Research on Heat Treatment of Metal Materials for Building Steel Structures (Part 1)

In today’s era, technology and craftsmanship are constantly improving, and metal materials are more and more widely used in production and life. One of the most important application areas is the steel structure of buildings. However, in actual construction, metal materials cannot be used directly in many cases, and need to be processed on the basis of materials before they can be used in construction or enter the next processing stage. In these processing procedures, heat treatment of metal materials is a very important aspect, which is widely used in metal processing and has been applied to production activities. The heat treatment of metal materials not only plays an important role in production, but also involves many fields such as energy saving and environmental protection. Therefore, the heat treatment of metal materials for building steel structures is of great research value and necessity.

1、Heat treatment of building steel structure metal materials

1.1 The concept of heat treatment of metal materials

Heat treatment of metal materials refers to putting the workpiece made of metal into a certain medium and heating it to a suitable temperature. cool down. In this way, the microstructure of the surface or inside of the metal material will change, so that the metal workpiece will exhibit different properties.

1.2 Classification and characteristics of heat treatment of metal materials

According to the different treatment methods, the heat treatment process of metal materials can be roughly divided into three categories, namely surface heat treatment, overall heat treatment and chemical heat treatment. And each type of method is different in medium, temperature and cooling method, so it can be divided into several sub-categories. Using different heat treatment processes to process the same metal can make the metal material exhibit different organizational structures and thus have different properties. In terms of building steel structures, steel is naturally the most widely used, and the microstructure of steel is also the most complex, and the corresponding treatment processes are also the most diverse. Compared with other processing techniques, metal heat treatment mainly changes the properties of the material by changing the internal structure or surface chemical composition of the material, and generally does not change the shape of the workpiece and the chemical composition of the material itself. Such treatments improve the inherent quality of the workpiece and are therefore specific and require strict supervision.

1.3 Process of heat treatment of metal materials

The process of heat treatment of metal materials generally includes three stages of heating, heat preservation and cooling, and sometimes heat preservation is not required. These links are linked together. Heating is one of the most important processes in the heat treatment of metal materials. There are many ways to heat metal materials. The initial heat source is coal and wood, and modern gas and liquid fuels are mostly used. Electricity can be used to accurately control heating without causing environmental pollution. Using these heat sources, metal materials can be heated directly, or indirectly heated through molten salt or metal, or floating particles. When the metal is heated, the metal material is exposed to the air, and it is easily oxidized and decarburized by the air (that is, the carbon content on the surface of the steel part is reduced). Such a situation will adversely affect the performance of the metal material after heat treatment. Therefore, metallic materials should be heated in a controlled or protected environment, in molten salts, in vacuum, or protected by coating or packaging.

When heating, temperature control is a very critical link in the heat treatment process. Selecting and controlling the heating temperature is of vital importance to ensure the quality of heat treatment. Due to the different metal materials to be processed and the different processing purposes to be achieved, the required processing temperatures are also different. In general, it needs to be heated above a certain temperature to obtain a change in performance. Since the change in performance takes a certain amount of time, it is also necessary to keep the high temperature for a certain period of time, so as to ensure the consistency of the internal and external temperature of the metal material and obtain a complete transformation of the performance. This period of time is called the holding time. When adopting high-energy-density heating and surface heat to handle, rate of heating is exceedingly fast, and generally just do not have soaking time, and the soaking time of thermo-chemical treatment is often longer. In the process of heat treatment of metal materials, cooling is also an essential link. There are many cooling methods, mainly due to different processes. In this link, the main thing to control is the cooling speed. Generally speaking, the cooling rate of normalizing is faster, and the cooling rate of annealing is slower. The difference of the material itself also has different requirements on the cooling rate, which requires effective control in the actual processing process.