KR20170001918A - Estimation testing welding method for welding joint of ultra high input welding - Google Patents

Estimation testing welding method for welding joint of ultra high input welding Download PDF

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KR20170001918A
KR20170001918A KR1020150091689A KR20150091689A KR20170001918A KR 20170001918 A KR20170001918 A KR 20170001918A KR 1020150091689 A KR1020150091689 A KR 1020150091689A KR 20150091689 A KR20150091689 A KR 20150091689A KR 20170001918 A KR20170001918 A KR 20170001918A
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test
steel
welding
steel strip
steel sheet
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KR101693589B1 (en
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김기혁
문인준
김병철
김기원
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동국제강주식회사
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
    • G01N23/225—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion
    • G01N23/2255—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion using incident ion beams, e.g. proton beams
    • G01N23/2258—Measuring secondary ion emission, e.g. secondary ion mass spectrometry [SIMS]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/095—Monitoring or automatic control of welding parameters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/07—Investigating materials by wave or particle radiation secondary emission
    • G01N2223/081—Investigating materials by wave or particle radiation secondary emission incident ion beam, e.g. proton
    • G01N2223/0816—Investigating materials by wave or particle radiation secondary emission incident ion beam, e.g. proton incident ion beam and measuring secondary ion beam [SIMS]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/60—Specific applications or type of materials
    • G01N2223/629—Specific applications or type of materials welds, bonds, sealing compounds

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Abstract

An evaluation test method of the present invention comprises: a step of preparing a thick steel sheet for a test having a thickness equal to or greater than 65 t and equal to or less than 90 t by overlapping and fixating two thick steel sheets less than 50 t manufactured by rolling a steel ingot in a compact electric furnace for testing, and a comparison target thick steel sheet having a thickness equal to or greater than 65 t and equal to or less than 90 t which has previously been used; a welding test target fixing step of fixing and arranging the thick steel sheet for testing and the comparison target thick steel sheet separately; a welding step of performing tandem electro gas welding between the thick steel sheet for testing and the comparison target thick steel sheet; and a welding joint evaluation step of evaluating a welding state of a welding joint formed between the thick steel sheet for testing and the comparison target thick steel sheet. The evaluation test method of the present invention is able to secure economic feasibility during the evaluation test of the welding joint of the ultra-high input welding and at the same time is able to accurately perform the evaluation test of the welding joint of the ultra-high input welding by performing the evaluation test of the welding joint of the ultra-high input welding of the thick steel sheet using the thick steel sheet for the evaluation test manufactured by the steel ingot in the compact electric furnace.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an evaluation test method for an ultra-

The present invention relates to a method for evaluating a welded joint of an ultra heat welded joint of a steel plate, more particularly, to a method of evaluating a welded joint of an ultra heat welded joint using a test plate made by rolling a steel ingot made of a small- To an evaluation method of a super heat welded joint.

Structures in various fields such as ships, buildings, and offshore structures are generally constructed by joining steel materials by welding. From the viewpoint of ensuring safety, the steel materials used in such structures are not limited to steel strength, Good toughness is required.

In recent years, along with the enlargement of the size of the welded structure, from the viewpoint of improvement of the construction efficiency of the structure and reduction of the construction cost, improvement of the welding construction efficiency is required and the increase of the heat input of the welding is aimed. Particularly, it is developed and applied to improve the productivity, which is excellent in characteristics of super heat-affected heat affected by heat input of about 570 ~ 640kJ / cm on 80t basis.

The application of the ultra-strong Tantem Electro Gas Welding to the general TMCP Plate may result in the formation of a coarse grain boundary structure and a weak ferrite side plate and Upper Bainite Tissue, There arises a problem that the toughness at the temperature is significantly lowered. In order to solve the problem of deterioration of the base plate material by Tantemoelectro-gas welding, related steel manufacturers have actively studied the microstructure control of the heat affected part by the welding heat welding.

In order to develop new types of new steels, vacuum melting, rolling, welding part simulation evaluation and test analysis of many conditions of pilot stage are carried out prior to utilization of on-site mass production facilities.

Electro arc welding in which the target heat input is determined according to the thickness of the post-welded steel sheet at the welding part evaluation stage for development of the new steel type requires the use of a post-steel plate having the same thickness as the actual post- It is possible to evaluate the welded joint.

