Large-diameter flanges are widely used in the machinery industry

Abstract: This article introduces the applicable scenarios and manufacturing processes of large-diameter flanges

Large-diameter flanges are widely used, and the scope of application is determined by their respective characteristics. They are mostly used in low-pressure (nominal pressure does not exceed 2.5MPa) non-purified compressed air, low-pressure circulating water and other occasions with relatively loose media conditions, and have the advantage of being relatively cheap. The materials are carbon steel, stainless steel and alloy steel, etc.

Common large-diameter flanges include flat welding flanges and butt welding flanges, and large-diameter threaded flanges are extremely rare. In actual production and sales, flat welding products still account for a large proportion. Flat welding large-diameter flanges and butt welding large-diameter flanges have different structures and use ranges, and the characteristics and advantages that can be displayed will also be different. Therefore, when using them, they should be used for different ranges to ensure that the flange plays an important role. Large-diameter flat welding flanges have poor rigidity and are suitable for occasions with pressure p≤4MPa; large-diameter butt welding flanges are also called large-diameter high-neck flanges, which have greater rigidity and are suitable for occasions with higher pressure and temperature.

There are three types of large-diameter flange sealing surfaces:

1. Flat sealing surface, suitable for occasions with low pressure and non-toxic media;

2. Concave and convex sealing surface, suitable for occasions with slightly higher pressure;

3. Tenon and groove sealing surface, suitable for flammable, explosive, toxic media and high pressure occasions. Flange pipe fittings of different properties have good product performance in different fields, and the effects produced will be different depending on the occasions and spaces they are suitable for.

The production process of large-diameter stainless steel flanges is divided into rolling and forging

Rolling process: The process of cutting strips from the middle plate and then rolling them into a circle is called rolling, which is mostly used in the production of some large stainless steel flanges. After the rolling is successful, welding is carried out, then flattening, and then the waterline and bolt hole processes are processed.

Forged large-diameter flanges generally have lower carbon content than large-diameter cast flanges, are not easy to rust, have better streamlined forgings, are more dense in structure, have better mechanical properties than large-diameter cast flanges, and can withstand higher shear and tensile forces

The forging process generally consists of the following steps, namely, selecting high-quality steel billets for blanking, heating, forming, and cooling after forging. The forging process methods include free forging, die forging and membrane forging. During production, different forging methods are selected according to the quality of the forgings and the number of production batches.

Free forging has low productivity and large machining allowance, but the tools are simple and versatile, so it is widely used to forge single pieces and small batches of forgings with simpler shapes. Free forging equipment includes air hammers, steam-air hammers and hydraulic presses, which are suitable for the production of small, medium and large forgings respectively.

Model forging is to place the heated billet in a forging die fixed on the die forging equipment for forging. Die forging has high productivity, simple operation, and is easy to mechanize and automate. Die forgings have high dimensional accuracy, small machining allowance, and more reasonable fiber structure distribution of forgings, which can further improve the service life of parts.