JP2003293450A - Joint structure of steel pipe column and diaphragm - Google Patents

Abstract

(57) [Problem] To provide a highly-reliable joint structure between a steel pipe column and a diaphragm capable of reducing manufacturing costs including material costs and improving the toughness of the entire member. SOLUTION: This is a joining structure in which a diaphragm 10 is welded and joined to an end of a square steel pipe 1 having at least one end beveled, and a standard of a tensile strength of an original steel sheet is 59.
A square steel pipe 1 having a shock absorption energy of 70 J or more at 0 ° C. in all cross sections of less than 0 N / mm ² class, and a diaphragm 10
Decorative welding 30 was applied to the welded joint of the above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint structure of a steel pipe column and a diaphragm, including structural members in the fields of construction and civil engineering, and other fields.

[0002]

2. Description of the Related Art As a method for joining steel materials, bolt joining and weld joining are mainstream, and in particular, weld joining is often used when manufacturing products in factories due to the popularization of welding robots. . However, there is a problem that the overheated coarse grain region and the toughness of the fusion line are significantly deteriorated due to heat input by welding.

In order to solve such a problem, TiN which is stably present at high temperature is uniformly dispersed and added by adding Ti or the like to the steel material, and by this action, the fusion line of the welded joint (hereinafter, There is a known technique to prevent the growth of austenite grains in the vicinity of (BOND) and obtain a fine structure with high toughness. However, the addition of elements such as Ti has a large effect on the cost of steel materials. Was not used.

On the other hand, a cold-formed rectangular steel pipe (hereinafter referred to as a press column) is a material having the same sectional performance as a welded four-sided box column to be assembled by welding, but at a low cost. Further, since an excellent cross-sectional performance can be obtained for H-shaped steel columns, this press column has been frequently used for columns of middle- and low-rise buildings in recent years. The strength of the press column here (tensile strength)
Indicates a 400 N / mm ² class and a 490 N / mm ² class.

[0005]

As described above, the press column is a material that is widely used as a column material for middle and low-rise buildings. However, when the conventional welding technique is applied to the welded portion of the press column column and the diaphragm. Had the following problems. Weld heat-affected zone (hereinafter referred to as HAZ) that is generated substantially parallel to the groove in the welded portion.
As for the factor that is controlled by the details near the welded part, such as the propagation of cracks along the fusion line and the fusion line, it is expected that sufficient improvement will be achieved only by improving the material quality by adding elements such as Ti to the steel materials shown in the prior art There were times when you couldn't. In addition, the material improvement by adding such elements is
It was a factor that caused a significant increase in cost.

Next, when viewed from the viewpoints other than the cost, since the bending stress is large in addition to the tensile stress at the joint between the column and the diaphragm, cracks propagate in the welded portion where strength and toughness are small. The above-mentioned problem that is going to happen will be noticeable. In particular, when a press column is used as the column, the stress concentration is further large even in the cross section, and there is a problem in safety at the corners where the toughness is lower than that of the steel sheet before forming.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to reduce the manufacturing cost including the material cost and to improve the toughness of the entire member. It is intended to provide a joint structure.

[0008]

(1) In the joining structure of a steel pipe column and a diaphragm according to the present invention, a diaphragm is welded and joined to the end of a square steel pipe having a groove at least one end thereof. The joint structure, the tensile strength of the original steel plate is less than 590 N / mm ² grade, and the square steel pipe with shock absorption energy of 70 J or more at 0 ° C in the entire cross section is welded to the diaphragm. It is welded.

(2) The makeup welding of the joint structure of the steel pipe column and the diaphragm of the above (1) is continued from the surface side of the square steel pipe continuously to the butt weld portion provided in the groove provided in the square steel pipe. The distance from the toe of the first weld bead to the toe of the second weld bead lap-welded on the first weld bead was set to 15 mm or less, which was 5 mm or more in the axial direction.

(3) In the welded structure of the steel pipe column and diaphragm of (1) or (2) above, the temperature between passes of the makeup welding is 300 ° C. or less and the heat input is 40 KJ / cm or less.

(4) A circular steel pipe was used instead of the rectangular steel pipe in the joint structure of the steel pipe column and the diaphragm according to any one of the above (1) to (3).

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In order to solve the above-mentioned problems, the inventors of the present invention have conducted a test on a makeup welding that expects strength, which is a toughness improving technique in a welded portion of a steel material forming a column, After repeated research, the result is Japanese Patent Application No. 2001-3
A patent application was filed as No. 01383. According to the present invention, it becomes possible to improve the reliability of the welded portion by an inexpensive method. Then, as a result of continuing tests and research after that, the effect of improving the toughness of the welded portion by the makeup welding depends on the characteristics of the base material of the steel pipe column (a steel plate before forming the steel pipe column, hereinafter referred to as a raw steel plate). I understood it.

