Boiler Steel Plate Performance Requirements

Boiler steel plate primarily refers to hot-rolled medium and thick plate used to manufacture superheaters, main steam pipes, and the heating surfaces of boiler fireboxes. Boiler steel plate is a critical material in boiler manufacturing, primarily consisting of hot-rolled special carbon steel and low-alloy heat-resistant steel medium and thick plate used to manufacture key components such as the boiler shell, drum, header end covers, and supports.

 

 

Primarily made from high-quality structural steel and low-alloy heat-resistant steel, boiler steels are commonly used, including low-carbon killed steel smelted in open-hearth furnaces or low-carbon steel smelted in electric furnaces, with a carbon content (Wc) ranging from 0.16% to 0.26%. Because boiler steel plate operates at medium temperatures (below 350°C) and high pressure, it is subject to not only high pressure but also impact, fatigue loads, and corrosion from water and air. Therefore, the performance requirements for boiler steel primarily include excellent welding and cold bending properties, adequate high-temperature strength, and resistance to alkaline corrosion and oxidation. Boiler steel plates often operate under medium-high temperatures and high pressures. In addition to enduring high temperatures and pressures, they are also subject to impact fatigue loads and corrosion from water and air. These harsh operating conditions require excellent physical, mechanical, and machinability properties to ensure safe operation.

Based on the material, boiler steel plates can be divided into two categories: specialized carbon steel plates and low-alloy heat-resistant steel plates. The chemical composition of the materials used for boiler steel plates is strictly controlled, particularly for harmful elements such as phosphorus and sulfur, and residual elements such as chromium, nickel, and copper. Deoxidation and removal of non-metallic inclusions during smelting ensure excellent plasticity and toughness. The microstructure must be uniform, and the grain size must be within a certain range (typically between grades 3 and 7). Stringent requirements are also placed on surface quality and internal defects. Furthermore, mechanical properties must be maintained at both room and high temperatures.

 

Depending on the operating conditions, boiler steel plates can be further divided into two categories: plates for manufacturing room- and medium-temperature pressure-bearing components, and plates for manufacturing high-temperature pressure-bearing components.

 

Widely used in the petroleum, chemical, power plant, and boiler industries, these steels are used to manufacture equipment and components such as reactors, heat exchangers, separators, spherical tanks, oil and gas tanks, liquefied gas tanks, nuclear reactor pressure vessels, boiler drums, liquefied petroleum gas cylinders, high-pressure water pipes for hydropower stations, and turbine volutes.

 

Performance Requirements

 

Boiler steel plates for room and medium temperatures (below the creep temperature) are mostly made of carbon steel, including carbon steel, carbon-manganese steel, and carbon-manganese-silicon steel. They are primarily used to manufacture pressure-bearing components such as boiler drums and header end covers below the creep temperature. They must exhibit high room-temperature strength, good impact toughness, and low notch sensitivity. Since components such as boiler drums require extensive cold deformation during machining, they must also exhibit good aging toughness, good machinability, weldability, and a good macrostructure.

 

Boiler steel plates for high temperatures (above the creep temperature) are generally made of low-alloy heat-resistant steels, commonly including chromium-molybdenum steel, chromium-molybdenum-vanadium steel, and chromium-molybdenum-tungsten steel. It is primarily used to manufacture high-temperature, pressure-bearing components such as high-temperature header end covers and steam pipe plugs. Requirements include sufficient high-temperature enduring strength and plasticity, good high-temperature structural stability, good high-temperature oxidation resistance (heat resistance), and good hot and cold processing properties (primarily cold bending deformation and weldability).