KR100757650B1 - Apparatus for multi mash seam welding and method of welding thereof - Google Patents

Abstract

An apparatus for multi-mesh seam welding and a method for multi-mesh seam welding using the same are provided to secure weldability and increase production efficiency in a continuous cold rolling process line by reducing a peculiar thickness difference of mesh seam welding between a weldment step height and a base welding metal through the arrangement of wheel electrodes constructed in two stages and a series of plenishing rolls. An apparatus for multi-mesh seam welding comprises: an entrance side clamp and an exit side clamp installed at left and right sides of a lower frame; and a shearer and a carriage formed between the entrance side clamp and the exit side clamp such that electrode wheels and plenishing rolls are installed in the carriage, wherein the electrode wheels include a pair of first electrode wheels(5) installed vertically and a pair of second electrode wheels(6) installed vertically, and the plenishing rolls include a pair of first plenishing rolls(7) and a pair of second plenishing rolls(8) vertically installed in rear of the second electrode wheels. The electrode wheels and the plenishing rolls are arranged in series in order of the first electrode wheels, the second electrode wheels, the first plenishing rolls, and the second plenishing rolls, the first electrode wheels and the second electrode wheels are respectively connected to a welding current distributor(13), and the welding current distributor receives an AC power source(11) through a welding transformer(12).

Description

Apparatus for multi mash seam welding and method of welding

1 is a perspective view showing a multi-stage mesh seam welding apparatus according to the present invention.

2 is a view showing the arrangement of the electrode wheel and the polishing roll in the multi-stage mesh seam welding apparatus according to the present invention.

3 is a view showing a process in which the mesh seam welding through the electrode wheel and the polishing roll in the multi-stage mesh seam welding apparatus according to the present invention.

Figure 4 is a graph showing the welding state is changed according to each electrode wheel and the polishing roll in the multi-stage mesh seam welding apparatus according to the present invention.

<Code Description of Main Parts of Drawing>

1. Underframe 2. Carriage

3. Entrance clamp 4. Exit clamp

5. No.1 electrode wheel 6. No.2 electrode wheel

7. No. 1 flashing roll 8. No. 2 flashing roll

11. AC power supply 12. Welding transformer

13. Welding current distributor 14. Shearer

The present invention relates to a multi-stage mesh seam welding apparatus in a cold continuous line and a welding method using the same. More specifically, high temperature baking and welding are simultaneously performed using high temperature generated during welding through a welding electrode and a polishing roll. In order to form a welded part having a smooth shape without welding step difference, the present invention relates to a multi-stage mesh seam welding device for reducing stress concentration, preventing breakage in a continuous process line and increasing productivity, and a welding method using the same. It is about.

In general, at the entrance of the cold continuous process line, the end of the leading strip and the leading end of the trailing strip are welded to continuously supply the strip to the line. Typical cold continuous processing lines such as continuous annealing line (CAL) and continuous galvanising line (CGL) are highly rolled to produce cold hard materials with very high work hardening and low elongation. Since it is used as a raw material, these high strength / low elongated iron strips are joined in a mesh seam welder installed at the line entrance side.

 Conventional mesh seam welding is a pair of electrode wheels installed on the upper and lower parts in the state where the iron plate and the iron plate are overlapped and energized while pressing the overlapping portion of the iron plate between the electrodes, and the wires having high electrical resistance at the contact portion of the iron plate and the iron plate ( Joule) A welding method in which a welding is performed by advancing an electrode in a state where heat is generated to generate a junction by melting a contact part. The welding machine is relatively simple, the welding speed is high, and the heat affected zone is narrow. As it is possible to obtain excellent weld quality, it is widely used for welding of homogeneous / dissimilar steel plates with relatively thin thickness such as welding of fuel tank and automotive welded blank (TWB) in addition to cold welding of iron continuous lines.

 However, this welding method has a fundamental disadvantage that the weld overlap part is thicker than the base material and causes stress concentration on the weld part by leaving a step on the upper and lower parts of the weld part.

In particular, high-strength and ultra high-strength steels, which have recently been increasing in volume as automotive interior and exterior panels and structural members, are cold-rolled materials (Full Hard) that have been rolled to a desired thickness and welded at the continuous line entrance with very low elongation. Carbon equivalents proportional to the hardness of welded parts due to the addition of reinforcing elements such as Mn and Si for the purpose of production of dual-phase steel and TRIP steel compared to conventional steel Is often higher than 0.4, so that hardening of the weld is remarkable, which lowers the crack resistance of the weld.

