RU2164186C2 - Method for profiling equal-flange channel bars - Google Patents

Abstract

FIELD: plastic metal working, namely, manufacture of cold bent rolled bars. SUBSTANCE: method comprises steps of successively bending up members of strip blank by means of rolls having different curvature radiuses in different passes and mounted with predetermined horizontal gaps. At first pass blank is fed between rolls mounted with mutual gap

mm; at second pass, with gap δ₂= (0,45...0,55)(δ₁-S)+S,, and at following passes with gap δ = S,, where H and S is, respectively, height and thickness of channel bar, mm; K is factor equal to 0.15-0,17 at ultimate strength of blank σ_в=250-460 MPa and K = 0.18-0.21 in condition when 460 MPa less than σ_в less than or equal to 640 MPa. EFFECT: cracking elimination, simple guiding of blank to roll grooved passes. 1 dwg, 1 ex

Description

 The invention relates to rolling production and can be used in the manufacture of bent equal-shelf channel profiles.

 These profiles are made by sequentially bending the edge elements of the strip blank in calibers of a multi-roll roll mill, taking certain values of the angles and bending radii in each pass, and the roll gaps are usually set equal to the nominal thickness of the blank. The most common bending channel shaping patterns are given, for example, in A.P. Chekmareva and V.B. Kaluzhsky "Bent profiles of hire", M., "Metallurgy", 1974, p. 44-46, fig. 17. In this case, molding can be carried out with a constant or variable distance between the centers of the bending radii of the cross section, as well as with constant or variable values of these radii, which is due to the specific conditions of profiling.

 When forming bent profiles, methods are often used that are aimed at reducing tensile stresses in bending places, which are inevitable during profiling, in order to improve the geometry of finished profiles and avoid the appearance of cracks in these places (in their outer sections).

 A known method of bending profiles of sheet material in which the material is additionally bent, for which a compressive force is applied to the shelves of the previously curved profile in the normal and tangent directions to its neutral axis (see AS USSR N 185287, class B 21 D from 10.21.63 g.). There is also a known method of manufacturing profiles from high-strength strip billets with simultaneous bending and compression of the billet in cross section by applying compressive forces to its edges, bending is carried out after compression, and the latter is carried out during heating and softening of the bending places (see A.S. USSR N 210806, CL B 21 D from 08.23.66).

 The disadvantage of the first of the known methods is the application of compression forces to an already bent profile, i.e., possibly, after the appearance of corresponding defects in its geometry, and the second method is the need to heat the metal using special equipment and with additional energy costs.

 The closest analogue to the claimed object is the method of profiling (calibration of rolls) equal channel channel 130x135x8 mm, given in the manual under the editorship of I.S. Trishevsky "Production and application of bent profiles of hire", M., "Metallurgy", 1975, p. 182-184 and fig. 72.

 This method consists in sequentially bending the passages of the strip billet elements with rolls with bending radii successively decreasing along the passages to a finite value for a given distance between the centers of these radii and the size of the roll gaps and is characterized by the fact that the wall of the channel formed is bent twice inward at certain radii with subsequent straightening this profile element.

 The disadvantage of this method is the possibility of tensile stresses appearing at the bend of the cross section, which can lead to the formation of cracks in the outer parts of these places, especially when profiling metal with insufficient ductility.

 The technical task of the invention is the prevention of cracking during profiling of equal-channel channels.

мм, во втором проходе - с зазором δ₂= (0,45...0,55)(δ₁-S)+S, а в последующих проходах - с зазором δ = S, где H и S - соответственно высота и толщина швеллера, мм, к - коэффициент, равный 0,15...0,17 при пределе прочности заготовки σ_в = 250...460 МПа и к = 0,18... 0,21 при 460 < σ_в ≅ 640 МПа.To solve this problem in the method of profiling, which consists in sequentially bending the elements of the strip billet with rolls with different bending radii along the passages installed with predetermined horizontal gaps, in the first pass the workpiece is passed through the rolls with a gap

mm, in the second pass - with a gap δ ₂ = (0.45 ... 0.55) (δ ₁ -S) + S, and in subsequent passes - with a gap δ = S, where H and S are the height and thickness sill mm, k - the coefficient equal 0,15 ... 0,17 for tensile strength _in the workpiece σ = 250 ... 460 MPa, and a = 0.18 ... 0.21 at 460 <σ _in ≅ 640 MPa.

