JP2014180684A - Roll for transportation of metallic material and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roll for transportation of a metallic material which is hard to occur a crack damage.SOLUTION: A roll 1 for transportation of a metallic material comprises a columnar shaft core 2, and an external cylinder 3 covering a peripheral surface of the shaft core 2. The external cylinder 3 is divided in an axial direction of the roll. Between the divided parts of the external cylinder 3, a clearance 31 for exposing a part of the peripheral surface of the shaft core 2 in a circumferential direction of the roll is formed. A groove 2a is formed in the exposed peripheral surface of the shaft core 2. At both ends of the groove 2a, a curve surface, which connects the groove 2a to the peripheral surface of the shaft core 2, is formed.

Description

  The present invention relates to a roll for transporting a metal material that is unlikely to cause breakage and a method for manufacturing the roll.

  In equipment used at steelworks, such as continuous casting equipment and hot rolling equipment, rolls for conveying metal materials are used. As a roll for transporting the metal material, there is an assembly-type roll formed by joining the shaft core and the outer cylinder, for example, by shrink-fitting in order to suppress breakage of the roll due to heat crack or the like. . The assembly-type roll has a mechanism in which heat cracks are generated from the surface of the outer cylinder and stop at the boundary with the shaft core, so that occurrence of heat cracks in the entire roll is suppressed. .

  In such an assembly-type roll, a metal having excellent wear resistance is used as the material of the outer cylinder, and a metal having excellent fatigue strength and toughness is used as the material of the shaft core. The coefficient of thermal expansion is different. In Patent Document 1, as this assembly-type roll, made of cemented carbide for sheet rolling having an outer cylinder made of a material having a thermal shock coefficient calculated from physical properties such as a coefficient of thermal expansion and Young's modulus equal to or higher than a predetermined value. Composite rolls have been proposed, which prevent initial cracking due to thermal shock.

  The assembly type roll described above is manufactured by heating and expanding a cylindrical outer cylinder, inserting an unheated columnar shaft core into the outer cylinder, and cooling the outer cylinder. As a result, the inner peripheral surface of the outer cylinder comes into contact with the peripheral surface of the shaft core. However, simply inserting the shaft core into the outer cylinder and then cooling the outer cylinder causes them to slip. there is a possibility. Therefore, in order to prevent this slip, the boundary between the shaft core and the outer cylinder at both ends in the axial direction of the roll is welded so that the outer cylinder and the shaft core rotate together. In the roll structure of the invention of Patent Document 1, since the coefficient of thermal expansion differs between the outer cylinder and the shaft core, depending on the heat, depending on the heat, one of the outer cylinder and the shaft core is the other. If it expands more, stress is applied to the welded portion between the shaft core and the outer cylinder, and the welded portion may be damaged.

  Therefore, the outer cylinder is divided in the axial direction of the roll, and an interval in which a part of the peripheral surface of the shaft core is exposed along the circumferential direction of the roll is formed between the divided outer cylinders. The outer cylinder can be expanded to the interval, and the welded portion is prevented from being damaged. FIG. 4 shows a conventional metal material transport roll having an outer cylinder in which the gap is formed. In this conventional metal material transporting roll 101, when the interval 103 is formed in the outer cylinder 102, the shaft core 104 welded to the outer cylinder 102 at the welded portion 106 is recessed in a portion corresponding to the corner portion 105 of the outer cylinder 102. It was observed that a flaw occurred and a crack occurred in the shaft core 104 therefrom. Generation | occurrence | production of such a crack leads to the downtime trouble in a continuous casting installation, for example.

Japanese Patent No. 2004-268140

  This invention is made | formed in view of the said phenomenon, The place made into the objective is to provide the roll for metal material conveyance which is hard to produce a crack, and its manufacturing method.

  As a result of earnestly examining the reason why a dent is generated at a corner portion of a conventional roll for transporting metal material, the present inventors have transported the metal material in a state where a load is applied to the outer cylinder when transporting the metal material. When the roll for rotation is rotated, it is assumed that stress may concentrate on the portion of the shaft core corresponding to the corner portion that becomes the inner peripheral end of the end surface of the outer cylinder, and the shape of the portion corresponding to the corner portion is The present invention was completed by changing the stress to suppress the stress applied to the portion.

