RU2255825C1 - Steel strip straightening method - Google Patents

Abstract

FIELD: metallurgy, namely finishing rolled strips, possibly straightening steel strips with lengthwise alternating corrugations.

SUBSTANCE: method comprises steps of multiple elastic-plastic sign-variable lengthwise bending of strip and simultaneous crosswise bending of it due to increased bending of edge ( along strip width) portions in comparison with mean portion of strip; providing bending value of edge portions more than that bending value of its mean portion at first bending operation and at each next bending operation providing bending value of edge portions less than that of previous bending operation; successively reducing values of lengthwise bending along straightening process direction from predetermined value to zero.

EFFECT: lowered wear of rollers, enhanced quality of straightening.

1 dwg, 1 ex

Description

The invention relates to the finishing of strip steel and can be used when dressing steel strips with periodic longitudinal corrugations.

The technology for editing strip (sheet) metal is described in sufficient detail in the book by A.Z. Slonin and A.L. Sonin “Editing sheet and high-quality metal”. - M .: Metallurgy, 1981. For editing, special roller machines are used in which alternating elastoplastic longitudinal bending of moving metal, for example strip steel, is carried out.

Sheet profiles with periodically repeating corrugations (high stiffness profiles) are made by cold local deformation; corrugated strips before cutting into measured lengths are subjected to editing on regular machines containing rollers with gauges for passing corrugations, since editing is carried out only on flat inter-arch sections of these strips.

A known method of editing sheet metal, mainly boxy, in a multi-roller machine with an asymmetric arrangement of section support rollers along the length of the barrel of the working rollers (see US Pat. Cl. 153-86, No. 3078908, publ. 02.26.63). There is also a known method of straightening a strip, in which to improve the quality of editing the arrow of the bending of the strip by rollers and the magnitude of its tension is selected depending on the yield strength and thickness of the metal (see AS USSR No. 1469660, class B 21 D 1/02, publ. 09.01.87 g.).

A disadvantage of the known methods for editing strip metal is their inapplicability for editing corrugated strips with periodic corrugations.

The process of editing sheet profiles with periodic (closed) corrugations has a number of features due to both the geometry of these profiles and the patterns of formation of closed corrugations. Their formation is carried out due to local extraction of metal in the deformation zone, and metal comes from this plane zone in the middle of the strip width both from flat near-planar sections and (partially) from near-edge sections of the workpiece.

As a result, an excess of metal is formed in the corrugation areas, which leads to the formation of undulation in the middle of the corrugated strip width, i.e. boxing, and this affects the performance of the profiles. Therefore, when editing corrugated strips, only mainly near-edge sections of the strip are subjected to repeated bending by rollers in order to equalize their length with the middle part along the width of the workpiece by drawing, or make drawing these sections more than the middle part.

The closest analogue to the claimed object is a way to edit the strip A. with. USSR No. 1532115, class B 21 D 1/02, publ. in BI No. 48, 1989

где S - толщина полосы.This method includes multiple elastoplastic alternating bending of the corrugated strip with simultaneous lateral bending due to an increase in the deflection of the edge sections along the width of the strip in comparison with its middle part and is characterized in that the deflection of the edge sections is greater by (3.18 ... 3, 22)

where S is the thickness of the strip.

The disadvantage of the described editing method is the increased wear of the rollers of the leveling machine.

Indeed, when editing by this method, the overlap of all the rollers of the correct machine (δ - see drawing) is the same, i.e. the value f of the bending arrow of the strip remains constant along its course. But as the number of strip bends increases, its hardening (hardening) also increases, which inevitably increases the metal pressure on each subsequent roller of the machine. As a result of this, the wear of each such roller is greater than the previous one, and the maximum (in the direction of the strip) pair of rollers has the maximum wear, which forces them to be replaced when the first rollers are operational.

The technical task of the invention is to reduce the wear of the rollers of the straightening machine when dressing strips with periodically repeating longitudinal corrugations.

а при каждом последующем изгибе меньше, чем при предыдущем в

раз, где К=3,48... 3,52 для полос с пределом прочности σ _В>465 МПа и К=2,98... 3,02 - с σ _В>465 МПа, a n - число изгибов полосы при правке, при этом величину продольных изгибов последовательно уменьшают по ходу правки от заданной до нуля.To solve this problem, with multiple elastoplastic alternating longitudinal bending of a strip of thickness S with its simultaneous transverse bending due to an increase in the deflection of the edge sections along the width of the strip in comparison with its middle part, the deflection of the edge sections is made larger than that of the middle part of the strip, during the first bend value

and with each subsequent bend less than with the previous in

times, where K = 3.48 ... 3.52 for bands with a tensile strength σ _B > 465 MPa and K = 2.98 ... 3.02 with σ _B > 465 MPa, an is the number of bends of the strip at dressing, while the value of longitudinal bends is successively reduced along the dressing from a predetermined to zero.

The above mathematical relationships are obtained by processing the experimental data and are empirical.

The essence of the proposed technical solution is to consistently reduce the values of both transverse and longitudinal bends of the formed strip. In addition to reducing the load on the rollers of the straightening machine (see above), a decrease in the absolute value of the longitudinal bend (i.e., its boom f) well corrects the waviness and warping of thin sheets (with S 4.9 mm; see V.F. Zotov and B .I. Elin “Cold rolling of metal.” - M .: Metallurgy, 1988, p. 121), which include high-rigidity profiles with a thickness of 2 ... 4.5 mm.

