EFFECT OF WELDING HEAT INPUT ON THE CORROSION RATE OF CARBON STEEL MMA WELDING

Steel is one of materials which often used on steel construction, bridge construction, and high rise building construction. Construction using welding joint is expected able to withstand construction loads for a long time. After a while weldment will be exposed to corrosion that will be construction failure in turn. One of the most important parameter in welding is heat input, however it hasn’t obtain correlation between heat input and corrosion rate on MMA (Manual Metal Arch) weldment on mild steel. This paper aims to obtain correlation between heat input and corrosion rate of low carbon steel with MMA welding. The result was show that corrosion rate tend to decrease with adding of duration, where higher corrosion rate at heat input 0,8108 kJ/mm was 68,68 gm/m2 hr at duration 5 hour.

Assessing MMA Welding Process Stability Using Machine Vision-Based Arc Features Tracking System

Arc length is a crucial parameter of the manual metal arc (MMA) welding process, as it influences the arc voltage and the resulting welded joint. In the MMA method, the process’ stability is mainly controlled by the skills of a welder. According to that, giving the feedback about the arc length as well as the welding speed to the welder is a valuable property at the stage of weld training and in the production of welded elements. The proposed solution is based on the application of relatively cheap Complementary Metal Oxide Semiconductor (CMOS) cameras to track the welding electrode tip and to estimate the geometrical properties of welding arc. All measured parameters are varying during welding. To validate the results of image processing, arc voltage was measured as a reference value describing in some part the process stability.

Controlling Angular Distortion in Manual Metal Arc Welding of Austenitic Stainless Steels Using Back-step Technique

Nowadays, austenitic stainless steels (A.S.S.) have many industrial applications in the fields of chemical and petrochemical processing, marine, medicine, water treatment, petroleum refining, food and drinks processing, nuclear power generation etc. The secret behind this wide range of applications is the fact that A.S.S. have great corrosion resistance, high strength and scale resistance at elevated temperatures, good ductility at low temperatures approached to absolute zero in addition to notable weldability. On the other hand, manual metal arc (MMA) is probably the most common process used for the welding of A.S.S. Unfortunately, MMA welding of A.S.S. could be associated with considerable distortion. Uncontrolled or excessive distortion usually increases the cost of the production process due to the high expense of rectification or replacing the weldment by a non-distorted one. MMA welding of A.S.S. was carried out using the back-step technique with various bead lengths, and without using this technique for comparison. Results have showed that the angular distortion was a function of the bead length in the back-step welding of A.S.S. The angular distortion decreased by (14.32%) when the back-step technique was used with a (60 mm) length for each bead, and by (41.08%) when the bead length was (40 mm). On the other hand, it increased by (25%) when the back-step technique was done with a (30 mm) length for each bead.

Morphology and Optimisation of Impact Energy of Weldment of High Strength Low Alloy Steel

Morphology and optimisation of impact energy of weldment of low alloy-high strength steel were investigated in this work. The study involved the use of design of experiment via Taguchi method based on three variables, each having three levels. Minitab 16 software was used for the analysis of variance (ANOVA) and signal to noise (S/N) ratio of the impact energy. Direct current electrode positive (DCEP) was used in the electric manual metal arc (MMA) welding. The input parameters at the three levels were current (60 A, 70 A, and 80 A), metal thickness (5 mm, 7 mm, 9 mm) and root gap (2.0 mm, 2.5 mm, 3.0 mm). It was found that the input variables significantly affected the microstructure of the weldment in all the nine experiments conducted. Optimization of welding parameters was carried out to obtain the optimal input values required to give the optimal impact energy of weldment. The optimal values for the input values were 80 A for current, 9 mm thickness and 2.5 mm root gap and these were substituted in the regression equation to obtain the optimal impact energy. It was equally observed that the input variables affected the microstructure of each of the nine samples.