RU2814544C1 - Piercing mill line - Google Patents

Abstract

FIELD: milling.

SUBSTANCE: invention relates to a line of piercing mill. The ruler contains a ruler input cone, on which a profiled section is made, having a convex radius and the longitudinal profile of which begins at the starting point of the ruler profile, and its apex is in the horizontal plane below the level of the ruler pinch point. The profiled section ends at the point of double extension of the mandrel beyond the clamp and turns into a concave profile with a radius that smoothly aligns it with the input cone of the ruler.

EFFECT: accuracy of the geometric parameters of the rolled sleeve increases.

1 cl, 1 dwg, 1 tbl, 1 ex

Description

The invention relates to pipe rolling production and can be used to produce liner blanks in helical rolling mills.

A known guide line for a piercing mill [Danilov F.A., Gleiberg A.Z., Balakin VT. "Hot rolling of pipes." - M.: Metallurgizdat, 1962, p. 223÷224]. The known ruler of a piercing mill has input and output sides separated by a ridge, inclined in the longitudinal section to the base at angles where the slope of the input side of the ruler is usually 1-3° greater than the angle of the input cone of the rolls, and the slope of the output side of the ruler is equal to or slightly less than the output cone rolls

There is a well-known ruler for a piercing mill (USSR Patent No. SU 789171 A1 02/26/1979), which is the closest in technical essence (prototype), having a horizontal base and a profile working surface composed of inlet and outlet sections with oppositely inclined generatrices and a horizontal section adjacent to the end to the beginning of the output section, in which, in order to increase the accuracy of the sleeves by stabilizing the position of the mandrel in the deformation zone and increasing the wear resistance of the ruler, an additional section is made between the input and horizontal sections with a length equal to 0.1-0.2 the length of the ruler with an inclined generatrix directed opposite and at an angle 2-8 times greater than the inclination of the generatrix of the inlet section.

The disadvantages of the known piercing mill rulers are the insufficient contact of the continuously cast billet and the piercing mill ruler at its input cone, which leads to the problem of a continuously cast billet not along the rolling axis and, as a consequence, a large degree of freedom of the workpiece at the input section of the piercing mill ruler, this leads to the end curvature of the pierced sleeve (the continuously cast workpiece shifts relative to the rolling axis during the piercing process), while the mandrel enters the workpiece with a deviation, which leads to a transverse difference in thickness along the length of the pierced sleeve, i.e. to a general decrease in the accuracy of the geometric parameters of the rolled sleeve.

The listed shortcomings entail unnecessary metal losses due to the cutting of defects in pipes due to the non-compliance of their geometric parameters with the requirements of regulatory and technical documentation.

The technical objective of the invention is to create a piercing mill line that ensures the retention of a continuously cast billet along the rolling axis at the stage of the piercing process and the task of a workpiece with an end defect in the primary gripping zone.

The technical result consists in ensuring the accuracy of the geometric parameters of the liner and reducing its end curvature by holding the continuously cast billet along the rolling axis at the stage of the piercing process.

The technical result is achieved due to the fact that the proposed line of piercing mill contains a horizontal base and a profile working surface, including input and output sides separated by a ridge, inclined in the longitudinal section to the base at angles. According to the invention, on the input cone of the ruler there is a section responsible for holding the workpiece along the rolling axis, at the stage of the piercing process, in the form of a convex radius, the longitudinal profile of which begins at the starting point of the ruler profile, and its apex is in the horizontal plane, below the level of the pinching point of the rulers by the value of coefficient k, which is calculated by the formula:

k=kз×kд, where

kз - coefficient taking into account the type of workpiece and ranges from 1.0 to 1.1;

kd is the tolerance coefficient that takes into account the structural accuracy of the mill and ranges from 1.029 to 1.036.

The profiled section ends at the point of double extension of the mandrel beyond the clamp and turns into a concave profile with a radius that smoothly aligns it with the input cone of the ruler.

A comparable analysis with the prototype shows that the claimed invention has significant distinctive features and meets the criterion of novelty.

The profile of the piercing mill line is made as follows.