In addition, to ensure high-quality editing, the values of the first transverse bends of the strip are taken somewhat larger (taking into account their subsequent reduction) than by the known editing method, taken as the closest analogue.

The proposed editing method can be implemented on the correct machine described in A.S. USSR No. 1532115, in which all the lower rollers are made smooth cylindrical, and the upper - with circular grooves for the passage of the formed corrugations.

The editing scheme according to the claimed method is shown in the drawing (arrow - strip direction, Roman numerals - serial numbers of bends); shows editing the middle part along the width of the strip.

The upper 1 and lower 2 rollers of the correct machine are staggered, with each row of rollers - upper and lower, lying on the same axis: χ ₁ χ ₁ and χ ₂ χ ₂ .

The amount of overlap of the rollers δ decreases in the direction of the strip so that in the yy plane the value of the arrow of the longitudinal bending of the strip is f = 0. The design of the upper rollers was chosen so that simultaneously with the longitudinal bending shown in the drawing, the transverse bending of the strip 3 occurred with a maximum value at I bending and gradually decreasing to its minimum value in the yy plane (V bending), where the straightened strip becomes almost flat .

The recommended values of δ and Δ were selected (empirically - see below) so that the load on all the rollers from the strip hardening with each bend was approximately the same, which ensures uniform wear of the rollers and prolongation of their working campaign.

An experimental verification of the proposed method was carried out on a seven-roller straightening machine of a roll forming unit 1-5 × 300-1650 of OJSC Magnitogorsk Iron and Steel Works, intended for the production of high-rigidity sheet profiles with longitudinal closed corrugations, a part of the assortment of which is given in the reference book, under the editorship of I.S. Trishevsky “Bent profiles of hire”. - M.: “Metallurgy”, 1980, p.230-231.

For this purpose, when editing profiles made of steel 3, 10kp, 09G2 and 10KhNDP with a thickness of 2 ... 4.5 mm, the values of the transverse bending of the strips were varied, i.e. the difference in the values of the deflection of the marginal sections and the middle part along the strip width. In the experiments, the quality of editing (by the value of non-flatness of the profiles) and the degree of wear of the rollers of the correct machine were recorded.

The best results (wave height within 2 ... 8 mm and the absence of cracks in the places of bending of the corrugations with a maximum duration of the working campaign of the rollers) were obtained when implementing the proposed method. Deviations from the recommended parameters worsened these indicators.

для сталей с σ _В>465 МПа и до (3,03... 3,60)

для сталей с σ _В<465 МПа вызывали повышенный износ первых трех роликов машины, а на профилях из более прочной стали в отдельных случаях наблюдалось появление трещин у гофров. Уменьшение Δ (ниже рекомендуемых величин) ухудшало геометрию полос (возрастала неплоскостность).So, an increase to (3.53 ... 4.05)

for steels with σ _B > 465 MPa and up to (3.03 ... 3.60)

for steels with σ _B <465 MPa, increased wear of the first three rollers of the machine was caused, and in some cases, the appearance of cracks in corrugations was observed on profiles of stronger steel. A decrease in Δ (below the recommended values) worsened the geometry of the bands (non-flatness increased).

With a decrease in the difference in the values of the transverse deflections of individual sections of the corrugated strips, basically, uneven wear of the rollers occurred with a reduction in their working campaign by 12 ... 45%.

Check editing using technology according to the known method, taken as the closest analogue (see above), almost gave the same level of quality profiles, but the duration of the working campaign of the videos was reduced by almost 1.5 times.

Thus, the pilot test confirmed the acceptability of the claimed technical solution to perform the task and its advantages over the known object.

The recommended method (with other Δ values) was also tested when dressing box-shaped roll strips on a 9-roller straightening machine, where it showed good results.

According to the Central Control Laboratory of OJSC MMK, the use of the straightening method found will extend the working campaign of the rollers of the correct machine for editing high stiffness profiles by at least 1.5 times with a corresponding reduction in production costs.

Concrete example

1. A corrugated strip of thickness S = 2 mm made of steel with σ _B > 465 MPa is corrected with n = 5 (ie, in a seven-roller straightening machine - see drawing). The amount of overlap δ is successively reduced from 1.9 mm to 0.

Edit Options:

2. A corrugated strip of thickness S = 4 mm made of steel with σ _B ≤ 465 MPa is corrected in the same machine with a value of 5 decreasing from 1.6 mm to 0. Edit parameters:

Claims (1)

A method of straightening a steel strip mainly with periodic longitudinal corrugations, including multiple elastoplastic alternating longitudinal bending of a strip of thickness S with its simultaneous transverse bending due to an increase in the deflection of the edge sections along the width of the strip in comparison with its middle part, characterized in that the amount of deflection of the edge sections is made larger the deflection of the middle part at the first bend by

and with each subsequent bend less than with the previous in

times, where K = 3.48 ... 3.52 for strips with a tensile strength σ _in > 465 MPa and K = 2.98 ... 3.02 - with σ _in ≤ 465 MPa, an is the number of bends of the strip at dressing, while the value of longitudinal bends is successively reduced along the dressing from a predetermined to zero.