That is, the gist of the present invention for solving the above problems is as follows.
(1) A metal material transport roll comprising a cylindrical shaft core and an outer cylinder covering the peripheral surface of the shaft core, the outer cylinder being divided in the axial direction of the roll, and between the divided outer cylinders Is provided with an interval in which a part of the peripheral surface of the shaft core is exposed along the circumferential direction of the roll, and a groove is formed in the exposed peripheral surface of the shaft core, and both ends of the groove are formed. The metal material transporting roll is characterized in that a curved surface connecting the bottom of the groove and the peripheral surface of the shaft core is formed in the part.
(2) The metal material transport roll according to (1), wherein an end surface of the outer cylinder forming the gap is chamfered toward a peripheral surface side of the shaft core.
(3) A manufacturing method of a roll for conveying a metal material comprising a cylindrical shaft core and an outer cylinder covering the peripheral surface of the shaft core, the peripheral surface of the shaft core along the circumferential direction of the shaft core A groove is formed on both ends of the groove, and a curved surface connecting the bottom of the groove and the peripheral surface of the shaft core is formed, and the roll is divided in the axial direction so as to form an interval at which the groove is exposed. A manufacturing method of a roll for conveying a metal material, wherein the shaft core is inserted into an outer cylinder.
(4) The method for manufacturing a roll for conveying a metal material according to (3), wherein an end surface of the outer cylinder that forms the interval is chamfered toward the peripheral surface side of the shaft core.

  According to the present invention, in a roll for conveying a metal material that includes a cylindrical shaft core and an outer cylinder that covers the peripheral surface of the shaft core, the roll is exposed at an interval provided between the divided outer cylinders. The stress applied to the shaft core portion is suppressed, so that the shaft core is less likely to break. As a result, the life of the metal material transport roll can be extended.

It is explanatory drawing which shows the roll for metal material conveyance of this invention. It is explanatory drawing which shows the method of forming a curved surface in the both ends of a groove | channel. It is a graph which shows the relationship between the stress which generate | occur | produces in the both ends of a groove | channel, and the center of a groove | channel, and curvature radius (rho) in this invention. It is explanatory drawing which shows the conventional roll for metal material conveyance.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an explanatory view showing a metal material transport roll of the present invention, and is also a side sectional view of the metal material transport roll. The metal material transfer roll 1 includes a columnar shaft core 2 and a cylindrical outer tube 3 that covers the peripheral surface of the shaft core 2. A plurality of metal material conveyance rolls 1 are arranged in the conveyance direction in which the metal material is conveyed, and a metal material such as a steel piece is conveyed by a plurality of rotating metal material conveyance rolls 1.

  The shaft core 2 includes a body portion 21 and a shaft portion 22 projecting outward from both ends of the body portion 21. A bearing 23 is attached to the shaft portion 22, and the shaft core 2 rotates while being supported by the bearing 23.

  The outer cylinder 3 includes two first outer cylinders 3a and a second outer cylinder 3b divided in the axial direction of the roll. The outer cylinder 3 is arranged in the first outer cylinder 3a and the second outer cylinder 3b. A core 2 is fitted. The body portion 21 serving as the peripheral surface of the shaft core 2 is covered with the outer cylinder 3, and the circumference of the roll 1 for transporting the metal material is provided between the first outer cylinder 3 a and the second outer cylinder 3 b. An interval 31 is provided along the direction to expose a part of the peripheral surface of the body portion 21.

  As shown in FIG. 1, welded portions 4 are formed by welding the boundary between the shaft core 2 and the outer cylinder 3 at both ends in the axial direction of the roll. Since the shaft core 2 and the outer cylinder 3 are fixed at the welded portion 4, the outer cylinder 3 also rotates together with the shaft core 2. Although depending on the usage environment of the metal material transporting roll 1, even if the outer cylinder 3 expands larger than the shaft core 2 due to heat, the outer cylinder 3 expands to the interval 31, so the interval 31 is only narrowed. In this way, the interval 31 prevents the force due to thermal expansion of the shaft core 2 or the outer cylinder 3 from being applied to the welded portion 4.

