In view of the reason that the directly forming to square pipe mill is fully convex on all sides, the adjustment methods of four-sided convex, three-sided convex, two-sided convex, and single-sided convex are made respectively.

For rectangular tubes that are convex on all sides, corresponding measures must be taken to eliminate them for specific reasons.

(1) Appropriately increase the cutting width. Especially when trial-manufacturing special-shaped pipes of new specifications, the width of the material used must be based on the principle of “narrowing width but not narrowing”.

(2) Strictly control the process margin of each section. So that there is sufficient sizing margin when entering the sizing section.

(3) Reasonably allocate the sizing allowance in the sizing section. It must be ensured that sufficient materials are available for the last three pass patterns at least.

(4) Anti-deformation pass should be used for the final deformation roller. According to the principle of over-correction, for the convex surface caused by hard material, thin material, wide side length, etc., the anti-deformation pass can be used to over-roll the convex pipe to ensure that the pipe surface just returns after leaving the pass. Bounce into a plane.

(5) Double plane hole type. That is to say, the final vertical roller and flat roller pass are all designed according to the flat pass. This method is more effective when deforming thick-walled rectangular tubes and is most used.

(6) Negative difference method. For the narrow material that has been drawn, the square tube can be adjusted according to the negative tolerance if the standard allows or the customer accepts, which is equivalent to increasing the bandwidth.

(7) Hole type repair. It is found that the hole type wears and becomes concave, which can be repaired for individual hole types that are severely worn; relatively speaking, the repair frequency of the last hole type is a little higher, but the repair amount is mostly small.

According to the above 7 methods, the method to adjust the tube of the directly forming to square pipe mill is convex on all sides.

Convex on three sides. The reason is similar to the four-sided convex, so I won't repeat it.

Convex on both sides. Two-sided convex is divided into two types, namely adjacent convex and opposite convex.

The following table gives some basic reasons and adjustment measures for representative adjacent side convexity and opposite side convexity. (Double click to zoom in to view or save)

Single convex.

The one-sided convexity of the rectangular tube is not common in the oblique hole type. In essence, it is a kind of double-sided convexity that is hidden. Single-sided convexity mostly occurs on rectangular pipes produced with box-type pass and four-section arc disjoint pass.

The formation mechanism is different from the oblique exit hole. If the left side of the rectangular tube produced with four disjoint arc holes is convex, then one of the possible reasons is that the left side of the first upper and lower rollers has been pressed too much. Too much, resulting in a shorter left side when dividing the material.

In terms of adjustment convenience and flexibility, the four-section disjoint arc hole pattern is higher than the oblique hole pattern and the box hole pattern. The premise is to be familiar with the application and find the reason.

When adjusting the directly forming to square pipe mill make tube, the method of full convexity on all sides should be distinguished from the reason of single-sided convex, double-sided convex, three-sided convex, and four-sided convex.