1, diameter tolerance
ERW steel pipe: the use of roll forming, reducing diameter by 0.6% to complete the sizing, the process temperature is almost constant at room temperature, and therefore accurate diameter control, fluctuation range is small, will help eliminate black buckle;
Seamless steel pipe: The hot forming process, the sizing is completed in about 8000C, steel raw materials, components, cooling conditions and the cooling roll status, and its diameter has a greater impact, and therefore difficult to accurately control the diameter, and the fluctuations larger in scope.
2, wall thickness tolerance
ERW steel pipe: the use of hot-rolled coils as raw material, modern hot strip rolling thickness tolerances can be controlled within 0.05mm, while the seamless steel tubes produced using round hole, a larger wall thickness deviation, then the hot wall can be partly eliminated thick, uneven, but the most advanced control unit can only ¡À 5 ~ 10% t less, corresponding to 8.94mm thickness of the pipe.
Seamless steel pipe: wall thickness control accuracy limit is 0.9mm.
3, the ellipticity
ERW steel pipe: the use of roll forming, and thus control the precise diameter, a small fluctuation range.
Seamless steel pipe: The hot forming process, steel raw materials, components, cooling conditions and the cooling roll status, and its diameter has a greater impact, and therefore difficult to accurately control the diameter and larger fluctuation range.
4, the tensile test
Seamless steel pipe and ERW pipe tensile performance indicators are in line with API standards, but generally at maximum strength seamless steel pipe, plastic in the lower, comparatively speaking, ERW steel pipe strength index at its best, the plasticity index 33.3% higher than standard because the raw material for the ERW steel pipe - hot rolled coil is to rely on the performance of micro-alloying smelting, refining, and other means of controlled rolling and controlled cooling to ensure; seamless steel tubes mainly depends on the means of increasing carbon content, it is difficult to ensure strength, plasticity a reasonable match.
ERW steel pipe raw materials - hot rolled coils in the process of controlled rolling and controlled cooling high precision, to ensure uniformity with the volume of each part of the performance.
6, the grain body
ERW steel pipe raw materials - hot rolled coil is used in generous slab, with a thick layer of fine-grained surface of the solidified, columnar grain zone and no shrinkage and loose, composition bias is small, compact structure; in the subsequent rolling process , the controlled rolling and controlled cooling technology to further ensure the raw material of grain size.
7, anti-collapsing test
ERW steel pipe because of its raw materials, manufacturing process control features. The thickness uniformity, ellipticity is far superior to seamless steel pipe, anti-collapsing performance is the main reason for higher than seamless.
8, the impact test
ERW steel pipe because the impact toughness of the base material several times in the seamless steel pipe, weld impact toughness is the key to ERW steel pipe, by controlling the impurity content of raw materials, slitting burr height and direction, forming edge shape, weld angle, weld speed , heating power and frequency, the amount of extrusion welding, IF withdraws from the temperature and depth, air-cooled length to ensure the weld process parameters such as the impact energy to over 60% of the base material, such as further optimized to achieve the weld impact energy close to home material, in order to achieve seamless performance.
9, the burst test
ERW steel pipe burst test performance is much higher than standard, mainly due to high ERW steel pipe wall thickness, diameter of uniform size.
ERW pipe is cold, and in a state with a reduced diameter line straightening, with double length is infinite, so the line is better; seamless molded in plastic state, plus one times the foot (rolling 3 ~ 4-fold scale) is relatively straight pipe end is difficult to control.
11, the appearance of
Seamless outer surface of the blank used by the hot rolling process to eliminate defects not only in the finished product after grinding out defects; for perforated left spiral Road, in the process of reducing the wall, only a partial elimination. ERW steel pipe used as a raw material hot rolled coil, coil surface quality is the quality of ERW pipe surface, and surface quality of hot-rolled coil and high quality easy to control, therefore ERW steel pipe seamless steel pipe surface quality is far superior to .
12, the amount of ten thousand meters of steel pipe footage
ERW steel pipe wall thickness, the wall thickness tolerances can be ignored, but poor control precision seamless steel pipe wall thickness limit of ¡À 5% t, the general control of ¡À 5 ~ 10% t. In order to ensure the minimum wall thickness to meet the standards and performance, increased wall thickness is only appropriate to resolve. Thus in the same size, same weight of the casing, ERW steel pipe seamless steel pipe longer than 5 to 10% or more, which reduces the amount of ten thousand meters footage steel casing 5 to 10%. Even in the same price, ERW casing virtually the user saves 5 to 10% of the purchase cost.