 The above mathematical dependences are obtained as a result of processing experimental data and are empirical.

 The essence of the proposed technical solution is to create an excess of metal in the places of bending due to the fact that the perimeter of the middle part of the workpiece between the horizontal sections of the first two calibers is larger than the width of these sections (since the middle part of the workpiece bends down with a bend arrow close to the horizontal roll gap) . As a result of this, the conditions and pattern of deformation of the places of bending of the formed channel with the decrease (or absence) of their thinning in subsequent calibers change.

 In principle, it is possible to create an excess of metal in the first calibers due to the use of middle elements in them with generators curved in an arc, the radial clearance between which is equal to the thickness of the workpiece. However, in this case, firstly, the manufacture of gauges is complicated (the presence of generators in the form of arcs of large radius), the inaccurate execution of which can lead to a deterioration of the geometry of the profiles and, secondly, the possibility of adjusting the deflection arrow of a part of the cross section of the workpiece during profiling is excluded, which will increase labor costs.

From the above dependences it is seen that the value of the coefficient "k" (and the gaps δ ₁ and δ ₂ ) depend on the value of σ _{in the} workpiece, which is explained by the difference in the relative elongation of steel of different strengths. Indeed, the permissible bending radii (curvature) of the channel, as follows from GOST 8278 “Steel bending equal-equal steel channels”, are different for steels of different strengths (for steel with σ _in ≅ 47 kgf / mm ² they are about 1.5 times larger than for σ _in > 47 kgf / mm ² ), i.e. for stronger steels, a larger “reserve” of metal is also required (large horizontal gaps in the first two calibers) in order to increase the compressive stresses at the bending points, which are a guarantee against cracking.

 It should be noted that creating a bend in the middle part of the workpiece in the first passes requires a certain increase in the width of the workpiece (by 1.0 ... 1.5%), however, such an increase in metal consumption is excessively compensated by a decrease in waste and labor costs when profiling channels (see. below).

 The drawing schematically shows calibers (only the main ones are shown) that implement the proposed method of profiling.

и δ₂= (0,45...0,55)(δ₁-S)+S.
В этих калибрах (I и II) углы наклона α₁ и α₂ конических образующих 5 и 6 соответственно верхних и нижних валков в каждом калибре одинаковы, т.е. валки выполнены без углов освобождения, когда по всей ширине конических элементов зазоры не меняются (см., например, книгу С.Ф. Березовского "Производство гнутых профилей", М., "Металлургия", 1985, с. 78). Это сделано с целью улучшения захвата заготовки валками (особенно - при поштучном процессе профилирования) и для исключения взаимного проскальзывания валков и металла, которое травмирует поверхность профилей и увеличивает износ валков. Последующие калибры (III) могут иметь разные величины упомянутых углов

Так как зазоры δ₁и δ₂ в калибрах I и II больше S, то профилируемая полоса при заходе в них имеет вид, показанный на фиг. 1, т.е. прогибается вниз на величину, определяемую величинами S, δ₁ и δ_2. При заходе же в калибр III, где δ = S, средняя часть заготовки 4 "осаживается" валками и металл заполняет углы 7 и 8 нижней части этого калибра, создавая в местах изгиба схему деформации, близкую к схеме всестороннего сжатия, что и предотвращает появление трещин.Each of the gauges is formed by the upper 1 and lower 2 rolls installed with horizontal gaps (δ _1, δ ₂ and δ), the first three (draft) calibers I. . III are made with closing by the flanges of 3 lower rolls to prevent lateral displacement of the formed strip 4. The gap δ is equal to the nominal thickness S of the workpiece (and channel), and the gaps of calibers I and II are equal, respectively

and δ ₂ = (0.45 ... 0.55) (δ ₁ -S) + S.
In these calibers (I and II), the tilt angles α ₁ and α _{2 of the} conical generators 5 and 6, respectively, of the upper and lower rolls in each gauge are the same, i.e. the rolls are made without release angles, when the gaps do not change across the entire width of the conical elements (see, for example, the book by S. F. Berezovsky "Production of bent profiles", M., "Metallurgy", 1985, p. 78). This is done with the aim of improving the capture of the workpiece by the rolls (especially with a single-piece profiling process) and to prevent mutual slippage of the rolls and metal, which injures the surface of the profiles and increases the wear of the rolls. Subsequent gauges (III) may have different sizes of the mentioned angles

