Proposal of welding technology for trimetal production.

Turna, Milan ; Ondruska, Jozef ; Sahul, Miroslav 等

Abstract: The contribution deals with evaluation of quality of trimetal produced by explosion welding. Technically pure copper, aluminium and structural carbon steel were investigated as welded materials. Semtex S 35 was chosen as the explosive. Paralell set up of welded metals was used in the experiment. Optical microscopy, microhardness measurement across Al--Cu--steel interface and EDX analysis were used for the quality control of the produced trimetal. The Al-Cu interface turned out to be an irregularly wavy interface, while the Cu-steel interface was regularly undulated

Key words: explosion welding, copper, structural carbon steel, aluminium, quality control of welds

1. INTRODUCTION

In technical practice there is a large number of classic and special materials of high technical parameters such as welding and soldering technologies. They might be applied to join aluminum to steel and this was previously not common in order to achieve high quality of welded joints suitable for practical implementation.

For the production of bimetals of given combination of materials and overall dimensions using special welding methods for example cold pressure welding, diffusion welding or explosion welding.

Experiments concerning with this issue are solved all over the world. For example welding steel to copper with explosion (Durgutlu, 2005), laser beam remelting of steel--aluminium bimetal produced by explosion welding (Tricarico, 2010). The research is performing also in the field of simulation of welding process (Wang, 2011).

2. EXPERIMENTAL

Following materials were used for the experiment: base material 11373 steel according STN 41 1373 (S235JRG1 according EN 10025A1) with the thickness of 36 mm, the Cu interlayer with the thickness of 2 mm and A199,9E as the main cladded plate (thickness of 16 mm).

The final bimetal was pbtained by explosion welding. Paralell arrangement of the welded materials was used in experiment. The welding process was performed gradually. Copper was selected as the first material to be cladded. Subsequently, aluminium was cladded onto the produced steel--copper bimetal. Semtex S35 was used as an explosive in the experiment. Parameters of the Semtex S35explosive are given in Tab. 1.

Overlaps of accelerated metals including explosives were selected in order to produce high quality joint up to the edge of the stable material (Fig. 1). In practice the overlaps are usually proposed to be as a multiple of the explosive thickness.

The following methods were used for evaluation of the quality of produced trimetal:

--macrostructural analysis

--microstructural analysis

--microhardness measurement across bimetal interface

--RTG microanalysis.

The macrostructure of trimetal is given in Fig. 1. It can be seen that the Cu-steel interface is regularly undulated. The presence of small islands was also observed. Wavy interface at the Al--Cu side was also observed but it is not clearly visible due to the presence of other phases.

[FIGURE 1 OMITTED]

Close to the interface the deformation of steel as well as of copper was recorded. The interface has the characteristic deformed structure. The grains lost their polyhedral shape. Increasing the distance from the interface it turns out that the microhardness decreases (Fig. 2).

[FIGURE 2 OMITTED]

The microscopic analysis across the Fe-Cu interface proved regularly wavy interface with a small wavelength [lambda]. It is noticeable that the intermixing between Cu and structural carbon steel occured. At the interface the steel is deformed to a depth of 45 [micro]m measured from the bimetal interface.

[FIGURE 3 OMITTED]

Cu-Al interface (Fig. 3) is characterised with irregular wavy interface with high wavelength. Measurement of microhardness (Fig. 4) confirmed the expected increase in hardness and thus the materials reinforced at the interface of trimetal.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

3. CONCLUSION

The paper deals with explosion welding of trimetal consisting of steel, copper and aluminium. Welded interfaces were examined by optical microscopy, microhardness measurement and EDX analysis. The mechanical intermixing was observed. Intermetalic compounds, such as Cu[Al.sub.2], [Cu.sub.11] [Al.sub.9], [Cu.sub.33] [Al.sub.17], [Cu.sub.9][Al.sub.4] and [Cu.sub.4]Al can be assumed according to Al-Cu binary diagram. SEM should be utilized for precise identification of the phases at interface. It can be concluded that the produced joints are suitable.

4. ACKNOWLEDGMENT

The submitted work was supported by the Slovak Grant agency VEGA MS VVS SR and SAV project No. 1/0842/09.

5. REFERENCES

Ahmet Durgutlu, a kol.: Examination of copper/stainless steel joints formed by explosive welding, Materials and Desing, Volume 26, Issue6, 2005, Pages 497-507

L. Tricarico, R. Spina.: Experimental investigation of laser beam welding of explosion-welded steel/aluminum structural transition joints, Materials and Desing, Volume 31, Issue 4, April 2010, Pages 1981-1992

Yuxin Wang, H.G. Beom, Ming Sun, Song Lin.: Numerical simulation of explosive welding using the material point method, International Journal of Impact Engineering, Volume 38, Issue 1, January 2011, Pages 51-60

Tab. 1. Parameters of used explosive

Name Designation Value

The thickness of the lower [H.sub.dm] [mm] 9,605
intelayer

[h.sub.e]/[h.sub.dm] index ([h.sub.e]/[h.sub.dm] < 1 match

Detonation density [[rho].sub.E] (g x [m.sup.-3]) 1,145

Ideal detonation velocity [v.sub.dil] [m x [s.sup.-1]] 2044,20
at p = 1,0 g x [m.sup.3-]

Change of detonation [d.sub.D] 3515,44
velocity with density

Ideal detonation velocity [v.sub.dil] [m x [s.sup.-1]] 2553,18
at arbitrary density

Thickness of upper [h.sub.hm] [mm] 41,610
interlayer

Resultant detonation [V.sub.D] [m x [s.sup.-1]] 2251,92
velocity

Gurney velocity [(2[E.sub.G]).sup.1/2] 1014,2
 [m x [s.sup.-1]]

Detonation presses [P.sub.cj] [GPa] 2,11

Tab. 2. Parameters of collision in cladding of Cu onto steel

Name Designation Value

Time constant t [[micro]s] 5,35

Deflection angle of the plate [[??].sub.D] [rad] 0,2614
at the selected distance [[??].sub.D] [deg] 14,9771

Impact velocity at the selected [v.sub.dD] [m x [s.sup.-1]] 586,98
distance

Velocity of collision point at [v.sub.kD] [m x [s.sup.-1]] 2251,92
the selected distance

Tab. 3. Parameters of collision in cladding of Al onto Al + steel
bimetal

Name Designation Value

Time constant t [[micro]s] 5,35

Deflection angle of the plate [[??].sub.D] [rad] 0,2614
at the selected distance [[??].sub.D] [deg] 14,9771

Impact velocity at the [v.sub.dD] [m x [s.sup.-1]] 395,01
selected sistance

Velocity of collision point [v.sub.kD] [m x [s.sup.-1]] 2501,06
at the selected distance