  As shown in FIG. 1, a groove 2a is formed along the circumferential direction of the circumferential surface of the shaft core 2 corresponding to the interval 31, and the bottom of the groove 2a is formed at both ends of the groove 2a. A curved surface connecting the peripheral surface with the shaft core 2 is formed. That is, the curved surface which inclines toward the bottom of the groove | channel 2a from the edge of the surrounding surface of the axial core 2 corresponding to the both ends 24 of the groove | channel 2a is formed. As shown in FIG. 4, in the conventional metal material transport roll 101, when a load is applied to this roll, the inner surface of the end surface of the outer cylinder 102 that forms the interval 103 is formed in the portion of the shaft core 104 corresponding to the corner portion 105. It is inferred that the peripheral ends come into contact with each other and stress concentrates on that portion. On the other hand, in this invention, the part which contacts the end surface inner end 32a of the end surface 32 which forms the space | interval 31 of the outer cylinder 3 in the peripheral surface part corresponding to the corner part 105 is made into the edge (both ends) of the groove | channel 2a. . As a result, the end surface inner end 32a comes into contact with the curved surface edge of the shaft core 2 instead of the surface, so that the force caused by the contact of the end surface inner end 32a is not the peripheral surface of the shaft core 2 but the circumferential line (curved surface). The stress applied to both ends 24 is suppressed.

Furthermore, it is preferable to incline the end surface 32 of the outer cylinder 3 so that the outer peripheral surface of the outer cylinder 3 protrudes from the both ends 24 of the groove 2a to the interval 31. That is, it is preferable to chamfer the end surface 32 of the outer cylinder 3 toward the peripheral surface side of the shaft core 2. This is because the smaller the portion of the outer cylinder 3 that covers the interval 31 and is closer to the shaft core 2, the less stress is applied to both ends 24.

  In particular, when the roll 1 for transporting a metal material is used in a continuous casting apparatus in an ironworks, the shaft core 2 is preferably an internal member of the roll and is made of a metal having excellent fatigue strength and toughness. An example of this metal is alloy steel for mechanical structure such as SCM material. Since the outer cylinder 3 becomes an external member of the roll 1 for conveying a metal material and comes into contact with the conveyed metal material, the outer cylinder 3 is preferably made of a metal having excellent wear resistance. Examples of the metal include alloy steels such as high speed steel and SUS material.

Next, the manufacturing method of the roll for metal material conveyance of this invention is demonstrated. This manufacturing method generally includes the following three steps.
Step 1: Grooves are formed in the circumferential surface of the shaft core 2 along the circumferential direction.
Step 2: A curved surface connecting the bottom of the groove and the peripheral surface of the shaft core 2 is formed at both ends of the groove 2a.
Step 3: A cylindrical first outer cylinder 3a and a second outer cylinder 3b are prepared, and the first outer cylinder 3a and the second outer cylinder 3b are formed so as to form an interval 31 between which the groove 2a is exposed. The shaft core 2 is inserted into the outer cylinder 3b (shrink fit).

  Hereinafter, each of the steps 1 to 3 will be described.

<Step 1>
In the shaft core 2, grooves 2 a exposed at the intervals 31 shown in FIG. 1 are formed. FIG. 2 is an explanatory diagram showing a method of forming curved surfaces at both ends of the groove. First, the position at which the groove 2 a is formed in the shaft core 2 is determined according to the intended use of the metal material transport roll 1. Next, in the groove 2a, the groove parallel part length x of the parallel part parallel to the peripheral surface of the metal column and the groove depth z from the peripheral surface of the shaft core 2 to the parallel part of the groove 2a are determined, and the length A space (groove) determined by the depth x and the depth z is formed.

  Specifically, with a lathe or the like, the circumferential surface of the shaft core 2 may be cut by the groove parallel portion length x and the groove depth z, or a dent having such dimensions may be formed. The metal pillar may be molded so as to be formed and used as the shaft core 2.

<Process 2>
Together with step 1 and / or after step 1, as shown in FIG. 2, both end portions along the axial direction of the shaft core 2 in the space determined by the length x and the depth z are processed. Assuming a curvature circle 41 having a curvature radius ρ so that both end portions thereof are curved surfaces connecting the bottom of the groove and the peripheral surface of the shaft core 2, a curved surface along the circumference along the curvature radius ρ is assumed. Grooves 2a are formed at both end portions.

  Making the shaft core 2 thin is synonymous with making the roll a portion where stress that causes the core core 2 itself to become brittle, and reducing the cross-sectional area perpendicular to the axial direction of the roll to increase the load stress. Since it was also an act to do, it was never done before. However, as shown in FIG. 4, the present inventors consider the possibility that stress is concentrated on the portion of the shaft core 104 corresponding to the corner portion 105 in the conventional metal material transfer roll 101. As shown in FIG. 1, in order to form curved surfaces at both ends of the groove 2a, the idea of deliberately reducing a part of the shaft core 2 from the beginning has been reached. As a method of forming a curved surface, the shaft core 2 obtained in step 1 may be scraped along the circumference of the curvature circle 41, or curved surfaces along such a circumference are formed at both ends thereof. The metal pillar having the groove formed may be molded and used as the shaft core 2.

