Used in oil and gas transmission pipe, often referred toughness is the Charpy V-notch impact energy test, or sample the plastic fracture morphology percentage share of the entire sample to measure the fracture area. Charpy absorbed energy on the one hand weld pipe weld material is a measure of toughness, brittleness index, more importantly, it is a comprehensive reflection of the level of control ERW steel pipe weld quality. Charpy absorbed energy value is high and stable ERW seam weld quality control level must be higher, poor weld quality steel, the weld or low impact energy definitely large dispersion. In order to prevent brittle fracture and request pipeline pipeline plastic cracking after a good stop cracking performance in the design of the pipeline on the toughness of steel made increasing demands, the use of the pipeline at a lower temperature also need to have good low temperature toughness.
ERW pipe without heat treatment after welding, the weld usually consists of not more than 0.2 mm wide a bright line (fusion line) and was sub-drum-shaped symmetrically distributed on both sides of the bright lines of the heat affected zone constituted. Tests show that the pipe, whether carried out or not carried weld heat treatment, the toughness of the performance of the weakest parts of the vast majority of the weld fusion line. Of course, as raw materials for the production of pipe itself quality in general, if good control of welding conditions, and to take reasonable seam weld heat treatment process, it is possible to make the performance better than the base metal weld parts, this situation provided that: there is room for further improvement in base metal properties by heat treatment, welding and heat treatment parameters under control. In the processing of ERW weld Charpy impact test specimens when the notch position and weld fusion line, have a decisive influence on the test data in the case: the notch root of the weld fusion line, the resulting test result is objective and accurate welding shock absorption function joints; slight deviation (bright line position has deviated from the bottom notch impact toughness of the arc, the arc radius of 0.25 mm), but also make a lot of test data mutation occurs, then the resulting The data has been essentially non-weld steel base material impact absorbed energy.
The biggest problem in the domestic steel appearance and geometry control the management, control is extensive, there are more product surface scratches, bumps, burns. Individual perspective, the appearance of defects in the pipe surface seems to use little effect on the performance of steel, the existence of appearance defects will reduce the effective wall thickness of steel, thus affecting the life of the pipeline; And with corrosion related the damage often have local appearance from the damaged part of the beginning; production plant in terms of the appearance of poor quality, the buyer will suspect that the intrinsic quality of the product, the impact of competitive products. Products in the geometric dimensions of the problem mainly in the geometry of the pipe end portion control, steel pipe roundness, straightness, diameter tolerance control, cut diagonally large pipe end, uneven blunt edge size. These issues of intrinsic quality seems to be little impact of steel, but the construction of the pipeline assembly quality, assembly efficiency, cost has a significant impact. Such as steel factory to provide for a project, although according to the standard, the indicators are qualified, but there is a certain bending (bending are qualified within the allowed range specification), which affects the subsequent processing of steel corrosion insulation, If raceway can not be delivered smoothly curved steel, corrosion pipe insulation made a€?a€?Bohou bending unequal. As technology advances, automatic, semi-automatic ring welding device applications in the pipeline laying more and more popular.
