JPS60152302A - Method for precision rolling of steel bar - Google Patents

Abstract

PURPOSE:To achieve economically the precision rolling of a steel bar excellent in dimensional accuracy by regulating a reduction rate of area by a sizing mill constituted of three or more sets of specifically arranged rolling mills for performing the titled rolling after the finishing rolling of hot rolling process. CONSTITUTION:After passing the horizontal rolls 10 at the final stage of a line of finishing mills in a hot rolling process, a steel bar 12 is formed into a prescribed cross-sectional shape, which is not yet sufficient for desired final cross- sectional shape and dimensional accuracy. Then the steel bar 12 is successively fed to a seizing mill 14 consisting of >=3 sets of rolling mills arranged on the downstream side. Each pair of rolling rolls of these mills is arranged so that its rotating axes are displaced alternately by 90 deg. with respect to an adjoining pair of rolls, and the mills consist of vertical, horizontal, and vertical pairs of rolls 16, 18, and 20 respectively. And the total sum of the reduction rates of area of these pairs of rolls is regulated to <=15%, and the reduction rates of area of the rolls 18, 20 of the final two sets of mills are regulated to <=3% respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a precision rolling method that can satisfactorily improve the rolling dimensional accuracy of a steel bar manufactured through a hot rolling process.

Steel bars are produced as long materials with various cross-sectional shapes by hot rolling raw steel, and most of them are processed into various products by secondary and tertiary processing manufacturers, and are used in many industrial fields. It has come into widespread use. Processing manufacturers, which are the users of these steel bars, generally use the delivered steel bars as raw materials for cold forging and warm forging, and perform forming processes such as heat treatment, drawing, and flow cutting as necessary. However, recently there has been a demand for the supply of high-quality rolled steel bars that allow users to omit these steps. This high-quality rolled steel bar is hot-rolled after passing through groove rolls, and has a high degree of dimensional accuracy in terms of cross-sectional shape, length, and bending. After finish rolling in the process, precision rolling techniques are increasingly applied.

As this precision rolling technique, the following various means have heretofore been known, but all of them have some drawbacks and cannot be called perfect. That is, (a) Hole shape improvement method: This method improves the hole shape (caliber) of the rolling rolls used in the finishing row for precision rolling, and although it is economical, the accuracy obtained is 50φ±0. The limit is about 25 mm, which is difficult to call precision rolling.

(b) Skin pass method This method aims to improve the precision of the first method by preforming the material by normal finishing rolling and then passing it through a temper rolling mill with a reduced area ratio (1 to 3%). There is a limit to accuracy (50φ±0.20mm) due to the
It has shortcomings such as a short lifespan.

(c) Sizing guide method This method uses rollers to shape the left and right sides immediately after finish rolling.

There are disadvantages such as adjustment requires skill and tends to cause variations, and lacks reliability due to lack of rigidity and short life.

The precision rolling method for bars according to the present invention has been proposed in order to solve the above-mentioned drawbacks inherent in the conventionally known precision rolling techniques. A dedicated sizing mill is provided, and this sizing mill is composed of at least three rolling mills, and the rotation axes of adjacent rolling rolls of each rolling mill are alternately set at 90°.
The steel bars are passed through in an array that is offset by °, and at this time, the area reduction ratio of each rolling roll is the same! ! 115% or less, and the area reduction ratio of the final two rolling rolls is 3% or less, and furthermore, the rolling speed between the final roll of the finishing mill and each rolling roll of the sizing mill is gradually increased toward the downstream side. By controlling the operation, precision rolling of steel bars with excellent dimensional accuracy can be achieved economically.

Next, regarding the precision rolling method for steel bars according to the present invention.

A preferred embodiment will be described below. FIG. 1 schematically shows a preferred embodiment of the method according to the present invention, in which reference numeral 10 indicates the last horizontal roll in the finishing row of the hot rolling process, and the steel bar 12 is the horizontal roll. Although it has been rolled and formed into a predetermined cross-sectional shape through 10 steps, the final cross-sectional shape and other dimensional accuracy have not yet been sufficiently improved. Therefore, the steel bar 12 that has undergone finish rolling is
The product is subsequently supplied to a sizing mill 14, which is comprised of at least three rolling mills, located downstream, where precision rolling is performed. That is, the rolling rolls of the at least three rolling mills constituting the sizing mill 14 are arranged so that their rotation axes are alternately offset by 90' with respect to the adjacent rolling rolls. In the example, on the downstream side of the horizontal rolls IO of the finishing row, the vertical rolls 16. Horizontal rolls 18 and vertical rolls 20 are arranged alternately in this order. As an alternative example, a horizontal roll
Of course, it is also possible to arrange the rolls in the order of vertical rolls and horizontal rolls.

The area reduction rate of each rolling roll 16.18° 20 of the sizing mill 14, which is composed of at least three rolling mills, is 15% or less on the overall side, and the horizontal roll in the final two rolling mills is The area reduction ratios of the rolls 18 and the vertical rolls 20 are each set to be 3% or less. Also, the final horizontal roll 10 of the finishing row and the sizing mill 1
The rotation of each roll is controlled so that the rolling speed between each of the rolling rolls 16, 18, and 20 of No. 4 gradually increases from the upstream side to the downstream side.

Note that various embodiments other than the illustrated embodiment can be assumed for the arrangement relationship between the finishing row rolls 10 and the rolling rolls 16 of the first rolling mill in the sizing mill 14. For example, as shown in FIG.
6 may also be arranged vertically, or, as shown in FIG. 3, both rolls 10, 1.6 may be arranged horizontally. However, it is generally preferred that the rotational axes of each roll 10.16 are offset from each other by an angle of 90 DEG as shown in FIG.

As described above, according to the precision rolling method for steel bars according to the present invention,
When a steel bar formed into a predetermined cross-sectional shape after finish rolling in the hot rolling process is passed through a sizing mill located downstream for precision rolling, the area reduction rate is determined by the rate of reduction of each rolling roll in the sizing mill. Since the total is set to be 15% or less, and the area reduction rate of the final two rolling rolls is set to be 3% or less, the dimensional accuracy can be reasonably improved to, for example, 50φ±O, 15mm. be able to. Furthermore, since a sizing mill dedicated to precision rolling is used and the rolling is carried out with a reduced area ratio, it has useful advantages such as excellent rigidity and high reliability.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an embodiment of the precision rolling method for steel bars according to the present invention, and FIGS. 2 and 3 are schematic explanatory diagrams of still other embodiments. Patent applicant: Daido Steel Co., Ltd. FIG. 2 FIG. 3 0

Claims (1)

[Claims] When further precisely rolling a steel bar that has been rolled into a predetermined cross-sectional shape through a hot rolling process, the rotation axes of adjacent rolling rolls alternately rotate the steel bar that has passed through a finishing mill in the hot rolling process. It passes through a sizing mill consisting of at least three rolling mills arranged sequentially so as to be offset at an angle of 90°, and at this time, the area reduction of each rolling roll in the sizing mill is 15% or less in total, and the final The area reduction ratio of each of the two rolling rolls is 3% or less, and the rolling speed between the final roll of the finishing rolling mill and each rolling roll of the sizing mill is controlled so as to gradually increase toward the downstream side. Precision rolling method for steel bars.