JPH08155657A - Welded steel manufacturing method and manufacturing apparatus - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a method and an apparatus for producing high-quality welded steel at low cost. [Structure] (1) In a method for manufacturing a welded shaped steel, in which a steel strip is butt-shaped into an H or T shape, a high-frequency current is passed to heat a welded portion, and an upset is welded, a flange material is welded. A method of manufacturing welded steel in which the weld is preheated to 500 ° C or less when passing through the high-frequency heating contact tip. (2) In addition to a high-frequency heating device consisting of a welding power source and a contact tip, as a preheating device, the flange material to be welded is connected to a power source that generates a frequency of 100 to 20000 Hz upstream of the contact tip. For manufacturing welded section steel with an induction heating coil for preheating parts. [Effect] Non-uniform heating on the web material side and the flange material side is alleviated, welding can be performed without excessive heat input on the web material side, the bead cross-sectional area can be reduced, and the amount of welding defects is generated. Is also reduced. As a result, the bead cutting process is unnecessary, and the generation of bead scraps and defective welding is reduced, and the yield is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing shaped steel for welding using high frequency heating.

[0002]

2. Description of the Related Art A method for producing H-section steel is roughly classified into a rolling method and a welding method. The latter is easy to manufacture thin H-section steel,
It has advantages such as the ability to manufacture H-section steels having different flange widths and different flange thicknesses, and is widely used mainly for the manufacture of materials for housing construction.

FIG. 5 is a schematic diagram showing the structure of a conventional welding H-section steel manufacturing apparatus. In the figure, 1-1 is a steel strip of a first member to be a web (hereinafter referred to as a web material), 1-2 and 1-3 are steel strips of a second member and a third member to be a flange (hereinafter, respectively). Flange material). 2- in the figure
Reference numerals a and 2-b are a pair of contact tips, which are respectively connected to welding power sources 3-a and 3-b which generate a high frequency current of about 100 to 500 kHz. In the figure, 4-a and 4-b are a pair of upset rolls for pressure-welding a heated welded portion, point C is a contact tip passage point (heating start point for welding), point D is a welded surface. Contact point (heating end point for welding).

FIG. 6 is a diagram showing heating and cooling patterns of a welded portion of a web material and a flange material in a conventional welded H-section steel manufacturing method. Points C and D on the horizontal axis correspond to the positions shown in FIG. To do.

In the apparatus shown in FIG. 5, both side edges 1-1-a and 1-1-b of the web material 1-1 are butted against the central portions of the flange materials 1-2 and 1-3, respectively. It is guided by a predetermined guide roll (not shown).
The welding current supplied by the welding power source 3-a flows through the pair of contact tips 2-a, the edge portion 1-1-a of the web material 1-1 and the central portion of the flange material 1-2, and The weld is heated. In addition, the other edge portion 1-1-b of the web material 1-1 and the other flange material 1
-3 also has a pair of contact tips 2-
It is similarly heated by the electric current supplied from the welding power source 3-b via b. The heated welded portion is then pressure-welded by the upset rolls 4-a and 4-b to obtain a predetermined welded H-section steel 5.

Such a welding method is generally called a high frequency resistance welding method and is the same as the welding method adopted as a method for manufacturing an electric resistance welded pipe.

However, in the conventional welding method for welded H-section steel, the surface to be welded to be heated is an edge end on the web material side and near the central portion of its width on the flange material side, which is asymmetric. Because of the shape, there is a problem that the welded portions of the flange materials 1-2 and 1-3 are less likely to be heated than the welded portions of the web material 1-1, as shown in FIG.

That is, the high frequency current has a property of flowing on the surface of the object, that is, a so-called skin effect, and therefore, the edge portions 1-1-a and 1-1-b of the web material 1-1.
Current concentrates on the flanges 1-2 and 1-3
In this case, since the current is shunted to the edge portion unrelated to welding, it is difficult for the current to concentrate on the welded portion, and the welded portions of the flange materials 1-2 and 1-3 are more likely to be welded to the welded portion than the web material 1-1. Not enough heat is supplied.

Further, in the web material 1-1, the diffusion direction of the amount of heat supplied by the high frequency current is determined by the edge portion 1-1.
It is one direction from -a and 1-1-b to the central part of the web material 1-1. On the other hand, the flange material 1-
In Nos. 2 and 1-3, it is difficult to maintain the amount of heat because the supplied amount of heat diffuses from the central portion in the direction of the edge portions on both sides.