However, the steel ingot manufactured by the miniature electric furnace for the simulated evaluation test at the welded part evaluation stage for the development of the new grade is rolled into the pilot facility, so that the steel sheet having a thickness of less than 50t and having a normal steel sheet thickness of 65t to 90t Welded joint evaluation test is impossible.

 That is, in the evaluation test of the welded joint of the superheated heat steel of the steel sheet satisfying the thickness between 65t and 90t, it is impossible to accurately test the steel ingot made of the small electric furnace for the simulation evaluation test. It is necessary to use electric furnace and rolling equipment but it is a problem that test cost of small quantity production for new type development greatly increases. Therefore, it is practically used to evaluate the evaluation of ultra heat welded joint of post steel sheet by using actual electric furnace and rolling facility Evaluation of Welded Joints for Tests There is a problem that it is practically impossible to manufacture steel sheets for test.

Therefore, it was impossible to evaluate the weldability of Tandem EGW, which is welded by ultra-high heat input of 600kJ / cm due to the small size, low thickness problem and flatness problem. Indirectly, Simulation has been used to simulate the amount of heat input. However, since the impact test result of the simulated heat affected part is different from that of the actual welded part and the change of the texture and toughness due to the diffusion phenomenon of the welding material is neglected, it is inaccurately evaluated so that the thickness between 65t and 90t is satisfied It is difficult to accurately evaluate the weldability of the welded joint of the welded steel plate. Therefore, it has been difficult to develop a welded joint having excellent weldability.

It is an object of the present invention to provide an evaluation test method for a superalloy heat-welded joint of a post-steel plate, which can accurately perform an evaluation test of a super-heat-welded joint of a post-steel plate by using a post- .

It is another object of the present invention to provide a standard for judging the suitability of a super heat welded joint and to provide a standard for evaluating the feasibility of a super high heat welded joint, The present invention provides an evaluation test method for a welded joint of an ultra heat welded steel sheet which enables effective development of functional steel.

In order to achieve the above object, the present invention provides a method for evaluating test results of a welded joint of an ultra heat welded joint of a steel strip according to the present invention, the steel strip having a thickness of 65 t or more and 90 t or less, Preparing a test steel sheet body having a thickness of 65 t or more and 90 t or less by stacking two sheets of test steel sheets of less than 50 t prepared by rolling with the equipment so as to overlap the test steel sheet body and the comparative steel sheet A welding step of welding a test object to be welded to the test steel strip and a welded joint between the test steel strip and the steel strip to be compared with each other, a welding step of performing tandem electromagnet welding between the steel strip for test and the steel strip to be compared, And a weld joint evaluation step of evaluating the weld joint.

The post-test steel sheet according to the present invention is formed to have a half thickness of the steel sheet to be compared, and two sheets of the post-test steel sheet may be formed so as to overlap with each other and have the same thickness as the steel sheet to be compared.

The step of preparing the post-test steel sheet according to the present invention comprises the steps of rolling a steel ingot manufactured in the test small electric furnace to a pilot facility, rolling the rolled pilot rolled steel through a press and milling process, And forming a post-test steel sheet body by fixing two sheets of the post-test steel sheet by welding and fixing them.

In the process of forming the post-test steel sheet body according to the present invention, a plurality of post-test steel plates of different kinds of steel may be disposed on a steel sheet after a test, and the sheet may be fixed in two layers.

In the process of forming the post-test steel sheet body according to the present invention, the two post-test steel sheets may be superimposed and clamped, and only a part of the periphery may be stitch-welded.

The step of preparing the steel strip for test according to the present invention may further include a step of machining one side of the steel strip to be compared to a slope and a step of machining one side of the steel strip after the test to be sloped .

The inclined surface of the steel strip to be compared and the inclined surface of the steel strip after the test may be 7 to 10 °, respectively.

In the fixing step of the welding test object according to the present invention, the inclined surfaces of the steel strip for test and the steel strip for comparison are opposed to each other in such a manner as to widen toward the front side, and the steel strips are separated from each other by a root gap of 6 to 10 mm And a ceramic backing member may be disposed between the steel strip for test and the backside of the steel strip for comparison between the steel strip for test and the steel strip for comparison between the work bases .

