Effects Of Different Wall Thicknesses On The Properties Of Weld Heat Affected Zone

Weld steel pipe supplier china to share with you: In the case of fixed output power of high-frequency equipment in China, the thinner tube wall is affected by the skin effect and proximity effect, and the tube blank before the welding point The isotherms at the edges are more evenly distributed on the cross section, so the range of the metal melting zone and the heat affected zone is relatively small. Applying a small pressing force is sufficient to eliminate the slag and reasonably weld together to form a narrow, ideal thermal influence. For thicker pipe walls, the isotherms at the edges of the tube blank are distributed over a wider section. When the neutral layer reaches the welding temperature, the edges and corners are partially overburned.

Obviously, the closer to the welding junction temperature, the higher the temperature, and when the tube wall is thicker, one, because the tube blank edge under the skin effect and proximity effect peculiar to the high-frequency current, the neutral layer has not reached the welding temperature when Overheating may occur in the corners, and in order to perform reasonable welding, the melting zone must be widened so that the neutral layer can be properly welded. As a result, the heat-affected zone must be correspondingly widened, and the corners may overheat; Then, although everyone is pursuing the two sides of the tube blank to contact as parallel as possible during welding, and think of many methods for the design of the forming roller and the adjustment of the extrusion force, in practice, the thicker the tube wall, the more the deformation stress will be. The larger the rebound, the greater the rebound phenomenon, especially in the production of thick-walled small-diameter welded pipes.

In fact, when thick-walled pipes are welded, the inside of the wall is often contacted first, which is why the metal streamline angle of thick-walled pipes is prone to two asymmetries inside and outside the wall thickness. As long as this asymmetry is not serious and the angle is not less than 40 °, the quality of the weld can still be guaranteed. As long as the extrusion force can squeeze the overheated Weiss structure and slag into the burr, the quality can be guaranteed. Purpose without having to deliberately pursue the heat affected zone must reach 1/4 ~ 1/32 of the wall thickness. 2

solution:

When the thick-walled pipe process is adjusted, the position of the induction coil should be appropriately moved backward to increase the heating time; the V-shaped opening angle should be appropriately reduced to increase the proximity effect, so that the high-frequency current in the load circuit is highly concentrated and the heating efficiency It can be significantly improved; at the same time, the extrusion force is appropriately increased to effectively prevent reflow inclusions to ensure welding quality.

ERW Welded Steel Pipe

solve the disadvantages of ERW steel pipe construction pipe during welding, the following 4 measures can be taken:

(1) When the roll forming unit has only one pre-bending roller, an additional pre-bending roller may be added when the equipment layout allows;

(2) The steel strips are coiled in a reasonable arrangement direction when slitting the steel strips, that is, two adjacent strips are coiled in opposite directions, so that each strip can enter the forming machine with a positive trapezoidal section. Make it easier for the two edges to be parallel before welding;

(3) When designing the squeeze roll, consider making the tube blank near the oblate circle at the welding point, leaving space for the two sides of the tube tend to be parallel;

(4) A planing and milling device is added in front of the forming machine to make the steel strip plan and mill the edges and corners on the two sides before entering the forming machine to avoid the welding quality being affected by the overheating of the edges during the welding process.

Conclusion:

The shape of the ERW welded steel pipe welding heat affected zone is closely related to the selection of welding process parameters. For welded pipes with different wall thicknesses, the width of the welding heat affected zone and the metal streamline allow a certain difference. When the t / D ratio increases, corresponding technical measures should be taken to seek reasonable heat affected zone properties, which is conducive to the stable improvement of welded pipe quality.