Frequent surface cracks on aluminum extrusion molds, optimization of heat treatment process becomes key

　　In the aluminum profile processing industry, aluminum extrusion molds are the core tools, and their performance directly affects production efficiency and product quality. However, the frequent occurrence of surface cracks on aluminum extrusion molds in recent times is seriously troubling many enterprises. These cracks not only shorten the service life of the mold and increase production costs, but also have a negative impact on product quality, posing severe challenges to the development of the industry. In this context, optimizing the heat treatment process has become the key to solving this problem.

　　Aluminum extrusion molds need to withstand high temperatures, high pressures, and prolonged high friction during operation, and the working conditions are extremely harsh. Once cracks appear on the surface of the mold, they will gradually propagate during the subsequent extrusion process, causing damage to the mold and affecting the continuity of production. According to relevant data statistics, due to surface cracks in molds, enterprises spend tens of millions of yuan annually on mold replacement and maintenance, while also causing significant production delays.

　　The reasons for surface cracks in aluminum extrusion molds are multifaceted. From the perspective of the material itself, some mold steels have excessively high carbon content, such as Cr12MoV mold steel, which has a carbon content of up to 1.5%, making the mold steel brittle and prone to cracking. Some mold steels still exhibit carbide segregation, resulting in a large number of micro fine cracks in the microstructure. During the extrusion process of aluminum materials, the detached aluminum slag is prone to infiltrate into the mold along these fine cracks, accelerating the propagation of cracks. During the machining process, there is a significant tensile stress on the surface of the mold after electrical discharge machining, which promotes the formation of microcracks in the white bright layer of the electrical discharge machining, causing stress concentration and reducing the fatigue strength of the mold.

　　In such a situation, optimizing the heat treatment process becomes particularly important. Firstly, in the quenching process, the heating rate in the high-temperature section should be fast, and the insulation time should not be too long to prevent the extrusion mold from overheating or overheating. Overheating can cause coarse grains, while overburning can dissolve low melting point elements and inclusions, which can reduce the performance of the mold and increase the risk of crack formation. Aluminum extrusion molds should be tempered in a timely manner after quenching to prevent cracking. For example, during the heat treatment of molds, a certain enterprise caused multiple sets of molds to crack due to delayed tempering, resulting in serious losses.

　　For molds that have undergone electrical discharge machining, tempering treatment should be carried out, and the re tempering temperature should be 20 ℃ lower than the secondary tempering temperature of the quenched mold. This can effectively remove residual tensile stress on the surface of the electrical discharge machining and improve the fatigue resistance of the mold. It is also necessary to add a stress relief tempering process for large aluminum extrusion molds or complex finished molds, which can eliminate electrical and mechanical processing stresses, that is, eliminate thermal stress and structural stress.

　　In order to obtain a good final heat treatment structure, the tool and mold must undergo good pre-treatment before quenching. For high alloy steels such as 3CrW8V and 4Cr5MoSiV1, it is necessary to strictly control the process system, strengthen temperature measurement and control during quenching and tempering, otherwise defects such as heat treatment cracks or uneven hardness may occur.

　　The problem of frequent surface cracks in aluminum extrusion molds urgently needs to be solved, and the optimization of heat treatment process is a key link in it. By adjusting the heat treatment process parameters reasonably, strictly controlling each link, and selecting appropriate mold materials, enterprises are expected to effectively reduce the occurrence of surface cracks on molds, improve the service life of molds, reduce production costs, and enhance product quality, occupying a more advantageous position in the fierce market competition. I believe that with the industry's increasing attention to this issue and continuous technological innovation, the aluminum profile processing industry will usher in more efficient and stable development.