The welding step according to the present invention is performed by using a Tandem EGW apparatus, and the tandem electro-gas welding apparatus is in close contact with the front and rear surfaces of the steel strip for test and the steel strip for comparison, And a gas flow path for discharging the CO 2 gas to the steel strip after the test and the steel strip for comparison are formed in the inside of the steel strip, -Shoe); A root electrode disposed on the root side between the steel strip for test and the steel strip for comparison and having an electrode wire and moving up and down together with the copper alloy member; And a face electrode which is disposed on the front side between the copper plating member and moves up and down together with the copper plating member, and the welding step includes a step of fixing the root electrode when the copper plating member is welded while lifting the copper plating member The face electrode can be welded while moving the face electrode to the left and right.

The copper plating member according to the present invention can be plated with chromium on the surface and finely finished.

The copper-clad member according to the present invention may have a width of 36 mm to 50 mm to facilitate the discharge of molten pool and welding slag during welding.

The stainless steel mesh may be inserted into the gas channel according to the present invention to prevent the gas flow rate from being increased.

The evaluation of the welded joint according to the present invention may evaluate the weldability of the welded joint with the boron distribution of the welded joint at a distance apart from the boundary between the steel plate after test and the welded joint.

In the step of evaluating the weld joint according to the present invention, a reference point spaced from a boundary portion between the steel strip for test and the welded joint is set in the steel strip for test, A reference boron distribution confirming process for confirming the boron distribution of the steel sheet body; designating a plurality of comparison points spaced apart from a boundary portion between the steel strip after the test and the welded joint to the welded joint; A comparative boron distribution identification process for verifying the boron distribution in the database; And comparing the reference boron distribution with the comparative boron distribution to determine the suitability of the welded joint.

The reference boron distribution checking process according to the present invention is characterized in that a point within 0.1 mm to 0.7 mm of the boundary between the test steel strip and the welded joint is set as a reference point on the steel strip for test, A plurality of comparison points may be assigned to the welded joint within a range of 0.1 mm to 5 mm between the steel strip body and the welded joint after the test.

The comparative boron distribution checking process according to the present invention sets the first comparison point at 0.1 mm or more and 0.3 mm or less at the boundary portion, sets the second comparison point at 0.3 mm or more and 0.7 mm or less, Hereinafter, the third comparison point can be set.

The reference point according to the present invention is 0.5 mm at the boundary between the steel strip after the test and the welded joint and the first comparison point is 0.1 mm away from the boundary, And the third comparison point may be a point 3 mm apart from the boundary portion.

The reference boron distribution checking process and the comparison boron distribution checking process according to the present invention can be confirmed using SIMS (Secondary Ion Mass Spectrometry).

The analysis conditions of SIMS in the reference boron distribution checking process and the comparison boron distribution checking process according to the present invention are O2: 10 to 15 kV, sample voltage: -3 kV to -6 kV, primary ion beam current: 180 nA to 220 nA, : 11 B 16 O 2 , area range: 50 to 150 μm in dia.

If the amount of boron in the region of the first comparison point is 80 to 100% of the boron amount in the region of the reference point, the weld joint is judged to be good and the boron amount in the region of the reference point And the boron amount in the region of the third comparison point is greater than the boron amount in the region of the reference point when the amount of boron in the region of the second comparison point is 60 to 80% If it is more than 0 to 20%, it can be judged that the welded joint is good.

The present invention is based on the evaluation test of the ultra heat welded joint of the steel plate by using the steel sheet for evaluation test made of the small capacity electric furnace steel to ensure the economical efficiency in the evaluation test of the superheated welded joint and the evaluation of the ultra heat welded joint So that the test can be accurately performed.

The present invention has the effect of providing a quick and effective evaluation method for research and development of a steel plate after being made of a pilot rolling material by providing a criterion for judging the suitability of the super heat welded joint.

1 is a block diagram showing an evaluation test method of a super high heat welded joint of a steel sheet according to the present invention
FIG. 2 is a schematic view showing an evaluation test method of a super-heat welded joint of a steel sheet according to the present invention
3 is a schematic view showing the welding step in the evaluation test method of the super heat welded joint of the steel sheet according to the present invention
4 is a schematic view showing another example of the step of preparing the post-test steel sheet body in the evaluation test method of the post-steel plate super heat welded joint according to the present invention
5 is a block diagram illustrating a step of evaluating a welded joint in an evaluation test method for a superheated steel welded joint according to the present invention
FIG. 6 is an enlarged view of a weld joint formed through the welding step in the evaluation test method of the superheated heat welded joint according to the present invention
7 is an enlarged view showing the distribution of boron using SIMS at points A to H in FIG. 6

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to the detailed description of the present invention, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

FIG. 1 is a block diagram showing an evaluation test method for a welded joint of a superalloy steel strip according to the present invention, and FIG. 2 is a schematic view showing an evaluation test method of a welded superalloy welded joint of a steel strip according to the present invention.