When the raw steel plate is a steel tube column having a tensile strength of 590 N / mm ² or more, it is often higher in quality than a steel tube column made of existing ordinary steel, and toughness (impact absorption energy at 0 ° C .: vE0) is also generally high. Therefore, it was found that the effect of improving the toughness was not great even when the makeup welding was performed, and sufficient toughness was obtained even in the normal welding.

On the other hand, the tensile strength of the original steel sheet is 590 N / mm.
^In the case of steel pipe columns of grade ^{2 or} less, it is general that the specifications are not as high in quality as those of 590 N / mm ² grade steel plate. The performance required for the joint was insufficient. On the other hand, in the case of a steel pipe column whose original steel sheet has a certain toughness even if there is a steel pipe column of less than 590 N / mm ² grade, the effect of improvement by the makeup welding is largely shown. In this case, the cost of the steel tube column is lower than that of the 590 N / mm ² class steel tube column, and even if the cost increase due to the increase in the makeup welding process is taken into consideration, the total cost is low, which is economical. is there.

Based on the above-mentioned tests and studies, the inventors of the present invention made a weld joint on a welded part when welding a diaphragm to a steel pipe column made of a raw steel sheet having a tensile strength of less than 590 N / mm ² class and having a certain degree of toughness. When welding is applied,
We have found that there is a critical point that makes it most economical. Hereinafter, this will be described in detail.

FIG. 2 is an explanatory view showing an example of joining a steel pipe column and a through diaphragm for explaining the present invention. 1 is a press column formed by forming a raw steel sheet having a tensile strength of less than 590 N / mm ^2. , Pillars 1a, 1b cut into a certain length,
The rectangular steel pipe 10 made of ... Is a through diaphragm installed between the pillar members 1a, 1b, ... And joined to the pillar members 1a, 1b. Reference numeral 11 is a beam having an H-shaped cross section that is joined to the through diaphragm 10.

FIG. 1 is a cross-sectional explanatory view of a joint portion between the steel pipe column 1 of FIG. 2 (specifically, the column members 1a, 1b, so will be referred to as column member 1 in the following description) and the through diaphragm 10. Is. In the figure, 1 is a pillar material, 10 is a through diaphragm, and 2 is a groove provided in the pillar material 1. Reference numeral 20 is a weld metal melted into the groove 2 by butt welding with a welding wire suitable for the strength of the steel material, and 30 is a makeup weld that is welded to the pillar material 1 side of the weld metal 20 in multiple layers (multi-pass). a is the first welding bead 31 of the makeup welding 30 at the position furthest from the open tip K on the surface side of the pillar 1 having the groove 2 in the material axis direction.
Is the distance from the toe of the first weld bead 31 of the makeup welding 30 to the toe of the second weld bead 32 welded over the first weld bead 31. It is a distance.

As is well known, there are single-layer bead welding with one bead and multi-layer (multi-pass) welding with a plurality of beads. Since the plate thickness is larger, multi-layer welding is often used, and the makeup welding in the present invention also employs multi-layer welding. When performing this multi-layer welding, the bead will be raised from below, but after performing the welding of the previous pass,
The temperature of the steel sheet immediately before the welding of the next pass is called the interpass temperature.

If the next pass welding is carried out while the temperature between passes is high, the work efficiency is improved because there is no waiting time until the temperature between passes is lowered, but the strength of the weld metal after welding is lowered. The problem arises. On the other hand, by waiting until the interpass temperature becomes low, the performance of the weld metal can be secured, but the work capacity decreases.

The amount of heat entering the steel plate, which is determined by the current, voltage and welding speed, that is, the heat input is given by the following equation. Heat input = 60 × E × I / v (KJ / cm) where E: voltage (V) I: current (A) v: welding speed (cm / min) As is clear from the above equation, If the heat input is too high, the heat input becomes large, but if the heat input is too large, the performance of the weld metal deteriorates. Further, if the welding speed is increased, the cross-sectional area of the bead is reduced and the number of passes is increased.

Next, examples of the present invention will be described. [Example 1] As shown in FIG. 3, a test body was adopted in which the surface of the Charpy impact test piece was located 1 mm below the surface layer from the test body manufactured to confirm the effect of the makeup welding. The notch C (notch) of the Charpy impact test piece was a surface notch placed at the BOND position, and three Charpy test pieces 40 were collected.

