The difference between rimming steel plates and killed steel plates lies in the degree of deoxidation during the steelmaking process. Steel can be categorized into three types: bubbling steel, killed steel, and semi-killed steel.
Bubbling steel plates are made from hot-rolled plates of ordinary carbon structural steel known as bubbling steel. Rimming steel is a type of steel with incomplete deoxidation, where only a certain amount of weak deoxidizers are used to deoxidize the steel liquid. The steel liquid has a high oxygen content. When the steel is poured into the ingot mold, the carbon-oxygen reaction produces a large amount of gas, causing the steel liquid to boil, hence the name bubbling steel. Bubbling steel has a low carbon content and, since silicon-iron deoxidation is not used, it also has a low silicon content (Si<0.07%). The outer layer of rimming steel is crystallized under the condition of violent stirring of the steel liquid caused by boiling, thus the surface is pure and dense with good quality, excellent plasticity and stamping performance, no large concentrated shrinkage pores, less cutting off, high yield, and the production process of bubbling steel is simple, with less consumption of iron alloys and lower steel cost.
Boiler steel plates are typically manufactured using killed steel rather than bubbling steel. This is due to the fact that boilers operate under high temperatures and pressures and require good toughness and weldability to ensure safety and reliability. Killed steel, which is fully deoxidized, provides better internal structure uniformity, higher purity, and fewer internal defects, making it more suitable for the manufacture of heavy-load structural components such as boilers.
Bubbling steel plates are widely used for manufacturing various stamped parts, architectural and engineering structures, and some less critical machine structural components. However, the interior of bubbling steel contains more impurities, more severe segregation, less dense structure, and uneven mechanical properties. At the same time, due to the higher gas content in the steel, the toughness is low, cold brittleness and time effect sensitivity are greater, and the welding performance is also poor. Therefore, bubbling steel plates are not suitable for manufacturing structures subjected to impact loads, welded structures that operate at low temperatures, or other important structures.
Under normal operating conditions, there are no bubbles in killed steel, the structure is uniform and dense; due to the low oxygen content, there are fewer oxide inclusions in the steel, higher purity, less cold brittleness and aging tendency; at the same time, the segregation in killed steel is smaller, the performance is more uniform, and the quality is higher. The disadvantage of killed steel is that there are concentrated shrinkage pores, lower yield, and higher price. Therefore, killed steel is mainly used for components that withstand impact at low temperatures, welded structures, and other components that require higher strength.
Low-alloy steel plates are all killed and semi-killed steel plates. Due to their higher strength and superior performance, they can save a large amount of steel, reduce structural weight, and their application has become more and more widespread.
1.Bubbling Steel Plate
Bubbling steel plates are made from hot-rolled plates of ordinary carbon structural steel known as bubbling steel. Rimming steel is a type of steel with incomplete deoxidation, where only a certain amount of weak deoxidizers are used to deoxidize the steel liquid. The steel liquid has a high oxygen content. When the steel is poured into the ingot mold, the carbon-oxygen reaction produces a large amount of gas, causing the steel liquid to boil, hence the name bubbling steel. Bubbling steel has a low carbon content and, since silicon-iron deoxidation is not used, it also has a low silicon content (Si<0.07%). The outer layer of rimming steel is crystallized under the condition of violent stirring of the steel liquid caused by boiling, thus the surface is pure and dense with good quality, excellent plasticity and stamping performance, no large concentrated shrinkage pores, less cutting off, high yield, and the production process of bubbling steel is simple, with less consumption of iron alloys and lower steel cost.
2.Killed Steel Plate
Killed steel plates are made from hot-rolled plates of ordinary carbon structural steel known as killed steel. Killed steel is a type of steel that is fully deoxidized, where the steel liquid is sufficiently deoxidized with manganese iron, silicon iron, and aluminum before pouring, resulting in a low oxygen content in the steel liquid (generally 0.002-0.003%). The steel liquid is calm in the ingot mold without boiling, which is how killed steel gets its name.Boiler steel plates are typically manufactured using killed steel rather than bubbling steel. This is due to the fact that boilers operate under high temperatures and pressures and require good toughness and weldability to ensure safety and reliability. Killed steel, which is fully deoxidized, provides better internal structure uniformity, higher purity, and fewer internal defects, making it more suitable for the manufacture of heavy-load structural components such as boilers.
3.Semi-Killed Steel Plate
Semi-killed steel plates have a degree of deoxidation between bubbling steel and killed steel. There is a boiling phenomenon during pouring, but it is weaker than that of bubbling steel. This type of steel has some advantages of both bubbling steel and killed steel, but it is more difficult to control in smelting operations.
4.Differences between rimming steel plates and killed steel plates
Bubbling steel plates are widely used for manufacturing various stamped parts, architectural and engineering structures, and some less critical machine structural components. However, the interior of bubbling steel contains more impurities, more severe segregation, less dense structure, and uneven mechanical properties. At the same time, due to the higher gas content in the steel, the toughness is low, cold brittleness and time effect sensitivity are greater, and the welding performance is also poor. Therefore, bubbling steel plates are not suitable for manufacturing structures subjected to impact loads, welded structures that operate at low temperatures, or other important structures.Under normal operating conditions, there are no bubbles in killed steel, the structure is uniform and dense; due to the low oxygen content, there are fewer oxide inclusions in the steel, higher purity, less cold brittleness and aging tendency; at the same time, the segregation in killed steel is smaller, the performance is more uniform, and the quality is higher. The disadvantage of killed steel is that there are concentrated shrinkage pores, lower yield, and higher price. Therefore, killed steel is mainly used for components that withstand impact at low temperatures, welded structures, and other components that require higher strength.
Low-alloy steel plates are all killed and semi-killed steel plates. Due to their higher strength and superior performance, they can save a large amount of steel, reduce structural weight, and their application has become more and more widespread.
