A hole design method to prevent rail bottom concave defects

Abstract

The present invention relates to a pass design method for preventing rail bottom concave defects, belonging to the field of rail rolling technology in the metallurgical industry. The technical solution is: (1) determining the rail characteristic parameter k based on the geometric dimensions of the rail shape; (2) experimentally measuring the rail bottom curve of the rail rolled out of the flat vertical roller in the unworn state after cooling, and regressing the rail bottom curve function y after cooling. 冷却 (3) By experimentally measuring the wear of the vertical roller hole, the difference between the wear of the vertical roller hole and the wear of the hole center point is obtained, and the relative wear function y of the vertical roller hole is regressed. 磨损 ; (4) y 冷却 with y 磨损 The algebraic sum of the wear rollers' underside profile after the rail cools down is the algebraic sum of the wear rollers' underside profile. The roller pass curve is designed to compensate for the wear rollers' inverse value. This invention has the beneficial effect of making the underside profile of the rail closer to a plane after cooling, significantly reducing the degree of rail underside concavity and improving the dimensional accuracy of the rail.

Description

Technical Field

[0001] The invention relates to a pass design method for preventing a rail bottom concave defect, and belongs to the technical field of rail rolling in the metallurgical industry. Background Art

[0002] Rails are generally produced by hot rolling on universal mills, where the rail bottom surface is flat and formed by the flat vertical rollers in the universal mill. However, in actual production, due to the rail's appearance, the rail bottom edge is thin and has a large heat dissipation area. During rolling, the rail bottom edge has a greater temperature drop than the rail bottom center. During final rolling, the rail bottom edge temperature is generally 50-100°C lower than the rail bottom center. Subsequently, during natural cooling, the rail bottom edge cools to room temperature first, and the rail bottom center cools to room temperature later. This results in a concave defect on the rail bottom surface after cooling is complete. At the same time, due to the low temperature and high deformation resistance of the rail bottom edge during final rolling, the roller pass area corresponding to the rail bottom edge wears more than the rail bottom center. As the rolling volume increases, the rail bottom concave defect becomes more serious, even exceeding the standard requirement of 0.4mm, causing serious economic losses. Summary of the Invention

[0003] The purpose of the present invention is to provide a hole design method for preventing the concave defect of the rail bottom, so that the rail bottom contour curve after the rail is cooled is closer to a plane, the degree of concave of the rail bottom is greatly reduced, the dimensional accuracy of the rail is improved, and the problems existing in the background technology are solved.

[0004] The technical solution of the present invention is:

[0005] A method for designing a pass profile to prevent the bottom of a rail from being concave comprises the following steps:

[0006] (1) Determine the rail characteristic parameter k based on the rail geometry; k is set to the center area of ​​the rail bottom S 中 and rail bottom edge area S 边 The ratio of the rail bottom center area S 中 S is the area of ​​the inscribed rectangle of half the width of the rail bottom in the middle of the rail bottom. 边 is the area of ​​the remaining rail bottom side;

[0007] (2) By experimentally measuring the rail bottom curve after cooling when the flat vertical roller is not worn, the rail bottom curve function y after cooling is regressed. 冷却 , function y 冷却 Take the center point of the rail bottom as the origin of the coordinate system and set it according to the following formula:

[0008]

[0009] Where: △T—the difference between the rail bottom center temperature and the rail bottom edge temperature during final rolling;

[0010] T1—center temperature of rail bottom during final rolling;

[0011] T0—center temperature of rail bottom after cooling to room temperature;

[0012] k—rail characteristic parameter;

[0013] (3) By experimentally measuring the wear of the plane vertical roller hole, the difference between the wear of the vertical roller hole and the wear of the hole center point is obtained, and the relative wear function y of the vertical roller hole is regressed. 磨损 , function y 磨损 Take the center of the vertical roller pass as the origin and set it according to the following formula:

[0014]

[0015] Where: △T is the difference between the rail bottom center temperature and the rail bottom edge temperature during final rolling;

[0016] D——roller rolling amount;

[0017] k——rail characteristic parameter;

[0018] (4)y 冷却 with y 磨损 The algebraic sum of the wear rollers is the rail bottom profile curve after the rail is cooled. According to the opposite value, the roller pass curve is compensated and designed, that is, f(x) = -(y 冷却 +y 磨损 ),

[0019]

[0020] Where: △T is the difference between the rail bottom center temperature and the rail bottom edge temperature during final rolling;

[0021] T1 - rail bottom center temperature during final rolling;

[0022] T0 - the center temperature of the rail bottom after cooling to room temperature;

[0023] k——rail characteristic parameter;

[0024] D——roller rolling amount.

