RU2212291C1 - Method for operation of supporting rolls in sheet mills - Google Patents

Abstract

FIELD: manufacture of rolled products, in particular, supporting rolls for hot and cold rolling of sheet steel. SUBSTANCE: method involves charging and discharging rolls; resharpening roll barrels as they wear; upon reduction of barrel diameter by 2.5-2.8%, discharging supporting rolls from hot rolling mill and positioning in one of two first stands of cold rolling mill having barrels of the same length, with roll shaft end configuration being preliminarily changed in accordance with requirements; setting single barrel surface removal value within the range of 0.20-0.23% of barrel diameter, when said barrel is worn in cold rolling mill. EFFECT: increased efficiency and reduced usage of supporting rolls. 1 ex

Description

 The invention relates to the processing of metals by pressure and can be used for hot and cold rolling on continuous broadband mills.

 Modern broadband mills contain quarto working stands, in which two backup rolls of large (up to 2.4 m) diameter and two workers carrying out direct rolling of metal are installed. The purpose of the backup rolls is to reduce the deformation (deflection) of the work rolls of a smaller diameter, which improves the geometry (flatness) of the finished sheet metal.

 One of the reasons for the appearance of the defect “transverse thickness thickness of strips” is the uneven wear of the barrels of the working and backup rolls of hot rolling mills (see the book by S. P. Efimenko and V. P. Slednev “Roller of sheet rolling mills”, M., Metallurgy. 1980, p. .54), which necessitates periodic dumping and regrinding with a decrease in barrel diameter, as a result of which the backup rolls become unsuitable for further operation after a certain amount of reduction in the specified diameter. In order to increase the resource (extension of the working campaign) of sheet rolling rolls, various technological methods are used.

 There is a method of preparing rolls of sheet rolling mills for work, in which their surface layer is strengthened by compressing rolls between them when they are bent forcibly of various sizes, and the rate of change in bending when rolling rolls in a compressed state is regulated (see AS USSR 1574302, class B 21 B 28/02, published on 06/30/90). There is also a method of preparing the rolls for work, including loading the rolls with a spacer force by installing a strip in the roll gap and rotating them with a predetermined metal compression for a certain number of loading cycles for each strip (see AS USSR 1135508, class B 21 V 28/02, published in BI, 1985, 3).

 The disadvantage of the described methods is the inability to use worn backup rolls of the strip hot rolling mill as backup rolls of the first stands of the cold rolling mill.

 The closest analogue to the claimed object is the technology of operation of rolls of sheet rolling mills, described in the book of Yu.V. Konovalova and others. Directory distributor. M., Metallurgy, 1977, p. 2018.

 This technology includes the regrinding of the rolls for wear with their preliminary dumping and subsequent filling in the stands, and is characterized by the fact that they are kept for 5-6 months or replaced by tempering before installing new rolls in the mill, and when the rolls are working, they are heated before filling into the crate.

 The disadvantage of this technology is the inability to use worn backup rolls of the hot rolling mill on a cold rolling mill, which reduces the resource of these rolls and increases the cost of production of strip steel.

 An object of the invention is to reduce the cost of sheet rolling backup rolls of quarto stands by extending their working campaign.

 To solve this problem, in the method of operating the support rolls of sheet rolling mills, including filling and dumping with regrinding of the roll barrels for wear, after reducing the barrel diameter by 2.5-2.8%, the backup rolls are dumped from the hot rolling mill and installed in one of the first two stands of a cold rolling mill having the same barrel length, with a preliminary required change in the configuration of the ends of the roll axis, while the size of one removal of the barrel surface when it is worn on a cold rolling mill is taken within 0.20-0.23% of the barrel diameter and.

 The essence of the technical solution found is that the backup rolls are removed from the strip hot rolling mill a little earlier than their full wear and used for their intended purpose in the first stands of the quarto continuous cold rolling mill.