In addition, high density MnO-SiO ₂ -based oxides are generated at the interface of the solid state bond that is located next to the fusion zone (FZ, Fusion Zone) generated by melting of the weld. Plates due to stress concentration in weld zones in sections with high tension such as tension leveler and skin pass mill (SPM) and continuous annealing furnace in the continuous process line. It has a problem that causes frequent breaks.

Conventional methods for solving this problem can be divided as follows. The upper and lower surfaces of the strip to be welded are cleaned with wire brushing, pickling (removal of oxide film by hydrochloric acid or sulfuric acid) and wire brushing before welding, and clean welding area by removing oxide film and oxidation by surface grinding. A method of simultaneously satisfying the effect of reducing the thickness of the overlapped part by removing the film and welding and securing a clean welded part is used or suggested.

However, these conventional methods deteriorate working conditions such as additional installation problems of piping and flow control devices for supplying acid and hydrochloric acid and sulfuric acid and cleaning liquids, and scattering of chips and acids and cleaning liquids by wire brushing and grinding. Entails a problem.

Therefore, the present invention is to reduce the difference in the thickness of the welding step and the base material unique to the mesh seam welding through the arrangement of the wheel electrode consisting of two stages and a series of polishing rolls in order to solve the conventional problems as described above It is an object of the present invention to provide a welding apparatus and a welding method using the same to secure weldability in a continuous process line and to increase production efficiency.

The object is, the entrance clamp and the exit clamp is installed on the left and right sides of the lower frame, between the entrance clamp and the exit clamp is provided with a carriage provided with a shear, an electrode wheel and a polishing roll, the electrode wheel is number 1 The upper and lower pairs of electrode wheels, and the upper and lower pairs of the second electrode wheel, and the upper and lower pairs of No. 1 flanking rolls, and the top and bottom pairs of No. 2 flanking rolls are installed on the rear side of the No. 2 electrode wheel. Seam welding device;

No. 1 electrode wheel of the multi-stage mesh seam welding device as described above applies pressure and current to the overlapped portions of the steel sheet to induce resistance heat at the overlapped interface of the steel sheet, resulting in a level of 60 to 80% of the final target nugget diameter. Allowing a melt to be formed; Forming a nugget of a desired size on the welding portion while a welding current and pressing force are applied to the melting portion by the second electrode wheel; Pressing the welded portion to 60 to 80% of the total reduction amount through the first rolling roll to make the thickness of the welded portion close to the thickness of the base material; It is achieved by a multi-stage mesh seam welding method comprising the step of applying the remaining reduction amount to the weld portion through the second number of flashing rolls so that the thickness of the weld portion matches the thickness of the base material.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration of the present invention.

1 and 2 illustrate the configuration of a multi-stage mesh seam welding apparatus according to the present invention, and the configuration thereof will be described in detail. The entrance clamp 3 and the exit clamp 4 are installed on the left and right sides of the lower frame 1. In addition, a shear 2, a carriage 2, and an carriage wheel are provided between the entrance clamp 3 and the exit clamp 4.

The electrode wheel is composed of a pair of upper and lower pairs of the first electrode wheel (5), and a pair of upper and lower pairs of the second electrode wheel (6), and the upper and lower limits of the first planetary roll (7) on the rear side of the second electrode wheel (6). A pair, the upper and lower pairs of the second number of the polishing rolls 8 are installed.

As described above, the arrangement of the upper and lower electrode wheels and the polishing rolls may include the first electrode wheel 5, the second electrode wheel 6, the first polishing roll 7, and the second polishing roll ( 8) arranged in series.

Further, the first electrode wheel 5 and the second electrode wheel 6 are connected to the welding current distributor 13, respectively, and the welding current distributor 13 is connected to the AC power source 11 through the welding transformer 12. It is configured to receive.

The iron strip 9 of the coil 10 is first passed through the first electrode wheel 5 and finally through the second polishing plate 8 to complete the mesh seam welding.

The multi-stage mesh seam welding apparatus of the present invention as described above has a combination of the first and second pairs of electrode wheels, the top and bottom pair of the second electrode wheels, the top and bottom pairs of the first polishing rolls, and the top and bottom pairs of the second polishing rolls. By arranging them in series in order to use the high-temperature firing of the weld metal by welding and welding heat more efficiently to obtain a good welded part (nugget), and to obtain a healthy welded part with no difference in thickness from the base material. It has its features.

In the case of mash seam welding in cold continuous processing line, relatively thin and highly hardened cold rolled material with a thickness of less than 2t is mainly targeted for welding. Therefore, air, steel plate, electrode, flashing roll, clamp, etc. Through convection and heat conduction through, the welding part has a very fast cooling rate.