Therefore, since the surface to be welded of the flange material is welded under pressure by the upset roll without reaching a sufficient melting temperature, a large amount of oxide is caught in the joint interface after welding, and The oxide remains as a welding defect and remains. However, it is impossible to individually adjust the heat input of the web material and the flange material, and at present, in order to raise the temperature of the flange material, excessive heat input on the web material side is forced.

When the welding heat input is excessive as described above, due to the characteristics of the high frequency resistance welding method as shown in FIG. 6, after the temperature of the welded portion of the web material once reaches the melting temperature, the welding temperature is Does not rise any further, and heat input is spent increasing the amount of molten steel, leading to the occurrence of excessive beads that cause problems such as corrosion and cracks due to stress concentration, and in some cases bead cutting is necessary. Become. Furthermore, even if welding defects due to unmelting of the flange material welded portion can be prevented,
On the contrary, due to the excessive melting of the web material, the oxide formation becomes remarkable and similarly remains as a welding defect, resulting in an unfavorable result in terms of quality. On the other hand, if the amount of upset is increased in order to prevent the presence of the oxide defects, the web material is likely to buckle or deviate from the position to be originally welded.

Means for solving such problems are disclosed, for example, in Japanese Patent Laid-Open No. 62-40978 and Japanese Patent Publication No. 45-4.
The method is disclosed in Japanese Patent No. 0774. In the former, the contact tip position of the flange material is moved away from the welding point, and a conductor is arranged between them to increase the current concentration on the welded portion of the flange material to promote heating. The latter is one of the web material wall thicknesses centered on two positions on the flange material facing the corner of the web material edge before supplying the welding current.
This is a method of preheating the width of ⅓ to ½ to 250 to 1050 ° C. by using another heat source such as high frequency induction heating or a gas heating device.

[0013]

The above-mentioned conventional method has the following problems, and cannot be a manufacturing method that can be put to practical use.

In the method disclosed in Japanese Unexamined Patent Publication No. 62-40978, even if the current is concentrated on the welded portion even on the flange material side, the contact tip is placed away from the welded portion. Becomes more significant, and the temperature of the welded portion of the flange material cannot be sufficiently raised, and a significant improvement effect cannot be obtained.

In the method disclosed in Japanese Patent Publication No. 45-40774, the center of the position on the flange material facing the two corners of the edge of the web material is 1/3 to 1/3 of the thickness of the web material.
It is necessary to heat each half width. However, it is necessary to use a very narrow high-frequency induction coil in order to separately heat such minute regions close to each other by the high-frequency induction coil shown in the present invention. It is practically impossible because the flow rate of the cooling water to be passed is insufficient and melted in a short time, and it is difficult to dispose the core for concentrating the magnetic flux on the heating target. Further, even if it is possible, at least two heating induction coils are required, which complicates the apparatus and increases the equipment cost, which is not necessarily a good measure. Furthermore, the preheating device and the contact tip have to be placed at a certain distance, but in reality heat diffusion occurs between them, and two pieces on the flange material facing the two corners of the web material edge are formed. It is difficult to obtain a temperature distribution with the maximum temperature at the center of the position. Even with a gas heating device, it is more difficult to heat only a minute region, and the heating efficiency is poor.

Furthermore, the frequency of the preheating power source is not specifically shown in the above invention, and since it is a heat source such as a high frequency induction coil, the power source used is 450 for welding.
It is estimated to be about kHz, but when using such a power source, it becomes necessary to preheat to a considerably high temperature range. This is because the preheating coil has to be arranged at a certain distance from the contact tip as described above, and the temperature drop due to thermal diffusion is large at high frequencies where the preheating region is limited to the vicinity of the surface. However, in the above-mentioned method of the invention, in order to obtain the effect of preheating, it is necessary to heat the flange material temperature to 250 to 1050 ° C. at the time of passing through the contact tip, and therefore, deterioration of appearance due to surface discoloration or microstructure abnormality, Depending on the situation, adverse effects may occur due to preheating such as once reaching the melting temperature.

As described above, according to the conventional method in which the realistic equipment arrangement and the change of the preheating width and the preheating temperature due to the heat diffusion are ignored, it is possible to produce the welded H-section steel of high quality at low cost. I have to say that it is difficult.

