In modern mechanical manufacturing, improving the surface hardness of parts is of great significance for enhancing their wear resistance, fatigue strength, and service life. Rolling process, as a commonly used surface hardening technology, is widely applied in the processing of various metal parts due to its simple process, high efficiency, and remarkable effects. This article will discuss the principles, mechanism of action, and its impact on surface hardness enhancement of rolling process.



1. Basic Principles of Rolling Process



Rolling process is a cold working process that applies pressure to the workpiece surface at room temperature through tools with high hardness rollers or balls, causing the workpiece to undergo plastic deformation. This process is usually used for the processing of shafts, holes, or flat parts. During the rolling process, the roller contacts the workpiece surface and produces high pressure, causing plastic flow of the material surface, thereby improving surface quality and mechanical properties.



2. Mechanism of Rolling on Surface Hardness Enhancement



1. Plastic Deformation and Hardening of Surface Material

Under the action of rolling pressure, the surface metal of the workpiece undergoes plastic deformation, the grains are elongated and refined, and the dislocation density is significantly increased, thereby causing the hardening phenomenon. This change in microstructure significantly improves the surface hardness of the material.



2. Introduction of Residual Compressive Stress

Rolling process not only improves surface hardness but also introduces residual compressive stress in the material surface. This compressive stress can offset part of the tensile stress caused by external loads, effectively improving the fatigue life and crack resistance of parts.



3. Improvement of Surface Smoothness

The rolling process can also reduce surface roughness, reduce stress concentration points, and indirectly improve the wear resistance and corrosion resistance of parts.



3. Factors Affecting Surface Hardness After Rolling



1. Original Material Properties

The material type and its initial hardness have a direct impact on the strengthening effect after rolling. Generally, metals with good plasticity (such as carbon steel, alloy steel) are more likely to achieve higher surface hardness through rolling.



2. Rolling Pressure and Rolling Times

The greater the rolling pressure, the more severe the surface plastic deformation, the better the hardness enhancement effect, but excessive pressure may cause cracking or other defects on the material surface. Increasing the number of rolling also helps to further improve the hardness, but there is a saturation effect.



3. Roller Geometric Parameters

The diameter, shape, and surface roughness of the roller will also affect the rolling effect. Reasonable selection of roller parameters can optimize the processing effect and improve surface quality.



4. Application Examples and Advantages



Rolling process is widely used in automotive, aerospace, heavy machinery and other fields. For example, key parts such as engine crankshafts, connecting rods, and hydraulic cylinder inner walls often adopt rolling strengthening process to extend service life and improve reliability. Compared with traditional heat treatment methods, rolling process does not require heating, saves energy and is environmentally friendly, and is suitable for complex structures that are difficult to heat treat.



Conclusion



In summary, rolling process induces surface hardening and introduces residual compressive stress by plastic deformation, thereby effectively improving the surface hardness and comprehensive mechanical properties of parts. As an efficient and environmentally friendly surface hardening technology, rolling process plays an increasingly important role in modern manufacturing industry and has a broad application prospect and development space. With the progress of materials science and manufacturing technology, rolling technology will also continue to be optimized and upgraded, providing stronger support for the manufacture of high-performance parts.