RU2257970C1 - Process for rolling strip with round thickened portions in its edges - Google Patents

Abstract

FIELD: rolled stock production, namely hot rolling of merchant bars, possibly manufacture of strips with round thickened portion in their edges such as blanks of door hinges of automobiles.

SUBSTANCE: method comprises steps of multi-pass reduction of strip by thickness in horizontal grooved rolls; in last pass reducing strip while forming fins on round thickened portions; providing elongation factor of mean part of strip in range 1.13 - 1.19 and elongation factor of round thickened portions in range 1.20 - 1.27.

EFFECT: possibility for making accurate profile of round thickened portions in edges of strip due to overfilling peripheral parts of roll groove pass.

1 dwg, 1 tbl, 7 ex

Description

The invention relates to rolling production, and more particularly, to hot high-quality rolling, and can be used in the manufacture of strips with round thickenings along the edges, in particular blanks of car door hinges.

For the manufacture of links of car door hinges, hot-rolled strips with round thickenings along the edges are used. Calibrated hot rolled strips with round thickenings along the edges are cut along the longitudinal axis of symmetry and then divided in the transverse direction into blanks of door hinges.

Known methods of rolling strip profiles with round thickenings along the edges for the manufacture of the movable link of the door hinge of the car. The method involves heating the strip and its compression in thickness for 9 passes in horizontal rolls with calibers [1].

The disadvantages of the known methods are that the rolled strip has defects on round thickenings along the edges in the form of non-fulfillment of the profile. As a result, the quality of the finished product is reduced.

There is also known a method of hot rolling strips with round thickenings along the edges, including its multi-pass reduction in thickness in horizontal rolls with calibres: rough, pre-finishing and finishing. Rolling in horizontal rolls with calibers is carried out to obtain the final thickness of the strip [2].

The disadvantages of this method are that on round thickenings of the edges there is a failure profile. This leads to a decrease in the accuracy of strips with round thickenings along the edges.

The closest in its technical essence and the achieved results to the proposed invention is a method of rolling a strip with round thickenings along the edges, including its multi-pass compression in thickness in horizontal rolls with calibers, according to which when the ratio of strip width to its thickness is equal to 15-19, the strip is crimped in width in vertical rolls with a caliber with a compression ratio of 1.2-2.2%, after which it is again crimped in horizontal rolls with calibers to a final thickness [3].

The disadvantage of this method is that after compression in horizontal rolls with calibers to a final thickness, the profile of round thickenings along the edges is not fulfilled. This occurs as a result of displacements of the strip from the axis of rolling, unevenness of the temperature field of the strip, wear of the gauges of the rolls of the finishing mill. The decrease in the accuracy of round thickenings along the edges leads to increased rejection of hot-rolled strips.

The technical problem solved by the invention is to increase the accuracy of round thickenings along the edges and reduce the rejection of hot rolled strips.

To solve the specified technical problem in the known method of rolling strips with round thickenings along the edges, including its multi-pass compression in thickness in horizontal rolls with calibers, according to the proposal in the last pass, the strip is squeezed with the formation of burrs on round thickenings, with the hood of its middle part equal to 1 , 13-1.19, and with a hood of round thickenings equal to 1.20-1.27.

The drawing shows the sequence of changes in the cross section of the strip with round thickenings along the edges in the penultimate (A) and last (B) passes when implementing the proposed method.

The invention consists in the following. In a real rolling technological process, the adjustment and calibration of the last (finishing) mill stand does not in itself provide high accuracy of the finished strip: inevitable strip displacement from the rolling line, violation of the size and shape of the gauge of the penultimate stand due to wear, uneven temperature field of the strip leads to distortion of the size of the round thickenings. To exclude the influence of disturbing factors on the accuracy of the size of round thickenings, they are compressed with a deliberate overflow of peripheral sections of the caliber and the formation of longitudinal burrs. Due to the fact that the drawing coefficient in these sections λ _k = 1.20-1.27 exceeds the drawing coefficient in the middle part of the strip λ _c = 1.13-1.19, an "excess" metal appears, which is forced out of the gauges onto free surfaces profile in the roll connector in the form of burrs. A more intense compression of round thickenings blocks the effect of disturbing factors, thereby increasing the accuracy of the strip dimensions. The longitudinal burrs are subsequently mechanically removed by dividing the calibrated profile into blanks of door hinges.

