If you want to understand the annealing properties of mold materials, read this article

Everyone knows that if you want to use a product better, you need to have a clear understanding of its performance. Molds are certainly no exception. The quality of mold products not only affects the quality and performance of production, but also directly affects industrial production efficiency and costs. The quality of the mold mainly depends on the material and heat treatment process of the mold. Therefore, it is important to understand the performance requirements of mold materials.

According to the mold materials used for different purposes, the following aspects should be mainly considered in terms of usage performance and process performance.

1. Hardness and hardenability. Hardenability and hardenability are a major requirement for mold steel. Hardenability is mainly related to the chemical composition of the steel, especially the carbon content, and also to the original structure of the steel before quenching. The requirements for these two properties of mold steel have different emphasis according to the use conditions of different molds. For example, for requirements Hardenability is more important for blanking die and drawing die steels with high surface hardness, but for hot hammer forging die steels that require uniform performance across the entire section, hardenability is even more important.

2. Hardness and thermohardness (thermal stability). The mold should be able to maintain its shape and size without rapid changes under the action of compressive stress. Hardness is an important performance indicator of mold steel. Therefore, the mold after heat treatment should have a sufficiently high hardness. For example, the hardness of cold work molds is generally around 60HRC, while the hardness of hot work molds can be appropriately reduced, generally in the range of 42 to 50HRC.

Thermal hardness refers to the ability of the mold to maintain stable structure and performance under heating or high-temperature working conditions and to resist softening. The thermal hardness of steel is mainly determined by the chemical composition and heat treatment system of the steel. It is one of the important performance indicators of hot work die steel.

3. Processability. Workability refers to the hot working performance of forging and rolling as well as the cold working performance in the form of cutting and grinding. They are related to the chemical composition, metallurgical quality, organizational state and sulfur and phosphorus content of the steel. Most mold steels contain a variety of alloy elements. Especially for high carbon and high alloy steel, the heating system and cooling method must be strictly controlled during hot processing to avoid or reduce hot processing waste. Before cold processing, the organizational state should be improved to reduce tool wear during cold processing. , and improve the surface quality of the mold.

4. Wear resistance. The mold is subject to considerable compressive stress and friction during work. It is required that the mold should be able to maintain its size and shape during use and be durable, so the mold material should have good wear resistance. The wear resistance of the mold not only depends on the composition, structure and performance of the steel, but also has a great relationship with the operating temperature, load (pressure) state, lubricating medium, etc. Increasing the hardness of steel is beneficial to improving the wear resistance of steel, but after reaching a certain hardness value, the effect on improving wear resistance is not significant.

5. Decarburization sensitivity. Decarburization on the mold surface will reduce the performance of the mold surface layer. Therefore, the lower the decarburization sensitivity of the mold steel, the better. Under the same heating conditions, the decarburization sensitivity of steel mainly depends on the chemical composition of the steel, especially the carbon content.

6. Heat treatment deformation and quenching temperature. The final heat treatment of the finished mold requires that the size and shape of the mold be as small as possible. Therefore, the degree of deformation produced by the mold during heat treatment is very strict. At the same time, the quenching temperature range is required to be wide enough to reduce overheating. .

7. Strength and toughness. Molds bear heavy loads and complex stresses such as impact, vibration, torsion and bending during operation. Heavy-loaded molds are often damaged early due to insufficient strength and toughness, resulting in mold edges or partial fractures. Therefore, mold materials are required to have good strength and toughness. The grain size of the steel, the number, size and distribution of carbides in the steel, and the amount of retained austenite have a great impact on the strength and toughness of the steel. Practice has shown that by rationally selecting the chemical composition, organizational state and heat treatment process of mold steel based on usage conditions and performance requirements, a better combination of sufficiently high strength and toughness can be obtained.

In addition, according to the working conditions of various molds, properties such as high-temperature strength, thermal fatigue, thermal conductivity and corrosion resistance should also be considered respectively. Since mold steel is mostly used in a state of high hardness, high strength, high wear resistance and sufficient toughness, the metallurgical quality of mold steel is required to be high, and the gas content, non-metallic inclusions and harmful elements (sulfur) in the steel should be minimized. , phosphorus, etc.) content. At the same time, in order to ensure that the steel has good performance, it must undergo correct hot pressure processing (forging, rolling) to change the cross-sectional shape, change the cast structure and properties, and then make it through cold cutting. The mold of a certain shape is then subjected to final heat treatment (normalizing, quenching and tempering) to obtain the required performance of the mold. Therefore, the process performance of mold steel is also very important to mold manufacturing.

Understanding the properties of mold materials allows us to better perform heat treatment processes such as quenching and tempering on mold steel. Understanding the properties of mold materials can reduce or avoid the occurrence of unnecessary defects. Understanding the performance requirements of mold materials is also very important for us to use molds. All in all, understanding the properties of mold materials is indispensable. Today, Zhengzhou Gou's electromagnetic induction heating equipment manufacturer only introduced a little bit of knowledge in this area, I hope it will be helpful to you.