SU1616742A1 - Method of preparing billet before screw rolling - Google Patents

Abstract

The invention relates to the field of metal forming and can be used in the preparation of billets of alloyed stainless, high-speed steels before helical rolling. The purpose of the invention is to save metal by increasing the yield of rolled products. This is achieved due to the deep cleaning of the blanks (up to 8-10% of the diameter), as well as the correct choice of the ratio of the depth of the stripping to the width in the range 0.16-0.25. 2 tab.

Description

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The invention relates to the processing of metals by pressure and can be used in the preparation of billets of alloyed stainless high-speed steels before helical rolling.

The purpose of the invention is to save metal by increasing the yield of rolled products.

The essence of the method consists in removing the unacceptable surface defects (flaws, cracks, sunsets, hairs.) Of steelmaking and preliminary rolling production with local shearing with a depth of 8-10% of the diameter of the original billet at a ratio of the stripping depth to the width of the stripping section 0.16 -0.25.

The proposed ranges are established during experimental studies.

conducted under the conditions of the rolling mill.

. The determination of the optimal values of the above ratios was carried out experimentally by rolling the metal into a series of heats of various steel grades, the relative depth of the boron clearing of the blanks in each of the heats was uniform and amounted to 5-14% of the diameter of the blanks.

Analysis of the results (Table 1) showed that the minimum values of the through-flow ratio; Kp correspond to a stripping depth of 8-10% of the diameter of the workpiece.

From Table 1 it can be seen that selective stripping with a depth of 5-7% of the diameter of the workpiece ensures high-quality finished rolled products, but leads to greater metal loss

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at the stage of rejection of the original preparation. Only 68% of all billets cleared in the specified interval, not deeper surface defects and were allowed to be rolled. Despite the high quality of finished rolled products, the through consumption ratio of the metal for this group of billets is quite high significant loss of sheet metal. at the stage of control and rejection of the initial billet,

In the case of local cleaning of surface defects with a depth of the billet diameter, the value of the through expenditure coefficient is also high.

Notwithstanding the minimal losses at the stage of rejection of the original billet, a significant cross-sectional expenditure coefficient is due to the mass rejection of rolled products in the finished grade due to surface defects such as captivity and sunset. characteristics, where there were no blanks, which caused the appearance of surface defects during rolling.

Optimum values of the through flow rate coefficient pfin of all steel grade groups are obtained at the depth of stripping diameter, when the likelihood of new surface defects during subsequent rolling is reduced to a minimum, which allows saving metapp by reducing the scrap rate of finished rolled products as a result of expansion permissible limits of deviations of geometric dimensions from nominal,

Stripping depths of less than 8% of the workpiece diameter will not allow for penetration of deep penetrating defects, for example, 10 mm deep flaps on steel blanks of P 18 with a diameter of SO-UZ mm or hair depths lying at a depth of 7 mm on blanks of I tool steels 40X9C2M, 40X1OC2M diameter .90 i. The stripping depth of more than 10% of the billet diameter is not practical: TiK “lead to a significant change in the geometric characteristics of the blanks and the following transformation of the local stripping zones in captivity.

In order to determine the optimal ratio of depth and width (h / S) of the stripping zone, studies were conducted during which billets of structural steel 40X rolled, rolled with the same depth of local stripping (10% of the diameter), but with different width of stripping zones. (cm,

tabv2). The ratio of depth to stripping width 4: 3 (0.33) and more leads to an increase in the expenditure ratio of the metal of the CP due to the mass from the rejection of finished rolled products by quality

5 wu surface. Non-observance of the gentle stripping zones leads to the formation of sunsets in the finished variety, respectively, the through expenditure coefficient increases sharply, Optimal

0 is the ratio of the depth and width of the stripping zone (0.25 0.16).

Workpiece processing with a ratio of depth and width of the stripping zone

5 1 ° 4 o6ecne4jiBaeT metal saving during the stripping, since with 1 brush of the stripping area at least 4 times the depth of the defect, only a metal layer is removed;

Q prevents the formation of pling-i on the outer surface of the car. In addition, when the proposed site for the clean of the site is provided once the gate grinding wheels ddt remove

g traces of the exit of grinding wheels in the form of sharp edges, which does not require the use of additional devices for their removal,

When the ratio is less than 0.16, the metal layer is removed, which significantly exceeds the amount of foam required on the outer surface of the car, which leads to an unjustified increase in the consumption of 5 tal

Preparation of the billet for screw rolling according to the proposed method is carried out in the following manner,

SP Initial procurement is set to

device for mechanical cleaning, where abrasive circles are used to remove chips from separate areas (flat), cleaning at these sites is carried out with a depth of at least 4 times the depth of the defect, except for TorOj, sharp traces of abrasive output on the same wheel

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machine tooling by trimming and light cutting around.

Example:. In the course of the research, workpieces from the EP 222 alloy with a diameter of 100 mm were cleaned, and artificial defects imitating flaws such as flaws were preliminarily applied. Scraping was carried out on the machine with abrasive circles with a diameter of 600 mm and a width of 30 mm. Selective cleaning of defects was carried out to a maximum depth of 8 mm (8% of the diameter of the workpiece) with the ratio of the depth of cleaning to width I; 6 (0.16). Then the prepared billets were rolled on an experimental helical rolling mill. The through consumption ratio was 1.09, while no surface defects were detected on the finished car.

Example; 2. In accordance with the method described in Example 1, blanks were made from EP 222 alloy with a stripping depth of 80 mm (10% of the diameter of the blank) at a ratio of stripping depth to width of 1: 4 (0.25). 1.06. There were no defects in the surface and finished rolled products.

The average through-use coefficient for a given steel grade is

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is 1.25-1.3, Tie. for the proposed values of the stripping interval, this indicator is noticeably lower.

The blanks prepared by the proposed method satisfy the requirements for obtaining defect-free rolled products with high surface quality and accurate geometric characteristics.

The proposed method of preparation of the billet before helical rolling, as compared to the known one, allows 5 to ensure the production of defect-free finished products that do not require regrinding to a smaller profile size or complete rejection, thereby allowing to obtain metal savings.

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Claims (1)

Formula invented and The method of preparation of the workpiece prior to helical rolling, which includes a selective cleaning of surface defects, characterized in that, oh, in order to save metal by increasing the yield of rolled steel, cleaning is carried out to a depth of 30 8-10% of the diameter of the workpiece when the ratio of the depth of stripping to the width of the stripping section is 0.16-0.25. Tab Ma I