Due to the improvement of hardenability, in the quenching can be used a moderate coolant cooling (the cooling medium is nitrate), which can also reduce the quenching deformation of the gear shaft.

The affinity between chromium and carbon is larger, and can promote the surface of the carburizing layer carbon content tends to saturation, increase the carbon concentration gradient, so that the carburizing speed increases, so that the gear shaft in the carburizing and quenching has a higher hardness and better wear resistance.

It is because of the greater affinity of carbon and chromium, the steel in the carburizing layer is easy to form a network of carbides on the surface of the gear shaft, so carburizing should be strictly controlled when the atmosphere of the carbon potential in the carburizing furnace.

Although 20Cr steel is essentially fine grain steel, but in the carburizing temperature of long-term heating carburizing, the grain will significantly grow up, so the gear shaft carburizing can not be directly quenched.

In order to overcome the defects brought by carburizing, refine the grain size, further improve the strength and toughness of the core, to prepare the organization for the subsequent heat treatment, so after carburizing to normalize.

Then it is reheated and quenched.

The whole heat treatment process of the gear shaft is the first carburizing, carburizing after normalizing, normalizing and then quenching and tempering, and then high-frequency annealing of the shaft cone.

The purpose of carburizing is to increase the carbon content of the surface of the shaft, so that the gear shaft after the subsequent quenching treatment to obtain a high surface hardness and wear resistance, to meet the technical requirements of the surface of the gear.

The original low carbon content of 20Cr steel is still maintained in the core of the shaft, which makes the core of the gear shaft still have high toughness after quenching.

Carburizing after adding a normalizing process is to eliminate the formation of carburizing network carbide and other organizational defects, grain refinement, further improve the strength and toughness of the core, for quenching as a storage organization.

The purpose of shaft quenching is to improve the surface hardness, strength, wear resistance, to obtain a suitable structure.

Axis after quenching, although has the very high hardness, but also brings a lot of quenching stress, gear shaft surface quenching after the formation of the high carbon acicular martensite also has the very high brittleness, therefore cannot be used directly, so you must eliminate the quenching stress by tempering, appropriate to reduce the intensity, reduce the brittleness, improve the toughness, and can also improve the dimensional stability,

In this way, the surface of the gear can obtain high hardness and high wear resistance after carburizing and quenching to meet the technical requirements of the gear parts.

And the cone part in the high frequency annealing can be carburized after quenching the high hardness down to meet the requirements of medium hardness.

The process parameters of each process of heat treatment are shown in the figure.

The hardness of the residual component reflects the anti-invasion ability of the metal, which not only has an approximate empirical relationship with the static strength and fatigue strength of the material, but also has some relations with the process properties such as cold formability and machinability. Therefore, the hardness has a certain reference significance for the control of the cold and hot processing quality of the KCB gear oil pump material.

In the process of heat treatment production, hardness is often taken as one of the indicators to test the quality of heat treatment. At the same time, hardness detection also has the characteristics of rapid, intuitive and accurate, so the shaft can also be tested by hardness method to test the quality of heat treatment.

According to the working principle of the shaft, the gear of the shaft constantly pushes the roller kernel to rise alternately when it is working, so the surface of the gear is constantly affected by the cyclic contact stress of the roller when it is working.

This article is brought to you by Botou Pumps http://www.youbeng1.com.