<Step 3>
Cylindrical first and second outer cylinders 3a and 3b are prepared and thermally expanded. On the other hand, the shaft core 2 is not heated. Next, the shaft core 2 is inserted into the first outer cylinder 3a and the second outer cylinder 3b so as to form an interval 31 where the groove 2a is exposed. By cooling the first and second outer cylinders 3a and 3b in a state where the shaft core 2 is inserted, these are contracted and the shaft core 2 is fitted into the first and second outer cylinders 3a and 3b. . In this way, the shaft core 2 is inserted into the outer cylinder 3.

  Prior to step 3, it is preferable to chamfer the end surfaces 32 of the first and second outer cylinders 3 a and 3 b that form the interval 31 toward the peripheral surface side of the shaft core 2.

[Setting of radius of curvature ρ]
As can be seen from FIG. 2, when the groove parallel part length x and the curvature radius ρ are increased, the length of the interval 31 along the axial direction is increased, and when the groove depth z is increased, the interval along the radial direction is increased. Since the depth of 31 will become large, the area of the outer cylinder which contacts the metal material of the roll 1 for metal material conveyance will also become small. For this reason, the groove parallel portion length x is 1/20 to 1/10 of the total length X (see FIG. 1) along the axial direction of the trunk portion 21, and the groove depth z is in the radial direction of the trunk portion 21. It is set to 1/20 to 1/10 of the total length (diameter of the shaft core 2) Z (see FIG. 1).

The curvature radius ρ can be determined as follows, for example.
(1) First, the groove depth z is determined.
(2) Next, a calculation simulation for applying a load to the metal material transport roll 1 is performed using a three-dimensional model based on the finite element method. Simulation conditions other than the determined groove depth z may be determined as appropriate depending on the shape of the metal material transport roll 1 and the like.
(3) While applying the load, the curvature radius ρ and the groove parallel part length x are changed to calculate the stress generated at both ends 24 of the groove and the stress generated at the central part of the groove 2a. Then, an isoline diagram (contour diagram) representing the distribution of the larger stress (referred to as “maximum generated stress”) on the ρ-x plane is created.
(4) From the contour map, the range of ρ−x that minimizes the maximum generated stress is obtained.
(5) The allowable stress limit value is determined based on the minimum value of the maximum generated stress. For example, a stress that is about 20% larger than the absolute value of the minimum value than the minimum value can be set as an allowable stress limit value.
(6) The groove parallel part length x and the radius of curvature ρ can be obtained from the range of ρ−x that gives the limit value obtained in (5) above.
Further, the above (2) to (6) are performed by appropriately changing the groove depth z determined in (1), and further, an optimal curvature radius ρ according to the groove depth z and the groove parallel part length x is set. You may ask for it.

  FIG. 3 is a graph showing the relationship between the stress generated at both ends of the groove and the center of the groove and the radius of curvature ρ in the present invention. The graph of FIG. 3 assumes a roll 1 for conveying a metal material having a length of the body portion 21 of 1981 mm and a diameter of the shaft core 2 of 255 mm, a groove parallel part length x is 20 mm, and a groove depth. This is a result of obtaining the stress generated at the center along the axial direction of the both ends 24 of the groove 2a and the groove 2a by changing the radius of curvature ρ, assuming that the length z is 3 mm.

  As can be seen from FIG. 3, when the radius of curvature ρ exceeds 20 mm, the stress generated at the center of the groove 2a starts to increase. On the other hand, the stress generated at both ends 24 sharply decreases when the radius of curvature ρ is about 4 mm to 20 mm, but gradually approaches a constant value when the radius exceeds 20 mm. Further, if the radius of curvature ρ is continuously increased, the stress generated at both ends 24 continues to decrease gradually, the stress generated at the center of the groove 2a continues to increase, and these stresses coincide. The curvature radius ρ with which the stress coincides was 58 mm.