1 and 2, an evaluation test method for a welded joint of a steel sheet with a large number of steel plates according to the present invention includes: a comparison steel plate 10 having a thickness of 65 t or more and 90 t or less in actual use; A step (S100) of preparing a post-test steel sheet 20 having a thickness of 65 t or more and 90 t or less by stacking two test strips 20a of less than 50 t prepared by rolling the steel ingot by a pilot facility, A welding test object fixing step S200 of disposing and fixing the post-steel plate 20 and the post-comparison steel plate 10 so as to be spaced apart from each other, (S300) for tandem electro-gas welding; And a weld joint evaluation step (S400) for evaluating the weldability of the weld joint formed between the steel strip for test (20) and the steel strip (10) to be compared.

The step (S100) of preparing the post-test steel plate 20 includes a process of rolling the steel ingot manufactured in the test small electric furnace to a pilot facility, a rolling mill of the rolled pilot, (20a) and fixing the test strips (20a) by welding and fixing the test strips (20).

The piloted rolling mill rolled with the pilot facility has unevenness in flatness on both sides, so that the both sides are flatly formed on both sides through press and milling.

The post-test steel sheet 20a is formed to be 40t (mm), and the test post-steel sheet body 20 has 80t since the post-test steel sheet 20a of 40t is formed by overlapping two sheets. (10) are formed in the same 80t.

That is, the test steel strip 20a is formed so as to have a half thickness of the steel strips 10 to be compared with each other, and the two steel strips 20a are formed so as to overlap with each other and to have the same thickness as the steel strip 10 will be.

The post-test steel plate 20 is manufactured in actual use, and the post-test steel plate 20a is manufactured for the development of a new steel product, that is, It is manufactured in other composition.

In the process of forming the post-test steel sheet body 20, two sheets of the post-test steel sheet 20a are superimposed and fixed with clamps, and only a part of the circumference is stitched together by constraint welding. , That is, the length of 20 to 40 mm is preferably stitch-welded.

The step (S100) of preparing the post-test steel plate 20 includes a step of machining one side of the steel plate to be compared to an oblique plane, and a process of machining one side of the steel plate for test 20 to an oblique plane .

The inclined surface of the steel sheet to be compared and the inclined surface of the steel sheet after test 20 are each 7 to 10 degrees.

The welding test object fixing step S200 is a step of setting the inclined surfaces of the test steel plate 20 and the steel plate 10 to be opposed to each other in a widening manner toward the front side, The test steel plate 20 and the comparative steel plate 10 are fixed to the front surface of the work base 40 so as to be spaced apart from each other by 10 mm. 20 and the ceramic backing material 50 which covers the steel plate 10 to be compared with each other.

The root gap means the shortest distance between the steel strip for test 20 and the steel strip 10 to be compared and the lower gap between the lower end of the steel strip for test 20 and the steel strip 10 As shown in Fig.

The welding test object fixing step S200 is a step of fixing the test steel sheet body 20 and the steel sheet 10 to be compared to the ceramic backing material 20 on the front surface of the work base 40 which is erected and fixed using clamping, (50) can be mounted and fixed with an interval at which it can be inserted into the rear side.

The welding step S300 is performed by using a tandem EGW apparatus and the tandem electro-gas welding apparatus 30 is used to weld the steel strip 20 for test and the steel strip 10 to be compared, The cooling water channel 31a, the test steel sheet body 20, and the test steel sheet body 20, which are in close contact with the front surface of the test steel strip body 20, A copper foil member 31 (Cu-Shoe) having a gas flow path 31b for discharging CO 2 gas to the steel sheet 10 to be compared; A root electrode disposed on the root side between the steel strip for test 20 and the steel strip for comparison 10 and having an electrode wire 30a and moving up and down together with the copper alloy strip 31; And an electrode wire 30a disposed on the front side between the steel strip 20 for test and the steel strip 10 to be compared and moving upward and downward together with the copper strip 31 And a face electrode (33).

The electrode wire 30a is a flux core wire having a diameter of 1.6 mm. The copper wire member 31 has a width of 36 mm to 50 mm so as to facilitate the discharge of the molten pool and the welding slag at the time of welding. .

