1. Outer diameter tolerance
ERW steel pipe: it is cold formed and dimensioned by reducing the diameter by 0.6%. The process temperature is substantially constant at room temperature. As a result, the outer diameter can be precisely controlled with less fluctuation, which helps eliminate black leather buckles.
Seamless steel pipe: hot rolling forming process is adopted, and the shape is shaped at about 8000C. The raw material composition of silver in steel pipes, cooling conditions and cooling conditions have a great influence on its outer diameter, so it is difficult to accurately control the outer diameter and fluctuate in a wide range.
2. Wall thickness tolerance
ERW steel pipe: using hot-rolled strip steel as raw material, the thickness tolerance of modern hot-car strip steel can be controlled within 0.05mm, and the non-dimensional steel pipe is produced by piercing round steel, and the subsequent hot rolling can partially eliminate the thickness deviation . The thickness is not uniform, but the most advanced device can only be controlled within +5~10%t, which is equivalent to a steel pipe with a thickness of 8.94mm.
Seamless steel pipe: the limit of wall thickness control accuracy is 0.9mm.
ERW steel pipe: cold-formed, with accurate outer diameter control and small fluctuations.
Seamless steel pipe: adopt hot rolling forming process. The raw material composition of the roll, cooling conditions and cooling conditions have a great influence on the outer diameter of the steel pipe. Therefore, it is difficult to precisely control the outer diameter and the fluctuation range is large.
4. Tensile test
The tensile properties of seamless steel pipes and ERW steel pipes meet the AP standard, but the strength of seamless steel pipes is generally at the upper limit, and the plasticity is at the lower limit. In contrast, ERW steel pipe has the highest strength, and its plasticity index is 33.3% higher than the standard. The reason is that through microalloying, refining outside the furnace, and controlled cold rolling, the properties of the raw materials of ERW steel pipes and hot-rolled strips are guaranteed. Seamless steel pipes mainly rely on increasing carbon content
The raw material of ERW steel pipe, that is, hot-rolled strip coil, has high precision of controlled cooling and rolling during the rolling process, which can ensure the uniform performance of each part of the strip coil.
The raw material of ERW steel pipe is a hot-rolled strip coil, using a wide continuous casting plate bad, the solidified surface has fine crystals, the crystals are fine and dense, there is no columnar crystal area, shrinkage and looseness, the composition deviation is small, and the structure is dense; in the subsequent rolling During the manufacturing process, the application of intermediate cold rolling technology further ensures the grain size of raw materials.
7. Anti-collapse test
ERW steel pipe is characterized by its raw material and pipe manufacturing process. Its wall thickness uniformity and ellipticity are far superior to seamless steel pipes, which is the main reason why the pressure resistance is higher than that of seamless steel pipes
8 impact test
Since the impact toughness of the ERW steel pipe base material is several times that of the seamless steel pipe, the impact toughness at the seam is the key to the ERW steel pipe. By controlling the impurity content in the raw material, the height and direction of the longitudinal burr, the shape of the forming edge, the welding angle and welding speed, the heating power and frequency, the coal joint extrusion amount, the intermediate frequency extraction temperature and depth, the length of the air cooling section and other processes The parameters can ensure that the impact energy of the weld reaches more than 60% of the base metal, and if further optimized, the impact energy of the weld close to the base metal can be achieved to achieve seamless performance.
9. Burst test
The burst test performance of ERW steel pipes is much higher than the standard requirements, which is mainly due to the uniform wall thickness and uniform outer diameter of ERW steel pipes10. Straightness
ERW steel pipe is cold-worked, and can be straightened online in the state of reduced diameter, and has an infinite multiple rule, so the straightness is better, seamless steel pipe is formed in a plastic state, and the single-addition rule (continuous rolling is 34 times rule) the straightness of the tube is more difficult to control.
The defects on the outer surface of the bad material used in the seamless steel pipe cannot be eliminated by hot rolling, and can only be polished after the finished product is completed. The helical channel remaining after perforation can only be partially eliminated during the reduction process. ERW steel pipes are made of hot-rolled coils. The surface quality of the coil is that of the ERW steel pipe. The surface quality of hot rolled coils is easy to control and high quality. Therefore, the surface quality of ERW steel pipe is far better than that of seamless steel pipe
12. Steel consumes 10,000 feet long
The wall thickness of ERW steel pipe is uniform, and its wall thickness tolerance is negligible. The control accuracy limit of the wall thickness difference of the seamless steel pipe is +5%t, and it is generally controlled at +5~10%t. In order to ensure that its minimum overall thickness can meet the standard requirements and performance, it can only be solved by appropriately increasing the wall thickness. Therefore, in casings of the same specification and weight, ERW steel pipes are 5-10% longer than seamless steel pipes or even more, thereby reducing the steel pipe consumption of 10,000 meter feet by 5-10%. Even if the price is the same, ERW sets can actually save users 5% to 10% of the purchase cost.