RU2388565C1 - Profile-iron bending mill - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metal forming, particularly specialised roll mills to produce roll-formed shapes. Mill comprises two various-diametre roll-stands, larger-diametre roll making top roll and rolls running in pads-bearings. Top rolls of all stands, apart from two last stands, can move horizontally long formed strip travel through amount depending upon bottom roll diametre. Note here that vertical edges of shifted top roll pads rests upon compression springs fitted stand posts on the stand outlet side. Spring compression force in every stand depends upon maximum tolerable metal pressure in shaping at given stand.

EFFECT: higher quality of roll-formed shapes, reduced wear of rolls.

1 dwg, 1 ex

Description

The invention relates to equipment for the processing of metals by pressure and can be used in the production of high-quality cold-formed sections on specialized multi-cell mills.

Such mills usually contain two-roll forming stands with calibrated rolls, of which the upper roll, as a rule, is of a larger diameter. Roll forming mills for the production of high-quality profiles are described in sufficient detail, for example, in the book under the editorship of I.S. Trishevsky "Production of bent profiles (equipment and technology)", M., "Metallurgy", 1982, pp. 71-78 and 83-97. The quality of bent profiles largely depends on the wear resistance of the forming rolls of the mill.

A roll forming mill is known for which, in order to reduce roll consumption and improve the quality of profiles, the upper rolls of all stands except the first are made with a cylindrical belt at the top of the forming curve that is symmetrical with respect to the vertical center line of the gauge (see AS USSR No. 1690892, cl B21D 5/06, published in BI No. 42, 1991). However, this mill is only suitable for profiling corners.

The closest analogue to the claimed object is a bending mill according to US Pat. RF №2113928, class B21D 5/06, publ. in BI No. 18, 1998

This mill contains sequentially installed duo cages with pillows and calibrated rolls placed in them, and the lower cushion of the penultimate cage is made with the possibility of movement in the direction of profiling by 4 ... 6 roll gaps and elastic elements with a predetermined set between the vertical faces of the lower cushion and the stands of the cage the total force of their compression, which eliminates the "dump" of the vertical elements of the profile. The design of the known mill does not allow to increase the wear resistance of its rolls.

The technical task of the present invention is to improve the quality of bent profiles and reduce wear of the rolls of the mill when passing through them strips with a thickness greater than permissible.

To solve this problem, the proposed mill contains two-roll stands with rolls of different diameters, the larger of which is at the upper roll installed in pillows, and the upper rolls of all stands, with the exception of the last two, are made with the possibility of horizontal displacement along the formable strip the value of 0.045 ... 0.048 of the diameter of the lower roll, while the vertical faces of the pillows of the displaceable upper rolls on the output side of the stand abut against compression springs installed in the stands of the stands, and the compression force of the spring in each fly with a movable roll is equal to 0.035 ... 0.045 of the value of the maximum allowable metal pressure during profiling in this stand.

The given dependences for the values of the displacement of the rolls and the compression forces of the springs were obtained empirically and are empirical.

The essence of the proposed technical solution is to increase the roll gap when passing through the rolls of a thickened (in excess of the permissible values) section of the profiled strip, for example, its front and rear ends, which when rolled in billet rolling are thicker than the average lengths of its sections.

Indeed, the displacement of the upper roll during rolling (the displacement of the lower roll would require more effort due to the weight of the upper roll, the pillows of which lie on the lower pillows), increases the roll gap and prevents metal “rolling” and wear of the roll. However, the amount of displacement should be minimal, since an increase in the roll gap leads to an increase in bending radii against the permissible values. That is why in the last two stands of the mill (prefinishing and finishing), the rolls are not shifted, which makes it possible to obtain the required bending radii on the final profile.

The magnitude of the compression force of the spring between the cushion of the upper movable roll and the stand of the bed can also not be arbitrary: this force should not be greater than the horizontal force that occurs when the elastic deformation of a steel strip billet of minimum dimensions of steel of minimum strength in the assortment of the mill. Both of the above values are most appropriate to establish experimentally.

