The influence of filler material at TIG welding of heat-resistant steels.

Valova, Marie ; Kolarik, Ladislav ; Dunovsky, Jiri 等

1. INTRODUCTION

This paper summarises results of research, which was solved on Department of manufactoring technology, Faculty of mechanical engineering, CTU in Prague, on cooperation with Department of materials engineering and industrial companies Bohler Uddeholm CZ, s.r.o. and Air Products s.r.o. in 2007 (Benak et al.,2008). The purpose of this research was influence detectection of different types of filler materials (in combination with various shielding gas) at TIG welding of tanks destined for quenching. This paper takes up to research published in (Kolarik et al., 2008).

2. PARENT MATERIAL CHARACTERIZATION

As parent material for welding was used heat-resistant chromium steel type CSN 17 153, which is resistant to oxidation on air to the 1100 [degrees]C and in carburizing environment to the 1000 [degrees]C. This material is suitable for equipment and components for application in heat engineering, especially in atmospheres containing sulphate compound and in atmospheres, where attend to intensive carbonization. Next this material is used for heat-resistant components of caldrons with high service temperature and low mechanical stress.(Olson, 2000).

3. TECHNOLOGY AND WELDING PARAMETERS

At the experiment were welded single-run samples of butt I weld (t = 3 mm), manually by technology 141 conformably to CSN EN 4063 (TIG) with parameters mentioned in follow tables No. 4. Samples were welded by inverter source Migatronic PI 200, direct current with direct polarity, with use of fixture for root of weld protect. There was used tungsten electrode W2 about average 2,4 mm.

For the influence detection of FM were used three types of filler welding wires (about average 2,4 mm and longitude 1 m further information are shown in next tables).Material 17153 is usually welded by austenitic heat-resistant materials, it is for example Bohler FFB-IG and Thermanit CSi.

If is product used in sulphur environment, then are used types of FM similar parent material, for example Bohler FA-IG and Thermanit L, because above-mentioned austenitic materials have not necessary resistivity.

Vantage is welding by combination of these materials, especially for bigger thicknesses. It is used e.g. Thermanit CSi and then is weld surfaced by capping run Thermanit L.

The last select variation is filler material Bohler Nibas 70/20IG or anologous type UTP A068HH, which has the best mechanical properties. His using is necessary especially when working temperature run over 300[degrees]C and heterogeneous join between very different materials, e.g. among austenitic and ferritic material (it is also c.2x more expensive than the last mentioned FM) is welded.

4. STRUCTURE AND MICROHARDNESS EVALUATION

Influence of filler material to weld metal structure:

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5. CONCLUSION

In respect of creation mixed structure (where single phase forms ferrite--which dissolve S and P and austenite--which has big gas solubility) it did not create cracks in any samples (Folkhard, 1988; Maronek et al., 2005). The best maechanical properties at high temperatures embody structures with steady mixing and steady substitution of both phase (from this standpoint is the most suitable filler material Thermanit CSi). In weld metal structure is with growing Cr quantity created Widmanstaetten structure, which however does not decline mechanical properties of weld metal, as well as secondary austenite occurrence is not unadvisable.

From the viewpoint of the fire-resistance is suitable to use filler material type A068HH, which contains big part of nickel.

6. ACKNOWLEDGEMENT

This work is a part of the research plan of the project MSM6840770021--"Diagnostic of materials", that is financed by the Ministry of Education of the Czech Republic.

7. REFERENCES

Benak, M.; Vondrous, P. & Kolarik, L. (2008). Study of welded joints fabricated by gtaw process and nd:yag laser, International doctoral seminar 2008, Smolenice, 2008, pp 35-43

Folkhard, Erich (1988). Welding Metallurgy of stainless Steels, Springer-Verlag Wien New York, 1988

Kolar, V.; Brezina,M.; Vesely, P.; Dunovsky, J. & Kolarik, L. (2007). Heterogeneous welds in field of tracked vehicles produce--Siemens KV s.r.o.In: Dny svarovaci techniky 2007. Praha: Cesky svaz vedeckotechnickych spolecnosti, 2007, pp 111-118. ISBN 978-80-02-01924-4

Kolarik, L.; Dunovsky, J.; Valova, M. & Ruzicka, D. (2008). Mechanical properties of weld joints of Al alloy EN AW 6005 after TIG welding, ERIN 2008, Bratislava, 2008

Maronek, M.; Lazar, R.; Domankova, M. & Kotras, P. (2005). Microstructure analysis of weld joints from nitrooxidation treated low carbon steel sheets. In Zvarac, 2005, roc. 2, c. 1, pp 23-28. ISSN 1336-5045

Olson D.L. (2000). "ASM Handbook, Volume 6, Welding, Brazing, and Soldering", 2000

Tab. 1. Chemical constitution of parent material

Steel CSN 17 153

 C Mn Si Cr Ni P S

max max max 23,0 to max max max
0,15 1,0 1,3 27,0 2,0 0,045 0,040

Tab. 2. Mechanical properties of parent material

Steel CSN 17 153

 Rp0,2 Rm [A.sub.5] Z [%] HB E
 [MPa] [MPa] [%] min [GPa]

min 300 500 min 15 min 30 144 196

Tab. 3. Creep resistivity of parent material

Temperature 600 700 800 900 1000 1100
[[degrees]C]

[R.sub.mT]/
[10.sup.4] 29 10,7 4,8 2,3 1,2

[R.sub.T]/
[10.sup.3]/1 34 10 4 1,5 0,7 0,3

Tab. 4. Welding parameters

 Welding Welding
No. of Filler Current Voltage
sample material [A] [V]

 1 CSI 62 12,5

 2 CSI 55 12,2
 3 FA IG 55 12,2
 4 FA IG 62 12,5
 5 A=068HH 62 12.5
 6 A=068HH 55 12,2

 Welding Schielded Robot
No. of Gap Gas protect
sample [mm] [l/min] [l/min]

 1 1 Ar 8 Without
 protect
 2 0,5 Ar 7 Ar 4
 3 0,5 Ar 7 Ar 4
 4 0,5 Ar 7 Ar 4
 5 0,5 Ar 7 Ar 4
 6 0,5 Ar 7 Ar 4

Tab. 5. Chemical constitution of filler
material Thermanit CSi

Thermanit CSi

EN 12072: 1999:
W 25 20 Mn,
W. No. 1.4842

 C Mn Si Cr Ni

0,13 2,5 1 25,0 20,5

Tab. 6. Mechanical properties of filler
material Thermanit CSi

Mechanical properties

Re Rm A5 KVJ
[MPa] [MPa] [%] +20
 [degrees]C

350 550 25 80

Tab. 7. Chemical constitution of
filler material Thermanit L

Mechanical properties

 C Mn Si Cr Ni
0,08 1,2 0,8 25,7 4,5

Tab. 8. Mechanical properties of filler
material Thermanit L

 Re Rm [A.sub.5] KVJ
[MPa] [MPa] [%] +20[degrees]C

 540 710 22 70

Tab. 9. Chemical constitution of filler material A068HH

UTP A068HH
EN ISO 18274: 2004:
S Ni 6082 (NiCr 20 Mn 3 Nb)
W.No. 2.4806

 C Mn Si Cr Ni Ti Nb Fe

[less than 3,0 0,1 20,0 [greater + 2,5 <1,7
or equal than or
to] 0,03 equal to]
 67,0

Tab. 10. Mechanical properties of filler material A068HH

 Mechanical properties

 Re Rm KVJ KVJ
[MPa] [MPa] [A.sub.5] +20[degrees]C -196[degrees]C

 440 680 42 190 100