International Journal of Applied Engineering Research

ISSN 0973-4562 Volume 10, Number 1 (2015) pp. 1737-1749

© Research India Publications

http://www.ripublication.com

Destructive and Non-Destructive Testing of the Weldment of

Dissimilar Metals

Ahmad AL_Fasfous1, Suleiman Obeidat

2 and Mohammad Aljarrah

3

Hashemite University, Zarqa, Jordan 1Civil Engineering Department, Non- Destructive Testing, Email:

ahmed_30042001@yahoo.com 2Industrial Engineering Department, Email: sulobeidat@hu.edu.jo

3Industrial Engineering Department, Email: maljarrah@hu.edu.jo

Abstract

Joining dissimilar metals is very important in manufacturing, and automotive

industry. In this research weldment strength and fatigue life of brazing of high

Carbon steel (H.C), medium Carbon steel (M.C), and low Carbon steel (L.C)

with Aluminum, Brass, and Copper will be studied using Bronze C as filler

material. Two joint types of butt joints (closed square butt joint and Single-V

butt joint with 30ο) are studied. Non-Destructive tests were performed on all

samples using die penetrant method to show if any surface defects or cracks

appear to help expect the way the weldment fails. Brazing aluminum with HC,

MC, and LC had failed due to no wetting, and closed square butt joint proved

that. It failed when Manual torch brazing is used because the melted filler

metal did not inter the gap. Single-V butt joint with 30ο is the best way to

braze the joint with Manual torch brazing because the melted filler material

has filled most of the gap between the materials. Brazing HC, MC, and LC

with brass gives higher strength than brazing it with copper. The fatigue

endurance limit for HC, MC, and LC with brass is higher than that with

copper.

1. Introduction Joining dissimilar metals is very important in manufacturing, construction,

automotive industry, aerospace, aviation, shipbuilding and railway transportation.

Joining dissimilar metal is to compose different properties like corrosion resistibility,

strength and low weights. Dissimilar metal welding minimizes material costs and at

the same time maximizes the performance of the equipment and machinery. In this

research brazing is studied as joining process where the filler metal is heated above

1738 Ahmad AL_Fasfous, Suleiman Obeidat, and Mohammad AlJarrah

melting point. Capillary action is helping filler metal to fill the joint. The filler metal

is brought slightly above its melting temperature while protected by a suitable

atmosphere, usually a flux. Then it flows over the base metal (known as wetting) and

it cools to join the work pieces together. It is similar to soldering, except the

temperatures used to melt the filler metal are lower, and the bonds formed. Brazing

forms metallurgical bonds while soldering produces mechanical bonds.

The brazing process will be illustrated by the classical model of wetting and

spreading. In this model, we will take a droplet of the liquid on the surface, and

neglect the reaction between liquid and the solid surface. The classical model of

wetting is based on the behavior of a liquid drop on an inert solid surface. There are

three surface tensions control the spreading, as shown in figure 1.

Fig. 1: Surface tension force acting when a liquid droplet wets a solid surface, [1].

According to the forces in figure 1:

γSL = γSV - γLV cosθ (1)

Where, γSL is the surface tension between the solid and liquid. γSV is the surface

tension solid and vapor. γLV is the surface tension between the liquid and vapor. And θ

is the angle between the liquid droplet and solid surface. Equation 1, is known as

Young's equation or wetting equation. If θ < 90ο then γSV > γSL, this means that the

droplet will spread on the solid surface, and on the other hand if 90ο < θ < 180

ο a

liquid droplet will not spread on the solid surface.

In this research high Carbon steel (H.C), medium Carbon steel (M.C), and low

Carbon steel (L.C) are brazed with Aluminum, Brass, and Copper. According to

Classification of Carbon and Low-Alloy Steels and Engineering fundamentals page

on medium carbon steel [3,4,5] the percent of carbon will be illustrated as, low carbon

steel (L.C) less than 0.29 % carbon content, medium carbon steel (M.C)

approximately 0.30–0.59% carbon content, and high carbon steel (H.C)

approximately 0.6–0.99% carbon content. All the types brazed using Bronze C as a

filler material. The Chemical composition of the metals is illustrated in table 1.

Destructive and Non-Destructive Testing of the Weldment of Dissimilar Metals 1739

TABLE 1 Chemical Composition of Materials

Non destructive testing methods perform feasibility study in detecting defects.

Penetrant test is used mainly to reveal the surface defects using a colored dye. The

principle here depends on the capillary action for the cracks making a contrast so they

can be visible to the inspector by the naked eye.

