RU2784961C1 - Roughing pass system for rolling railway rails - Google Patents

Abstract

FIELD: railway engineering.

SUBSTANCE: invention relates to a system of roughing passes for rolling railway rails. The system of roughing passes contains rectangular box calibers with rectilinear sections of filling and slopes of the lateral faces to the vertical, square-type box caliber with the bottoms of streams made along radii of counter-directional curvature, trapezoidal axial unilaterally closed and trapezoidal rib semi-closed calibers with the values of gaps on the support cones and collars, making it possible to position streams relative to each other by these elements up to the capture of metal by rolls. The square-type box caliber has a rectilinear section symmetrical with respect to the vertical axis along the bottom of the lower stream and the slopes of the lateral faces to the horizontal, equal respectively to the length of the rectilinear section in terms of filling and the slopes of the lateral faces to the vertical in a rectangular-type box caliber, as well as the concavity of the bottom of the upper stream within 4-7 mm. The boring of a trapezoidal axial unilaterally closed caliber is performed with a preliminary shift of the closed stream relative to the open stream by the amount of the gap along the support cones before the metal is captured by the rolls.

EFFECT: as a result, the qualitative design of the geometric parameters of the roll profile from these calibers is stabilized.

1 cl, 4 dwg, 1 ex

Description

The invention relates to the field of ferrous metallurgy and can be used in the calibration and subsequent rolling in rough gauges of railway rails or other similar profiles using duo stands.

When rolling rails, two stages of shaping can be distinguished (Technical progress in the technology of rolling production. Metallurgizdat. Sverdlovsk. 1960. P. 239. Paragraph 3):

1) formation of a T-section strip from a rectangular billet in preparatory calibers;

2) the final formation of the finished rail in rail gauges.

The first stage of formation largely determines the quality of the finished product, so the choice of a rational design of preparatory passes is one of the most important tasks in designing the calibration of rolls for rolling rails. When rolling rails from ingot metal, despite the comprehensive and intensive processing of metal in preparatory trapezoidal calibers, the base and head of the rails had many surface cracks and hairlines. The study of the nature of these defects showed that a rough dendritic structure is preserved there, in which the dendrites are oriented perpendicular to the surfaces of the sole and head, and as they approach the edges of the sole, their perpendicular direction becomes oblique. In this case, the direction of the cracks coincides with the direction of the dendrites. Fundamentally new in the method of calibrating rails was the use of the Bartscherer scheme, in which the original workpiece was deformed from the side of the future sole with a split ridge.

Deep cutting of the billet and extension of the future flanges of the sole in subsequent calibers led to the fact that the subcrustal bubbles and columnar crystals, located perpendicular to the faces of the ingot, change their orientation and are parallel to the base of the sole. Surface defects in the form of detectable subcrustal blisters and hairline cracks are stretched, abraded and, as a result, disappear from the surface of the rolled rail. As a result, rails with a better surface are obtained, with higher indicators in the pile test for deflection of the sole.

One of the effective ways to improve the quality of rolled products is to produce them from continuously cast billets. The first continuously cast metal rails were rolled in the UK in 1974 at a plant in Workington (Polyakov V.V. Fundamentals of railway rail production technology / V.V. Polyakov, A.V. Velikanov // M .: Metallurgy. - 1990. - S. 416).

Studies of rolling rails from a continuously cast billet in the direction of studying the effect of calibration schemes, the shape of calibers, and reduction modes in draft calibers on the transformation of axial porosity and central segregation have shown that the main thing when rolling rails from a continuously cast billet is to prevent axial looseness and segregation zone of the billet from getting into rail head. This is due to the fact that axial segregation and friability in the rail head are stress concentrators that occur during operation under cyclic rail loads. As a result, the rail prematurely fails due to insufficient contact fatigue strength of the metal. Further improvement of the technology for rolling rails from a continuously cast billet using a trapezoidal rib gauge with deep cutting of the edge leading to the formation of the rail sole was associated with an increase in the quality of the rails by increasing the displacement of the segregation zone and the axial looseness of the billet into the rail neck (Patent 2254941 Russian Federation, MPK ⁷ V. V. Dorofeev, E. M. Pyataykin, E. L. Kravchenko, and S. P. Grishin, Applicant and patentee OAO Novokuznetsk Metallurgical plant ". - No. 2003136327/02; application 12/15/2003; published 06/27/2005, Bull. No. 18). Rail rolling schemes with billet cutting in a trapezoidal groove are optimal when using initial continuously cast billets with significant axial porosity and central segregation.

