Method of boring on ultrahigh tensile strength steel plate

Abstract

To provide a method of boring on an ultrahigh tensile strength steel plate having high hardness with a relatively inexpensive general drill not corresponding to the ultrahigh tensile strength steel plate.SOLUTION: After a boring plan location 2 on an ultrahigh tensile strength steel plate 1 is heated by heating means 3, the boring plan location 2 is cut by a cutting component 4.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a drilling method for plug welding ultra-high tensile steel plates used in automobile bodies. [Background technology]

[0002] For example, paragraph 0007 of the above-mentioned Patent Document 1 states that "there is provided a drill which is suitably used as a drill for removing spot welds from automobile bodies, and which is particularly capable of handling high-hardness steel plates having HRC30 or more."

[0003] Paragraph 0027 of Patent Document 1 states that "As the material for the drill, high-speed steel (HSS) or tool steel such as carbon tool steel or alloy tool steel is preferably used, taking into consideration the resistance to chipping when used with a hand drill. However, it is also possible to adopt other materials generally used for drills, such as cemented carbide. As the high-speed steel, high-speed steel sintered after powder molding (commonly known as powdered HSS) or high-speed steel containing cobalt (commonly known as cobalt HSS) is preferably used, and powdered HSS capable of drilling holes in steel plate with a hardness of HRC45 is more preferably used." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-88267 A Summary of the Invention [Problem to be solved by the invention]

[0005] Paragraph 0010 of the above-mentioned Patent Document 1 states that "the spot weld removal work can be easily performed with a hand drill even for high-hardness steel plates with HRC30 or more," but it is pointed out that such special drills are expensive.

[0006] In view of the above circumstances, the present invention aims to provide a drilling method that makes it possible to drill holes in ultra-high tensile steel plates even when using a relatively inexpensive, general-purpose drill that is not suitable for high-hardness ultra-high tensile steel plates. [Means for solving the problem]

[0007] The method for drilling holes in ultra-high tensile steel plate according to the present invention is characterized in that a portion of the ultra-high tensile steel plate where a hole is to be drilled is heated by a heating means, and then the portion where a hole is to be drilled is cut by a cutting part.

[0008] According to this configuration, the tensile strength and hardness (e.g., Rockwell hardness: HRC) of the intended hole-drilling location are reduced by heating the intended hole-drilling location, which makes it possible to drill the intended hole-drilling location of the ultra-high tensile steel plate using a relatively inexpensive general drill that is not compatible with the ultra-high tensile steel plate having high hardness. Effect of the Invention

[0009] According to the present invention, a drilling method can be provided that makes it possible to drill holes in ultra-high tensile steel plates even when using a relatively inexpensive general-purpose drill that is not suitable for high-hardness ultra-high tensile steel plates. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing an initial stage of a method for drilling holes in ultra-high tensile steel plate according to one embodiment of the present invention. FIG. [Diagram 2] FIG. 2 is a side view showing a continuation of FIG. [Diagram 3] This figure is used to explain a drilling method for an example of an application of ultra-high tensile steel plate. (a) is a side view showing the B-pillar of an automobile, and (b) is a cross-section of line (3)-(3) in (a) viewed from the direction of the arrow. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.

[0012] One embodiment of the present invention is shown in Figures 1 to 3. First, as shown in Figure 1, an ultra-high tensile steel plate 1 is heated at a location 2 where a hole is to be drilled by arc welding as a heating means. The ultra-high tensile steel plate 1 is used, for example, for automobile bodies, and has a tensile strength of, for example, 780 MPa to 2000 MPa and a Rockwell hardness (HRC) of 21 to 53.

[0013] In the above-mentioned arc welding, an electrode (welding rod or wire) 3 is placed on the intended drilling location 2, and a positive voltage is applied to the electrode 3 and a negative voltage is applied to the base material, ultra-high tensile steel sheet 1, thereby generating an arc from the ultra-high tensile steel sheet 1 to the electrode 3, and heating is performed by spot welding on the intended drilling location 2 using arc welding.

[0014] In this case, for example, ultra-high tensile steel plate 1 has a tensile strength of 1980 MPa and a Rockwell hardness of 53.6. In the arc welding, for example, the output current is about 70 A, the output voltage is about 9.8 V, and the arc temperature is about 5000°C or higher. As a result, the tensile strength of the planned hole drilling location 2 of ultra-high tensile steel plate 1 is reduced to, for example, about 600 MPa and the Rockwell hardness to about 6.

[0015] 2, the tip of a drill 4 as a cutting part is applied to the planned hole drilling location 2 whose tensile strength and hardness have been reduced by the heating, and a hole 5 is drilled. The drill 4 used here is a relatively inexpensive general drill that is not suitable for use with ultra-high tensile steel plate 1 having high hardness.

[0016] Now, an example in which the drilling method of this embodiment is effective will be described. For example, as shown in Fig. 3(a) and (b), in a B-pillar 6 of an automobile, a portion where a rail reinforcement 7 and a B-pillar reinforcement 8 are overlapped is joined by spot welding.

[0017] The rail reinforcement 7 and the B-pillar reinforcement 8 are made of ultra-high tensile steel plate 1. The rail reinforcement 7 is joined to an inner panel 9.

[0018] In such a configuration, when attaching the B-pillar reinforcement 8 to a component in which the rail reinforcement 7 and the inner panel 9 form an assembly, it is not possible to apply one end and the other end of a spot welding gun to the front and back sides of the overlapping portion (planned joining point 10) of the rail reinforcement 7 and the B-pillar reinforcement 8.

[0019] Therefore, if holes are drilled in the area corresponding to the intended joining location 10 of the B-pillar reinforcement 8 by the drilling method of this embodiment while the B-pillar reinforcement 8 is left as is, the B-pillar reinforcement 8 can be overlapped with the rail reinforcement 7 and joined by arc welding in the overlapping portion so as to fill the holes at the positions of the holes in the B-pillar reinforcement 8. This type of joining form is generally called plug welding.

[0020] In this way, by drilling holes in the B-pillar reinforcement 8 using the drilling method of this embodiment, it becomes possible to drill holes in the ultra-high tensile steel plate 1 relatively easily by using a relatively inexpensive general drill 4 that is not compatible with the high hardness ultra-high tensile steel plate 1, without using a special drill that is compatible with the high hardness ultra-high tensile steel plate 1.

[0021] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the claims and a range equivalent to the claims.

[0022] In the above embodiment, the heating means is spot-welded by arc welding, but the present invention is not limited to this.

[0023] For example, although not shown, the heating means may be in the form of spot welding the planned hole drilling location 2 to create a molten metal portion (nugget) to reduce the tensile strength and Rockwell hardness, or in the form of stud welding the planned hole drilling location 2 to create a molten metal portion (nugget) to reduce the tensile strength and Rockwell hardness. In the case of such an embodiment, the same actions and effects as those of the above embodiment can be obtained. [Industrial Applicability]

[0024] The present invention can be suitably used in a method for drilling holes in ultra-high tensile steel plates. [Explanation of symbols]

[0025] 1 Ultra-high tensile steel plate 2. Planned drilling location 3 electrodes 4. Drill 5 holes 6 B-pillar 7 Rail Reinforcement 8 B-pillar reinforcement 9 Inner Panel 10 Joint location

Claims

[Claim 1] A method for drilling holes in ultra-high tensile steel plate, comprising the steps of heating a portion of the ultra-high tensile steel plate where a hole is to be drilled by a heating means, and then cutting the portion by a cutting part.

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