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The influence of the manufacturing process on the pressure resistance capacity of the flange is mainly reflected in forging, heat treatment, welding, machining, etc. The following is a specific analysis:
Forging process
Tissue densification: through forging, the internal defects of the metal material such as looseness, porosity, etc., are compacted, the grains are refined, and the organization is denser and more uniform. This makes the flange better able to resist deformation and crack expansion when under pressure, thus improving pressure resistance. For example, flanges that have been forged in multiple passes have good internal organization uniformity and more stable performance under high pressure.
Fibrous tissue formation: The metal flow lines are distributed along the shape of the forging during the forging process, forming a fibrous tissue. This fiber organization makes the flanges have better mechanical properties in different directions, especially when bearing shear force and tensile force, it can give full play to the strength of the material and improve the overall pressure resistance of the flanges.
Heat treatment process
improve strength and toughness: suitable heat treatment process, such as quenching and tempering, can improve the strength and toughness of flange material. Quenching can make the material obtain martensitic organization, greatly improve the hardness and strength, but the toughness will be reduced; tempering can eliminate the quenching stress, improve the toughness, so that the material has a high strength at the same time, but also has a good impact resistance, thus improving the pressure resistance of the flange. For example, for flanges made of medium-carbon steel or medium-carbon alloy steel, after tempering treatment (quenching + high temperature tempering), their strength and toughness reach a better match and can withstand higher pressure.
Stabilize the organization performance: the normalizing treatment can refine the grain, make the material organization uniform, improve the strength and toughness of the material, and also improve the cutting performance of the material. For some flanges used at high temperature, stable organization helps to maintain the stability of performance under long-term pressure and high temperature conditions, preventing the decline in pressure resistance due to organizational changes.
Welding Process
Welding Quality Impact: Welding is an important process for connecting different parts in flange manufacturing. Good quality welding can ensure a good combination between the weld and the base material, with dense weld organization and no obvious defects, such as porosity, slag entrapment, cracks and so on. Such a weld can work together with the base material under pressure and bear pressure together, which has less influence on the pressure resistance of the flange. On the contrary, if the welding quality is poor and there are defects, these defects will become a source of stress concentration, which will easily trigger crack expansion under pressure, leading to a significant decrease in the pressure resistance of the flange.
Welding heat-affected zone: the organization and properties of the heat-affected zone will change during the welding process. If the heat input is not properly controlled, the heat-affected zone may have coarse grains, overheating of the organization and other problems, resulting in a decrease in the strength and toughness of the region. Under pressure, the heat affected zone is prone to become a weak link, affecting the overall pressure resistance of the flange. Therefore, reasonable control of welding heat input and the use of suitable welding process parameters, such as welding current, voltage, welding speed, etc., are essential to reduce the adverse effects of the heat affected zone on the pressure resistance of the flange.
Machining process
Dimensional accuracy guarantee: through precise machining, the dimensional accuracy of the flange can be guaranteed, including the accuracy of the flange's dimensions such as outer diameter, inner diameter, thickness, bolt hole spacing and so on. Flanges with high dimensional accuracy can cooperate well with pipes, bolts and other components during installation and use, transfer pressure evenly, avoid local stress concentration due to dimensional deviation, and thus improve the pressure resistance of the flanges.
Surface quality improvement: machining can obtain good surface quality, reduce the roughness of the flange surface and minimize surface defects. Smooth surface can reduce the stress concentration phenomenon under pressure, and also help to improve the sealing performance between the flange and gasket, prevent medium leakage, and ensure the flange's safe operation under design pressure.