In accordance with the Figure, on the existing line of the piercing mill, on the input cone, a section is made that is responsible for holding the workpiece in the piercing cone in the form of a convex radius R ₁ . The height of the completed section is in the horizontal plane below the level of the pinching point Lper of the rulers by the value of the coefficient k, which is determined by the formula:

k=kз×kд, where

kз - coefficient taking into account the type of workpiece and ranges from 1.0 to 1.1;

- when piercing a continuously cast billet after machining, kз=1.0;

- after continuous casting of the billet, kз=1.1;

kd is the tolerance coefficient, which takes into account the structural accuracy of the mill, and ranges from 1.029 to 1.036;

- when piercing a continuously cast billet with a diameter of 290 mm, kd=1.029;

- when piercing a continuously cast billet with a diameter of 360 mm, kd=1.036.

The completed section ends at the point of double extension of the mandrel beyond the pinch 2Lper and turns into a concave profile with a radius R ₂ that smoothly aligns it with the input cone of the ruler, ensuring the task of the workpiece with an end defect in the primary gripping zone.

Piercing of a continuously cast billet on a piercing mill using the proposed line of piercing mill is carried out as follows. The heated continuously cast billet is set by a pusher along a profiled section made on the input cone of the ruler, consisting of: a convex radius section responsible for holding the continuously cast billet along the rolling axis and a concave radius profile smoothly aligned with the input cone of the ruler, enters the primary gripping zone . The continuously cast billet captured by the rollers moves along the rolling axis to the secondary gripping zone and directly to the piercing of the continuously cast billet on the mandrel, while the metal flows smoothly and evenly.

An example of the application of the proposed line of piercing mill.

Two pairs of piercing mill rulers were manufactured with experimental calibration of their input section, intended for rolling continuous cast billets (CCB) with a diameter of 290 mm and a diameter of 360 mm on a piercing mill. To ensure equal conditions during the experimental work, rolls of the same diameter (1470 mm) were used.

Based on the testing results, an assessment was made of the level of pipe metal losses due to defects: “internal rolling film”, “curvature” and “wall deviation plus/minus”, depending on the calibration of the input section of the applied piercing mill lines and using the same pairs of rolls of this mill, the results of which are shown in Table 1.

According to Table 1, it can be seen that the use of experimental piercing mill lines, ensuring retention of the continuously cast billet along the rolling axis, at the stage of the piercing process, due to the convex radius section, made it possible to reduce pipe metal losses for the following reasons:

- defect “internal rolling film” from 0.26% to 0.16% when rolling continuous cast iron with a diameter of 290 mm and from 0.65% to 0.39% when rolling continuous cast iron with a diameter of 360 mm;

- “curvature” from 0.38% to 0.08% when rolling continuous cast iron with a diameter of 290 mm and from 0.71% to 0.38% when rolling continuous cast iron with a diameter of 360 mm;

- “wall deviation plus/minus” from 0.21% to 0.10% when rolling a continuous cast iron with a diameter of 290 mm and from 0.20% to 0.12% when rolling a continuous cast iron with a diameter of 360 mm.

The use of the proposed piercing mill line made it possible to ensure the retention of the continuously cast workpiece along the rolling axis, at the stage of the piercing process, due to the convex radius section located on the input cone of the piercing mill line, which increased the accuracy of the geometric parameters of the sleeve and reduced its end curvature, resulting in decreased loss of pipe metal due to cutting defects.

Claims (4)

A piercing mill ruler containing a horizontal base and a profiled working surface, including input and output sides separated by a ridge, inclined in the longitudinal section at an angle to the base, characterized in that it contains an input cone of the ruler, on which a profiled section is made, which is responsible for holding the workpiece along rolling axis at the stage of the piercing process, having a convex radius, the longitudinal profile of which begins at the point of the beginning of the profile of the ruler, and its top is in the horizontal plane below the level of the pinch point of the ruler by the value of the coefficient k, and the profiled section ends at the point of double extension of the mandrel beyond the pinch and transforms into a concave profile with a radius that smoothly combines it with the input cone of the ruler, and the value of the coefficient k is determined by the formula k=kз×kд, where kз – coefficient taking into account the type of workpiece and ranging from 1.0 to 1.1; kd is the tolerance coefficient that takes into account the structural accuracy of the mill and ranges from 1.029 to 1.036.

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