Further, it is preferable that the copper plating member 31 is plated with chromium on the surface, and the finish is strengthened to enhance abrasion resistance, and cracks and the like of the weld metal due to dilution with respect to existing copper material are prevented.

Flow rate of the CO 2 gas discharged by the same immersion member 31 is an example in that the 40LPM, and the gas passage (31b) in the insert a stainless net body to prevent the flow velocity of the gas faster CO 2 gas It is preferable that the arc and the molten pool be purified and purified.

The Tandem EGW apparatus includes a cooling water circulation device (not shown) connected to the inlet and outlet sides of the cooling water flow path 31a, CO 2 (not shown) connected to the inlet side of the gas flow path 31b, And a supply unit (not shown).

The welding step S300 preferably welds the face electrode 33 while moving the face electrode 33 in a state in which the root electrode 32 is fixed when the copper plating member 31 is welded while being raised and lowered.

In the welding step (S300), electric power is supplied to the root electrode (32) and the face electrode (33) to generate an arc, and the electrode wire (30a) is melted and welded by the arc heat.

4 is a schematic view showing another example of a step (S100) of preparing a post-test steel plate 20 in an evaluation test method for a post-steel plate super heat welded joint according to the present invention, wherein the post-test steel plate 20 ) Can be formed by arranging a plurality of test steel plates 20a and 20a 'of different steel types on a steel plate 20a after a test, and fixing them in two layers.

That is, a part of the test steel plate 20a and the rest of the test steel plate 20a are covered with two steel plates of different steel types to keep two layers as a whole, and two test steel plates 20a and 20a 'are coexistent, so that it is possible to simultaneously perform the weld joint evaluation test on the two post-test steel plates 20a.

5 is a block diagram illustrating a step S400 of evaluating a welded joint in the evaluation test method of the superheated welded joint of a steel sheet according to the present invention. Referring to FIG. 5, in the step S400 of evaluating the welded joint, It is preferable to evaluate the suitability of the welded joint with the boron distribution of the welded joint at a distance apart from the boundary between the steel plate body 20 for test and the welded joint.

In the step of evaluating the welded joint (S400), a reference point spaced from a boundary portion between the steel strip body for test (20) and the welded joint is set in the steel strip body for test (20) A reference boron distribution confirmation step (S410) of confirming the boron distribution of the steel strip body after the test (20);

A plurality of comparison points spaced apart from a boundary between the steel plate body for test (20) and the welded joint are designated to the welded joint and a boron distribution is confirmed in a region around the comparison point, (S420); And

And comparing the reference boron distribution with the comparative boron distribution to determine the suitability of the welded joint (S430).

In the reference boron distribution checking step S410, a point within 0.1 mm to 0.7 mm of the boundary portion between the test steel strip body 20 and the welded joint is set as a reference point on the test steel strip body 20, The reference point is preferably 0.5 mm at the boundary between the steel strip body 20 and the welded joint.

In the comparative boron distribution checking step S420, a plurality of comparison points are designated to the welded joint within a range of 0.1 mm to 5 mm between the steel strip body 20 and the welded joint, , A first comparison point is set at 0.1 mm or more and 0.3 mm or less, a second comparison point is set at 0.3 mm or more and 0.7 mm or less, and a third comparison point is set at 2.5 mm or more and 3.5 mm or less .

It is preferable that the first comparison point is a point spaced 0.1 mm from the boundary portion, the second comparison point is a point spaced 0.5 mm from the boundary portion, and the third comparison point is 3 mm apart from the boundary portion Do.

It is preferable that the reference boron distribution checking step (S410) and the comparison boron distribution checking step (S420) are confirmed using SIMS (Secondary Ion Mass Spectrometry).

FIG. 6 is an enlarged view of a weld joint formed through the welding process of the ultra-pure titanium steel strip after the rear steel plate, and FIG. 7 is an enlarged photograph showing the distribution of boron at the points A to H in FIG. 6 using SIMS.

The analysis conditions of the SIMS in the reference boron distribution checking step (S410) and the comparison boron distribution checking step (S420) are O2: 10 to 15 kV, a sample voltage: -3 kV to -6 kV, a primary ion beam current: 180 nA to 220 nA, The detection ion: 11 B 16 O 2 , and the region range: 50 to 150 μm in dia.

6, a point A is a point spaced 0.5 mm from the boundary portion to the test steel plate 20 side, a point B is 0.1 mm apart from the boundary portion to the test steel plate 20 side, A point is the reference point.

