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This article was downloaded by: [Columbia University] On: 13 November 2014, At: 23:29 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Welding International Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/twld20 Automatic welding vertical butt joints in 12Kh18N10T steel V N Dikun a , Yu P Pelevin a & V F Karev a a All-Union Scientific Research Institute of Assembly and Special Operations , Published online: 05 Jan 2010. To cite this article: V N Dikun , Yu P Pelevin & V F Karev (1990) Automatic welding vertical butt joints in 12Kh18N10T steel, Welding International, 4:8, 635-637, DOI: 10.1080/09507119009447793 To link to this article: http://dx.doi.org/10.1080/09507119009447793 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and- conditions

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Page 1: Automatic welding vertical butt joints in 12Kh18N10T steel

This article was downloaded by: [Columbia University]On: 13 November 2014, At: 23:29Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41Mortimer Street, London W1T 3JH, UK

Welding InternationalPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/twld20

Automatic welding vertical butt joints in 12Kh18N10T steelV N Dikun a , Yu P Pelevin a & V F Karev aa All-Union Scientific Research Institute of Assembly and Special Operations ,Published online: 05 Jan 2010.

To cite this article: V N Dikun , Yu P Pelevin & V F Karev (1990) Automatic welding vertical butt joints in 12Kh18N10T steel, WeldingInternational, 4:8, 635-637, DOI: 10.1080/09507119009447793

To link to this article: http://dx.doi.org/10.1080/09507119009447793

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in thepublications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations orwarranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinionsand views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsedby Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified withprimary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings,demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectlyin connection with, in relation to or arising out of the use of the Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction,redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expresslyforbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

Page 2: Automatic welding vertical butt joints in 12Kh18N10T steel

Welding InrernationaI1990 4 (8) 63s-637 Selected from Svarochnoe Proizvodstvo 1989 36 (3) 5-7; Reference SPl891315; Translation 861

Automatic welding vertical butt joints in 12Kh18NlOT steel ~~ ~

V N D IKUN, Y u P P E L E V I N a n d V F KAREV All-Union Scientific Research Institute of Assembly and Special Operations

12KhlSNlOT chromium-nickel austenitic steel is charac- terised by satisfactory weldability. Consequently, high- quality welded joints can be produced by all methods of fusion arc welding. When producing large structures of a chromium-nickel steel using automatic submerged-arc welding with rotation in a manipulator, the edges can be greatly misaligned.'

Mechanisation of the welding process of assembly joints in large structures of chromium-nickel steel can be achieved mainly by arc welding in shielding gases with a consumable electrode. Experimental results show that the formation of high-quality vertical joints with free formation when welding chromium-nickel steel is associated with problems in removing lack of fusion defects and the pro- cess itself is characterised by low productivity. It is always necessary to clean the individual weld layers to remove oxide films?

It is well known that welded assembly butt joints in low- carbon and low-alloy steels are produced by CO, automatic welding with complicated oscillations of the electrode at the contour of the gap in the joint (the CO method). This welding technique is single-pass, with free weld formation? In welding by the CO method in a single pass the angular strains are considerably lower.'

In this article, the results are presented of examining the possibilities of producing vertical butt joints in a chromi- um-nickel steel by automatic welding using the CO method with gas shielding (in argon, a mixture of CO, and argon, and CO,) and of the effect of gas shielding on the mechani- cal properties and intercrystalline corrosion resistance of welded joints.

Welding butt joints with V-shaped edge preparation by the CO method was carried out from one side in a single pass with reverse formation of the weld by a copper back- ing sheet. The opening angle of the edges of the joint was accepted at 20' as when welding low-alloy steels. It was thus possible to produce welded joints with the mass of deposited metal 2530% lower than for the standard gap. The welding speed was high. Butt welded joints in 12Kh18N10T steel 20 mm thick had V-shaped edge prepa- ration and the weld gap was 5 mm. Welding was carried out with an SK-4 automatic system using Sv-OlKh19N9 welding wire 1.2 mm in diameter. The shielding medium included argon, a mixture containing 75% CO, and 25% argon, and CO,. The flow rate of the shielding medium was 1.5 m3/hr. These conditions resulted in the formation of a weld in the vertical position. The welding speed was 1.5 m/hr at an arc voltage of 20-23 V, a welding current of 130-160 A and a constant wire feed rate of 230 m/hr.

A special feature of welding by the CO method is the formation of a weld in filling the gap to the entire thickness of the joint by depositing beads on top of each other by displacing the electrode through the depth of the gap in a reciprocal motion from the root to the top of the gap and back. When welding in argon, the stability of the process was disrupted as a result of wandering of the arc on the edges of the joint and a reduction of the electrode wire extension. Consequently, the molten pool was situated above the level of the weld root and prevented immersion of the arc into the depth of the gap thus causing lack of fusion defects in the weld root. This phenomenon formed because the transverse directions of the column of the welding arc in molecular gases (N,, CO,) are smaller than in atomic gases (Ar)? Consequently, the arc in argon is characterised by a lower current density and pressure. Large droplets in transfer from the electrode into the molten pool try to occupy a position above the level of the weld root along the path with lowest resistance. An increase of weIding current aimed at increasing arc pressure and immersing it into the weld root does not give positive results because the mass of the pool becomes higher than the critical value capable of staying in the weld gap.

When the opening angle of the gap of the butt welded joint was increased to 40°, no lack of fusion defects were detected in the weld root. Consequently, the butt welded joints in 12KhlSNlOT steel welded in argon and used for mechanical and physical tests were produced with this opening angle.

When using the gas mixture (75% C0,+25% Ar) as the shielding medium, ihe stability of the welding process improved. The arc became capable of penetrating into the depth of the gap down to the weld root as a result of the reduction of length and cross section.

