Selection of quenching medium for 45# steel roller chain: performance, application and comparison

Selection of quenching medium for 45# steel roller chain: performance, application and comparison
In the field of mechanical manufacturing, roller chain is a key transmission component, and its performance directly affects the operating efficiency and reliability of mechanical equipment. 45# steel roller chain is widely used due to its low cost and moderate mechanical properties, and the quenching process is crucial to improving its hardness, strength and wear resistance. The choice of quenching medium determines the quality of quenching effect. This article will explore in depth the quenching medium suitable for 45# steel roller chain to help international wholesale buyers and manufacturers optimize product performance and maximize commercial value.

1. Characteristics and quenching requirements of 45# steel roller chain
45# steel is a medium carbon steel with good comprehensive mechanical properties, such as high strength, hardness and toughness, as well as good processing technology, which makes it an ideal material for manufacturing roller chains. However, its hardenability is relatively low, especially in larger parts, and it is difficult to obtain a uniform martensitic structure during quenching. Therefore, in order to meet the requirements of roller chains in terms of high strength, wear resistance and fatigue life, it is necessary to select a suitable quenching medium to achieve rapid and uniform cooling and improve the depth of the hardened layer and overall performance of the parts.

2. Common quenching media and their characteristics
(I) Water
Water is the most common and lowest-cost quenching medium with a high cooling rate, especially in the high temperature zone. This enables it to provide rapid cooling for 45# steel roller chains, which helps to form martensitic structure, thereby improving hardness and strength. For example, after the final forging, the small modulus gear made of 45# steel is quickly clamped and transmitted to a water bath for quenching using a quenching machine. The hardness of the gear can reach above HRC45, and there is no quenching crack, and the performance is better than that of traditional processes. However, the cooling rate of water in the low temperature zone is too fast, which may cause large thermal stress and structural stress on the surface of the workpiece, increasing the risk of cracking, especially for roller chain parts with complex shapes or large sizes.
(II) Oil
The cooling rate of oil is slower than that of water, and the speed is more uniform throughout the cooling process. This makes oil a milder quenching medium, which can effectively reduce the tendency of quenching deformation and cracking. Mineral oil is one of the commonly used quenching oils, and its cooling capacity can be adjusted by adjusting the oil temperature, additives, etc. For some 45# steel roller chain parts with high precision requirements and complex shapes, such as chain plates, oil quenching can obtain better dimensional stability and mechanical properties. However, the cooling rate of oil is relatively slow, which may lead to poor hardening effect of some small-sized or thin-walled parts, and cannot meet the requirements of high hardness and high strength.
(III) Brine solution
The cooling rate of brine solution is between that of water and oil, and the cooling characteristics can be changed by adjusting the salt concentration and water temperature. Generally speaking, the cooling capacity of brine solution increases with the increase of salt concentration, but too high concentration may cause the solution to become more corrosive and cause damage to workpieces and equipment. For example, 10% salt water solution is a commonly used quenching medium. Its cooling speed is faster than pure water and its uniformity is better. It can alleviate the cracking problem during pure water quenching to a certain extent. At the same time, it has higher cooling efficiency than oil and is suitable for some medium-sized and simple-shaped 45# steel roller chain parts.
(IV) Calcium chloride aqueous solution
As an efficient quenching medium, calcium chloride aqueous solution performs well in the quenching of 45# steel roller chain. Its unique cooling characteristics can provide rapid cooling in the high temperature stage, and the cooling speed is appropriately slowed down in the low temperature stage, thereby effectively reducing the quenching stress and reducing the deformation and cracking tendency of the workpiece. Studies have shown that when quenching 45# steel rollers with 20℃ saturated calcium chloride aqueous solution, the hardness of the rollers can reach 56~60HRC, and the inner diameter deformation is very small, the hardening ability is strong, and the comprehensive performance and service life of the rollers can be significantly improved.

