Heat treatment technology of Weld-neck flange
Weld-neck flange is a kind of pipe fittings, which refers to the flange with neck and transition of round pipe and Weld-neck connection with pipe.
Weld-neck flange with neck is a kind of steel hot pressed or forged flange. Its connection form is directly Weld-neck the flange and steel pipe. The main manufacturing standards of Weld-neck flange with neck are generally GB / t12459, GB / T13401, asmeb16.9, sh3408, sh3409, Hg / t21635, Hg / t21631, Sy / t0510 and GB / t10752-1995.
The neck Weld-neck flange needs normalizing + tempering heat treatment and machining port, and the wall thickness needs to leave burning loss and machining allowance. The general allowance is 10% – 20% of the theoretical wall thickness of the flange. Flange wall thickness δ The smaller the ratio to the section diameter D is, the better the bonding performance with the die is, but the more easily the flange inner arc is unstable and wrinkled. According to the characteristics that the volume of metal remains unchanged during plastic deformation, the wall thickness remains unchanged during push forming (actual slight thinning), and the length of outer arc of flange is equal to the length of tube blank, the formula of outer diameter of tube blank is deduced: if the outer diameter of tube blank selected is smaller than the DP value calculated by the formula, the fitting performance with the die is good, but the inner arc of flange is prone to instability and wrinkling. If the actual diameter of the tube blank is larger than the DP value calculated by the formula, the result is just the opposite. The principle of determining the heating temperature of carbon steel flange is that the austenitizing temperature of the material is higher than that of the material, and the main compressive stress of the inner wall of the flange is less than the yield limit of the material at this temperature. The higher the austenitizing temperature, the higher the heating temperature; The higher the high temperature yield limit, the higher the heating temperature.
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