[0025] In order to ensure that the vertical roll and the horizontal roll are pressed against each other sideways when the universal rolling mill calibrates the roll gap, the two sides of the vertical roll hole curve are designed as straight line segments.

[0026] Considering the dimensional tolerance of the rail bottom width L and the rolling line offset of the universal rolling mill, the coverage range of the groove curve segment is 10 mm larger than the rail bottom width of the ideal rolled product on one side, that is, the value range of the function independent variable x is -L / 2-10≤x≤L / 2+10.

[0027] The beneficial effects of the present invention are as follows: when applied to the design of rail rolling pass, the rail bottom profile curve becomes closer to a plane after the rail is cooled, the rail bottom concavity value is controlled within 0.1 mm in the later stage of roller rolling, the rail bottom concavity is greatly reduced, the dimensional accuracy of the rail is improved, and significant economic and social benefits are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the division of the rail bottom center area and rail bottom edge area;

[0029] Figure 2 Schematic diagram of rail bottom curve function y after cooling of the rail rolled out when the vertical rollers are not worn;

[0030] Figure 3 Schematic diagram of the relative wear function y of the vertical roller after wear;

[0031] Figure 4 Graph showing the relationship between the pass curve function f(x) of the neutral roller and y cooling and y wear of the present invention;

[0032] Figure 5 Schematic diagram of the pass design of the neutral roller of the present invention.

[0033] In the figure: the curved part 1 of the vertical roller hole profile, and the straight part 2 of the vertical roller hole profile. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and through examples.

[0035] Refer to the attached Figure 1-5 A method for designing a hole pattern to prevent the bottom of a rail from being concave comprises the following steps:

[0036] (1) Determine the rail characteristic parameter k based on the rail geometry; k is set to the center area of ​​the rail bottom S 中 and rail bottom edge area S 边 The ratio of the rail bottom center area S 中 S is the area of ​​the inscribed rectangle of half the length of the rail bottom in the middle of the rail bottom. 边 is the area of ​​the remaining rail bottom side;

[0037] (2) By experimentally measuring the rail bottom curve after cooling when the flat vertical roller is not worn, the rail bottom curve function y after cooling is regressed. 冷却 , function y 冷却 Take the center point of the rail bottom as the origin of the coordinate system and set it according to the following formula:

[0038]

[0039] Where: △T—the difference between the rail bottom center temperature and the rail bottom edge temperature during final rolling;

[0040] T1—center temperature of rail bottom during final rolling;

[0041] T0—center temperature of rail bottom after cooling to room temperature;

[0042] k—rail characteristic parameter;

[0043] (3) By experimentally measuring the wear of the plane vertical roller hole, the difference between the wear of the vertical roller hole and the wear of the hole center point is obtained, and the relative wear function y of the vertical roller hole is regressed. 磨损 , function y 磨损 Take the center of the vertical roller pass as the origin and set it according to the following formula:

[0044]

[0045] Where: △T is the difference between the rail bottom center temperature and the rail bottom edge temperature during final rolling;

[0046] D——roller rolling amount;

[0047] k——rail characteristic parameter;

[0048] (4)y 冷却 with y 磨损 The algebraic sum of the wear rollers is the rail bottom profile curve after the rail is cooled. According to the opposite value, the roller pass curve is compensated and designed, that is, f(x) = -(y 冷却 +y 磨损 ),

[0049]

[0050] Where: △T is the difference between the rail bottom center temperature and the rail bottom edge temperature during final rolling;

[0051] T1 - rail bottom center temperature during final rolling;

[0052] T0 - the center temperature of the rail bottom after cooling to room temperature;

[0053] k——rail characteristic parameter;

[0054] D——roller rolling distance.

[0055] In this embodiment, Figure 1 It is shown that for the geometric profiles of rails of different specifications, an inscribed rectangle of half the width of the rail bottom in the middle of the rail bottom can be constructed, and its area is S 中 , the area of ​​the remaining rail bottom side is S 边 , the center area of ​​the rail bottom S 中 and rail bottom edge area S 边The ratio of is taken as the characteristic parameter k of rails of different specifications.