  As the radius of curvature ρ increases from 58 mm, the stress generated at the center of the groove 2 a increases beyond the stress generated at both ends 24 and gradually decreasing. This increasing stress was 90 mm in radius of curvature ρ exceeding the stress generated at both ends 24 when the aforementioned radius of curvature ρ was 20 mm (not shown in the graph of FIG. 3). For this reason, if it is the roll 1 for metal material conveyance of this dimension, it is preferable that the curvature radius (rho) shall be 20-90 mm in consideration of the stress which generate | occur | produces in these parts. In this way, the dimension of the interval 31, the relationship between the groove parallel part length x, the groove depth z, and the curvature radius ρ, and the stress generated at both ends 24 of the groove 2a and the center of the groove 2a are taken into consideration. Then, it is preferable to set the curvature radius ρ so that these stresses are equal to or less than the matching curvature radius ρ.

  As described above, in the metal material transporting roll 1 including the cylindrical shaft core 2 and the outer cylinder 3 covering the peripheral surface of the shaft core 2, the shaft core 2 and the outer cylinder 3 at both ends in the axial direction of the roll. This prevents the welded portion 4 from being damaged and suppresses the occurrence of excessive stress at both ends 24 of the groove 2a forming the gap 31, thereby extending the life of the roll 1 for conveying a metal material. Can be planned.

A metal material conveying roll 1 as shown in FIG. 1 was prepared (example of the present invention). The dimensions of the metal material transport roll 1 are as follows.
Total length of roll 1 for conveying metal material: 2426 mm
Diameter of metal material transfer roll 1: 330 mm
Total length X of the body part 21: 1981 mm
Diameter Z of shaft core 2: 255 mm
Groove parallel part length x: 20 mm
Groove depth z: 3 mm
Curvature radius ρ: 20mm
The material of the shaft core 2 is SCM440, and the material of the outer cylinder 3 is SUS431M.

  Meanwhile, a conventional metal material transport roll 101 as shown in FIG. 4 was prepared (comparative example). The dimensions of the outer cylinder 102 and the shaft core 104 of the metal material transport roll 101 are the same as those of the metal material transport roll 1 of the present invention.

While repeatedly applying heating and cooling to the metal material conveying rolls 1 and 101, while applying a load of 100 kgf / mm ² , these were rotated to check whether cracks occurred in the metal material conveying rolls 1 and 101. In the metal material transport roll 101, cracks occurred in the portion of the shaft core 104 corresponding to the corner portion 105 after 481 hours from the start of the test. However, the metal material transport roll 1 passed 900 hours from the start of the test. No cracks occurred. Also from this, it can be seen that the life of the roll 1 for transporting the metal material can be extended by suppressing the generation of excessive stress at both ends 24 of the groove 2a forming the interval 31.

DESCRIPTION OF SYMBOLS 1 Metal material conveyance roll 2 Shaft core 2a Groove 3 Outer cylinder 3a 1st outer cylinder 3b 2nd outer cylinder 4 Welding part 21 Trunk part 22 Shaft part 23 Bearing 24 Both ends of groove 31 Space | interval 32 End surface 32a End surface inner end 41 Curvature circle 101 Conventional roll for conveying metal material 102 Outer cylinder 103 Spacing 104 Shaft core 105 Corner portion 106 Welded portion

Claims (4)

A roll for conveying a metal material comprising a cylindrical shaft core and an outer cylinder covering the peripheral surface of the shaft core,
The outer cylinder is divided in the axial direction of the roll, and between the divided outer cylinders, an interval exposing a part of the peripheral surface of the shaft core is provided along the circumferential direction of the roll,
Grooves are formed on the exposed peripheral surface of the shaft core, and curved surfaces connecting the bottom of the groove and the peripheral surface of the shaft core are formed at both ends of the groove. Roll for conveying metal materials.   2. The metal material transport roll according to claim 1, wherein an end surface of the outer cylinder forming the gap is chamfered toward a peripheral surface side of the shaft core. A manufacturing method of a roll for transporting a metal material comprising a cylindrical shaft core and an outer cylinder covering a peripheral surface of the shaft core,
Forming a groove in a circumferential surface of the shaft core along a circumferential direction of the shaft core;
Forming a curved surface connecting the bottom of the groove and the peripheral surface of the shaft core at both ends of the groove;
A manufacturing method of a roll for conveying a metal material, wherein the shaft core is inserted into an outer cylinder divided in an axial direction of the roll so as to form an interval at which the groove is exposed.   The manufacturing method of the roll for metal material conveyance of Claim 3 which chamfers the end surface of the said outer cylinder which will form the said space | interval to the surrounding surface side of the said shaft core.

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