The point C in Fig. 6 is a point spaced 0.1 mm from the boundary portion toward the welded joint, and a point D is 0.3 mm away from the boundary portion toward the welded portion, Is the first comparison point.

6 is a second comparison point at a point spaced 0.5 mm from the boundary portion to the weld joint side, and F point in Fig. 6 is a point at 1.5 mm from the boundary portion to the weld joint side, and Fig. 6 The G point is a point spaced 2.0 mm from the boundary portion to the weld joint side, and the H point in FIG. 6 is a point 3 mm apart from the boundary portion to the weld joint side, which is a third comparison point.

If the amount of boron in the region of the first comparison point is 80 to 100% of the boron amount in the region of the reference point (S430), the weld joint is judged to be good.

If the amount of boron in the region of the second comparison point is 60 to 80% of the boron amount in the region of the reference point (S430), the weld joint is judged to be good.

If the amount of boron in the region of the third comparison point is greater than 0% to 20% of the boron amount in the region of the reference point, the quality evaluation process (S430) determines that the welded joint is good.

The present invention is based on the evaluation test of the ultra heat welded joint of the steel plate by using the steel sheet for evaluation test 20a made of the small capacity electric furnace steel to ensure the economical efficiency in the evaluation test of the ultra heat welded joint, It is possible to accurately perform the evaluation test of the joint.

The present invention has the effect of providing a quick and effective evaluation method for research and development of a steel plate after being made of a pilot rolling material by providing a criterion for judging the suitability of the super heat welded joint.

As described above, an optimal embodiment has been disclosed in the drawings and specification. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit of the invention, The scope should be determined by the technical idea of the appended claims.

10: steel strip after comparison 20: steel strip after test
20a: steel plate after test 30: tandem electrogas welding device
30a: Electrode wire 31: Copper plating member
31a: cooling water flow path 31b: gas flow path
32: root electrode 33: face electrode
40: Working base 50: Ceramic backing material
S100: Step of preparing steel sheet after test
S200: Welding test object fixing step
S300: welding step
S400: Welded joint evaluation step

Claims (20)