3. Effect of different quenching media on the performance of 45# steel roller chain
(I) Hardness and strength
Due to its rapid cooling characteristics, water quenching can usually make 45# steel roller chain obtain higher hardness and strength. However, if the cooling speed is too fast, it may cause greater residual stress inside the workpiece, affecting the dimensional stability and toughness of the workpiece. Although the hardness and strength of oil quenching are slightly lower than those of water quenching, it can ensure that the workpiece has better toughness and less deformation. Salt solution and calcium chloride aqueous solution can achieve a better balance between hardness, strength and toughness according to specific process requirements. For example, under the same conditions, the surface hardness of the 45# steel pin after quenching with saturated calcium chloride aqueous solution is significantly improved compared with the pin after quenching with 20# engine oil, and the tensile strength is also significantly improved.
(II) Wear resistance
The quenching medium also has an important influence on the wear resistance of the roller chain. High hardness and uniform structure are key factors to improve wear resistance. Using a medium with uniform cooling and good hardenability, such as calcium chloride aqueous solution, can make the 45# steel roller chain obtain higher hardness and good uniformity of organization, thereby enhancing its wear resistance. In practical applications, the service life of roller chains treated with appropriate quenching media can be significantly extended under the same working conditions.
(III) Fatigue life
Fatigue life is very important for roller chains. The residual stress distribution and organizational structure formed during the quenching process have a great influence on fatigue life. Water quenching may cause large residual stress to concentrate on the surface of the workpiece, reducing fatigue life. Oil quenching and brine quenching can form a more reasonable residual stress distribution, which helps to improve fatigue life. In addition, after quenching with calcium chloride aqueous solution, because it can effectively reduce the quenching stress, the workpiece can obtain a more uniform organization and residual stress distribution, which also has a positive effect on improving the fatigue life of the roller chain.

4. Factors to consider when selecting quenching media
(I) Workpiece size and shape
For small-sized or simple-shaped 45# steel roller chain parts, such as small rollers, water quenching can quickly cool and obtain good hardening effects due to their relatively large surface area to volume ratio. For large-sized or complex-shaped parts, such as large chain plates, oil quenching or brine quenching is more suitable to reduce deformation and cracking tendencies. Because the cooling rate of these media is relatively uniform, it can effectively avoid stress concentration problems caused by excessive cooling rates.
(II) Material composition and organizational state
The chemical composition and original organizational state of 45# steel have a significant effect on its quenching properties. For example, if the carbon content and alloying element content of the material change, it will affect its critical cooling rate and hardenability. For 45# steel with slightly poor hardenability, a quenching medium with a faster cooling rate, such as calcium chloride aqueous solution, can be selected to ensure that a sufficient hardened layer depth is obtained. At the same time, the original organizational state of the material, such as whether there is a banded structure, Widmanstatten structure, etc., will also affect the quenching effect and need to be adjusted according to the specific situation.
(III) Production batch and cost
In large-scale production, cost is an important consideration. Water as a quenching medium is low-cost and easy to obtain. It is an economical choice for small roller chain parts produced in large quantities. However, for the production of high-precision and complex parts, although the cost of oil quenching or brine quenching is relatively high, its comprehensive cost may be more advantageous in the long run because it can effectively reduce the scrap rate and improve product quality. In addition, the maintenance cost and service life of the quenching medium also need to be considered comprehensively.

5. Use and maintenance of quenching medium
(I) Precautions for use
When using water as a quenching medium, pay attention to factors such as water temperature, cleanliness and hardness. Too high water temperature will reduce the cooling rate and affect the quenching effect; impurities and too high hardness in the water may cause problems such as reduced surface quality of the workpiece and scaling of the equipment. For oil quenching, the oil temperature, oil quality and stirring conditions must be strictly controlled. Excessive oil temperature will slow down the cooling speed and even cause a fire; and the deterioration of oil will affect the quenching performance, and it needs to be replaced and filtered regularly. The use of brine solution and calcium chloride solution requires attention to the concentration, temperature and anti-corrosion measures of the solution to ensure the stability of its cooling performance and the safe operation of the equipment.
(II) Maintenance points
Regular testing of various parameters of the quenching medium, such as water hardness, oil viscosity and flash point, and the concentration of brine solution and calcium chloride solution, is the key to ensuring the quality of quenching. At the same time, the quenching tank should be kept clean and the sediment and impurities should be cleaned in time. For oil quenching, fire prevention measures should also be taken and corresponding fire-fighting equipment should be equipped. In addition, the use of appropriate cooling and circulation systems can extend the service life of the quenching medium and improve its cooling efficiency and stability.

6. Conclusion
In summary, the selection of a suitable quenching medium plays a vital role in the performance improvement and quality control of 45# steel roller chain. Water, oil, brine solution and calcium chloride solution have their own characteristics. In practical applications, the size, shape, material composition, production batch and cost of the workpiece should be considered comprehensively to achieve the best quenching effect. International wholesale buyers and manufacturers should have a deep understanding of the characteristics and applicable scope of different quenching media, strengthen cooperation with heat treatment suppliers, optimize the quenching process, thereby improving the market competitiveness of 45# steel roller chain and meeting the global market demand for high-quality transmission components.