Normalizing Processing of Alloy Steel Pipes for 12Cr1MoVG High-Pressure Boiler Steel Pipes

First, the material composition of 12Cr1MoVG high-pressure boiler steel pipes

Chemical composition: 12Cr1MoVG is an alloy steel pipe, the main alloying elements include chromium (Cr), molybdenum (Mo), and vanadium (V). The chromium content is generally 1.0-1.5%, which can effectively improve the oxidation resistance and corrosion resistance of steel; the molybdenum content is about 0.25-0.35%, which enhances the thermal strength of steel, that is, the strength and creep resistance at high temperatures; the vanadium content is 0.15-0.30%, and the addition of vanadium can refine the grains and improve the strength and toughness of steel. At the same time, its carbon (C) content is usually 0.08-0.15%, which ensures the basic strength of steel. It also contains elements such as silicon (Si) and manganese (Mn). Silicon can increase the strength and elastic limit of steel, and manganese can improve the toughness of steel.

Second, the production process of 12Cr1MoVG high-pressure boiler steel pipe

1. Smelting link: Electric furnace or converter steelmaking is mostly used. In the smelting process, precise control of the amount and time of alloying elements is the key. For example, alloying elements such as chromium, molybdenum, and vanadium should be added at the appropriate molten steel temperature and composition stage to ensure that they are evenly dissolved in the molten steel and evenly distributed.

2. Rolling process: including hot rolling and cold rolling (cold drawing). During hot rolling, the steel billet is heated to about 1100-1200℃, pierced by a piercing machine, and then rolled by a tube rolling mill to obtain a steel pipe with the required outer diameter and wall thickness. Cold rolling (cold drawing) is based on hot rolling and is drawn or cold rolled by a die at room temperature to make the steel pipe have higher dimensional accuracy and better surface quality, but the production efficiency is relatively low and the cost is high.

3. Heat treatment process: normalizing + tempering treatment is used. Normalizing temperature is usually 980--1020℃. Normalizing can refine the grains, make the steel structure more uniform, and improve the strength and toughness of the steel. The tempering temperature is about 720--760℃. The purpose of tempering is to eliminate the internal stress generated during the normalizing process and improve the comprehensive performance of the steel.

Third, the performance characteristics of 12Cr1MoVG high-pressure boiler steel pipe

1. High-temperature mechanical properties: excellent performance in high-temperature environments. For example, in a high-temperature steam environment of about 580℃, 12Cr1MoVG high-pressure boiler tubes can still maintain high strength and creep resistance, and the allowable stress can reach about 100MPa. It can withstand the high-temperature and high-pressure steam in the boiler and ensure the safe operation of the boiler.

2. Corrosion resistance: Due to the presence of chromium and molybdenum elements, the steel pipe has good resistance to high-temperature steam, water vapor, and some corrosive gases (such as sulfur dioxide), which can effectively prevent corrosion of the tube wall and extend the service life.

3. Welding performance: The welding performance is good, but a strict welding process is required. Generally, preheating is required before welding, and the preheating temperature is between 200-300℃. After welding, post-weld heat treatment is required to ensure the quality of the welded joint and avoid defects such as cracks.

Fourth, the application field of 12Cr1MoVG high-pressure boiler steel pipe

In the power industry, it is the main pipe material for high-pressure boilers. It is used to manufacture superheaters, reheaters, water-cooled walls, and other components of boilers. These components are directly in contact with high-temperature and high-pressure steam. 12Cr1MoVG high-pressure boiler pipes can meet their performance requirements. In the petrochemical industry, it is used to transport high-temperature and high-pressure fluids such as oil, natural gas, and chemical raw materials to ensure the safe and stable operation of industrial processes.