First, in order to clarify the relationship between the toughness of the original steel plate to be welded and the decorative fill of the welded joint, regarding the effect of improving the toughness by the decorative fill welding, vE0 of the steel plate to be welded
A test piece having a parameter of (impact absorption energy at 0 ° C.) was manufactured. The vE0 of the steel plate used for the test body is
There are four types, 45J, 70J, 150J, and 300J, and for each steel plate, the distance a from the open tip to the toe of the welding bead is 2 mm, 5 mm, 10 mm, 15
A total of 16 test bodies were manufactured so as to have a size of mm.
The welding wire used at this time was 490 N / mm ² grade, and the welding conditions were a heat input of 40 KJ / cm or less and an interpass temperature of 250 ° C. or less. Table 1 shows the results of testing vE0 of the welded joint using the above test body.

[0023]

[Table 1]

FIG. 4 shows the test results of Table 1, with the vertical axis representing vE0,
Take the distance a from the open tip to the bead toe on the horizontal axis, and
The relationship between the two types of specimens is shown. In FIG. 4, the one with a ≧ 5 mm has “makeup”
This means that vE0 does not decrease even if the makeup distance a increases from vE0 ≧ 70J.

FIG. 5 shows the above vE0 = 70J, a = 5m.
When the value of m is 1.0, the horizontal axis shows the distance of makeup welding a
The vertical axis represents the ratio of vE0 at each point, and the vertical axis value less than 1.0 with respect to the makeup welding distance a indicates that there is no effect of the makeup welding. .
From FIG. 5, in the case of the steel plate with vE0 of 70J, the toughness of the welded joint portion is improved by the make-up welding and it does not decrease due to the increase of the distance a, but in the case of the steel plate with vE0 of 45J, It can be seen that the toughness of the welded joint decreases as the distance a increases. From the above results, it was confirmed that vE0 of the steel plate needs to be 70 J or more in order to obtain the effect of improving the toughness of the welded joint portion by the makeup welding.

[Embodiment 2] In Embodiment 1, it was revealed that vE0 of the steel sheet needs to be 70 J or more for the effect of the makeup welding under one welding condition. In Example 2, the vE0 of the steel sheet was 70J.
In this case, a test was conducted on the relationship between vE0 of the welded joint portion when the temperature between passes was changed and the distance a of the makeup welding. The test results are shown in Table 2.

[0027]

[Table 2]

FIG. 6 shows the results of the test shown in Table 2, in which the vertical axis represents vE0 of the welded joint portion and the horizontal axis represents the distance a of the make-up welding, and the temperatures between passes are 250 ° C. and 300. ℃
In the case of, vE0 does not decrease even if the distance a increases,
It was found that when the interpass temperature is 350 ° C., vE0 decreases as the distance a increases. In this test, the welding heat input was 40 KJ / cm.

Further, in FIG. 7, in order to make the test results of Example 2 more understandable, the case where the temperature between passes = 300.degree. C. and the distance a for makeup welding a = 5 mm is 1.0, and the distance a is plotted on the horizontal axis.
The vertical axis represents the vE0 ratio of the welded joint at each point. As is clear from the figure, when the interpass temperature is 300 ° C. or lower, the toughness of the welded joint is improved by increasing the distance a, while when the interpass temperature is 350 ° C., It can be seen that the toughness of the welded joint decreases as the distance a increases. From the above results, it was confirmed that in order to obtain the toughness improving effect by the make-up welding, it is necessary to perform welding at an interpass temperature of 300 ° C or lower.

[Embodiment 3] Next, the limiting value of the welding heat input, which can obtain the toughness improving effect by the makeup welding when the temperature between passes is kept constant, was examined. Therefore, the temperature between passes is fixed at 300 ° C, and the welding heat input is 30 KJ / cm, 3
Table 3 shows the results of a test conducted on the relationship between vE0 of the welded joint and the distance a of the makeup welding in the case of 5 KJ / cm, 40 KJ / cm, and 45 KJ / cm.

[0031]

[Table 3]

FIG. 8 shows the test results shown in Table 3, in which the vertical axis represents vE0 of the welded joint portion and the horizontal axis represents the distance a for makeup welding. When the heat input is 40 KJ / cm or less, It can be seen that vE0 is high and does not change greatly even if the distance a is increased, but when the heat input is 45 KJ / cm, vE0 is low and further decreases as the distance a increases.

In order to make the test results of Example 3 easier to understand, FIG. 9 shows that vE0 of the welded joint portion is 1.0 when the welding heat input is 40 KJ / cm and the distance of the makeup welding is a = 5 mm, and the horizontal axis is Is the distance a, and the vertical axis represents the ratio of vE0 of the welded joint at each point. As is clear from the figure, when the heat input is 40 KJ / cm or less, the toughness is improved with the increase of the distance a in the makeup welding, while the heat input exceeds 40 KJ / cm. However, in the case of (heat input 45 KJ / cm), it can be seen that vE0 of the welded joint portion decreases as the distance a increases. From the above results, it was confirmed that in order to obtain the effect of improving the toughness of the welded joint portion by the make-up welding, it is necessary to carry out welding with a welding heat input of 40 KJ / cm or less.