The problem of insufficiently high quality of the internal structure of the initial continuously cast billets in the production of rails has been studied quite well and is successfully solved on the basis of the obtained scientific data, by improving the main technological parameters of the continuous casting of rail steel (temperature regime, casting speed, intensity of secondary cooling, etc.). ), studies of the influence of the chemical composition and cross section of the workpiece on axial segregation and porosity, the introduction of electromagnetic melt mixing and the technology of "soft reduction" in the casting of steel at the CCM.

Currently, in the world practice, the production of railway rails is carried out using universal rolling stands at the last stage of their rolling. During the construction of new and modernization of existing rail production, as a rule, three-stand reversible direct rolling groups with two universal and one auxiliary (edger) two-roll stands, called a tandem mill, are installed.

A typical modern universal rail and beam mill includes one or two reversing swaging duo stands, a continuously reversing group of stands (tandem mill) and a universal non-reversing finishing stand.

The method of rolling rails on such a mill is implemented as follows. In the swaging stands, a rough rail roll is produced, which is transferred during rolling to a continuously reversible group of stands and rolled in it in three or five passes, and the final profile formation is carried out in a finishing three-roll universal stand.

Rolling schemes in rough passes of universal rail-rolling mills designed by SMS Meer, Danieli, etc. provide for the use of a system of calibers including box calibers, a trapezoidal axial caliber and a trapezoidal rib pass without one-sided cutting of the section along the sole for the purpose of subsequent bending of the elements (Dorofeev V .V., Yunin GN, Golovatenko AV et al. Stages of development of the process of rolling rails using reversible universal stands in their historical sequence.

The closest to the claimed system of calibers for rolling rails in rough passes (prototype) is the caliber system that currently exists in the rolls of the BD1 reduction stand of the universal rail and beam mill of EVRAZ ZSMK JSC (Golovatenko A.V., Dorofeev V.V., Dobryansky A. V. et al. Development of an energy-efficient technology for rolling long railroad rails on the universal rail and beam mill of EVRAZ ZSMK JSC // Chernye Metally, 2019, No. 6, pp. 29-34). The gauge system of the prototype (the above article, p. 31, Fig. 3) consists of three box gauges, a trapezoidal axial one-sidedly closed and a trapezoidal ribbed semi-closed gauge. The trapezoidal semi-closed ribbed caliber excludes cutting the section along the sole for the purpose of subsequent bending of the elements.

In this system of gauges, a box gauge of square type, preceding the trapezoidal axial one-sidedly closed one, can be a box gauge, the bottoms of the streams of which are made along the radii of unidirectional or counter-directed curvature.

The disadvantages of the prototype caliber system include the following:

- the use of a square-type box gauge, the bottom of the streams of which is performed along the radii of unidirectional curvature with its usual functions, where the bottom of the stream of this gauge is designed with a concavity of 1÷3 mm (Chekmarev A.P., Mutiev M.S., Mashkovtsev R.A. 1971. S. 174), the slope of the side walls is taken within 5÷20% (Bakhtinov B.P., Shternov M.M. Calibration of rolling rolls / M.: Metallurgizdat. 1953. P. 201) shows that the rolling of rolled stock from a given square-type box caliber, in a trapezoidal axial unilaterally closed caliber (Mikhailenko A.M., Schwartz D.L. Classification of calibers for rolling rails // Production of rolled products. 2017. No. 4. S. 19-25) does not allow to completely fill the caliber from the side of the future head and leads to the rapid development of a closed groove of the caliber from the side of the future sole, due to the fact that the deformation conditions of the roll in this caliber correspond to the deformation of the metal in the wedges a similar caliber, where uneven deformation along the width of the roll leads to its “serpension” to the side with a lower coefficient of metal deformation, i.e. towards the closed caliber stream;

- the use of a box gauge of a square type, the bottoms of the streams of which are made along the radii of counter-directional curvature (A.S. 348248 of the USSR, declared 08/13/1968, publ. 08/23/1972, bull. No. 25) does not allow when capturing the roll obtained and scanned from the previous rectangular box caliber, to clearly fix it in the lower groove of this caliber, which does not ensure the stability of the rolling process and the uniform development of the caliber;

- the use of a trapezoidal axial unilaterally closed caliber in the system of rough passes leads to axial displacement of the roll with a closed groove, due to the arising axial forces, which does not allow obtaining the rolled profile in accordance with the given geometry of this and the subsequent trapezoidal rib semi-closed calibers in the course of rolling. This destabilizes the rolling process and leads to the formation of surface defects in the finished rails.

