Large-diameter flanges refer to flanges that exceed the dimensions specified by the relevant national authorities. Generally refers to the flange of the size above DN2000. Such products are all welded products without threading. The largest size among the pressure standards of 0.25 MPa and 0.6 MPa in the national flange standard GB/T9119-2010 is DN2000. In the 1.0MPa pressure standard, the largest is the DN600. The production of such flanges is to be produced by the construction party. The production process includes forging, rolling and splicing. Excessive product size can only be achieved by rolling and splicing. The product process first cuts the middle plate into suitable slivers, and the length of the sliver is determined according to the specifications of the large flange. Then, the ring is rolled into a circle, and the joint is welded firmly with the electrode, and the X-spectrum test is performed at the joint. Then use a press to flatten it, and then use a lathe to process the waterline, chamfering, etc. Finally, the indexing disc is used in conjunction with the drilling machine to machine the hole of the bolt hole.
The cost of a rolled flange is lower than that of forging. But some oversized flanges are forged. Most of these products are weighed by the theoretical weight. In the calculation, the weight of the water line, the stop, the bolt hole and the chamfer are not reduced. The price of a flat product is lower, but if a large flange with a process such as a dovetail is expensive, the price will be higher. The theoretical weight is calculated according to the following formula. The material is made of stainless steel 304, 316, 316L, 201, 304L, 321 and other materials, carbon steel A3, Q235, A105, 20#, Q345, A182, 16MN and other materials, alloy steel 12cr1mov, 15crmov910, 15Mo3 15CrMoV, 12CrMoV, 45Cr, 50Cr and other materials.