2. Literature Review

Many studies have been conducted on welding of dissimilar metals and its

significance in specific strengths which has been recognized as being better than

mechanical fastening and adhesive bonding [2,3].The capillary force is the driving

force to flow in the joint [4]. The filler metal is brought slightly above its melting

temperature while protected by a suitable atmosphere, usually a flux. It then flows

over the base metal known as wetting and is then cooled to join the work pieces

together [5]. The selection of filler metal is the basic idea [6]. (Matthey and Sloboda,

1961) [7] studied the flow of the brazing alloy and the effect on the joint and the

perfect gap for the joint which is for Copper-Zinc 0.051mm to 0.254mm. (Cao, et al.,

2011) [8] brazed brass to steel using Ag25CuZnSn filler metal and tested by tensile

strength which gave 445 MPa. When Ag has been increased it gave higher strength.

(Shabtay, 2004) [9] brazed copper with steel using laser and Cu-Al as a filler metal

and he found that the maximum stress of the joint is 250 MPa. He established a new

brazing process and evaluates the technology through prototype building. (Xueqin, et

al., 2004) [10] and (Mingfang, et al., 2011) [11] studied the effect of brazing time on

microstructure of the joints and the new phases will appear. ( Borrisutthekul, et al.,

2010) [12] indicated that TIG welding process is feasible to be used in dissimilar

metals welding of steel/aluminum alloy.

Many researchers studied friction welding to join dissimilar metal, (Malarvizhi

and Balasubramanian, 2007) [13] studied many types of welding and they stated that

friction stir welding (FSW) is better than gas tungsten arc welding (GTAW) in tensile

strength and the fatigue strength, while GTAW exhibits better pitting corrosion

resistance compared to FSW. Brazing is the same as GTAW which has better

corrosion resistance compared to FSW [14,15], and GTAW is better than FSW in

fatigue because there is small internal cracks[16].

Manual torch brazing is a procedure where the heat is applied using a gas flame

placed on or near the joint being brazed. The torch can either be hand held or held in a

fixed position depending on if the operation is completely manual or has some level

of automation. Manual brazing is most commonly used on small production volumes

or in applications where the part size or configuration makes other brazing methods

impossible [17].

1740 Ahmad AL_Fasfous, Suleiman Obeidat, and Mohammad AlJarrah

(Xueqin, et al., 2004) [18] and (Mingfang, et al., 2011) [19] studied the effect of

brazing time on microstructure of the joints and the new phases will appear.

(Traxler, 2002) [20] used colored dye fluorescent to reveal the surface flaws seen

under the black light (Ultraviolet). In this research ordinary penetrant test has been

used to inspect the surface crack using naked eye.

3. Results and Discussions Brazing aluminum with any steel types (H.C, M.C and L.C) failed in this research

because the filler metal (Bronze C) does not make any wetting on the aluminum side

in the joint which means that is no brazing operation. Figure 2 shows how the wetting

on the aluminum surface.

Fig. 2: Surface tension forces acting when a liquid droplet wets aluminum surface.

The closed square butt joint failed because of the heat source (Manual torch).

Manual torch can't keep the amount of heat, because of the human error, it is changing

the melting filler metal under these circumstances to turn into viscous metal because

the viscous filler metal can't inter the gap between two welded metal. As shown in

figure 3.

Fig. 3: Experimental results show that the closed square butt welding and the filler

metal don't inter the gap.

Destructive and Non-Destructive Testing of the Weldment of Dissimilar Metals 1741

3.1 Analysis of Tensile Testing Results

For the tensile test, all samples failed suddenly under a constant uniaxial tension

loading rate as a brittle material in the welding region. Figure 4 shows the stress-

strain curve of the welding joint made between L.C and brass, and between L.C and

copper.

Fig. 4: Stress-strain curve for L.C welded with Brass and Copper samples.

In figure 4, it is noticed that there is a difference in stress-strain curve behavior

between the six samples. This is noticed for sample 2 in which the highest stress is

204.1 MPa at strain 0.027. This can be justified by the picture no.2 in figure 5.

Fig. 5: Surface cracks noticed in penetrant test for samples (1) to (6).

In figure 5 sample 1, there are two surface cracks (no wetting because of some

oxides or other coating). The crack is big and the shapes of paint give us an indication

of the shape of the crack which looks like longitudinal crack. For sample 2, there is no

surface crack. For samples 3,4 and 6 no defect but there is some roughness noticed on

the surface from the pictures. For sample 5, there is surface crack. It looks like

circular which indicates that the point has more strength. On the other hand the

difference in strain because of the ductility of the sample becomes smaller when there

are many cracks.

1742 Ahmad AL_Fasfous, Suleiman Obeidat, and Mohammad AlJarrah

Fig. 6 Stress-strain curve for M.C welded with Brass and Copper samples.

In figure 6, it is noticed that there is a difference in stress-strain curve behavior

between the six samples. This is noticed for sample 2 in which the highest stress is

233.3 MPa at a strain of 0.028. This can be justified by picture no.2 in figure 7.

Fig. 7 Surface cracks noticed in penetrant test for all samples.

