JP2003113415A - Method and apparatus for quenching splice plate for friction-bonding high strength bolt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively and rapidly manufacture a splice plate with high performance, which has high coefficient of friction by heat treatment with a laser having a controlled power density. SOLUTION: A quenching method for the splice plate for friction-bonding a high strength bolt, which has a continuous angular unevenness concentrical to a bolt hole, comprises adjusting a beam width and spatial distribution of power density of a linearly condensed laser beam and the scanning speed, to harden an angular salient so as to give higher hardness than that of a base metal, when linearly condensing the laser beam so as to give a longer line than a diameter of the angular uneven part, and scanning the angular uneven part for heat treatment. In particular, the laser beam has preferably a relatively lower power density in the central part of the longitudinal direction than in the end part of the longitudinal direction, of linearly or prolate elliptically condensed laser beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for quenching a splice plate suitable for manufacturing a splice plate for high-strength bolt friction joining, which is used for friction joining of structures in buildings and bridges. is there.
In particular, the present invention relates to a technique capable of inexpensively and rapidly manufacturing a high-performance splice plate having a high friction coefficient by laser processing.

[0002]

2. Description of the Related Art When joining building steel materials in series,
Butt steel to be joined, attach splice plates on both sides and tighten by bolts to join,
High strength bolt friction welding is commonly used. In high strength bolt friction welding, according to the design and construction guidelines of the Japan Institute of Architecture, the friction surface that is important in terms of joining strength is a good red rust surface with black skin removed, and a treatment with a slip coefficient of more than 0.45 is applied. In addition, the slip coefficient must be confirmed by a slip proof test. Normally, it is known that the slip coefficient exceeds 0.45 in a good red rust state, but there is a possibility that variations will occur due to differences in the rust generation state due to the environment etc. is there. For this reason,
In addition to the method of generating red rust on the surface of steel material, JP-A-11-
As disclosed in Japanese Unexamined Patent Publication No. 247831, a method of making unevenness on a joint surface by a processing method such as rolling has been proposed. At this time, the uneven portion was subjected to surface treatment by a high frequency heating method or the like in order to improve its original purpose of frictional force.

However, in these surface treatment methods, since the entire surface of the uneven portion is treated, it is unavoidable to cure the concave portion other than the convex portion which requires high hardness. Therefore, when pulling, bending, or shearing components are applied to the splice plate,
There was a problem that cracks propagated from the recesses and the splice plate cracked. In addition, since sufficient heat for hardening is applied to the entire surface of the splice plate, it deforms during cooling and the pressing around all bolts, which is a necessary item of the splice plate, becomes insufficient, and as a result, a gap is created, resulting in sufficient friction welding. There was also a problem that I could not get.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above problems and makes it possible to supply a high-performance splice plate having a high friction coefficient at low cost and at high speed by using heat treatment with a laser whose power density is controlled. An object is to provide a laser heat treatment method and apparatus.

[0005]

In order to solve the above-mentioned problems, the present invention provides a high-performance splice plate by constructing and irradiating a laser beam whose power density is controlled. The places to be are as follows. (1) In a quenching method of a high-strength bolt friction welding splice plate having concavities and concavities that are concentric with a bolt hole, a laser beam is condensed into a linear shape longer than the diameter of the concavities and convexities. When scanning and heat-treating the chevron-shaped concavo-convex portion, the hardness of the chevron-shaped convex portion is adjusted by adjusting the spatial distribution of the line width and power density of the linearly focused laser beam and the scanning speed. A method for quenching a splice plate for high-strength bolt friction joining, which is characterized by making it harder than the hardness of the material. (2) The power density of the linearly focused laser beam in the central portion in the longitudinal direction is relatively low as compared with the power density in the end portion in the longitudinal direction. A method for quenching a splice plate for high-strength bolt friction joining described in the above. (3) In a quenching treatment device for a high-strength bolt friction bonding splice plate having concavities and convexities contiguous to a bolt hole, a first optical element for concentrating a laser beam in a uniaxial direction, and a first optical element Optical element position adjusting mechanism for adjusting the distance between the workpiece and the workpiece, and a second optical element for superposing the laser beam focused by the first optical element in the uniaxial direction by left-right switching in the direction orthogonal to the focusing direction. A second optical element position adjusting mechanism for adjusting the distance between the second optical element and the workpiece, a third optical element for spreading the laser beam on the exit side of the second optical element in a direction perpendicular to the focusing direction, A third optical element position adjusting mechanism for adjusting the distance between the three optical elements and the workpiece,
And a scanning mechanism configured to scan the linear laser beam obtained on the output side of the third optical element in a direction perpendicular to the linear direction on the plane of the workpiece, and each of the workpieces of the first to third optical elements. A quenching device for a high-strength bolt friction welding splice plate that makes it possible to make the hardness of the chevron-shaped protrusions harder than the hardness of the base material by adjusting the distance and the scanning speed of the scanning mechanism.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. First, in the splice plate according to the present invention, as shown in FIG. 1, the concavities and convexities produced by cutting or rolling are continuously concentrically formed around the bolt hole 1 in a region approximately three times the bolt diameter. There is. For this reason, the apex 2 of the convex portion projects from the base material, and it is configured to bite into the steel material to be welded by tightening the bolt and increase the slip coefficient. The half of the height of the convex portion from the apex tip of the convex portion of the splice plate is about twice as hard as the surface hardness of the pre-treatment base material, so that the biting effect becomes more remarkable. On the other hand, the hardness in the vicinity of the bottom 3 of the concave portion and the portion other than the concave-convex portion is substantially the same as the hardness before quenching. Therefore, mechanical properties such as tensile strength and fatigue strength of the splice plate itself are not changed by the heat treatment, and the characteristics as designed can be stably obtained. For this reason, this method of manufacturing a splice plate cannot be performed by heat treatment such as high-frequency heating that cannot heat the entire base material to perform selective heat treatment. This can be achieved by performing heat treatment by scanning the surface with a beam having a power density.

