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Friction welding of C6191 aluminum bronze to SUS304L stainless steel was carried out to examine its weldability. Joint strength was evaluated by fatigue strength. The C6191 and the SUS304L at the weld interface were hardened, while the heat affected zone of the SUS304L was slightly softened. A reaction layer of 1–5 μm that consisted of component elements of the base metals was observed at the weld interface. The fatigue limit of the joint welded under the optimum welding condition was higher than those of the base metals because of the hardening of C6191 and SUS304L, and the fatigue limit of joints decreased as the friction time or the upset pressure varied. In particular, the fatigue strength of joints welded under the conditions varied the upset pressure which was lower than that of the C6191 base metal.

Stud joints of 5083 aluminum alloy were welded by arc stud welding and friction welding, and their joint strengths were examined. In the weld zone of the arc stud welded joint, no change occurred in the hardness distribution. In contrast, the weld zone of the friction-welded stud joint softened slightly on the plate side and hardened on the bar side. The tensile strengths of the arc stud welded joints with weld reinforcement and without weld reinforcement, and the friction-welded stud joints without burrs were 233, 231 and 180 MPa, respectively, and all joints fractured at the weld zone. In the bending test, all joints fractured near the weld zone at a bending angle of approximately 20°. In the fatigue test, the fatigue strengths of the arc stud welded joints were higher than those of the friction-welded stud joints, and the fatigue limits of the arc stud welded joints with weld reinforcement and without weld reinforcement, and the friction-welded stud joints without burrs were 43, 40 and 13 MPa, respectively.

Stud joints of 2017 aluminium alloy were friction welded and its joint strength was examined. A stair zone was formed at the weld interface. Although the hardness of the stair zone was almost the same as base metals, the heat-affected zone of the bar and the plate was softened. The tensile strength of joints tended to increase with a pressure and a friction time, and the highest tensile strength was 275 MPa (63.1% joint efficiency for the bar base metal). In the bending testing, joints were cracked in the weld zone at a bending angle of less than 5°. In the fatigue testing, joints fractured near the weld interface and the fatigue strength of joints increased as the tensile strength of joints was high.

Friction welding of SUS304 stainless steel to C1100 tough pitch copper was carried out and tensile strength of joints was examined. Also, a statistical analysis of the tensile strength data was investigated for judging a suitability of friction welding conditions on this joint. It was found that the SUS304 and the C1100 near the weld interface hardened and softened, respectively. There were fine-grained structures composed of much copper and a little of iron, chromium and nickel near the axial center at the weld interface. Tensile strength tended to increase with a friction time and with an upset pressure, and the maximum joint efficiency for the C1100 base metal was 101%. The shape parameter in Weibull distribution increased with an increase in mean value of tensile strength and with a decrease in dispersion of tensile strength. It seemed that the shape parameter is useful for judging the suitability of friction welding conditions.

t. Friction welding of FC250 common grade cast iron was carried out to examine the weldability and temperature distribution near the weld interface during welding. The joint strength of both solid and pipe joints was evaluated by tensile tests. The highest tensile strengths in the solid joints and pipe joints were 317 MPa (79% joint efficiency) and 381 MPa (95% joint efficiency), respectively. A fine-grained interfacial layer of FC250 formed near the axial center at the weld interface in the solid joints, whereas there was no fine-grained interfacial layer in the pipe joints. The welding material temperature at the axial center was higher than that at the periphery in the solid joint. There was little difference in the temperature distribution between the solid joints and pipe joints.

The relationship between joint strength and deformation heat input at the upset stage and the relationship between joint strength and upset bum-off length were examined on friction welded joints of 1050 pure aluminum to C1100 tough pitch copper. Joint quality was evaluated from the tensile strength and fatigue strength. It was found that both the deformation heat input at the upset stage and the upset burn-off length correlated well with joint strength. Additionally, when the deformation heat input at the upset stage or upset burn-off length exceeded a certain value, stable tensile strength was obtained. The mixing layer, intermetallic compounds of Al-Cu were interpolated into A1050, formed at the weld interface, and joints having a thick mixing layer fractured at the weld interface. Joint efficiencies of sound joints for the fatigue limit of the A1050 base metal were 88-100%. Judging from the fatigue limit, sound joints could be produced when either the deformation heat input at the upset stage or the upset burn-off length exceeded a certain value.

