JPS62220289A - Manufacturing method for weld h-shaped steel - Google Patents

Abstract

PURPOSE:To certainly weld even difficult material to weld and to stabilize the quality by forming projections with the specific size on a place to join the plates for the upper and lower flanges to a plate for web and performing the high frequency resistance welding. CONSTITUTION:The top face width W of the projection 9 of the flange 1 is formed so that its ratio (W/t) with respect to the thickness (t) of the web 3 is made <=3. An equal welding condition between the flange 1 and the web 3 is obtained by concentrating an electric current on a projecting part and uniformalizing an electric condition between the projecting part and the web 3 and eliminating the scales in accordance with this by the means. The height (h) of the projection 9 is made >=0.3 to obtain this effect. The manufacture of weld H-shaped steel of the difficult material to weld is made possible and moreover, a pertinent welding condition range is extended and the welding is stabilized and the large effect is brought about to improve the welding quality by providing such projection 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing high-quality welded H-section steel by high-frequency resistance welding upper and lower flanges and webs under as uniform conditions as possible.

[Conventional technology]

In general, the H-shaped welding amount is as shown in Fig. 2. The upper and lower flange plates +11 +2) and the web plate (3) are fed between pressure rolls F41 (41), where they are pressure-joined into an H-shaped cross section. , is manufactured by integrating the joints by welding.High-frequency resistance welding, which is also used for the manufacture of ERW pipes, is the standard specification due to its ease of power supply and high speed. In the figure, (5) is a high frequency power source for this high frequency resistance welding, and (6) and (6) are the same (representing a contact tip).

[Problem that the invention seeks to solve]

In this high frequency resistance welding, as is well known, current is concentrated at the corners. In manufacturing an electric resistance welded pipe, the corner portion is located on the surface to be joined, and both surfaces to be joined have the same dimensions and the same shape, so efficient heating is performed. However, in the case of welded H-shaped steel, as shown in Fig. 3, the corner portion of the web plate (3) is located on the welded surface (7), but the upper and lower flange plates +11 +2 ), part of the plane is the surface to be joined (8)
(shown by hatching), and the corners are not held together. As a result, the heating conditions differ between the web side and the flange side, and in terms of -S, the flange side has lower heat. Therefore, welding defects called cold welding are likely to occur in welded I type meshes, and prevention of such defects has become an extremely important issue.

One possible countermeasure to this problem is to increase the total heat input. However, in this case, if the heat input on the flange side is made appropriate, the heat input on the web side will be excessive, leading to deterioration of the bead shape, poor upsetting, and even other welding defects such as weld flash. Heat cannot be increased. As a result, the range of appropriate n-receptivity conditions is extremely narrow.

Furthermore, it is possible to automatically control welding heat input with high precision, as in the method described in Japanese Patent Application Laid-Open No. 59-104281. However, in the production of welded H-beam steel, welding defects occur even if there is a slight change in the surface condition of the flange plate (11(2)), and no matter how automatic control is, welding defects occur even if there is a slight change in the surface condition of the flange plate (11 (2)). Therefore, this heat input control cannot completely guarantee quality.

The present invention corrects the heat input imbalance between the web side and the flange side, which could not be solved with conventional technology, and thereby makes it possible to use welding conditions and stabilize welding quality. The purpose is to enable reliable welding even with difficult materials.

[Means for solving problems]

When the manufacturing method of welded H-section steel is viewed from the technical standpoint, as described above, it is impossible to prevent heat input imbalance between the web side and the flange side. As a result, although it does not make welding impossible, the range of appropriate welding conditions is significantly narrowed, and even within the appropriate range, welding becomes unstable. On the other hand, when this manufacturing method is viewed from the material standpoint, mild steel is used for -C. This mild steel has good weldability, and conventional manufacturing methods are greatly aided by this material. In fact, experiments conducted by the present inventors have confirmed that it is difficult to manufacture welded H-section steel using conventional methods when high-strength steel is used.

However, welded H-beams made of high-strength steel take advantage of the material's advantages to become lightweight, high-strength products, and are expected to be in wide demand in the future. In addition, high-quality welded H-section steel with different materials for the flange and web is being considered, but welding of dissimilar materials has poor weldability similar to high-strength steel, so it is difficult to manufacture using conventional methods. .

The first cause of deterioration of weldability in the conventional manufacturing method of welded H-section steel is the imbalance of heat input between the flange side and the web side, but the scale of the surface to be welded also has a considerable influence. Since hot-rolled materials are used for welded H-section steel, a large amount of scale adheres to the surface of the materials. In high-frequency resistance welding, even if the material has scale attached to it, the scale is discharged outside during welding upset, so there is no particular problem. Being able to weld with scale attached has many advantages in terms of manufacturing costs. is producing. In fact, in the production of ERW pipes, the scale is hardly an obstacle.However, in the production of welded H-section steel, although there is no problem with the scale of the welded surface on the web side, the scale on the welded surface on the flange side is not a problem. Almost no scale is discharged, and this is one of the causes of deterioration in weldability.

The reason why scale is not discharged from the welded surface on the flange side during welding upset is thought to be that the scale on the welded surface is not stably melted. If the surface to be welded on the flange side is made to protrude in advance, the current will concentrate on the protruding part during welding, and the scale will stably melt on the flange side as well as on the web side, and will be completely discharged to the outside by upset. can be done. Moreover, according to this means, the current is concentrated on the protrusion, and the electrical conditions are equalized between the web side and the flange side and the web side. This ensures uniform welding conditions. As a result, when welding mild steel materials, the range of appropriate welding conditions has been expanded, making i8 welding work easier, and improving welding quality and stabilizing the welding condition. It is now possible to reliably weld materials that were previously impossible to weld.