By comparing two existing steel plates less than 50t, which are manufactured by rolling the steel strips manufactured from the comparative steel strips and test electric furnaces with a thickness of 65t or more and 90t or less in actual use, by piloting equipment, Preparing a post-test steel plate body having a predetermined thickness;
A welding test object fixing step of disposing and fixing the post-test steel plate and the post-comparison steel plate so as to be spaced apart from each other;
A tandem electro-gas welding step between the steel strip for test and the steel strip for comparison; And
And a weld joint portion evaluation step of evaluating a weld joint portion formed between the steel strip for test and the steel strip to be compared. The method according to claim 1,
Wherein the post-test steel sheet is formed to have a thickness equal to one-half of the thickness of the post-test steel sheet, and two sheets of the steel sheet are overlapped with each other to have the same thickness as the steel sheet to be compared. Evaluation test method. The method according to claim 1,
The step of preparing the post-test steel sheet comprises:
Rolling a steel ingot manufactured in a small test furnace to a pilot facility;
A process of forming a test steel sheet having both sides thereof flattened by pressing and milling the rolled pilot roll material; And
And a step of forming a post-test steel sheet body by stacking two sheets of the post-test steel sheet by welding so as to form a test post-test steel sheet body. The method of claim 3,
Wherein the test steel sheet body is formed by arranging a plurality of test steel plates of different types of steel on a steel plate after a test and fixing the test steel plates in two layers. The method according to claim 3 or 4,
The process for forming the post-test steel sheet comprises:
Wherein the two steel plates for test are superimposed on each other and fixed with clamps, and then, only a part of the circumference is subjected to stitch welding in a stitch manner. The method of claim 3,
Wherein the step of preparing the post-test steel sheet further comprises a step of machining one side of the post-test steel sheet to be sloped, and a step of machining one side of the post-test steel sheet to an inclined surface. Test method for evaluation of ultra heat welded joints. The method of claim 6,
Wherein the sloped surface of the steel strip to be compared and the sloped surface of the steel strip after the test are respectively 7 to 10 °. The method of claim 6,
The welding test object fixing step is performed such that the inclined surfaces of the steel strip for test and the steel strip for comparison are opposed to each other in such a manner as to widen toward the front side so as to be spaced from each other by a root gap of 6 to 10 mm, And a ceramic backing member is disposed between the steel strip for test and the backside of the steel strip for comparison between the steel strip for test and the steel strip for comparison between the work bases. Test method for evaluation of ultra heat welded joints. The method according to claim 1,
The welding step is to weld using a Tandem EGW apparatus,
Wherein the tandem electro-gas welding apparatus is provided with a cooling water flow path and a cooling water flow path which are closely attached to the front and rear surfaces of the steel strip for test and the steel strip to be compared and cover the portion between the steel strip for test and the steel strip for comparison, A copper foil member (Cu-Shoe) having a test steel sheet body and a gas flow path for discharging CO 2 gas to the steel sheet to be compared; A root electrode disposed on the root side between the steel strip for test and the steel strip for comparison and having an electrode wire and moving up and down together with the copper alloy member; And a face electrode which is disposed on the front side between the electrodes and has an electrode wire and moves up and down together with the copper plating member,
Wherein the welding step comprises welding the face electrode while moving the face electrode in a state in which the root electrode is fixed when the copper plating member is welded while being lifted and lowered. The method of claim 9,
Wherein the copper plating member is plated with chromium on the surface and finished. The method of claim 9,
Wherein the copper alloy member has a width of 36 mm to 50 mm so as to facilitate the discharge of the molten pool and the welding slag during welding. The method of claim 9,
Wherein a stainless steel net is inserted into the gas flow passage to prevent a gas flow rate from being increased. The method according to claim 1,
Wherein the weld joint evaluating step evaluates the weldability of the welded joint by a boron distribution of the welded joint at a distance apart from a boundary portion between the steel sheet after test and the welded joint, . The method according to claim 1,
In the weld joint evaluation step,
A reference point spaced apart from a boundary portion between the steel strip after test and the welded joint is set in the steel strip for testing and a reference boron distribution for confirming the boron distribution in the steel strip after the test within the region around the reference point Verification process;
Specifying a plurality of comparison points spaced apart from a boundary portion between the steel strip after the test and the welded joint to the welded joint and confirming the boron distribution within a region around the comparison point; And
And comparing the reference boron distribution with the comparative boron distribution to determine the suitability of the welded joint. 15. The method of claim 14,
Wherein the reference boron distribution checking step sets a point within 0.1 mm to 0.7 mm at a boundary portion between the test steel strip and the welded joint as a reference point on the steel strip after the test,
Wherein the comparison boron distribution checking step specifies a plurality of comparison points within a range of 0.1 mm to 5 mm between the steel strip body and the welded joint at the boundary between the steel strip and the welded joint. 16. The method of claim 15,
Wherein the comparative boron distribution checking step sets a first comparison point at a boundary portion of 0.1 mm or more and 0.3 mm or less, sets a second comparison point at 0.3 mm or more and 0.7 mm or less, And the comparison point is set. 18. The method of claim 16,
The reference point is 0.5 mm at the boundary between the steel strip after test and the welded joint,
The first comparison point is a point spaced 0.1 mm from the boundary part, the second comparison point is 0.5 mm apart from the boundary part, and the third comparison point is 3 mm apart from the boundary part Of the welded joints. 15. The method of claim 14,
Wherein the reference boron distribution checking step and the comparison boron distribution checking step are confirmed by SIMS (Secondary Ion Mass Spectrometry). 19. The method of claim 18,
SIMS analysis conditions were O2: 10 to 15 kV, sample voltage: -3 kV to -6 kV, primary ion beam current: 180 nA to 220 nA, detected ions: 11 B 16 O 2 , and the region range is 50 to 150 μm in dia. 18. The method of claim 16,
If the amount of boron in the region of the first comparison point is 80 to 100% relative to the boron amount in the region of the reference point, the quality evaluation process determines that the welded joint is good,
If the amount of boron in the region of the second comparison point is 60 to 80% of the boron amount in the region of the reference point, it is determined that the welded joint is good,
Wherein the weld joint is judged to be good if the amount of boron in the region of the third comparison point is greater than 0 to 20% of the boron amount in the region of the reference point.
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KR200320108Y1 (en) * 2003-04-18 2003-07-22 주식회사 한진중공업 Copper shoe for electro gas welding thick plate
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20190076206A (en) * 2017-12-22 2019-07-02 동국제강주식회사 Method for quantifiable test of tenacity of welded part of steel plate having taper and welding structure for quantifiable test of steel plate having taper

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