The mechanism of this quenching will be described based on the temperature rise simulation result at the time of laser quenching shown in FIG. The conditions used in this simulation are a laser power of 10 kW, a beam shape on the workpiece of 70 mm x 2 mm rectangular shape, and 2 m / m in the direction parallel to the short side.
It was scanned at a speed of min. The material to be processed is a carbon steel for machine structural use having a carbon content of 0.35%, a height from a convex portion to a concave portion of 2 mm, and a splice plate having a protrusion having an apex angle of 60 °. The simulation result is
The maximum temperature reached by the part is displayed on the contour line. Since the laser heat input from the left and right slopes is added to the convex portion of the workpiece, the convex portion is easily heated and becomes a transformation point necessary for hardening. In this example, the transformation point is 850 ° C. On the contrary, the heat input by the laser beam 4 is easily diffused by heat transfer in the concave portion, and the temperature rise is suppressed below the transformation point, so that the concave portion is not cured.

However, when the linear laser beam is irradiated with a uniform power density, the beam longitudinal direction is closer to the beam longitudinal direction at the apex of the concentric convex portions than the beam longitudinal direction. And the convex part is close to parallel,
Quenching with a sufficient depth cannot be realized by one scan because the temperature at the apex is likely to be raised and melted easily. For this reason, when processing a portion where the beam longitudinal direction and the convex portion are nearly parallel to each other, the laser power density should be reduced or the scanning speed should be increased in response to processing conditions such as the portion where the convex portion is nearly a right angle. Therefore, it is necessary to perform processing without melting. Although these methods can be realized, it is inevitable that the apparatus and the processing procedure become complicated. In addition, when the operations in which the irradiations are overlapped are performed, there is a problem that annealing conditions occur and the hardness decreases.

Therefore, in the present invention, in order to further improve the processing method, a space having a controlled power density in the longitudinal direction of the linear beam is used instead of a beam having a uniform power density in view of the problem. By irradiating with a laser beam having a distribution, it becomes possible to process the vertices of the convex portions arranged in the concentric circles without melting by one scan. Specifically, a portion where the beam longitudinal direction and the convex portion are parallel to each other is treated with a laser beam having a reduced power density of the irradiation laser beam. The required reduction amount of the processing laser beam power density in the portion where the longitudinal direction and the convex portion are parallel to each other needs to be changed depending on the concavo-convex shape, but a reduction of approximately 15% to 20% is desirable. If it is less than that, melting occurs in the convex portion and the desired friction coefficient cannot be obtained, and if it is more than that, the depth of the hardened portion of the convex portion becomes shallow and the desired mechanical strength does not occur.

