In modern production, molds are important process equipment for the production of various industrial products. The development of social economy, especially the rapid development of aerospace, automotive, electronic information, and home appliance industries, has made people have higher and higher requirements for the reliability, life and performance of molds, because molds directly determine the quality and cost of related products. And service life.
According to the National Bureau of Statistics, the market size of my country's mold industry in 2018 reached 275.3 billion yuan, and the demand for automotive-related molds accounted for about 1/3 of the total mold demand. For the automobile industry, which takes light weight, energy saving, and environmental protection as its development strategy, fuel consumption can be reduced by 6% to 8% and emissions can be reduced by 4% for every 10% reduction in vehicle weight. Therefore, reducing the quality of vehicles is one of the basic ways to save energy and environmental protection. The application of high-strength steel and aluminum alloy can greatly reduce the weight of the vehicle, but it also puts forward higher requirements for the forming of automobile molds. Therefore, how to improve the quality, service life and reduce production costs of molds has become an urgent problem to be solved.
During the working process, the mold is under a certain force and heat, and the mold blank flows and slides along the surface of the cavity when plastic deformation in the mold cavity, so that the surface of the cavity and the blank generate violent friction with time, and the cyclic stress Long-term action often leads to fatigue fracture of the mold, so the performance requirements of the mold material are mainly reflected in the wear resistance, strength and toughness, fatigue fracture performance, high temperature performance, and cold and heat fatigue resistance. Although a variety of new mold materials have been developed and the heat treatment process of the original mold steel has been improved and optimized, it still cannot meet the requirements of high performance and low cost of the mold. And through surface treatment technology can often get twice the result with half the effort.
Mold surface treatment mainly refers to the use of surface technology to modify or coat the surface of the mold. There are dozens of surface treatment techniques currently in use, which can be mainly summarized as physical surface treatment, chemical surface treatment and surface coating treatment.
The physical surface treatment methods mainly include high frequency quenching, flame surface quenching, laser surface quenching, shot peening, etc. The process method has the advantages of simple equipment and low cost, but the productivity is low, the mold surface has different degrees of overheating, and quality control is difficult , Mainly suitable for single-piece, small batch and mold surface treatment with low quality requirements.
Chemical surface treatment methods can be divided into carburizing, nitriding, carbonitriding, boronizing, and aluminizing. Compared with carburizing, the temperature of nitriding is lower (500-600℃), the deformation of the mold after nitriding is small, the surface wear resistance, fatigue resistance, heat resistance, corrosion resistance, hardness and seizure resistance after nitriding treatment The performance is better than that after carburizing, but the carburizing process is complex, time-consuming, and costly. It is generally used for molds that require high wear resistance and precision or heat resistance. However, salt bath boronizing and solid boronizing are widely used at home and abroad. Japan has developed the TD method of liquid boronizing mainly based on borax molten salt and other elements, which can increase the service life of molds by 4-20 times. The amount of deformation has a great influence, the number of repeated treatments is low, and the mold is damaged.
