大口径法兰常见的有平焊法兰和对焊法兰。丝扣法兰是没有大口径的。在现实的生产与销售中，还是平焊产品的比例占得多。平焊大口径法兰和对焊大口径法兰的结构和使用的范围不同，能够展现的特点和优点也会不同，所以在使用时要针对不同的范围进行使用，保证法兰发挥重要的作用。大口径平焊法兰的钢性较差，适用于压力p≤4MPa的场合；对焊法兰又称高颈法兰，刚性较大，适用于压力温度较高的场合。
Large diameter flange has common flange and butt welding flange. There is no large diameter threaded flange. In the production and sale of reality, or welding products accounted for much. The structure and use range of large caliber flanges and large bore flanges are different, and the features and advantages of the flanges can be different, so the use of different ranges should be used to ensure that the flange plays an important role. Large caliber flat welding flange is poor in steel property, suitable for pressure P less than 4MPa. The welding flange is also called high neck flange, and the rigidity is larger. It is suitable for high pressure temperature occasions.