Analysis of the causes and preventive measures for wear of castings in mechanical processing.

Wear is a very common phenomenon in the process of machining, which may be caused by many factors such as workpiece materials, environment, processing methods and so on. Mechanical wear will adversely affect the machining quality, machining accuracy and processing efficiency of products. Therefore, it is very important to do a good job in preventing mechanical wear and tear for friends engaged in the industry of machining.

Common types and characteristics of mechanical wear:

The common wear types in machining include running-in wear, hard particle wear, surface fatigue wear, thermal wear, phase change wear and hydrodynamic wear.

Running-in wear is the wear of machinery under normal load, speed and lubrication conditions. This wear generally develops slowly, and has little effect on machining quality in a short time.

Hard particle wear is caused by the part itself dropping abrasive particles or from the outside into the machine tool hard particles, mixed into the processing area, by mechanical cutting or grinding, causing damage to the parts, which is a more serious impact on the quality of processing.

Surface fatigue wear is a kind of micro-cracks or pits caused by alternating loads, which cause damage to parts. This kind of wear is closely related to the size of pressure, load characteristics, machine material and size.

Hot wear is a phenomenon that the heat produced in the process of friction acts on the parts, making the parts soften by tempering, burn and wrinkle. This kind of wear usually occurs in high-speed and high-pressure sliding friction, wear is more destructive, and accompanied by the nature of accidental wear.

Corrosive wear is a chemical action, that is, chemical corrosion causes wear. When the surface of the part contacts with acid, alkali, saline liquid or harmful gas, it will be eroded by chemistry, or the surface of the part combines with oxygen to form hard and brittle metal oxides which are easy to fall off and cause wear of the part.

Phase change wear is a kind of wear that the parts work at high temperature for a long time. The metal grain on the surface of the parts becomes larger when heated, and the grain boundary is oxidized around, resulting in a small gap, which makes the parts fragile and wear-resistant.

Hydrodynamic wear is the wear on the surface of parts caused by the impact of liquid or particles mixed in the liquid at a faster speed.

Causes and preventive measures of parts wear:

Some wear belong to normal wear category, such as friction between parts, wear caused by hard particles, fatigue wear caused by long-term alternating load, corrosion of chemical substances to parts, and changes of metallographic structure or matching properties of parts surface under high temperature.

For the friction between parts, ensure that the parts have enough cleanliness and lubrication. For wear caused by hard particles, parts need to be exposed to ensure that parts are clean and covered. For the fatigue wear of parts caused by long-term alternating load, clearance can be eliminated and suitable lubricating grease can be selected to reduce the extra vibration of the system and improve the machining accuracy of parts. For the corrosion of chemical substances to parts, it is necessary to remove harmful chemical substances and improve the corrosion resistance of parts. For the change of metallographic structure on the surface of parts or the change of matching properties under high temperature, we should try to improve the working conditions, or adopt high temperature resistant and wear resistant materials to make parts.

Abnormal wear includes wear caused by failure of repair or manufacturing quality to meet design requirements, wear caused by violation of operating procedures and wear caused by improper transportation, loading and unloading, storage. To prevent this kind of wear and tear, we should strictly check the product quality, familiar with mechanical properties, careful operation, and master enough lifting knowledge, be careful in operation, to avoid improper operation.

If the machine is overhauled, the life of the machine may be shortened, which may be due to several reasons, such as deformation of the base parts, damage to the balance of the parts, failure to perform running-in and lower hardness of the parts.

Deformation of basic parts will change the relative position of each part, thus accelerating the wear of parts and shortening the life of parts. Reasonable installation and adjustment can be taken to prevent deformation. Balance failure of parts refers to the unbalanced high-speed rotating parts, accelerating the damage of parts under the action of centrifugal force, shortening the life of parts. Strict action should be taken to balance the test measures. The replacement parts do not perform the running-in of the mating surface will increase the wear amount, so the fitting must be run-in. The selected parts are not properly selected, the surface hardness is not up to the standard, or the heat treatment is not qualified. Materials should be selected according to the requirements and reasonable heat treatment should be carried out.