The aim of the invention is to stabilize the rolling process in the roughing passes of a rail and beam mill, to reduce surface defects in finished rails and to reduce the wear of rolling rolls.

This goal is achieved by the fact that in the system of calibers for rolling rails in roughing passes, consisting of box calibers of rectangular type with straight sections in filling and slopes of the side faces to the vertical, a box caliber of square type with bottoms of streams of oppositely directed curvature, trapezoidal axial one-sidedly closed and trapezoidal rib semi-closed calibers, with gaps along the support cones (a) and collars (S), allowing the positioning of the streams relative to each other along these elements, the square-type box gauge has a straight section symmetrical about the vertical axis along the bottom of the lower stream and slopes of the side faces to horizontals equal, respectively, to the length of the straight section in terms of filling and slopes of the side faces to the vertical in a rectangular box gauge, the value of the concavity (k) of the bottom of the upper stream is within 4÷7 mm, and the boring of the trapezoidal axial unilaterally closed gauge is carried out They are cast with a preliminary shift of the closed relative to the open stream by the amount of the gap along the support cones until the metal is captured by the rolls (a).

With such a preparation of a square-type box gauge with bottoms of streams of counter-directional curvature, the resistance against twisting and stalling, the roll deformed in it, obtained and scanned from the previous rectangular-type box gauge, increases.

The formation of the future rolling surface of the rail head in a trapezoidal axial one-sidedly closed groove from a convex edge of the roll formed in a square-type box groove with the bottoms of streams of opposite curvature makes it possible to completely fill the trapezoidal axial one-sidedly closed groove and get on the surface from which the rail head is formed, more intense stretching of the metal, which leads to increased disclosure of surface defects (cracks, wrinkles, scratches, etc.) and their rolling out during rolling.

In order to obtain the specified profile parameters in a trapezoidal axial unilaterally closed caliber during rolling, the boring of this caliber in the rolls is carried out with a preliminary shift of the closed relative to the open stream by the gap (a) along the support cones until the metal is captured by the rolls (where a is determined according to patent No. 2684126 Russian Federation, MPK ⁷ V21V 1/085 (2006.01) A method for calibrating oblique calibers with alternating direction of slopes in the rolls of a duo stand for rolling railway rails / A. B. Yuryev, A. V. Golovatenko, V. V. Dorofeev, etc.; applicant and patent holder JSC EVRAZ United West Siberian Metallurgical Plant - No. 2018107192; filed 02.26.2018; published 04.04.2019, Bull. No. 10).

Below are the disadvantages of going beyond the accepted range of the concavity (k) of the bottom of the square-type box-type upper strand with the bottoms of the strands of counter-directional curvature:

- at k<4.0 mm, the rolling of rolled stock from a square-type box gauge with bottoms of streams of opposite curvature in a trapezoidal axial one-sidedly closed pass leads to a significant development of a closed stream along the side that forms the surface of the base of the rail sole due to the lack of compensation for broadening during metal compression and obtaining surface defects on the finished rail;

- at k>7.0 mm, the rolling of rolled stock from a square-type box gauge with the bottoms of streams of opposite curvature in a trapezoid axial one-sidedly closed caliber leads to a wrinkle when the side face is compressed, from which the base of the rail foot is formed, due to insufficient broadening, compensating the resulting concavity on the roll from the concavity of the bottom of the upper stream in a square-type box gauge with the bottoms of the streams of opposite curvature.

