JP2003028128A - Splice plate for friction-gripping high-strength bolt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply a splice plate with unevenness having durability and a stable slip factor by applying high-speed low-cost laser heat treatment. SOLUTION: This splice plate for friction-gripping a high-strength bolt has the chevron-shaped unevenness 2 concentric with a bolt hole 1, or linearly continuous near the bolt hole 1. The chevron-shaped unevenness part 2 is quenched such that hardness of projecting parts is higher than surface hardness near bottom parts of recessed parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a splice plate for high-strength bolt friction welding, which is used for friction welding of structures such as buildings and bridges. INDUSTRIAL APPLICABILITY The splice plate of the present invention can inexpensively and stably obtain a friction coefficient with a high slip coefficient, and by using this, the joint efficiency is improved, the number of bolts fastened is reduced, and the stability of the steel structure is improved. Can be increased.

[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 should be applied. Also, 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 if the rust formation state differs due to factors such as the environment, variation may occur and it may not be reached. .

For this reason, in addition to the method of generating red rust on the surface of the steel material, a method of making unevenness on the joint surface by a processing method such as rolling has been proposed, as disclosed in JP-A-11-247831. . 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 a tensile, bending, or shearing component is applied to the splice plate portion, there is a problem that cracks propagate from the concave portion and the splice plate is broken. 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 It is an object of the present invention to provide a splicing plate with unevenness which is durable and has a stable sliding coefficient, which is subjected to high-speed and inexpensive laser heat treatment.

[0005]

In order to solve the above-mentioned problems, the present invention is intended to obtain a stable sliding coefficient and durability by only quenching a portion requiring hardness.
The main points are as follows. (1) In a high-strength bolt friction welding splice plate having concentric circles with bolt holes or linear concavities and convexities in the vicinity of the bolt holes, the concavo-convex portions of the chevron are hardened and the hardness of the convex portions is increased. A high-strength bolt friction splicing plate characterized by being harder than the vicinity of the bottom of the recess. (2) The high-strength bolt friction welding splice plate according to (1), wherein the surface hardness near the bottom of the recess is substantially the same as the surface hardness before quenching. (3) For high-strength bolt friction welding according to (1) or (2), characterized in that the splice plate is irradiated with a laser beam from a right angle direction, and the chevron-shaped uneven portion is scanned and quenched. Splice plate.

[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 concentric circles that are continuous around the bolt hole 1 in regions d1 and d2 of approximately three times the bolt diameter, Alternatively, the linear unevenness 2 is provided. For this reason, the apex of the convex portion projects from the base metal, and has a structure in which the slip coefficient is increased by biting into the steel material to be welded by tightening the bolt. Only the convex portion of the splice plate is harder than the base material by the heat treatment, so that the biting effect becomes more remarkable. The shaded portion in the unevenness 2 of FIG. 1C indicates the hardened portion. On the other hand, the hardness in the vicinity of the bottom 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.

In the method of manufacturing the splice plate, a laser beam is focused into a rectangular or linear shape and the surface is scanned to perform heat treatment to rapidly heat only the convex portion to increase the hardness. FIG. 2 shows, as an embodiment of the present invention, a splice plate convex portion (2 in FIG. 1) after laser processing.
It shows the hardness data collected from a) to the bottom of the concave portion (2b in FIG. 2) in the vertical direction from the apex of the convex portion. The hardness measurement point is 3/4 of the height of the protrusion from the tip of the apex of the protrusion.
Is about twice as hard as the surface hardness of the untreated base metal. However, the vicinity of the recess has almost the same hardness as before the treatment.

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.

Here, it is well known that the cooling rate in laser quenching is generally sufficiently fast, unlike other induction hardening, so that all the parts reaching the transformation point become martensite and harden. Also in this simulation, 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. It is also well known that the martensite structure obtained by quenching has a hardness that is at least twice as high as that of the pearlite structure which is a structure at the time of manufacturing a general steel sheet. 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.

[0010]

[Example] As shown in FIG. 4, a total length of 500 mm and a total width of 200
Rolled protrusions with 8 mm of rolled concentric protrusions 2 having a diameter of 60 mm on a steel plate having a thickness of 15 mm and a thickness of 15 mm, a height from a convex portion to a concave portion of 2 mm, and an apex angle of 60 °. A carbon dioxide gas laser with a laser output of 10 kW is used for the splice plate 3 having a laser beam at the irradiation position, and a rectangular beam with a long side of 70 mm and a short side of 2 mm is used to form a rectangular beam that is perpendicular to the splice plate surface. Irradiation was performed from the direction and scanning was performed in the direction parallel to the short side, and quenching treatment was performed in two rows of four. As the material to be processed, carbon steel for mechanical structure having a carbon content of 0.35% and having a carbon-based absorbent applied to the surface to improve the laser absorptivity was used. Fig. 2 shows the distribution of hardening when the scanning speed is 2m / min. About 70% of the height of the convex part from the tip of the convex part is twice as high as Hv200 which is the surface hardness of the base metal before treatment. Hv above
It is 500. Further, the splice plate after cooling had no deformation such as warpage. 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.

Although the beam shape at the laser irradiation position used here is rectangular, 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.

[0012]

EFFECTS OF THE INVENTION In the high-strength bolt friction welding splice plate of the present invention having concentric circles with the bolt holes or linear contiguous concavities and convexities in the vicinity of the bolt holes, the concavo-convex portions of the chevron are hardened to form protrusions. By making the hardness of the portion harder than the surface hardness in the vicinity of the bottom of the recess, it is possible to stably obtain a high slip coefficient without deformation such as warpage or reduction in fatigue strength.

[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 measuring the hardness from the apex of the convex portion of the splice plate cured by laser heat treatment to the bottom of the concave portion.

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

FIG. 4 is an overall schematic view of a laser heat treated splice plate according to the present invention.

[Explanation of symbols]

1 bolt hole 2 unevenness 3 splice plate 4 laser light

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2E125 AA01 AA51 AB01 AB08 AC14                       AC15 AE13 AG03 AG12 BB03                       BB22 BB27 BB33 BB37 BD01                       BE07 BE08 BF06 CA14 CA19                       DA03 EA14                 3J034 AA09 BA03 BA15 CA03                 4K042 AA25 BA03 BA04 BA10 DA01                       DB04

Claims (3)

[Claims] 1. A high-strength bolt friction welding splice plate having concentric circles with a bolt hole, or linear concavities and convexities in the vicinity of the bolt hole, wherein the concavo-convex portion of the chevron is hardened to harden the convex portion. The splice plate for high-strength bolt friction joining is characterized in that the hardness is made harder than the hardness near the bottom of the recess. 2. The splice plate for high strength bolt friction joining according to claim 1, wherein the surface hardness near the bottom of the recess is substantially the same as the surface hardness before quenching. 3. A laser beam is applied to the splice plate from a right angle direction, and the chevron-shaped uneven portion is scanned,
The splice plate for high-strength bolt friction joining according to claim 1 or 2, characterized by being quenched.