Since the gaps δ ₁ and δ ₂ in calibers I and II are greater than S, the profiled strip when entering them has the form shown in FIG. 1, i.e. bends down by the value determined by the values of S, δ ₁ and δ _2. When entering caliber III, where δ = S, the middle part of the workpiece 4 is “deposited” with rollers and the metal fills corners 7 and 8 of the lower part of this caliber, creating places bending deformation scheme, close to the all-round compression scheme, which prevents the appearance of cracks.

 The shaping of the required section in subsequent calibers (up to the finishing IV) occurs in the usual mode.

 An experimental verification of the proposed method was carried out on high-quality roll-forming mills with continuous and single-piece processes at CJSC Rolled-Bent Profile of OJSC Magnitogorsk Iron and Steel Works.

For this purpose, when profiling channels with different sizes H, B and S from different steels with σ _in = 250 ... 640 MPa, the gaps in the horizontal sections of the first two calibers of mills were varied, fixing the presence or absence of cracks in the outer sections of the channel bending points. When using calibers with the recommended horizontal horizontal roll gaps, no cracking was observed, and there were no difficulties when the workpiece entered the gauges.

A decrease in the values of δ ₁ and δ ₂ (compared with the optimal values - see above) led to the appearance of cracks in individual sections of the strips (at the front and rear ends of the hot rolled billet, which have increased thickness and strength, as well as in the places of welding seams of joined strips having reduced ductility). The use of only one (I) gauge with an increased gap in some cases led to overfilling of the next caliber (with a gap of δ ₂ = S), which caused increased wear on the rolls. An increase in the gap in gauge III (more than S) and in gauges I and II (more optimal values of δ ₁ and δ ₂ ) worsened the geometry of the finished channels.

 Control profiling by known technology, taken as the closest analogue, led to sorting by cracks up to 1.5% of the rods (mainly from a workpiece 4 ... 6 mm thick from stations 3ps and 09G2).

 Thus, an experimental verification confirmed the acceptability of the technical solution found to fulfill the task and its advantage over a known object.

 According to the Central Control Laboratory of OJSC MMK, the use of the invention in the production of equal-bent bent channels will increase the yield by 1-2% with a corresponding increase in profits from the sale of rolled products.

δ = S = 4,0 мм.
Калибры I...III стана выполнены с закрытием ребордами нижних валков (см. фиг. 1) и без углов освобождения; в последующих калибрах Δα = α″-α′ = 1⁰.
2). Тот же швеллер из ст. 20 с σ_в = 550 МПа профилируется аналогичным образом, но величины горизонтальных зазоров в I и II клетях равны:

δ₂= 0,5·(6,3-4,0)+4,0 = 5,15 ≈ 5,2 мм.зConcrete example
1). Equal-channel channel 120x60x4 mm from st. 3ps with σ _in = 310 MPa (H = 120, S = 4 mm) is profiled with increased gaps in the first two draft calibers, and

δ = S = 4.0 mm.
Gauges I ... III of the mill are made with the flanges closing the lower rolls (see Fig. 1) and without release angles; in subsequent calibers Δα = α ″ -α ′ = 1 ⁰ .
2). The same channel from art. 20 σ = 550 MPa _{in the} profiled similar manner, but in the value of horizontal gaps I and II cages are:

δ ₂ = 0.5 · (6.3-4.0) + 4.0 = 5.15 ≈ 5.2 mm.s

Claims (1)

The method of profiling equal-channel channels, which consists in sequentially bending the elements of the strip billet with rolls with different bending radii along the passages installed with predetermined horizontal gaps, characterized in that in the first pass the workpiece is passed through the rolls with a gap

mm, in the second pass with a gap of δ ₂ = (0.45 ... 0.55) (δ ₁ -S) + S, and in subsequent passes with a gap of δ = S, where H and S are the height and, respectively channel thickness, mm; K - a factor of 0.15 ... 0.17 for tensile strength _in the workpiece σ = 250 ... 460 MPa, and K = 0.18 ... 0.21 at 460 <σ _in ≅ 640 MPa.