A comparative analysis of the proposed technical solution with the prototype shows that the proposed system of rough gauges for rolling railway rails in the rolls of the duo stand allows you to form the rolling surface of the rail head in a trapezoid axial one-sidedly closed caliber from a convex edge of the roll formed in a square-type box caliber with the bottoms of streams of opposite curvature having a rectilinear section symmetrical about the vertical axis along the bottom of the lower stream and slopes of the side faces to the horizontal equal, respectively, to the length of the straight section in terms of filling and slopes of the side faces to the vertical in a rectangular box gauge and the value of concavity (k) of the bottom of the upper stream within 4÷7 mm, increases the resistance to twisting and stalling of the roll deformed in it from the previous box caliber of a rectangular type, leads to the complete filling of the trapezoidal axial unilaterally closed caliber, improves the development of the edge , from which the rail head is formed due to its intensive stretching leading to the disclosure of surface defects, and the boring of a trapezoidal axial one-sidedly closed caliber in rolls with a preliminary shift of the closed relative to the open stream by the amount of gap (a) along the support cones until the metal is captured by the rolls, allows rolling according to the metal deformation calculated by the calibration in draft passes, it stabilizes the qualitative design of the geometric parameters of the roll profile from these passes.

The analysis of the state of the art carried out by the applicant, including searching through patent and scientific and technical sources of information and identifying sources containing information about analogues of the claimed invention, made it possible to establish that the applicant did not find a source characterized by features identical to all essential features of the claimed invention. The definition from the list of identified analogs of the prototype, as the analogue closest in terms of the set of features, made it possible to establish a set of distinctive features that are essential in relation to the technical result established by the applicant in the claimed method, set forth in the claims, therefore they provide the technical solution with the criterion "inventive step".

The essence of the invention is illustrated by the diagrams in Fig. 1-4.

In FIG. 1 shows a box gauge of rectangular type preceding the box gauge of square type with the bottoms of the streams made along the radii of unidirectional curvature. The shaded section of the pass corresponds to the shape and dimensions of the roll coming out of this pass.

In FIG. 2 "a" shows a scheme for capturing the roll after turning from a rectangular box gauge in a square type box gauge with bottoms of streams of opposite curvature; in fig. 2 "b" shows the shaded section of the caliber corresponding to the shape and size of the roll coming out of this caliber.

In FIG. 3 "a" shows a scheme for capturing a roll from a square-type box caliber with bottoms of streams of opposite curvature, after tilting, in a trapezoidal axial unilaterally closed caliber; in fig. 3 "b" shows the amount of deformation along the elements of the caliber (Δh _g and Δh _p - the magnitude of the deformation of the head and sole) and the direction of the resulting axial forces (P) from uneven deformation of the metal; in fig. 3 "c" shows the shaded section of the pass corresponding to the shape and size of the roll coming out of this pass, as well as the scheme of roll displacement during metal deformation in a trapezoidal axial one-sidedly closed pass by the amount of clearance along the support cones (a) due to the resulting axial forces.

In FIG. 4 "a" shows a scheme for capturing the roll, after tilting from a trapezoidal axial one-sidedly closed caliber, in a trapezoidal ribbed semi-closed caliber; in fig. 4 "b" shows the shaded section of the caliber corresponding to the shape and size of the roll coming out of this caliber.

The proposed system of rough gauges for rolling railway rails with the formation of the rolling surface of the rail head in a trapezoidal axial unilaterally closed caliber from a convex edge of the roll formed in a square-type box caliber with bottoms of streams of counter-directed curvature, having along the bottom of the lower stream a straight section symmetrical with respect to the vertical axis and slopes side faces to the horizontal are equal, respectively, to the length of the straight section in terms of filling and slopes of the side faces to the vertical in a rectangular box gauge, and the concavity (k) of the bottom of the upper stream is within 4÷7 mm, and the boring of a trapezoidal axial one-sidedly closed gauge in this system is carried out with a preliminary shift of the closed relatively open stream by the amount of gap along the support cones until the metal is captured by the rolls (a), which ensures, when the metal is shaped, in these calibers, a high-quality design of the geometric parameters of the rolls in accordance with roll sizing, reduces the production of calibers, stabilizes the rolling process, increases the productivity of the mill by reducing the time for setting up the profile, and reduces the occurrence of surface defects on the rails.