The nature of arcing in CO, welding is the same as in welding low-alloy steels.

The mechanical properties of the weld metal and welded joints were determined at a positive test temperature in tests on standard specimens (Table 1).

The mechanical properties of the weld metal of the weld- ed joints produced in different shielding media were almost identical. The relative elongation was slightly lower in the specimens produced by CO, welding. The bend angle of the specimens produced in welding in argon and CO, was high. However this parameter was lower with the gas mix- ture. In tensile tests on the welded joints, fracture took place through the parent metal in all the joints produced with different gas shielding.

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Page 3: Automatic welding vertical butt joints in 12Kh18N10T steel

636 Dikun et a1

Table I

Weld metal Welded joint

Shielding medium 0. 0. Bend

6.10 angle: MPa

Argon

co, (75%)

280-292 612-619 55.2-56.7 180 287 615 56.1

+ i g o n (g%) 278-281 583-669 56.7-60.0 80 280 601 58.5

278-283 6001411 46.7-50.0 180 280 6 0 6 . 48.3

Comment. The numerator gives the limiting values, the denominator the mean values obtained from the results of three tests.

Table 2

Impact toughness, MJ/m*. at a

Shielding Tested temperature of, 'C medium zone

20 -1%

Argon Weld metal 2.25-2.30 1.39-1.43 2.27 1.40

Fusion line 2.1 8-2.22 1.54-1.60 2.20 1.56

HAZ >3 2.27-2.59 2.40

CO, (75%) Weld metal 1.77-1.81 1 .&I .12 + argon 1.78 1.06 (25%)

Fusion line >3 1.18-1.26 1.20

HAZ >3 2.0-2.12 2.04

co2 Weld metal 1.29-1.33 0.72475 1.30 0.73

Fusion line 1.5 1-1 .60 0.63-0.96 1.57 0.73

HAZ >3 1.96-1.99 1.97

Comment. The numerator gives the limiting values, the denominator the mean values obtained from the results of three tests.

The impact toughness test was carried out on type VI specimens (GOST 6996-66) at 20 and -196" (Table 2).

The highest impact toughness of the weld metal at posi- tive and negative test temperatures was obtained in welding by the CO method in argon and then decreased to 0.73 MJ/m2 in CO, welding. This impact toughness level was higher than the values specified in technical conditions for structures (0.6 MJ/mZ at -196°C).

method in different gas media, and at -196°C was slightly lower than in argon. All the tested joints had a large reserve of impact toughness in all zones at positive and negative temperatures. The test results confirmed that the impact- toughness decreased in transition from neutral shielding to shielding with an active gas.

In CO welding vertical butt joints in chromium-nickel steel it was established that the angular strains in 120x150~800 mm specimens were in the range 0.018-0.022 rad.

To produce conditions capable of preventing intercrys- talline corrosion, it was necessary to produce an austenitic- femtic weld metal with a carbon content not higher than 0.O6%.5s6 For this purpose, Sv-OlKh19N9 wire was used in CO welding in different gas mixtures.

The microstructure of the weld metal in welding with different gas shielding is shown in the Figure.

The intercrystalline corrosion resistance was evaluated by the AM method (GOST 6032-74) without sensitising heating. The results of intercrystalline corrosion tests and the ferrite phase content in the weld are given in Table 3.

.E

depended On the medium. The impact toughness of the heat affected zone (HAZ) metal at 20°C was almost independent of the energy parameters of the CO weIding

Microstructure of weld metal (a), at fusion line (b) and HAZ (c) when welding in argon (11, a mixture of argon and CO, 111) and COZ (111).

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Page 4: Automatic welding vertical butt joints in 12Kh18N10T steel

Table 3

Shielding medium Ferrite phase content, %

1.8-2.0 1.8-2.2

Argon

C02 (75%) +argon (25%) 0-0.1 0.1-0.2

0 0-0.1

Comment. 1. The numerator gives the values for specimens cut out from the side of the weld root, the denominator for specimens cut out from the upper side. 2. In all cases the material wis resistant to intercrystalline corrosion.

Conclusions

1 Butt welded joints in the vertical position in 12Kh18NlOT steel can be produced using, as shielding medium, Tgon, a mixture of CO, and argon, and COP To ensure the required physico-mechanical properties of the welded joint and stable welding, shielding should be carried out using a mixture of CO, (75%) and argon (25%).

Automatic welding 637

2 When welding in a mixture of argon and CO, or in C 0 2 , welded joints can be prepared with V-shaped edge preparation with an opening angle of 20’. When

-welding in argon, the opening angle should be greater than20O. .

The welded joints have the required strength, ductility and impact toughness over a wide temperature range and sufficient resistance to intercrystalline corrosion.

3

References Muratov V M et al: ‘Permissible deformation of butt welded joints in spherical welded containers.’ Avt Svurku 1985 (5 ) 1442. Yushchenko K A et al: ‘Special features of formation of,vertical joints with free and forced formation in welding corrosion-resisting steels.’ In: ‘Information materials of COMECON, No.2.’ Publ Kiev, 1981.24-28. Malyshev V D et al: ‘Automatic gas-electric welding thick-plate metal.’ Avt Svurku 1973 (2) 23-25. Diken V N et al: ‘Effect of the arc welding method in a shielding gas on deformation of vertical butt welded joints.’ Svur Proiz 1980 (7)

Potap’evskii A G: ‘Consumable electrode welding and shielding gases.’ Publ Mashinosmnie. Moscow. 1974. Kakhovskii N I: ‘Welding corrosion-resisting steels.’ Pub1 Tekhnika. Kiev, 1968.

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