Similar and dissimilar joints of 2017 and 6061 aluminum alloys were friction welded. Fatigue strength and fatigue life distribution of these joints were examined. The S-N curve showed that the fatigue strength of A2017/A2017 was almost the same as that of A2017 base metal, while that of A6061/A6061 was lower than that of A6061 base metal. The fatigue strength of A2017/A6061 was lower than that of A6061/A6061. The fatigue limit at 108 cycles of A2017 base metal, A2017/A2017, A6061 base metal, A6061/A6061 and A2017/A6061 were 120MPa, 120MPa, 70MPa, 60MPa and 55MPa, respectively. The shape parameter m and the location parameter γ in Weibull distribution function of the joints were lower than those of the base metals. These results suggest that the scatter in fatigue life distribution is larger and the smallest fatigue life is shorter for the present joints compared to the base metals.

Conferring lightweight and good corrosion resistance, aluminium alloy joints are extensively required in the manufacture of various types of electrical and mechanical components. Research data previously obtained by the authors1, 2 show the efficiency of friction-welded joints, regardless of whether produced from similar or dissimilar materials, to be fairly well scattered under identical sets of friction welding conditions and underline the need for statistical analysis of a large number of joints to determine the suitability of any specific set of friction welding conditions. That is to say, joints with a high mean joint efficiency that are friction-welded under optimum friction welding conditions conform to a normal distribution with low scatter during such statistical analysis while simultaneously showing a large Weibull distribution shape parameter and small dispersion. On the other hand, joints with a low mean joint efficiency that are friction-welded under unsuitable friction welding condi...

Aluminum alloys to S25C carbon steel were friction welded, and the friction weldability and intermetallic formations at the weld interface of joints were investigated. Joints of A1050, A5052, A6061 and A6063 to S25C showed good-weldability, and A5056/S25C joint was somewhat poor than former one. An intermetallic compound of Al13Fe4 was formed at the weld interface of A5056/S25C and A6061/S25C joints, and their intermetallic formations were tend to increase with friction pressure, friction time and rotation speed. The joint strength of these joints was high when thin instermetallic conpound layer was formed under high upset pressure. Somewhat poor-weldability of A5056/S25C joint compared with A6061/S25C joint seemed a cause of the intermetallic formation accelated by high content of magnesium in A5056. Joints of A2011, A2017, A2024 and A7075 to S25C showed poor-weldability. Brittle intermetallic compounds of CuAl2 and Al7Cu2Fe were formed at the weld interface of A2011/S25C joint containing a copper.

Friction welding of aluminum alloys to copper was carried out in order to examine the weldability with particular reference to the effect of the intermetallic formation at the weld interface. The maximum joint efficiencies of A1050, 5000 and 6000 series alloys to copper were more than 80 %, while those of 2000 series and A7075 alloys joints were less than 50 % and scattered widely. For joints of A2024 and 5000 series alloys which contain rather high magnesium content, intermetallic compounds of Al-Cu-Mg system were formed at the weld interface in addition to that of Al-Cu system. In the other joints, only intermetallic compounds of Al-Cu system were formed. A mixing layer, in which pieces of copper and intermetallic compounds were incorporated into aluminum alloy, was formed near the weld interface. The mixing was very intense, in the joints with low efficiency, namely joints of A2011, A2024 and A7075 to copper, and these joints were fractured in this mixing layer and at the weld interface. On the other hand, the joints with high efficiency, namely joints of A5052 and A6061 to copper, had thin and even mixing layer. The mixing layers observed in the joints of A1050, A2017, A5056 and A6063 to copper were thinner than those of the other joints.

Friction welding is widely used for welding both similar materials and dissimilar materials. However, when friction welding dissimilar materials such as aluminum alloy and steel, it is very difficult to obtain a sound weld. In the present study, using statistical and Weibull analysis difference in joint performance between aluminum alloy pipe/carbon steel pipe and aluminum alloy pipe/stainless steel pipe is clarified.