The binding of the displacement of the rolls to the diameter d of the lower rolls is made because they try to keep the value of d constant, since it determines the level of formation of the mill. The value of the maximum allowable metal pressure during profiling is a passport parameter, i.e. also remains constant, which is convenient when choosing springs.

The drawing schematically shows the stand of the roll forming mill, in which the upper roll is made with possible displacement (the arrow shows the direction of movement of the formed strip and the displacement of the roll).

The upper 1 and lower 2 rolls are installed in pillows-supports 3 and 4, while the upper pillow 3 is supported on the lower 4 through adjusting bolts 5, and the upper pillow is moved vertically with these bolts and the pressure screw 6 installed in the cross beam 7 of the bed . An opening 9 is made in the right stand of the cage 8, in which a compression spring 10 is placed, one end of which abuts against the vertical face 11 of the upper cushion 3.

When passing through the cage of the thickened section of the formed strip, the upper roll 1 is displaced along the strip by Δ = (0.045 ... 0.048) d with the pillow 3 resting in the rack 8 of the cage. After passing the thickened section of the strip, the cushion of this roll under the action of the spring 10 returns to its original position.

An experimental verification of the proposed technical solution was carried out on a roll-forming mill 2 ÷ 8 × 100 ÷ 600 OJSC "Magnitogorsk Iron and Steel Works".

For this purpose, when molding various profiles with a thickness of 2 ... 8 mm, two versions of the mill were tested: with the possibility of displacement of the upper rolls in part of the stands and without such displacement. In this case, in the first embodiment, springs were tested with different values of force P _with their compression at different displacement values Δ of the upper roll. The experimental results were evaluated by the value of the wear of the rolls and the quality of the bent profiles.

The best results (maximum wear resistance of the rolls at the exit of high-quality profiles in the range of 99.3 ... 99.8%) were obtained using the present invention. Deviations from the recommended values of Δ and P _with worsened the achieved indicators.

So, at Δ <0.045 d, the wear of the rolls increased, and at Δ> 0.048 d part of the profiles were sorted out due to the failure of bending radii on them (they were more than the maximum permissible values). At Р _с <0.035 P _max (the maximum allowable metal pressure on the rolls for the mill “2 ÷ 8”), the shift of the upper rolls was observed when passing through the stands of a strip billet with a thickness within the plus tolerance, which accelerated the wear of the springs. At Р _с > 0.045 Р _max , the wear of the rolls increased due to the lack of the necessary displacement of the upper rolls, and “rolling” of individual sections of the strips was observed with a deterioration in the surface quality of the profiles.

The performance of all mill stands with the possibility of displacement of the upper rolls (at the recommended values of Δ and P _s ) reduced the yield of high-quality profiles, since in the finishing and finishing stands of the mill it was not possible to reduce the bending radii to the required values.

A version of the mill, taken as the closest analogue, was also tested (see above).

At the same time, the wear of the rolls increased, and the yield of high-quality profiles did not exceed 88.2%. Thus, an experimental verification confirmed the acceptability of the technical solution found to achieve the goal and its advantage over a known object.

The feasibility study showed that the implementation of the present invention on roll forming mills similar to the “2 ÷ 8” mill of OJSC MMK will reduce the roll consumption by approximately 10% and increase the yield of quality profiles by at least 1%.

Concrete example

All stands (except the last two) roll forming mill 2 ÷ 8 × 100 ÷ 600 made in accordance with the scheme shown in the drawing.

Values d = 280 mm and P _max = 30 tf;

value

spring compression force P _c = 0.04 · P _max = 0.04 · 30000 = 1200 kgf.

Claims (1)

A profile bending mill for forming high-quality bent profiles containing double roll stands with rolls of different diameters installed in pillows-supports, the upper roll being made with a large diameter, characterized in that the upper rolls of all stands, except for the last two, are made with the possibility of horizontal displacement in the direction of movement of the profiled strip blank by 0.045 ... 0.048 from the diameter of the lower roll, while the vertical faces of the pillow-supports of the displaced upper rolls on the output side of the stand abut against compression pressures installed in the stands of the stands, and the compression force of the spring in each stand with a movable roll is 0.035 ... 0.045 of the maximum allowable metal pressure during profiling in this stand.