The present invention has been made in view of the above facts, and an object of the present invention is to provide a method and an apparatus for producing high-quality welded steel at low cost. .

[0019]

The summary of the present invention is as follows.
The method is for manufacturing welded steel in (1) and manufacturing equipment in (2).

(1) While continuously supplying the strip steel of the first member and the strip steel of the second and / or third member, both side edges of the strip steel of the first member and the second and / or third strips are continuously supplied. The strip steel of the member is abutted in an H-shape or a T-shape, and high-frequency current is passed through to form both welded edges of the strip steel of the first member and the strip steel of the second and / or third member. In a method for manufacturing a welded shaped steel in which a central portion to be a welded portion is heated, and welding is performed by adding an upset, a welded portion on the second and / or third member facing the wall thickness of the strip steel of the first member is The weld
A method for manufacturing welded steel, characterized by preheating to a temperature up to 500 ° C when passing through a high-frequency heating contact tip.

(2) While continuously supplying the strip steel of the first member and the strip steel of the second and / or third member, both side edges of the strip steel of the first member and the second and / or third strips are continuously supplied. The strip steel of the member is abutted in an H-shape or a T-shape, and high-frequency current is passed through to form both welded edges of the strip steel of the first member and the strip steel of the second and / or third member. A welded shaped steel manufacturing apparatus for heating a central portion to be welded and welding by adding an upset, and in addition to the heating apparatus by the high frequency current consisting of a welding power source and a contact tip, this contact 100 to 20 upstream of the chip
An apparatus for producing welded steel, comprising an induction heating coil for preheating a welded portion of a steel strip of the second and / or third member, which is connected to a power source generating a frequency of 000 Hz.

[0022]

The structure of the method of the present invention and the apparatus of the present invention for realizing the method will be described with reference to FIGS.

FIG. 1 is a schematic diagram showing the construction of a welded H-section steel manufacturing apparatus of the present invention, which corresponds to FIG. 5 described above. FIG. 2 is a view showing heating and cooling patterns of the welded portions of the web material and the flange material in the welded H-section steel manufacturing method of the present invention, and corresponds to FIG. 6 described above. Figure 2
Symbols A to D on the horizontal axis correspond to points A to D shown in FIG.

In the method of the present invention, when the high frequency heating for welding is started, that is, when the high frequency heating contact tip is passed through, the temperature of the welded portion corresponding to the web material thickness of the flange material is 500 ° C. or less. Preheat to become.

In order to realize this, in the apparatus of the present invention, as shown in FIG. 1, in addition to the heating apparatus by the high frequency current composed of the welding power sources 3a and 3b and the contact tips 2a and 2b, the Contact tip 2
An induction heating coil 6 a for preheating the welded parts of the flange members 1-2 and 13 which is connected to preheating power sources 7 a and 7 b for generating a frequency of 100 to 20000 Hz upstream of a and 2 b. And 6b. In FIG. 1, point A is the induction heating coils 6a and 6
Preheating start point by b, point B is its end point, C and D
The points are the contact tip passage point (heating start point for welding) and the contact point of the surface to be welded (heating end point for welding) shown in FIG. Note that, in FIG. 1, other device configurations and reference numerals are the same as those in FIG.

When the flange members 12 and 13 are preheated by the above preheating device, as shown in FIG. 2, first, the welded portions of the flange members 12 and 13 facing the wall thickness of the web member 11 are welded. The temperature starts to rise from the point A, reaches the maximum value at the point B, and gradually decreases to the point C. From point C, the flange members 12 and 13 and the web member 1 1 are heated by the same heating device (power sources 3 a and 3 b, contact tips 2 a and 2 b) as in the conventional case,
It is possible to eliminate or alleviate the occurrence of temperature non-uniformity in the welded portion of these materials.

By preheating the above-mentioned flange material, even if the welding heat input is the same as in the conventional case, the temperature at the time of welding the flange material can be made higher than in the conventional method. As shown in Fig. 5, the edge of the web material can be heated up to above its melting temperature to generate sufficient amount of molten metal, and the temperature of the welded part of the flange material can be increased sufficiently, and the bead amount and welding Defects are reduced.

