The influence of polymer quenching liquid on roller chain performance

The influence of polymer quenching liquid on roller chain performance
In the industrial field, roller chain is an important transmission component, and its performance is directly related to the operating efficiency and stability of mechanical equipment. As the key link to improve the performance of roller chain, the selection and use of quenching liquid in heat treatment process plays an important role. As a common quenching medium, polymer quenching liquid is gradually being widely used in the heat treatment of roller chain. This article will explore in depth how polymer quenching liquid affects the performance of roller chain.

1. Materials and basic performance requirements of roller chain
Roller chain is usually made of carbon steel, alloy steel and other materials. After processing and forming, these materials need to be heat treated to improve their hardness, wear resistance, fatigue resistance and other properties to meet the use requirements under different working conditions. For example, in high-speed and heavy-load transmission systems, roller chains need to have higher hardness and strength to withstand huge tension and impact forces; in some equipment that starts and stops frequently, good fatigue resistance can ensure the service life of roller chains.

2. Overview of polymer quenching liquid
Polymer quenching liquid is made of a specific polyether non-ionic high molecular polymer (PAG) plus a composite additive that can obtain other auxiliary properties and an appropriate amount of water. Compared with traditional quenching oil and water, polymer quenching liquid has many advantages such as adjustable cooling speed, environmental protection, and low cost of use. Its cooling characteristics are between water and oil, and it can effectively control the cooling speed during the quenching process of the workpiece, reducing the deformation and cracking tendency of the workpiece.

3. The effect of polymer quenching liquid on the performance of roller chain
(I) Hardness and strength
When the roller chain is quenched in the polymer quenching liquid, the polymer in the quenching liquid dissolves at high temperature and forms a water-rich coating on the surface of the roller chain. This coating can adjust the cooling rate of the roller chain so that its cooling rate in the martensitic transformation range is moderate, thereby obtaining a uniform and ideal martensitic structure. Compared with water quenching, polymer quenching liquid can reduce the quenching cooling rate, reduce quenching stress, and avoid quenching cracks caused by excessive cooling speed of the roller chain; compared with oil quenching, its cooling rate is relatively fast, and it can obtain higher hardness and strength. For example, the hardness of the roller chain quenched with a suitable concentration of polymer quenching liquid can reach the range of HRC30-HRC40. Compared with the roller chain that has not been quenched or uses other quenching media, the hardness and strength are significantly improved, thereby improving the bearing capacity and wear resistance of the roller chain.
(II) Wear resistance
Good wear resistance is an important guarantee for the normal operation of the roller chain. The polymer film formed by the polymer quenching liquid on the surface of the roller chain can not only adjust the cooling rate, but also reduce the oxidation and decarburization of the roller chain during the quenching process to a certain extent, and maintain the metal activity and integrity of the roller chain surface. In the subsequent use process, the surface hardness of the roller chain quenched with the polymer quenching liquid is higher, which can effectively resist the friction and wear between the roller and the chain plate, pin shaft and other components, and extend the service life of the roller chain. At the same time, the uniform quenching microstructure distribution also helps to improve the overall wear resistance of the roller chain, so that it can still maintain good transmission accuracy and efficiency during long-term operation.
(III) Fatigue resistance
Under actual working conditions, roller chains are often subjected to repeated bending stress and tensile stress, which requires roller chains to have excellent fatigue resistance. Polymer quenching liquid can reduce the residual stress inside the roller chain by controlling the stress distribution during the quenching cooling process, thereby improving the fatigue strength of the roller chain. The existence of residual stress will affect the fatigue crack initiation and expansion behavior of the roller chain under cyclic load, and the reasonable use of polymer quenching liquid can optimize the residual stress state of the roller chain, so that it can withstand more cycles without fatigue damage when subjected to alternating stress. Experimental studies have shown that the fracture life of roller chains treated with polymer quenching liquid in fatigue tests can be extended several times or even dozens of times compared with untreated roller chains, which is of great significance for improving the reliability of mechanical equipment and reducing maintenance costs.
(IV) Dimensional stability
During the quenching process, the dimensional accuracy of the roller chain will be affected by many factors such as cooling rate and quenching stress. Since the cooling rate of polymer quenching liquid is relatively uniform and adjustable, it can effectively reduce the thermal stress and structural stress of roller chain during quenching, thereby improving the dimensional stability of roller chain. Compared with water quenching, polymer quenching liquid can reduce the quenching deformation of roller chain and reduce the subsequent mechanical processing correction work; compared with oil quenching, its cooling rate is faster, which can improve the hardness and strength of roller chain under the premise of ensuring dimensional stability. This enables the roller chain to better meet the design size requirements after quenching with polymer quenching liquid, improve assembly accuracy and transmission accuracy, and ensure the normal operation of mechanical equipment.