In view of the above, the present invention aims to equalize the welding conditions between the flange side and the web side in terms of current concentration and scale elimination due to dirt by making the welding surface on the flange side protrude in advance. As shown in Figure 1, the gist of this is that the thickness of the web plate (3) with the top surface width W is placed at the location where the upper and lower flange plates fi+(2) are to be joined to the web plate (3). The ratio to t is 3 or less and the height h is 0,
A method for producing a welded H-section steel, which comprises forming a protrusion (9) of 3 am or more, and joining the upper and lower flange plates (11+2) and the web plate (3) by high-frequency contact welding. It is in. The protrusions (9) can be easily formed by using grooved rolls during rolling. Therefore, if mass production can be expected as demand expands, the cost increase due to forming the protrusions will be small, and there will be no need for scale removal, so in the future it will be possible to achieve the same level of production as the conventional method. It is expected that manufacturing can be carried out at low cost.

In the manufacturing method of the present invention, the ratio (-8) of the top width W of the protrusion (9) to the thickness t of the web plate (3) is set to 3 or less. In contrast to 3), the meaning of providing the protrusion (9) becomes weaker, the current concentration effect during welding on the protrusion (9) and the accompanying scale removal effect are weakened, and the upper limit thereof is 3. This is due to the fact that it became clear as a result of various experiments.

Regarding the height h of the protrusion (9), based on various experimental results,
If h is extremely small, such as less than 0.31, the purpose of forming the protrusion (9) will be diminished and stable welding will not be possible, so it has become clear that h of 0.3 or more is required. Although there is no restriction on the large part due to the welding surface, since the welded part remains on the web, it does not look good, so consideration must be given to this point.

Due to processing constraints, the middle width of the bottom surface is usually the same as or greater than the width of the top surface W.

The cross-sectional shape of the protrusion (9) may be any shape as long as it satisfies the above-mentioned dimensional restrictions. Typical shapes are illustrated in FIG. 1, where (a) is a rectangular cross section, (b) is a trapezoidal cross section, (c) is a triangular cross section, and (d) is a semicircular cross section. (
The protrusions (9) shown in c) and (d) have no top surface and have a width W of O. Therefore, W/t is also all O, and this type of shape is entirely within the scope of the present invention.

In order to form the protrusions (9), as mentioned above, rolling is the most reasonable and most recommended method, but it is not limited thereto.

Plate for upper and lower flanges fil (2) and plate for web (3)
), the plate shape is determined based on the required product shape, and the material is also selected depending on the required mechanical properties, such as mild steel,
Appropriately selected from among high tensile steel, stainless steel, etc.

As for the welding method, high-frequency resistance welding is used, but since a general-purpose method can be applied, a detailed explanation will be omitted.

〔Example〕

Flange plate (
4.5mm thick x 100 width) and web board (3゜2 thick x
1401 width) was created. Regarding the flange plates, there are those that do not have protrusions (for conventional examples), those that have protrusions formed by rolling (for measurements of the present invention), and those that have protrusions that are outside the scope of the present invention (comparative examples). ) were prepared, and these were high-frequency resistance welded under the conditions shown in Table 2 to form welded H-beams. After welding, a 10 m long beer test was performed on the welded portion of the welded H-section steel, and weldability was evaluated based on the length of the cold weld crack portion in the fracture surface. The results are shown in Table 3 together with the shape and dimensions of the protrusions.

Table 1 (wt%) Table 2 *Product of nibrate voltage (KV) and plate current (A) Table 3 (*: confuse) *: Out of range In Table 3, the criterion for pass/fail is only complete bonding. However, all the examples of the present invention satisfy this standard and show good weldability. On the other hand, in the conventional example where no protrusions are formed, the cold weld area is as much as 20%,
In fact, it is judged that welding is impossible. Further, even if the protrusions are formed, cold welding occurs, although the size is outside the range of the present invention, and the product is not perfect.

〔Effect of the invention〕

As is clear from the above explanation, the manufacturing method of the present invention can produce welded H-beam steels made from materials that are difficult to weld, which could not be produced conventionally, and thereby various new welded H-beam steels have been put into practical use. This will have a great effect on expanding its uses. Furthermore, in the case of welded H-section steel made of materials that can be conventionally welded, the range of appropriate welding conditions is widened and welding is stabilized, which has a significant effect on improving welding quality.

[Brief explanation of drawings]

Figures 1 (a) to (d) are end views showing the shape of the protrusions according to the manufacturing method of the present invention, and Figure 2 is a side view schematically showing the manufacturing process of welded H-section steel by high frequency resistance welding. FIG. 3 is an end view showing the positional relationship between the flange plate and the web plate. In the figure, 1: Upper flange plate, 2: Lower flange plate, 3:
Web plate, 4: pressure roll, 5: high frequency power supply, 6: contact chip, 9: protrusion. Figure 1 (c) Figure 3

Claims (1)

[Claims] (1) Upper and lower flange plates (1) and (2) web plate (3)
) is to be joined with the web plate (3
) to the thickness t (w/t) is 3 or less and the height h is 0
．． Manufacture of welded H-section steel characterized by forming a protrusion (9) of 3 mm or more and joining upper and lower flange plates (1), (2) and web plate (3) by high-frequency resistance welding. Method.