FIGS. 2 and 3 show the results of temperature rise simulation during quenching when the laser beam according to the present invention is used. FIG. 2 shows the temperature rise result at the end of the long side of the laser beam (point A in FIG. 4) where the laser beam 4 is perpendicular to the convex portion, and FIG. 3 is the laser where the laser beam 4 is parallel to the convex portion. It is the temperature rise result of the central portion (point B in FIG. 4) of the long side of the beam. The condition used in this simulation is that the laser power is 1
The beam shape on the work material was 0 kW, the rectangular shape was 70 mm × 2 mm, and the measured laser power density was as shown in FIG. 5, in which the central portion was reduced by about 20% from the end portion.
The scanning speed is 2 m / min in the direction parallel to the short side of the beam. The material to be processed is a carbon steel for machine structural use having a carbon content of 0.35%, a height from a convex portion to a concave portion of 2 mm, and a splice plate having a protrusion having an apex angle of 60 °. In the simulation result, the maximum temperature reached by the part is displayed on the contour line. The convex part of the work material is
It is heated more easily than the recesses and becomes the transformation point necessary for hardening. In this example, the transformation point is 850 ° C. When the laser beam according to the present invention is used, both the result of the end portion of the long side of the laser beam where the laser beam is substantially perpendicular to the convex portion and the result of the central portion of the long side of the laser beam where the laser beam is substantially parallel to the convex portion are obtained. It can be seen that quenching is possible up to the same depth at the peak of about 1400 ° C. Incidentally, the cooling rate from the transformation point to the Ms point (about 450 ° C.), which is the transformation end point, was about 0.3 seconds, and the rate required for quenching was sufficient. For this reason, it becomes possible to increase the hardness of only the convex portion in the splice plate having irregularities formed by the above cutting, rolling, or the like.

FIG. 6 shows an example of an optical system used for forming this laser beam. The first optical element 20 is a cylindrical lens for focusing the laser in the short side direction, and the length 13 of the short side of the irradiation beam can be changed by changing the distance between this lens and the workpiece 14. Second
The optical element 21 is a prism having a convex portion, and the first optical element 2
It is possible to superimpose the laser beams uniaxially compressed at 0 by swapping the left and right. By changing the distance between the prism and the workpiece 14, the degree of left and right replacement (the amount of superposition in the figure) can be changed, and the power density distribution can be adjusted as described later. The third optical element 22 is a cylindrical lens for expanding the laser in the long side direction, and the length 12 of the long side of the irradiation beam can be changed by changing the distance between this optical element and the workpiece.

The laser beam used for this processing is a laser beam having a low-order multimode. As an example of this, the intensity distribution of the Mt. Fuji type laser beam shown in FIG. 7 is shown. The width 15 of the laser beam when the superposition parameter 11 in FIG. 6 is set to 0 is defined as D. As shown in FIG. 8A, the power density of this beam is higher at the center of the long side than at the end. However, if the overlapping parameter 11 in FIG. 6 which is the shift amount is set to D / 10 as shown in FIG. 8B, the laser beam becomes uniform in the longitudinal direction. When the superposition parameter is set to D / 10 or more as shown in FIG. 8C, the laser beam has a reduced central portion required in the present invention. The amount for the end of the central portion is represented in FIG. 9 by the superposition parameter. In this way, the beam shape and the power density can be changed by adjusting the positions of the three optical elements. This optical system can also be configured by using a mirror system other than the lens. In this case, it is necessary to perform beam superimposition with a mirror called a rooftop mirror instead of the prism. Further, it is more effective to protect the laser device and the optical system from the reflection of the laser light by irradiating the laser beam while inclining as viewed from the horizontal in the minor axis direction, rather than irradiating from the vertical direction.

[0013]

[Example] As shown in FIG. 10, a total length of 500 mm and a total width of 20
On a steel plate with a thickness of 0 mm and a thickness of 15 mm, there are 8 rolled concentric circular protrusions with a diameter of 60 mm, the height from the convex portion to the concave portion is 2 mm, and the apex angle is 60 °. A carbon dioxide gas laser with a laser output of 10 kW is used for the splice plate, and as the optical system, a cylindrical lens with a focal length of 300 mm is installed as the first optical element at a position 290 mm from the surface of the workpiece, and the second optical element is used as the second optical element. A prism having an angle of 179 degrees was set at 250 mm from the surface of the material to be processed, and a cylindrical lens having a focal length of -100 mm as the third optical element was set at a position 120 mm from the surface of the material to be processed. The laser beam at the irradiation position was focused into a rectangular shape having a long side of 70 mm and a short side of 2 mm, and the reduction of the power density at the central portion was 20% compared to that at the end portion. This beam was used to irradiate the surface of the splice plate at an angle of 10 degrees from the vertical direction, and scanning was performed in the direction parallel to the short side to perform quenching treatment in four rows in two rows. The work material was coated with a carbon-based absorbent to improve the laser absorption rate on the surface.
Carbon steel for machine structure having a carbon content of 0.35% was used.
When the scanning speed is 2 m / min, the hardening distribution of the convex portion is as shown in Fig. 11 at any irregular portion, and about 50% of the height of the convex portion from the tip of the apex of the convex portion is the surface hardness of the base metal before treatment. The Hv500 is more than twice the Hv200. Further, the splice plate after cooling was free from any deformation such as melting or warping. The bending test of this splice plate showed that it was equivalent to the fatigue property before heat treatment, and there was no crack extension from the recess.