The present inventors repeatedly investigated the preheating conditions,
According to the result of obtaining a suitable preheating temperature, the temperature of the flange material welded portion corresponding to the point C, that is, the thickness of the web material at the time of passing through the contact tips 2-a and 2-b is 500 ° C. or less. It is appropriate to set the temperature distribution so that

As will be described later, the upper limit of this preheating temperature is
When the preheating temperature of the flange material is too high, it is necessary to extremely reduce the welding heat input, and the heat input on the web material side inevitably decreases, and the welded part does not melt sufficiently, It has been determined that oxides remain in the weld and rather deteriorate the quality.

The preferred preheat temperature range is 100-250.
° C. Preheating below 100 ° C. has a small bead cross-sectional area reducing effect, as will be described later, while preheating above 250 ° C. requires a large output, but the welding defect suppressing effect becomes small.

The preheating power sources 7a and 7b connected to the preheating induction heating coils 6a and 6b in the apparatus of the present invention are power sources different from the welding power sources 3a and 3b, and are 100 to 20,000 Hz. It generates an electric current. The reason why it is necessary to set such a frequency range is as follows.

That is, at frequencies below 100 Hz,
In order to induce an electromotive force in the heated portion, it is necessary to pass a large current through the induction heating coil depending on the low frequency. Therefore, it is difficult to cool the coil, and as a result, the efficiency of energy conversion from the coil to the induction heating target is poor and the power loss becomes large. Therefore, in consideration of the fact that a large amount of power output is required, the facility cost is high, and the output of several hundred kW is required to preheat the flange material, cooling of such a coil is considered. Is almost impossible with today's technology.

On the other hand, if the frequency exceeds 20,000 Hz, only the surface is heated, as described above, so that the temperature immediately after preheating needs to be considerably high, and the microstructure of the flange material changes. Occurs. Further, as a power source for generating such a high frequency current,
Generally, a power supply using a vacuum tube is used, but in addition to the high equipment cost, such a power supply has a large energy loss and a high frequency as compared with the case of using a semiconductor, as is well known. Accordingly, even after subtracting that the energy conversion efficiency from the coil to the induction heating target is good,
After all, power loss is large.

In the present invention, not only the standard H-section steel for welding the web material to the central portion of the flange material, but also the eccentric welding H-type for welding the web material to a position slightly on the edge side from the central portion of the flange material. Even when steel is manufactured on the same line, the same effect can be obtained by arranging the preheating device at the position where the web material is welded on the flange material. In this case, a moving device may be provided if necessary. Furthermore, similar effects can be obtained not only in the H-section steel manufactured using two flange materials and one web material, but also in the case where T-section steel is manufactured using each one flange material and web material. Obtainable.

The method of the present invention is described in JP-B-45-407.
It is not essential to individually heat the points on the flange material facing the corners of the edge of the web material, as shown in Japanese Patent Publication No. 74-74.

[0036]

EXAMPLE Using the apparatus shown in FIG. 1, welding H was performed under the following conditions.
The manufacturing test of shaped steel was conducted, and the relationship between the preheating temperature, the amount of welding defects and the bead cross-sectional area was investigated.

The material used has a width of 2 for the web material.
00mm, plate thickness 3.2mm, width 100 for flange material
mm, plate thickness 4.5 mm, these are C: 0.1
It is a carbon steel containing 6% and Mn: 0.80%. The welding conditions were a speed of 40 m / min and an upset amount of 2 mm on each side. The welding heat input in the method of the present invention was appropriately decreased in accordance with the increase in the preheating temperature so that the welding temperature of the flange material was the same as that in the conventional method without using the preheating.

The preheating device used an induction heating power source with a frequency of 1000 Hz and a coil, and was placed at a position 3 m upstream of the welding contact tip.

FIG. 3 shows the relationship between the temperature (preheating temperature) of the flange material when passing through the contact tip, the amount of welding defects and the bead cross-sectional area when the apparatus and method of the present invention are used. It is a figure which shows the result of performing the relative comparison by setting the conventional method which does not use preheating as 1.

As shown in FIG. 4, the welding defect generation amount was obtained by measuring the total length of oxide defects on the weld line, which was recognized by observing the cross-section of the fracture of the weld, and the bead cross-sectional area was the same. Obtained from observation.