A specific example of building a system of draft gauges for rolling railroad rails

As an example, let's consider a system of rough gauges for rolling railway rails of the P65 type in the stand BD1 of EVRAZ ZSMK JSC. The location of the passes in the rolls of the stand is similar to the system of passes according to the prototype (Golovatenko A.V., Dorofeev V.V., Dobryansky A.V. and others. Development of an energy-efficient technology for rolling long rails on a universal rail and beam mill of EVRAZ ZSMK JSC // Chernye Metall, 2019, No. 6, p. 31).

After preliminary formation in the previous box pass, the workpiece is transferred to a rectangular box pass with slopes of the side faces to the vertical equal to tgα = 0.18, while the length of the straight section of the side face of the roll is determined based on the filling value of the rectangular box pass, according to the calculation of the broadening in this caliber according to the formulas of A.P. Chekmarev (Chekmarev A.P., Nefedov A.A., Nikolaev V.A. Theory of longitudinal rolling. Metallurgy Publishing House, 1965) or according to the formula of B.P. Bakhtinova (Bakhtinov B.P., Shternov M.M. Calibration of rolling rolls. Metallurgizdat. 1953). The length of the straight section of the side face of the roll according to the calculation is h=65 mm (Fig. 1). After turning the roll from a box gauge of rectangular type, it is set into a box gauge of square type with bottoms of streams of opposite curvature, in which the length of the straight section (b) and the magnitude of the slopes to the horizontal of the sections of the bottom of the lower stream (tgβ) (Fig. 2 "b"), forming the convex part of the caliber are made equal, respectively, to the length of the straight section of the side face of the roll from the box caliber of the rectangular type b=h=65 mm, and the slope to the vertical of the side faces in the box caliber of the rectangular type tgβ=tgα=0.18. This design of the lower square-type box groove with the bottoms of the counter-curvature streams ensures the stability of rolling of the square-type box-gauge roll by centering and improving the process of capturing the roll due to the conditions of simultaneous contact of the incoming roll with the inclined walls and the straight section of the bottom of the lower groove of the gauge (Fig. 2 "a").

(фиг. 3 «б»). За счет разности высотных деформаций по ширине калибра возникает разность вытяжек обжимаемых частей раската, что приводит к «серпению» его на выходе из калибра и прижатию к боковой стенке верхнего ручья трапециевидного осевого односторонне закрытого калибра формирующей подошву рельса.After the roll passes in a square-type box gauge with the bottoms of streams of opposite curvature, it is turned over with the convex edge oriented to the side of the profile head formation in a trapezoidal axial one-sidedly closed gauge (Fig. 3 "a"). The coefficient of high-altitude deformation of the section from which the future rail head is formed in a trapezoidal axial one-sidedly closed caliber significantly exceeds the coefficient of high-altitude deformation of the section from the side of the future sole

(Fig. 3 "b"). Due to the difference in high-altitude deformations across the width of the pass, a difference in the hoods of the pressed parts of the roll occurs, which leads to its "serpentine" at the exit from the pass and pressing against the side wall of the upper stream of the trapezoidal axial one-sidedly closed pass forming the rail sole.

The arising axial forces from the uneven compression of the roll along the width are perceived by the side wall of the upper stream of the trapezoid axial one-sidedly closed caliber, the upper shaft is shifted to zero clearance along the support cones. "Serpenya" roll at the exit of the caliber and the broadening of the metal lead to intensive development of the side wall of the upper stream. In order to reduce the development of the side wall of this caliber in a box caliber of a square type with bottoms of streams of opposite curvature, the concavity of the bottom of the upper stream (k) is designed, from which the recess obtained on the roll is in the zone of development of the greatest broadening in a trapezoid axial unilaterally closed caliber (Fig. 2 "b"), reducing the development of the side wall of the upper stream of this caliber.

The value of the concavity of the bottom of the upper stream is taken equal to k=4.5 mm.