As a result of the test based on the above Examples 1 to 3,
The following points were confirmed. (1) The distance “a” for makeup welding is 5 mm or more, and the distance “b” from the toe of the first weld bead to the toe of the second weld bead overlapped and welded thereon is 15 mm or less. (2) The tensile strength of the original steel sheet is less than 590 N / mm ² grade,
The effect of improving the toughness can be obtained by performing the make-up welding on the steel pipe column with vE0 of 70 J or more, the diaphragm, and the welded joint. (3) To obtain the effect of improving toughness by makeup welding,
The temperature between passes must be 300 ° C or less. (4) In order to obtain the effect of improving the toughness by makeup welding,
The welding heat input is 40 KJ / cm or less.

In the above description, the case where a rectangular steel pipe is used as the steel pipe column has been described, but the present invention can be similarly implemented by using a circular steel pipe having a circular cross section for the steel pipe column.

[0036]

According to the present invention, the standard of tensile strength of the original steel sheet is 5
Since the welded joint portion between the steel pipe column of less than 90 N / mm ² class and 0 ° C impact absorption energy in all cross sections of 70 J or more and the diaphragm is subjected to makeup welding, manufacturing cost including material cost is reduced, and It is possible to improve the toughness of the entire member and obtain a highly reliable joint structure of a steel pipe column and a diaphragm.

[Brief description of drawings]

FIG. 1 is an explanatory view of a welded joint portion between a steel pipe column and a diaphragm according to the present invention.

FIG. 2 is an explanatory view showing a joined state of a rectangular steel pipe and a through diaphragm embodying the present invention.

FIG. 3 is an explanatory diagram of a sampling position of a Charvi impact test piece in the example of the present invention.

FIG. 4 is a distance “a” for veneer welding and vE of an original steel plate in Example 1.
It is a diagram which shows the relationship with 0.

5 is a diagram showing a relationship between a and vE0 when vE0 = 70J and a = 5 mm in FIG. 4 is set to 1.0.

FIG. 6 is a diagram showing a relationship between a distance a, a temperature between passes, and vE0 of an original steel plate in a makeup welding of Example 2.

FIG. 7: The temperature between passes in FIG. 6 is 300 ° C., and a = 5 mm is 1
FIG. 6 is a diagram showing a relationship between vE0 and a in the case of.

FIG. 8 is a distance a for makeup welding, welding heat input, and vE0 and a of the original steel sheet when the temperature between passes of Example 3 is 300 ° C.
It is a diagram which shows the relationship with.

9 is a diagram showing the relationship between vE0 and a when the welding heat input of 40 KJ / cm and a = 5 mm in FIG. 8 is 1. FIG.

[Explanation of symbols]

1 Square steel pipe (column material) 2 bevel 10 through diaphragm 20 Weld metal 30 Make-up welding

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tadaki Katayama             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Haruhito Okamoto             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Nobuyuki Nakamura             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Toshifumi Kojima             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Osamu Hirano             2 Sano Industrial Park, 3 Sakaemachi, Sano City, Tochigi Prefecture               Seikei Co., Ltd. F-term (reference) 2E125 AA04 AA14 AB01 AB16 AB17                       AC15 AC16 AG03 AG04 AG12                       AG50 AG57 BB02 BD01 BE07                       BE08 BF04 EA33                 4E081 YB04

Claims (4)

[Claims] 1. A joining structure in which a diaphragm is welded and joined to the end of a square steel pipe having a groove at least one end thereof, and a standard value of tensile strength of a raw steel sheet is 590 N / mm. A joint structure of a steel pipe column and a diaphragm, wherein a welded joint between a square steel pipe having a shock absorption energy of 0 ° C. or more at 0 ° C. in all cross-sections of less than grade ² is applied to a weld joint portion of the diaphragm. 2. The first welding beat, wherein the decorative welding is 5 mm or more in the axial direction of the material from the surface side of the rectangular steel pipe in succession to the butt welded portion provided in the groove provided in the rectangular steel pipe. The joint structure between a steel pipe column and a diaphragm according to claim 1, wherein a distance from a toe of the second weld bead overlaid on the first weld bead to a toe of the second weld bead is 15 mm or less. . 3. A temperature between passes of the decorative welding is 300
The joining structure of a steel pipe column and a diaphragm according to claim 1 or 2, wherein the welding is performed at a temperature of ℃ or less and a heat input of 40 KJ / cm or less. 4. The joint structure of a steel pipe column and a diaphragm according to claim 1, wherein a circular steel pipe is used instead of the rectangular steel pipe.