In particular, the high tensile strength steel for automobiles has a very high hardenability, so under such cooling rates, hard structures such as martensite and bainite are formed in the welded portion, which increases the hardness compared to the base metal, but decreases toughness and ductility. After passing through the welding, the cold welding roll is rapidly cooled while the welding part is significantly cooled, and excessive pressure is applied to reduce the thickness of the welding part while accelerating the cooling rate of the welding part. In addition to the cold working effect, it will leave heat affected zone cracking and excessive residual stress.

Referring to the operation of the multi-stage mesh seam welding apparatus according to the present invention for obtaining a weld of the same thickness as the base material while alleviating the rapid cooling and cold working effect as follows.

First, the concept of serial pluralization of the electrode wheel was introduced to increase the welding energization time to increase the welding part heating time. The first electrode wheel induces resistance heating at the overlapping interface of the steel sheet while simultaneously applying pressure and energization to the overlapping portions of the steel sheet.

At this time, the welding current, pressing force, and welding speed of the first electrode wheel shall be until the molten portion is formed at the level of 60 to 80% of the final target nugget diameter at the overlapping interface of the steel sheet. Subsequently, the welding current and the pressing force applied by the second electrode wheel are applied to form a nugget having a desired size in the welding portion.

As the welding is performed with a time difference through the electrode wheel 1 and the electrode 2 as described above, a pulse is generated in the amount of heat input as shown in FIG. 4, and the growth of the nugget is divided into two stages of growth, thereby rapidly melting. Welds and process defects due to scattering of molten metal such as pores of molten parts, intermediate blowing, and spatter due to the formation of parts can be eliminated and alleviated.

In addition, the longer the time the weld is maintained at a high temperature can make the structure of the molten portion more uniform, and the high temperature firing phenomenon that the workability is improved at high temperatures can be effectively used through the pressing force of the electrode wheel, thereby significantly reducing the thickness of the weld.

Therefore, it is possible to reduce the thickness to be reduced in the subsequent process of the flashing process, it is possible to reduce the burden of cold welding the welding portion as described above.

When the nugget formation is completed by the electrode No. 2, the pressing process of the welding part by two pairs of the finishing rolls combined in series is performed to process the welding part thickness to the same thickness as the base material.

Considering the hardening and cooling of the welded part by rolling, the strength of the welded part is transmitted more strongly to the 2nd finishing roll than the 1st finishing roll. Therefore, 60 ~ 80% of the total rolling reduction to be performed in the process Adjust the pressing force so that the first polishing roll is borne and the remaining 20-40% is charged by the second polishing roll.

According to the present invention as described above, it is possible to perform welding and high temperature processing at the same time through the arrangement of the wheel electrode and the polishing roll composed of two stages, and to reduce the stress concentration caused by the weld step difference in the cold continuous process line Plate breakage can be prevented and production efficiency can be increased by increasing equipment life by eliminating step marks on various rolls in a line.

In addition, it is possible to form a weld having the same thickness as the base material without the weld step difference, thereby eliminating the stress concentration of the weld due to the step, and at the same time, a healthy weld structure with few weld defects can be obtained.

Claims (3)

An entrance clamp 3 and an exit clamp 4 are installed on the left and right sides of the lower frame 1, and a shearing machine 14, an electrode wheel, and a polishing roll are disposed between the entrance clamp 3 and the exit clamp 4. The provided carriage (2) is provided, the electrode wheel is composed of a pair of upper and lower pairs of the first electrode wheel (5), the upper and lower pairs of the second electrode wheel (6), after the second electrode wheel (6) Multi-stage mesh seam welding apparatus, characterized in that the upper and lower pairs of the first numbering rolls (7), the upper and lower pairs of the second number of polishing rolls (8) are installed on the side. The method of claim 1, The electrode wheel and the polishing roll are arranged in series in the order of the first electrode wheel (5), the second electrode wheel (6), the first planetary roll (7), the second planetary roll (8), and the 1 The first electrode wheel 5 and the second electrode wheel 6 are connected to the welding current distributor 13, respectively, and the welding current distributor 13 is configured to receive an AC power source 11 through the welding transformer 12. Multi-stage mesh seam welding device characterized in that the. The first electrode wheel simultaneously applies pressure and current to the overlapped portions of the steel sheet to induce resistance heat at the overlapped interface of the steel sheet to form a molten portion to a level of 60 to 80% of the final target nugget diameter; Forming a nugget of a desired size on the welding portion while a welding current and pressing force are applied to the melting portion by the second electrode wheel; Pressing the welded portion to 60 to 80% of the total reduction amount through the first rolling roll to make the thickness of the welded portion close to the thickness of the base material; The second step of the mesh seam welding method comprising the step of applying the remaining amount of reduction in the welding portion through the second rolling roll to match the thickness of the base material to the weld.

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