в процессе прокатки в нем раската с разной величиной обжатия по ширине (рис. 3 «в»), расточка этого калибра осуществляется с предварительным сдвигом закрытого относительно открытого ручья на величину зазора по опорным конусам (а) до захвата металла валками:In order to ensure a symmetrical design of the profile in a trapezoidal axial unilaterally closed caliber

in the process of rolling in it a roll with a different amount of reduction in width (Fig. 3 "c"), the boring of this caliber is carried out with a preliminary shift of the closed relative to the open stream by the amount of the gap along the support cones (a) until the metal is captured by the rolls:

- ширина подошвы в открытом ручье с предварительным сдвигом закрытого относительного открытого ручья, мм;where

- the width of the sole in the open stream with a preliminary shift of the closed relative open stream, mm;

- ширина подошвы в открытом ручье в процессе прокатки при а=0 мм, мм;

- the width of the sole in the open stream during the rolling process at a=0 mm, mm;

- ширина подошвы в закрытом ручье, мм. Величина зазора по опорным конусам (а) до захвата металла валками определяется исходя из уклона опорного конуса (tgγ), который обычно составляет 10÷20% (Литовченко Н.В., Диомидов Б.Б., Курдюмова В.А. Калибровка валков сортовых станов. М., Металлургиздат, 1964). Величину уклона опорных конусов к вертикали выбираем равную 20%, т.е. tgγ=0,2 и с учетом рассчитанного зазора S=0,01363⋅1100=15 мм по буртам в процессе прокатки, принимаемом в диапазоне рекомендованных значений для черновых калибров крупносортных станов, рассчитывается величина а=15⋅0,2=3,0 мм (Патент 2684126 РФ, МПК⁷ В21В 1/085. Способ калибровки косорасположенных калибров с чередующимся направлением наклонов в валках клети дуо для прокатки железнодорожных рельсов / Юрьев А.Б., Головатенко А.В., Дорофеев В.В. и др.; заявитель и патентообладатель АО «ЕВРАЗ Объединенный Западно-Сибирский металлургический комбинат». - №2018107192; заявл. 26.02.2018; опубл. 04.04.2019, Бюл. №10) (фиг. 3 «в»).

- width of the sole in a closed stream, mm. The size of the gap along the support cones (a) before the capture of the metal by the rolls is determined based on the slope of the support cone (tgγ), which is usually 10÷20% (Litovchenko N.V., Diomidov B.B., Kurdyumova V.A. Calibration of sectional rolls Stan. M., Metallurgizdat, 1964). The value of the slope of the support cones to the vertical is chosen equal to 20%, i.e. tgγ=0.2 and taking into account the calculated gap S=0.01363⋅1100=15 mm along the shoulders during rolling, taken in the range of recommended values for roughing passes of large-section mills, the value a=15⋅0.2=3.0 is calculated mm (Patent 2684126 of the Russian Federation, MPK ⁷ V21V 1/085. A method for calibrating oblique calibers with alternating direction of slopes in the rolls of a duo stand for rolling railway rails / Yuryev A.B., Golovatenko A.V., Dorofeev V.V. and others. ; applicant and patent holder JSC EVRAZ United West Siberian Iron and Steel Works. - No. 2018107192; application 26.02.2018; publ. 04.04.2019, Bull. No. 10) (Fig. 3 "c").

The use of the proposed system of rough gauges for rolling rails provides the following advantages compared to the existing system:

1. Stabilizes the quality design of the geometric parameters of the profile in trapezoidal calibers.

2. Improve rolling stability and productivity by reducing mill setup time.

3. Reduces the production of calibers, reduces the consumption coefficient of the rolls.

4. Increases the production of defects in the surface of the workpiece, going to form the rolling surface of the rail head.

Claims (1)

A system of rough gauges for rolling railway rails, containing rectangular box gauges with straight sections along the filling and slopes of the side faces to the vertical, a square-type box gauge with bottoms of streams made along radii of opposite curvature, a trapezoidal axial one-sidedly closed and a trapezoidal half-closed rib gauge with the values gaps along the support cones (a) and collars (S), allowing the positioning of the strands relative to each other along these elements until the metal is captured by the rolls, characterized in that the square-type box gauge has a straight section symmetrical with respect to the vertical axis along the bottom of the lower strand and side slopes faces to the horizontal, equal, respectively, to the length of the straight section in terms of filling and slopes of the side faces to the vertical in a rectangular box gauge, as well as the value of the concavity (k) of the bottom of the upper stream within 4-7 mm, while boring the trapezoidal axial about one-sidedly closed caliber is made with a preliminary shift of the closed stream relative to the open stream by the amount of the gap along the support cones (a) until the metal is captured by the rolls.

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