In figure 7 of samples 1, 2, 3 and 6, there is some roughness on the surface. For

samples 4 and 5 there is two lacks of fusion defects. It is very big because there is a

big amount of paint spreading out from the crack after sprayed the developer and the

shape of paint give us an indication that the shape of the crack looks like longitudinal

crack.

Destructive and Non-Destructive Testing of the Weldment of Dissimilar Metals 1743

Fig. 8 Stress-strain curve for H.C welded with Brass and Copper samples.

In figure 8, it is noticed that there is a difference in stress-strain curve behavior

between the six samples.

This is noticed for sample 1 in which the highest stress is 243.1MPa at a strain of

0.037. This can be noticed in picture no.1 of figure 9.

Fig. 9 Surface cracks noticed in penetrant test for all samples.

In figure 9 samples 1, 5 and 6 there is defect and some roughness on the surface.

For samples 2 and 4 there is a small crack. It can be detected from the amount of paint

noticed. In sample 3 there is a lack of fusion. It is very big because there is a big

amount of paint spreading out from the crack after sprayed the developer and the

shape of paint give us an indication of the shape of the crack which is kind of

longitudinal crack.

1744 Ahmad AL_Fasfous, Suleiman Obeidat, and Mohammad AlJarrah

TABLE 2 Tensile Test Results

3.2 Analysis of Fatigue Life Testing Results

In this section stress vs log(N) will be studied and all types of dissimilar welding will

be compared to determine endurance limit for each dissimilar welding. Using

nondestructive testing in all samples, any sample shows surface defect will be tested

in fatigue test and ignored in the curve to give us a perfect curve.

Fig. 10: (σ Vs log(N)) curve for H.C with copper fatigue samples.

In figure 10 there are two points that are out of the curve. All of these points were

detected before fatigue test using nondestructive testing has been performed. Figure

11, illustrates the case.

Fig. 11: Surface cracks noticed in penetrant test for fatigue samples (a1) and (a2).

Destructive and Non-Destructive Testing of the Weldment of Dissimilar Metals 1745

In figure 11 there are two samples in figure 11a which are out of the curve and

after tested by penetrant test, there are many surface cracks noticed from the picture.

Fig. 12 (σ Vs log(N)) curve for H.C with brass fatigue samples.

In figure 12 there is a point that is out of the curve. It is detected before fatigue

test using nondestructive testing has been performed especially for surface crack as in

figure 13. After tested by penetrant test, there is surface crack noticed from the

picture.

Fig. 13 Surface cracks noticed in penetrant test for fatigue samples H.C with brass.

1746 Ahmad AL_Fasfous, Suleiman Obeidat, and Mohammad AlJarrah

Fig. 14 (σ Vs log(N)) curve for H.C with copper fatigue samples.

In figure 14 there is a point that is out of the curve, which is detected before

fatigue test using nondestructive testing has been performed as shown in figure 15.

After tested by penetrant test, there is surface crack noticed from the picture.

Fig. 15 Surface cracks noticed in penetrant test for fatigue samples L.C with copper.

Fig. 16 (σ Vs log(N)) curve for L.C with brass fatigue samples.

Destructive and Non-Destructive Testing of the Weldment of Dissimilar Metals 1747

The same notes can be shown in figure 17 which is illustrated using penetrant test

in figure 18.

Fig. 18 Surface cracks noticed in penetrant test for fatigue samples L.C with brass.

Fatigue life test results for endurance limit for all welding types are shown in table

3.

TABLE 3 Fatigue Endurance Limit For All Welding Types.

4. Conclusions In this research HC, MC, and LC are joined with Aluminum, Brass, and Copper using Manual

torch brazing and Bronze C as filler metal. Brazing aluminum with HC, MC, and LC had

failed due to no wetting. Nondestructive technique has been used to check samples fatigue

and tension tests. All samples have been tested efficiently for cyclic loading and axial tension

test. Some conclusions are explained below:

1748 Ahmad AL_Fasfous, Suleiman Obeidat, and Mohammad AlJarrah

Closed square butt joint proved that, it is failed when Manual torch brazing is

used because the melting filler metal did not inter the gap.

Single-V butt joint with 30ο is the best way to braze the joint with Manual

torch brazing, as it better in comparing with closed square butt joint. Because

the melted filler material has filled most of the gap between the materials.

Brazing HC, MC, and LC with brass give higher strength than brazing it with

copper.

The fatigue endurance limit for HC, MC, and LC with brass is higher than that

with copper.

There is a small difference between maximum strength of brazing brass with

HC, MC, and LC. The maximum strength was of brass with H.C, it was

243.1MPa.

In brazing copper with HC, MC, and LC, the maximum strength was of

copper with M.C, it was 193.5MPa.

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1750 Ahmad AL_Fasfous, Suleiman Obeidat, and Mohammad AlJarrah