In present study, various aluminum alloys pipe to steels pipe were friction welded, and the mean value and scatter of welded joints were investigated. That is, thirty specimens for each combination of three aluminum alloys pipe to five steels pipe were friction welded under the optimum friction welding condition and the joint efficiency of welded joints were evaluated by tensile test. After performing statistical analysis and Weibull analysis on the joint efficiency, the following results were obtained, (1) The joint efficiency of A6061/steel showed a normal type distribution, but the A5052/steel and A6063/steel showed a distortional type and a double peak type distribution, respectively. (2) A difference was found in the joint efficiency of A5052/carbon steel and A5052/stainless steel showing high joint efficiency in the A5052/S45C and A5052/SUS304. (3) In the A606l/carbon steel and A6061/stainless steel, no difference was found in joint efficiency. (4) In the case of A6063/carbon steel, any difference of the joint efficiency was not found, while a difference was found in the case of A6063/stainless steel. (5) A reference table on the joint efficiency and joint strength for three aluminum alloys pipe to five steels pipe was presented.

Friction welding of various aluminum alloy pipes to SUS304 stainless steel pipe was carried out making clear weldability at dissimilar material pipe. A1050/SUS304, A5052/SUS304, A5056/SUS304, A6061/SUS304 and A6063/SUS304 joints showed good weldability and the maximum joint efficiencies of these joints in tensile test were about 91%, 71%, 60%, 79% and 97%, respectively. In these cases, the formation of Al13Fe4 intermetallic compound was induced by the interdiffusion through the weld interface. On the other hand, other joints had poor weldability. In the cases of A2011/SUS304, A2017/SUS304 and A2024/SUS304 joints, CuAl2 and Al7Cu2Fe were observed on the friction surface, and the maximum joint efficiencies of these joints were about 26%, 39% and 32%, respectively. For the case of A7075/SUS304 joint, Al23CuFe4 was observed on the friction surface, and the maximum joint efficiency was about 37%.

Comparatively thick pipes of 6061 aluminum alloy and S25C carbon steel were friction welded under a preferable welding condition and the strength distribution on the weld interface was investigated. The results obtained are as follows; (1) According to a decrease of the thickness ratio 0.30, 0.16, 0.15, 0.14, 0.13 and 0.12, the joint efficiency decreased 73.9%, 68.1%, 63.8%, 55.8%, 39.9% and 21.6%, respectively. (2) Friction welding of thin pipe having less thickness ratio t/D0 than 0.11 was difficult to produce a sound weld (D0: outer diameter, t: thickness of pipe). (3) The tensile strength of each 11.1% area from inner and outer edges of the weld interface was low, and the joint efficiencies were 30∼50%. (4) The joint efficiency of the joint removed inner and outer areas of the weld interface was about 95%.

Summary This paper describes the possibility of optimum friction welding conditions being selected through adoption of a joining evaluation equation derived from friction welding behaviour as determined by the response surface method in welding tests of 12 mm dia. SUS304 stainless steel. Through initial analysis of the relationship between the welding behaviour and tensile strength of friction-welded joints in a multiple regression analysis, a joining evaluation equation for non-destructive estimation of joint performance is derived. The optimum welding conditions are next selected by the response surface method using the joining evaluation values determined by the joining evaluation equation as dependent variables and the friction welding conditions as independent variables. This procedure enables the optimum friction welding conditions to be determined without the need for tensile tests to be conducted. The optimum friction welding conditions determined by this procedure are friction pressure P1 = 30 MP...

This paper discussed the posibility of selection of optimum welding condition by adopting the estimating equation for welding consisting of some welding behaviours to responce surface method using a 12 mm diameter SUS304 stainless steel. First, by analysing the relation between the welding behaviour and the tensile strength of welded joint using multiple regression analysis, an estimating equation for welding capable to estimate non-destructively was obtained. Next, by setting up the joining evaluation value obtained by the estimating equation for welding as a dependent variable and the welding condition as an independent variable, the optimum welding condition was selected using the responce surface method, namely, the posibility of selection of optimum welding condition without tensile strength was confirmed.The optimum welding condition obtained was the friction pressure P1=30 MPa, the upset pressure P2=170 MPa, the friction time t1=3.5 s and the rotating speed N=2425 rpm, and the joint efficiency was 102% with a satisfaction.