The beam shape used here at the laser irradiation position was rectangular, but a beam having a uniform power density in the longitudinal direction such as an ellipse can also be processed. Further, even when the shape and size of the protrusion are changed, it is possible to cure only the protrusion by the same mechanism by changing the power of the laser used, the shape of the focused beam, and the scanning speed.

[0015]

According to the present invention, in a high-strength bolt friction welding splice plate having concavities and concavities that are concentric with the bolt holes, the concavities are hardened without melting and the concavities are recessed. Since it was hardly quenched, it became possible to stably obtain a high slip coefficient.

[Brief description of drawings]

FIG. 1 is an explanatory view of a shape near a bolt hole of a splice plate according to the present invention.

FIG. 2 is a result of temperature rise simulation in processing a splice plate according to the present invention.

FIG. 3 is a result of temperature rise simulation in processing a splice plate according to the present invention.

FIG. 4 is a schematic representation of the location of the laser beam heat treated splice plate and laser beam according to the present invention.

FIG. 5 shows an example of the power density of a laser beam for heat treatment according to the present invention.

FIG. 6 shows an example of an optical system for heat treatment used in the present invention.

FIG. 7 shows an example of a spatial mode of a laser beam used in the present invention.

FIG. 8 is a power density distribution of a laser beam for heat treatment synthesized according to the present invention.

FIG. 9 is a ratio of power densities of a central portion and an end portion in the major axis direction with respect to a change of a superposition parameter.

FIG. 10 is an overall schematic view of a laser heat treated splice plate according to the present invention.

FIG. 11 is a result of measuring the hardness of the splice plate obtained by the heat treatment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 bolt hole 2 convex part vertex 3 concave part bottom 4 laser beam 10 quenching part 11 superposition parameter 12 beam long side 13 beam short side 14 work piece 15 beam width 20 first optical element 21 second optical element 22 third optical element

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F16B 5/02 F16B 5/02 HF term (reference) 3J001 FA05 GA02 HA02 JA10 KA02 KA11 KA21 KA26 KB04 4E068 AH00 CD05 DA00 4K042 AA23 BA03 BA13 DA01 DB04 EA01

Claims (3)

[Claims] 1. A method for quenching a high-strength bolt friction welding splice plate having concavities and concavities that are concentric with a bolt hole, the laser beam being linearly collected longer than the diameter of the concavities and convexities. In the heat treatment by scanning the uneven portion of the chevron, the hardness of the convex portion of the chevron is adjusted by adjusting the spatial distribution of the line width and power density of the linearly focused laser beam and the scanning speed. A method for quenching a splice plate for high-strength bolt friction welding, characterized in that the hardness is made higher than the hardness of the base material. 2. A laser beam in which the power density at the central portion in the longitudinal direction of the linearly focused laser beam is relatively lower than the power density at the end portions in the longitudinal direction. The method of quenching a splice plate for high-strength bolt friction joining according to 1. 3. A quenching treatment apparatus for a splice plate for high-strength bolt friction welding, which has concavities and convexities contiguous with a bolt hole, and a first optical element for concentrating a laser beam in a uniaxial direction, and a first optical element. A first optical element position adjusting mechanism for adjusting the distance between the optical element and the workpiece, and a second optical element for adjusting the distance between the laser beam focused in the uniaxial direction by the first optical element in the direction perpendicular to the focusing direction and superposing the laser beams. An optical element, a second optical element position adjusting mechanism that adjusts the distance between the second optical element and the workpiece, and a third optical element that spreads the laser beam on the exit side of the second optical element in a direction perpendicular to the focusing direction. A third optical element position adjusting mechanism for adjusting the distance between the third optical element and the workpiece, and the linear laser beam obtained on the output side of the third optical element at right angles to the linear direction on the workpiece plane. It consists of a scanning mechanism that scans in any direction. By adjusting the distance between each of the first to third optical elements and each workpiece and the scanning speed of the scanning mechanism, it is possible to make the hardness of the convex portion of the chevron higher than that of the base material. Equipment for quenching splice plates for friction welding of bolts.