ERW pipe weld zone tensile properties and corrosion resistance will cause a certain degree of damage.
ERW pipe billet edges were heated in an instant and squeeze butt together to form a weld, in the process with the skin effect and the proximity effect of high frequency current generated by the electric heat is highly concentrated, the current penetration depth and impact. The areas are small and limited to phase transitions within a small heat-affected zone. Heat affected zone phase transition and the unit coolants exist at the same time, the weld of steel pipe undergoes a rapid heating and rapid cooling process before and after welding, resulting in an undesired heat affected zone. The microstructure different from the base metal (ferrite + pearlite), the part of which contains untempered martensite or bainite. This is an undesirable organization that affects the strength and mechanical properties of the steel pipe. Therefore, most of the steel pipe standards (such as the API standard) require removal of untempered martensite.
Steel is usually made of welded steel pipe is basically Mn and M hot-rolled steel, the alloy elements in all the solid solution conditions, good overall performance. Mn and V series, M and aNb series and Mn and Ti series belong to normalized steel. In addition to solid solution strengthening, there is precipitation strengthening effect, which must be normalized to get the best comprehensive performance. Higher carbon weld hardened significantly, less ferrite, the main body of the intermediate tissue is martensite. After normalizing can be obtained ferrite and pearlite, improve toughness.
The main features are as follows: the microstructure of the weld zone is not uniform, the S and P impurity elements and alloying elements are segregated, and the precipitation of carbides and nitrides in the heat-affected zone makes the stress corrosion cracking easily occur in the weld zone. Post-weld heat treatment can largely eliminate the above-mentioned harmful factors. Heat treatment of erw pipe, but also can make the weld groove corrosion resistance is improved, is to prevent one of the important means of trench erosion.
Welding oil well pipe, boiler tubes and other high-frequency welding process prone to hardening phase and tissue stress, the weld brittleness increases, the overall mechanical properties decline, so these welded pipe welding heat treatment to weld and heat. The zone of influence has a consistent strength match with the parent and eliminates welding residual stresses. Welded steel pipe weld heat treatment process are normalizing, to stress annealing, quenching - tempering, normalizing - tempering and so on.
What are the precautions for storing seamless steel pipes?
1. Choose a suitable venue and warehouse; 2. Reasonable stacking, advanced first; 3. Packaging and protective layers of protective materials; 4. Keep warehouse clean and strengthen material maintenance.
Significance of Proximity Effect on the Production of High-frequency Longitudinal Welded Pipes
In addition to the skin effect, the proximity effect is another feature of current. When alternating currents of equal magnitude and opposite directions pass through two adjacent conductors, the current will flow through the adjacent inner surface layers of the two conductors, and when the two conductors pass When alternating currents of the same size and direction, the current will flow through the outer surface layers of the two conductors. The proximity effect of the current makes the current in the conductors further uneven. It is this unevenness that makes the high-frequency welded pipe(ERW).
Summary of Advantages and Disadvantages of High-Frequency Welded Pipe Forming Methods
Advantages and disadvantages of high-frequency welded pipe forming methods
