Carbon steel pipe flange
1. Raw material processing:
Carbon steel materials are relatively low in cost and widely available. Before manufacturing, the carbon content and other basic components of the material are mainly checked, because the carbon content will affect the strength and toughness of the flange. Usually, low carbon steel (carbon content less than 0.25%) is used to manufacture flanges that do not require extremely high strength, and medium carbon steel (carbon content 0.25% - 0.6%) can be used to manufacture flanges that withstand a certain pressure. During forging, due to the good forgeability of carbon steel, the heating temperature is generally around 1200 - 1250℃, and the heating equipment can be a more conventional gas heating furnace.

2. Manufacturing process selection:
1) Forging: Forging is a more common process for producing carbon steel pipe flanges. For flanges with small batch production or simple shapes, free forging is more suitable. For example, in the manufacture of flanges for some small repairs, free forging can be used to quickly form them using equipment such as air hammers. For flanges with large batch production and complex shapes, die forging is more advantageous. After die forging, the flange blank is trimmed, punched and other operations to remove excess material, and then normalized or annealed to refine the grain, eliminate forging stress, and improve the comprehensive performance of the flange.
2) Casting: Casting technology is also commonly used in carbon steel flange manufacturing. Sand casting is widely used in carbon steel flange production because carbon steel materials have good fluidity and are easy to form during the pouring process of sand casting. After casting, the cleaning and machining process is similar to other materials, but because carbon steel is relatively hard, in the process of turning, drilling and other processing, the cutting parameters (such as cutting speed, feed rate, etc.) should be appropriately selected to prevent excessive wear of the tool.
3) Cutting and processing method: For some small or special specifications of carbon steel flanges, cutting and processing methods are also feasible. For example, flame cutting can be used to cut thicker carbon steel plates, and then conventional machining is performed after cutting to meet the design requirements. However, the edges after flame cutting need to be polished to eliminate the hardness changes and surface unevenness caused by the heat-affected zone.

Stainless steel pipe flanges
1. Raw material processing:
Stainless steel materials have good corrosion resistance. When selecting raw materials, focus on their alloy composition, such as chromium (Cr) and nickel (Ni) content. For example, 304 stainless steel contains about 18% chromium and about 8% nickel. This combination of ingredients makes it have excellent corrosion resistance. The preparation of stainless steel materials before forging or casting is more stringent, because there must be no impurities such as oil, rust, etc. on its surface, otherwise it will affect its corrosion resistance. During the heating process, due to the relatively poor thermal conductivity of stainless steel, the heating speed should be properly controlled to prevent local overheating. The forging temperature is generally around 1150-1200℃.

2. Manufacturing process selection:
1) Forging: When forging stainless steel flanges, since stainless steel easily reacts with oxygen at high temperatures to produce oxide scale, it is important to control the forging environment. Generally, forging needs to be carried out under a protective atmosphere, such as using inert gas protection such as argon. During the subsequent heat treatment of stainless steel flanges after die forging, care should be taken to avoid the sensitization temperature range (such as 450 - 850℃ for some stainless steel models) to prevent intergranular corrosion.
2) Casting: Casting stainless steel flanges is relatively difficult because the fluidity of stainless steel liquid is not as good as carbon steel, and it is easy to produce defects such as insufficient pouring and cold shut. Investment casting is widely used in the manufacture of stainless steel flanges, especially for flanges with complex shapes and high precision requirements. After casting, the cleaning process of stainless steel flanges should be more meticulous because its surface quality has a great influence on corrosion resistance. During mechanical processing, due to the high toughness and viscosity of stainless steel, the requirements for tools are high. Generally, carbide tools are required, and suitable cutting fluids are used to improve the surface quality of the processing.
3) Cutting and processing methods: In terms of cutting and processing methods, laser cutting is a good choice for stainless steel pipe flanges. Laser cutting has high precision and small heat-affected zone, which can effectively avoid deformation and local corrosion of stainless steel materials during cutting. The mechanical processing after cutting should also pay attention to maintaining the surface quality. After processing, pickling and other surface treatments may be required to remove the scale and impurities generated during the processing and restore the corrosion resistance of stainless steel.

Alloy steel pipe flange
1. Raw material processing:
Alloy steel is a steel with alloy elements (such as molybdenum, vanadium, titanium, etc.) added to carbon steel. These alloy elements give the flange better strength, toughness, high temperature resistance, wear resistance and other properties. In the raw material preparation stage, the ingredients must be strictly prepared in accordance with the alloy composition standards, because the content and type of alloy elements have a great influence on the performance of the flange. For example, adding molybdenum can improve the high temperature creep resistance of the flange. The forging temperature of alloy steel varies depending on the alloy composition, generally around 1100-1200℃, and the heating rate and insulation time need to be precisely controlled according to the specific alloy composition.

2. Manufacturing process selection:
1) Forging: When forging alloy steel flanges, due to the addition of alloy elements, its forging performance is different from that of carbon steel. Some alloy steels have greater deformation resistance and require greater forging pressure. During the die forging process, the design of the die and the selection of materials should take into account the high strength and hardness of alloy steel to prevent premature wear of the die. Heat treatment after forging is very critical for alloy steel flanges, such as quenching and tempering treatments to give full play to its high strength and toughness. The selection of quenching temperature and tempering temperature should be determined according to the specific alloy steel composition to obtain the best organizational properties.
2) Casting: Cast alloy steel flanges also face challenges brought by alloy elements. Alloy elements may affect the fluidity and solidification characteristics of the metal liquid and increase the risk of casting defects. In terms of casting process selection, metal mold casting or investment casting may be more suitable for alloy steel flanges because these methods can better control the solidification process. In the mechanical processing process after casting, the cutting force of the alloy steel flange is large, and the requirements for processing equipment and tools are higher. High-hardness, high-strength tools and appropriate cutting parameters are required to ensure the processing quality.
3) Cutting and processing method: When cutting and processing are used for alloy steel flanges, plasma cutting can be used for cutting thicker materials, but the hardness of the edge may increase after cutting, and appropriate tempering treatment is required to reduce the hardness. During the machining process, attention should be paid to the reasonable selection of machining sequence and cutting parameters to give full play to the performance advantages of alloy steel and avoid damage during the machining process.

The above are the differences in the manufacturing processes of different pipe flanges. The flange supplier should consider the specific manufacturing process and material selection based on the flange's purpose, working environment, medium characteristics and other factors. In addition, attention should also be paid to the selection of quality inspection and processing technology control to ensure that the quality and performance of the flange meet the quality standards and customer requirements.