As shown in FIG. 3, since the heat input for raising the flange material preheating temperature to a predetermined temperature is small, the heat input on the web material side, which has been in the overheated state in the past, can be reduced. The amount of beads generated is reduced. The heat input on the web side approaches the appropriate heat input, and the amount of welding defects generated is reduced. The amount of welding defects is minimum when the preheating temperature is around 250 ° C, and if the preheating temperature is further increased, the welding temperature on the web material side is too low and the amount of welding defects begins to increase again. The amount of welding defects generated is almost the same as the method, and beyond that, it begins to deteriorate.

When the preheating temperature exceeds 500 ° C., the surface of the preheating portion is oxidized to cause discoloration of the surface, which causes a problem that the appearance is deteriorated. Further, when the temperature exceeds 500 ° C., the temperature difference between the preheated portion in the central portion of the flange material and other portions becomes too large, and a large thermal stress is generated to cause deformation, which may impair the dimensional accuracy of the product. .

From FIG. 3, when the preheating temperature is less than 100 ° C., the effect of reducing the bead cross-sectional area is small.
It can be seen that when preheating above 0 ° C., a large output is required, but the effect of suppressing welding defects becomes smaller.

[0044]

According to the method and apparatus of the present invention, heating unevenness on the web material side and the flange material side, which was difficult by the conventional method, is alleviated, and welding is performed without excessive heat input on the web material side. It becomes possible. Therefore, the bead cross-sectional area can be reduced and the amount of welding defects generated can be reduced. As a result, the step of bead cutting is not required, bead scraps are reduced, the number of defective welding products is reduced, and the yield is improved.

Since the cooling rate after welding is moderated by preheating the flange material, it is expected that the hardness of the welded portion will be reduced and the crack susceptibility can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic view showing a configuration of an apparatus for producing a welded H-section steel of the present invention.

FIG. 2 is a diagram showing heating and cooling patterns of the welded portions of the web material and the flange material in the method for producing a welded H-section steel according to the present invention.

FIG. 3 is a diagram showing a relationship between a preheating temperature in a welded portion of a flange member, a generation amount of welding defects, and a bead cross-sectional area.

FIG. 4 is a diagram illustrating a method for measuring a welding defect generation amount and a bead cross-sectional area.

FIG. 5 is a schematic diagram showing a configuration of a conventional welding H-section steel manufacturing apparatus.

FIG. 6 is a diagram showing heating and cooling patterns of the welded portions of the web material and the flange material in the conventional method for manufacturing a welded H-section steel.

[Explanation of symbols]

1-1: web material, 1-1-a, 1-1-b: edge portion of web material, 1-2, 1-3: flange material, 2-a,
2-b: contact tip, 3-a, 3-b: welding power source, 4-a, 4-b: upset roll, 5: welded H-section steel, 6-a, 6-b: induction heating coil for preheating. , 7 a, 7 b: induction heating coil power supply for preheating,
A: preheating start point, B: preheating end point, C: contact tip passage point (heating start point for welding), D: contact point of the surface to be welded (heating end point for welding)

Claims (2)

[Claims] 1. A steel strip as a first member and second and / or third steel strips.
While continuously supplying the strip steel of the member, both side edges of the strip steel of the first member and the strip steel of the second and / or third member are H
Both edge ends of the first member, which are welded portions of the steel strip, and the second and / or third members, which are welded portions of the steel strip. In a method for manufacturing a welded shaped steel in which a steel is heated and welded by adding an upset, a portion to be welded on the second and / or the third member facing the wall thickness of the strip steel of the first member is subjected to high-frequency heating contact. A method for producing welded steel, which comprises preheating to a temperature of 500 ° C. as an upper limit at the time of passing through a tip. 2. A steel strip as a first member and second and / or third steel strips.
While continuously supplying the strip steel of the member, both side edges of the strip steel of the first member and the strip steel of the second and / or third member are H
Both edge ends of the first member, which are welded portions of the steel strip, and the second and / or third members, which are welded portions of the steel strip. Is a manufacturing apparatus for welding shaped steel that heats and heats up and welds it, and in addition to the heating apparatus by the high frequency current consisting of a welding power source and a contact tip, 100 to 100 2000
An apparatus for producing welded steel, comprising an induction heating coil for preheating a welded portion of a strip steel of a second and / or a third member, which is connected to a power source that generates a frequency of 0 Hz.