4. Factors affecting the performance of polymer quenching liquid on roller chain
(I) Quenching liquid concentration
The concentration of polymer quenching liquid is one of the key factors affecting its cooling performance and roller chain quenching effect. Generally speaking, the higher the concentration of quenching liquid, the more polymer content, the thicker the coating formed, and the slower the cooling rate. Roller chains of different materials and specifications need to choose the appropriate quenching liquid concentration to achieve the best quenching performance. For example, for some small light-loaded roller chains, a lower concentration of polymer quenching liquid, such as 3%-8%, can be used; while for large heavy-loaded roller chains, the concentration of the quenching liquid needs to be appropriately increased to 10%-20% or even higher to meet its requirements for hardness and strength. In actual production, the concentration of the quenching liquid must be strictly controlled, and regular inspections and adjustments must be carried out to ensure the stability of the quenching quality.
(II) Quenching temperature
The quenching temperature also has an important influence on the performance of the roller chain. A higher quenching temperature can make the austenite grains inside the roller chain grow, but it is also easy to cause the hardness and toughness after quenching to decrease, increasing the risk of quenching cracks; if the quenching temperature is too low, sufficient hardness and martensitic structure may not be obtained, affecting the performance improvement of the roller chain. For different steel and roller chain specifications, it is necessary to determine the appropriate quenching temperature range according to their material properties and process requirements. Generally speaking, the quenching temperature of carbon steel roller chain is between 800℃-900℃, while the quenching temperature of alloy steel roller chain is slightly higher, usually between 850℃-950℃. In the quenching operation, the uniformity and accuracy of the heating temperature should be strictly controlled to avoid differences in roller chain performance due to temperature fluctuations.
(III) Circulation and stirring of cooling medium
During the quenching process, the circulation and stirring of the cooling medium have a significant effect on the heat exchange efficiency between the polymer quenching liquid and the roller chain. Good circulation and stirring can make the quenching liquid fully contact with the surface of the roller chain, accelerate the transfer of heat, and improve the uniformity of the quenching speed. If the flow of the cooling medium is not smooth, the temperature of the quenching liquid in the local area rises too fast, which will cause inconsistent cooling speeds in various parts of the roller chain, causing excessive quenching stress and deformation. Therefore, when designing and using the quenching tank, a suitable circulation stirring system should be equipped to ensure that the flow state of the quenching liquid is good and create favorable conditions for the uniform quenching of the roller chain.
(IV) Surface state of roller chain
The surface state of roller chain will also have a certain impact on the cooling effect and final performance of polymer quenching liquid. For example, if there are impurities such as oil, iron filings, scale, etc. on the surface of roller chain, it will affect the formation and adhesion of polymer film, reduce the cooling performance of quenching liquid, and lead to uneven quenching hardness or quenching cracks. Therefore, before quenching, the surface of roller chain must be strictly cleaned to ensure that its surface is clean and free of defects such as oil and scale, so as to ensure that polymer quenching liquid can fully play its role and improve the quenching quality of roller chain.
(V) Use of additives
In order to further improve the performance of polymer quenching liquid and improve the quenching effect of roller chain, some special additives are sometimes added to the quenching liquid. For example, adding rust inhibitor can prevent roller chain from rusting after quenching and extend its service life; adding defoaming agent can reduce the foam generated during quenching and improve the performance and safety of quenching liquid; adding surfactant can improve the wettability and adhesion of polymer quenching liquid, enhance its contact effect with the surface of roller chain, and improve cooling efficiency. When selecting and using additives, they should be reasonably matched according to the specific quenching process and roller chain performance requirements, and the amount of additives should be strictly controlled to avoid adverse effects on the performance of the quenching liquid.

5. Maintenance and management of polymer quenching liquid
In order to ensure the long-term stability and performance of the polymer quenching liquid during the heat treatment of the roller chain, it is necessary to effectively maintain and manage it.
Regular concentration detection: Use professional instruments such as refractometers to regularly detect the concentration of the quenching liquid, and adjust it in time according to the test results. It is generally recommended to test the concentration once a week. If the concentration is found to exceed the process requirements, it should be diluted or new polymer stock solution should be added in time.
Control impurity content: Regularly clean the impurities and floating oil at the bottom of the quenching tank to prevent excessive impurities from affecting the cooling performance and service life of the quenching liquid. A filtration system can be installed to circulate and filter the quenching liquid to remove solid impurities such as iron filings and oxide scale.
Prevent bacterial growth: Polymer quenching liquid is prone to breed bacteria during use, causing it to deteriorate and deteriorate in performance. Therefore, it is necessary to add bactericides regularly and keep the quenching liquid clean and well ventilated to avoid bacterial growth. Generally, bactericides are added every two weeks, and attention is paid to controlling the temperature and pH value of the quenching liquid to keep it within an appropriate range.
Pay attention to the cooling system: Regularly check and maintain the cooling system of the quenching tank to ensure that the temperature of the quenching liquid can be effectively controlled. Cooling system failure may cause the quenching liquid temperature to be too high or too low, affecting its cooling performance and the quenching quality of the roller chain. Regularly check whether the cooling pipe is blocked, whether the cooling water pump is working properly, etc., and carry out repairs and maintenance in time.

6. Conclusion
Polymer quenching liquid plays a vital role in the heat treatment process of roller chains. It significantly improves the comprehensive properties of roller chains such as hardness, strength, wear resistance, fatigue resistance and dimensional stability by adjusting the quenching cooling rate and optimizing the internal organizational structure. However, in order to give full play to the advantages of polymer quenching liquid and obtain ideal roller chain performance, it is necessary to comprehensively consider multiple factors such as quenching liquid concentration, quenching temperature, circulation and stirring of cooling medium, surface condition of roller chain and use of additives, and strictly maintain and manage the quenching liquid. Only in this way can we ensure that roller chains can operate stably and reliably in various mechanical equipment and meet the high performance requirements of modern industrial production for transmission components.