It was experimentally established that when the drawing coefficient in the middle part of the strip λ _s <1.13, the necessary accuracy of the flat element of the profile strip is not provided. If λ _c > 1.19, then the strip loses stability in the last pass and takes a curved shape, which is unacceptable.

The decrease in the coefficient of drawing during compression in the last pass of round thickenings less than 1.20 (λ _to <1.20) with the coefficient of drawing in the middle part λ _s = 1.13-1.19 leads to a decrease in the accuracy of round thickenings. An increase in λ _to more than 1.27 causes an increase in burrs and increases the consumption of metal in the production of car door hinges.

Method implementation examples

An initial billet of square section 100 × 100 mm made of grade 25 steel is heated to a temperature of 1230 ° C and rolled on a section rolling mill 350 in horizontal rolls with closed-type beam calibers in 9 passes with crimps in thickness and alternating positions of the gauge connectors.

After crimping in the penultimate, 8th passage, the strip takes the form of a cross section A (see drawing). The area of the flat section of the cross section of the strip S _c8 = 740.55 mm ² , and the area of each thickened edge S _k8 = 52.89 mm ² .

In the last, 9th pass, the strip is crimped to the final cross-sectional dimension B, having a flat area S _c9 = 638.4 mm ² and an area of each thickened edge S _k9 = 43.0 mm ² . Thus, in the last pass, the coefficient of extraction of the middle part of the strip is equal to:

and the drawing coefficient of each round thickening at the edge is:

Due to the fact that round thickenings along the edges in the last pass compress more intensively than the middle part of the strip, the "excess" metal is squeezed out of the thickenings into the connector between the rollers, forming burrs (see drawing). At the same time, disturbing factors acting during rolling cause only an increase or decrease in burrs and do not affect the accuracy of round thickenings along the edges. As a result, the rejection of hot rolled strips is reduced.

The burrs on the round thickenings of the strip are subsequently mechanically removed during milling of the blanks of the car door hinges.

Variants of the method and indicators of their effectiveness are given in the table.

Table Rolling modes and quality of strips with round thickenings along the edges No. p / p λ _s λ _to The accuracy of round thickenings, mm Sort% 1 1.12 1.19 ± 0.05 2.40 2 1.13 1.20 ± 0.01 0.13 3 1.16 1.23 ± 0.01 0.11 4 1.19 1.27 ± 0.01 0.12 5 1.20 1.28 ± 0.04 2.12 6 1.30 1.30 ± 0.09 2.69 (prototype)

From the table it follows that in cases of the implementation of the proposed method (options 2-4), an increase in the accuracy of round thickenings along the edges is achieved, which reduces the sorting of hot-rolled strips.

With exorbitant values of the declared parameters (options 1 and 5), the accuracy of round thickenings along the edges decreases. At the same time, the sorting of hot rolled strips increases. Strips rolled in accordance with the prototype method (option 6) also have lower accuracy of round thickenings along the edges and greater sorting of hot rolled strips.

The prototype method is adopted as the base object. The application of the proposed method will improve the profitability of the production of strips with thickenings along the edges by 15-22%.

 Sources of information

1. N.E. Skorokhodov and others. Calibration of complex profiles (reference). M .: Metallurgy, 1979, p. 48-51.

2. B. M. Ilyukovich and others. Rolling and calibration of shaped profiles. Directory. M .: Metallurgy, 1989, p. 188-190.

3. Patent of Russia No. 2184628, IPC B 21 V 1/08, B 21 V 108/4, 2002 - prototype.

Claims (1)

A method of rolling a strip with round thickenings along the edges, including its multi-pass reduction in thickness in horizontal rolls with calibers, characterized in that in the last pass the strip is crimped with the formation of burrs on round thickenings with a draw ratio of its middle part equal to 1.13-1, 19 and with a draw ratio of round thickenings equal to 1.20-1.27.