[0056] Figure 2 It shows that when the flat vertical roller is not worn, the rail bottom curve of the rolled rail after cooling is concave in the middle. Through a large number of experimental measurements and regression methods, the curve function y 冷却 .

[0057]

[0058] Figure 3 It shows that after the flat vertical roller is worn, the profile presents a convex shape in the middle. Through a large number of experimental measurements and regression methods, the curve function y can be obtained. 磨损 The corresponding bottom curve of the rolled hot rail is in the opposite direction and is concave in the middle.

[0059]

[0060] Figure 4 Display, through y 冷却 with y 磨损 The curve corresponding to the opposite value of the algebraic sum is used to compensate for the roller pass curve, which can offset most of the rail bottom concavity caused by uneven cooling of the rail bottom and roller wear, that is, f(x)=-(y 冷却 +y 磨损 ).

[0061]

[0062] Where: △T is the difference between the rail bottom center temperature and the rail bottom edge temperature during final rolling;

[0063] T1 - rail bottom center temperature during final rolling;

[0064] T0 - the center temperature of the rail bottom after cooling to room temperature;

[0065] k——rail characteristic parameter;

[0066] D——roller rolling amount.

[0067] Figure 5 The vertical roll pass profile is shown to consist of two parts: a curved section 1 and a straight section 2. Curved section 1 corresponds to the function curve f(x). Considering the dimensional tolerance of the workpiece rail width L and the offset of the universal mill's rolling line, the pass profile curve covers a range that is 10 mm larger than the ideal workpiece rail width on one side. In other words, the function's independent variable x ranges from -L / 2-10≤x≤L / 2+10. Straight section 2 is used to press against the side of the horizontal roll during roll gap calibration on the universal mill, achieving zero roll gap calibration.

[0068] The following three embodiments are used in the production site, and the specific details are shown in the table below:

[0069]

[0070] As can be seen from the above table, the present invention is applied to the rail rolling pass design, which makes the rail bottom profile curve closer to a plane after the rail is cooled, greatly reduces the concavity of the rail bottom, and improves the dimensional accuracy of the rail.

Claims

1. A pass design method for preventing rail bottom concave defects, characterized by: The following steps are involved: (1) Determine the rail characteristic parameter k based on the rail geometry; k is set to the center area of ​​the rail bottom S 中 and rail bottom edge area S 边 The ratio of the rail bottom center area S 中 S is the area of ​​the inscribed rectangle of half the width of the rail bottom in the middle of the rail bottom. 边 is the area of ​​the remaining rail bottom side; (2) By experimentally measuring the rail bottom curve after cooling when the flat vertical roller is not worn, the rail bottom curve function y after cooling is regressed. 冷却 , function y 冷却 Take the center point of the rail bottom as the origin of the coordinate system and set it according to the following formula: Where: △T—the difference between the rail bottom center temperature and the rail bottom edge temperature during final rolling; T1—center temperature of rail bottom during final rolling; T0—center temperature of rail bottom after cooling to room temperature; k—rail characteristic parameter; The function independent variable x takes the value range of -L / 2-10≤x≤L / 2+10, where L is the rail bottom width, mm; (3) By experimentally measuring the wear of the plane vertical roller hole, the difference between the wear of the vertical roller hole and the wear of the hole center point is obtained, and the relative wear function y of the vertical roller hole is regressed. 磨损 , function y 磨损 Take the center of the vertical roller pass as the origin and set it according to the following formula: Where: △T is the difference between the rail bottom center temperature and the rail bottom edge temperature during final rolling; D——roller rolling amount; k——rail characteristic parameter; (4)y 冷却 with y 磨损 The algebraic sum of the wear rollers is the rail bottom profile curve after the rail is cooled. According to the opposite value, the roller pass curve is compensated and designed, that is, f(x) = -(y 冷却 +y 磨损 ), Where: △T is the difference between the rail bottom center temperature and the rail bottom edge temperature during final rolling; T1 - rail bottom center temperature during final rolling; T0 - the center temperature of the rail bottom after cooling to room temperature; k——rail characteristic parameter; D——roller rolling distance.

2. A pass design method for preventing rail bottom concave defects according to claim 1, characterized in that: Straight line segments matching the horizontal rollers are provided on both sides of the vertical roller hole curve.

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