Hotline：
High neck flange, also known as long neck flange and neck flange, is a disc-shaped component mainly used for connecting pipelines. It has been widely used in petrochemical, urban water supply, and power systems. In recent years, with the planning and construction of ultra-high voltage transmission line projects in the State Grid of China, the demand for ultra-high voltage steel pipe towers has sharply increased.
As a new form of flange connection for steel pipe towers, high neck flanges have been proven to have certain reliability. It plays a crucial role in improving the production capacity and product quality of steel pipe towers.
1、 Welding method
There are two main methods for early circumferential welding of ultra-high pressure high neck butt welded flanges and steel pipes: manual gas shielded welding and fully automatic swing gas shielded welding.
Based on the above two welding methods, the manufacturer of GeBie ultra-high pressure steel pipe tower has independently developed an internal and external submerged arc welding special machine to achieve circumferential welding of high neck butt welding flanges and steel pipes according to the welding process characteristics. This process uses submerged arc welding to perform double-sided penetration welding on the workpiece, and there is no need for root cleaning treatment during the welding process, which improves welding efficiency while ensuring welding quality.
With the continuous production of high neck butt welding flanges, welding methods and techniques are also constantly improving. According to the actual specifications and dimensions of the workpiece, welding schemes such as manual gas shielded welding, fully automatic swing gas shielded welding, or submerged arc welding can be reasonably selected.
2、 Welding process
1. Tack welding
Tack welding must be carried out by welders with corresponding qualification certificates. The surface and both sides of the base metal near the weld seam should be uniform, smooth, and free of burrs, cracks, scale, rust, grease, water, and other impurities.
The thickness of the positioned welding seam should not be less than 3 mm and should not exceed 2/3 of the designed weld height. The length should not be less than 40 mm, and the spacing should be between 200 and 300 mm, and should be evenly distributed.
2. Welding environment
The wind speed during gas shielded welding is less than 2m/s; Air relative humidity ≤ 80%; The surface of the weldment should be kept dry.
3. Preheating and interpass temperature control
Preheating temperature and interpass temperature shall be determined according to comprehensive factors, such as chemical composition of steel, constraint state of joint, heat input, hydrogen content level of deposited metallic hydrogen and welding method.
4. During the welding process, the minimum interpass temperature is ≥ the preheating temperature, and the maximum interpass temperature is ≤ 230 ℃
At present, the production technology of high neck forged flanges has gradually matured and the overall quality is good. The total qualification rate of the weld seam is 98%, and each key quality can meet the technical requirements of steel pipe tower production, but the process needs further solidification.