What are the characteristics of high-frequency resistance welding (ERW) process?
High-frequency resistance welding uses high-frequency current to heat the edge of the steel plate and forms a weld by extrusion. It is suitable for producing welded pipes with a diameter of 20mm~600mm. This process has high production efficiency and low cost, and is suitable for mass production, but the quality of the weld is greatly affected by current, pressure and speed. ERW welded pipes are commonly used for water and gas transportation and building structures, but are not suitable for high-pressure environments. Modern ERW technology can produce higher-quality welded pipes and partially replace seamless steel pipes.
What are the advantages and disadvantages of submerged arc welding (SAW) process?
Submerged arc welding is divided into straight seam welding (LSAW) and spiral welding (SSAW), which are suitable for large-diameter thick-walled pipes, such as oil and gas pipelines. Its advantages are high weld quality, strong pressure bearing capacity, and suitable for long-distance transportation; its disadvantages are large equipment investment and slow production speed. The weld of LSAW is distributed in a straight line and has better mechanical properties, while SSAW can flexibly adjust the pipe diameter, but the stress distribution of the weld is complex. Submerged arc welding needs to be used with flux to prevent oxidation and improve welding quality.
How to choose between spiral welded pipe and straight seam welded pipe?
Spiral welded pipe (SSAW) is formed by spiral rolling, which is suitable for the production of large diameter pipes (such as diameters exceeding 1000mm) and has high steel strip utilization. The weld of straight seam welded pipe (LSAW) is straight, with better pressure bearing performance, and is suitable for high-pressure pipelines. The production cost of spiral welded pipes is low, but the weld is long, which may affect fatigue life; straight seam welded pipes are more suitable for high-stress environments, such as submarine pipelines. When choosing, the pipe diameter, pressure requirements and cost factors should be considered comprehensively.
How is laser welding used in the production of carbon steel welded pipes?
Laser welding uses a high-energy laser beam to melt metal, with a narrow weld and a small heat-affected zone, which is suitable for high-precision welded pipes, such as automobile exhaust pipes and precision mechanical parts. Its advantages are fast welding speed, small deformation, and automated production; its disadvantages are high equipment cost and strict requirements on material surface cleanliness. Laser welded pipes are mostly used in high-end manufacturing industries, such as aerospace and medical devices. With the advancement of technology, the application of laser welding in the field of carbon steel welded pipes has gradually expanded.
What are the key points of quality control in welded pipe production?
Quality control in welded pipe production includes raw material inspection, welding parameter control, weld inspection and finished product testing. The raw materials need to check the chemical composition and surface defects of the steel strip; the current, voltage and speed need to be adjusted during welding to ensure the strength of the weld. Common detection methods include ultrasonic flaw detection (UT), X-ray detection (RT) and water pressure testing. The finished product also needs to be tested for size, hardness and tensile properties. Strict quality control can prevent cracking or leakage of welded pipes during use.