 Indeed, as follows from the above-mentioned book by S.P. Efimenko and V.P. Sledneva "Roller of sheet rolling mills" (p. 68), the total value of the regrinding of rolls of thin-sheet mills (i.e. continuous broadband) is recommended within 3-6% of the diameter of new rolls. Studies conducted on 2500 hot and cold rolling mills of OJSC Magnitogorsk Iron and Steel Works found that after reducing the diameter of the backup rolls of the hot rolling mill by 2.5-2.8%, they can be used on a cold rolling mill (with the same length roll barrels).

 In this case, as the rolls are operated during hot rolling, the microstructure changes and their surface layers harden, and the inner layers (“core” of the barrel) of the backup rolls are not noticeably strengthened, i.e. serve as a kind of "pillow" for the surface layers. This circumstance prevents the occurrence of microcracks on the surface of the back roll barrel during cold rolling, which allows it to operate for a sufficiently long time.

 Since in the working stands of sheet mills of hot and cold rolling, different types of bearings of the backup rolls are used, before filling them into the cold rolling mill, it is necessary to slightly change the configuration of the ends of the axes of these rolls (see below).

 An experimental verification of the proposed method was performed on 2500 hot and cold rolling mills of OJSC MMK.

 To this end, during the rolling of the existing range of strip steel on both mills, at some point, back rolls were transferred from the hot rolling mill to the 2500 cold rolling mill, where they were installed in the first two stands in which they worked with maximum efficiency.

Before filling the backup rolls in the stand of the cold rolling mill, the following operations were carried out:
1. Cut the "profitable" part (with a groove) at the ends of the axes of the rolls.

 2. Processed the end surface of the chamfers.

 3. Drilled at the ends of the axes the center holes needed to adjust the rolls.

 4. Performed grooves for the cams of a roll grinding machine.

 5. Grinding of the conical sections of the axes and cylindrical necks of the rolls was carried out (until their vertical runout is not more than ± 0.1 mm).

 6. Perform keyways.

 During the operation of the obtained backup rolls in the first two stands of the cold rolling mill, it was found that a single removal of the barrel surface during its wear should be within 0.20-0.23% of the barrel diameter: a smaller removal did not provide the required quality of the cold-rolled strips, and a larger feed cuts the length of the working campaign of the backup rolls.

 The use of these rolls in the last two stands of the cold rolling mill 2500 did not give the desired effect due to the accelerated wear of their barrels, and the costs of preparing the rolls for operation under new conditions (see above) were comparable with the resulting savings.

 An attempt to use backup rolls from a hot rolling mill prepared according to the closest selected analogue (see above) also did not give the desired effect, since the known recommendations on the total amount of regrind of roll barrels (3-6%) were used, as a result of which the surface during subsequent operation on the cold rolling mill was subjected to accelerated wear.

 Thus, an experimental verification confirmed the acceptability of the technical solution found to achieve the goal and its advantages over a known object.

 According to the Central Control Laboratory of the Magnitogorsk Iron and Steel Works, the use of the proposed method for rolling on sheet broadband mills of the plant will reduce the consumption of backup rolls at the cold rolling mill 2500 by at least 40%, which will result in a corresponding reduction in redistribution costs and an increase in profits in the production of cold rolled sheet steel.

Concrete example
The backup roll with a diameter of 1500 mm of the hot rolling mill 2500 after reducing the diameter of the barrel (due to its overflow on wear) by 2.65% (about 40 mm) and after appropriate preparation of the ends of its axis is installed in the first stand of the cold rolling mill 2500.

 A one-time removal of the roll barrel surface by its wear during this rolling is taken within 3 mm, i.e. (3: 1460) • 100% = 0.21%.

 The roll is used on the cold rolling mill at least 6 times (after regrinding).

Claims (1)

 A method of operating support rolls of sheet rolling mills, including filling and rolling out with regrind of roll barrels for wear, characterized in that after reducing the barrel diameter by 2.5-2.8%, the support rolls are dumped from the hot rolling mill and installed in one of the first two stands a cold rolling mill having the same barrel length, with a preliminary required change in the configuration of the ends of the roll axis, while the size of one removal of the barrel surface when it is worn on a cold rolling mill is taken within 0.20-0.23% of the barrel diameter.