Pulsed ND YAG laser parameter effect on welding uncoated Advanced High Strength Steel (AHSS) for automotive

Pulse wave (PW) welding technique has become more adequate process to produce a deep penetration welding with smaller fusion zone and heat affected zone for automotive steel joint. A 1.6 mm thickness of N22CB boron steel from advance high strength steel (AHSS) type was welded by using PW mode from a low power Nd: YAG laser. The process parameters studied in this paper are pulsed energy, Ep, focal length, F, and welding speed, S. Bead-on-plate (BOP) welding was used in this experiment. The effect of parameters on the weld pool geometry was studied. Higher pulsed energy gives high weld penetration and higher weld width, contributing to the bigger weld pool size. Positive defocus position of focal length produces weld geometry with high penetration depth and smaller bead width compared to negative defocus position. Lower welding speed could produce deep penetration depth as the high heat input produced

Microstructure analysis and mechanical properties of dissimilar AA6061-AA7075 laser brazing with prefixed ER5356 filler

Laser brazing uses a filler metal for joining without melting the base material. This process is a versatile joining technique for a wide range of applications including automotive, aerospace, and medical field because of the ability in joining dissimilar metal and resulted good quality in surface's joint. This study consists of aluminium alloy of AA6061 and AA7075 as a base material with aluminium based ER5356 as a wire filler. Laser brazing was performed using 1.2 kW of laser power, while wire filler was let to be prefixed without using the wire feeder because of using the existing laser welding machine. Microstructure of the joints were studied using 3D measuring laser microscope OLS5000. Besides that, mechanical properties of the joints were evaluated by performing tensile test and hardness test. Microstructures of the brazed joints show the differences in the grain structure followed by the difference's hardness value on each region. The brazed joint shows the average ultimate tensile strength reached 154.71 MPa which was 50% of joint efficiency. However, there is porosities at the fracture surface of the joint

Effect of filler composition on microstructure and mechanical properties of MIG welded AA6061 and AA7075

Nowadays, aluminium alloy is hugely applied in the automotive and aircraft sector due to its lightweight and considerable hardness. For joining aluminium alloys, fusion welding methods are widely used due to its low cost. Apart from that, Metal Inert Gas (MIG) was generally applied by welders. Be that as it may, different filler compositions utilised in MIG welding dissimilar aluminum alloy can create a different microstructure, and defect happens during welding and influencing joint microstructure, and mechanical properties. The aim of this study is to identify the weldability, study the mechanical properties and investigate the effect of alloy element on microstructure of joining aluminium alloy AA6061 and AA7075. In order to achieve comparable welded quality and appearance, the welding parameters used for all setup must be the same. Four different types of filler metal were used, which were ER4043, ER4047, ER5183 and ER5356. For Vickers hardness and tensile test, a few samples from the welded specimens will be cut by using EDM wire cut machine, following the ASTM-E8 standard. The microstructure will be analysed using the same sample used for the hardness test. Meanwhile, for tensile test result, the ultimate tensile strength (UTS) of filler ER4047 with 13% silicon is the highest, 170.2 MPa, followed by filler ER5356 with 5% magnesium, 161.8 MPa, slightly decreased by filler ER4043 with 6% silicon and ER5183 with 4% magnesium are 159.78 and 159.6 MPa. All samples are fracture at AA6061 side for the hardness test. Base metal (BM) AA6061 gives a lower value than the heat affected zone (HAZ) and fusion (FZ) of both materials. The variations in the grain structure are seen by the microstructures of welded joints. By visual inspection, the defects presented in the welded joint were detected from its macrostructure

A study on double fillet lap welding of thin sheet AZ31B magnesium alloy by low power fiber laser

This thesis presents a study on laser welding of thin sheet AZ31B Magnesium (Mg) alloys using low power fiber laser. AZ31B is known as the lighter metal compared to aluminium alloys and steel with the density of 1.78 g/cm3. Thin sheet AZ31B finds its application in automotive, aviation and also electronic devices parts such as computer casing and thin plate part in smartphone. In joining thin sheet AZ31B, laser welding is promising the best joining method compared to arc and solid state welding in producing small weldments. A low power fiber laser welding has been chosen in this research work and the welding parameters are optimized by response surface method (RSM) using Box-Behnken design (BBD) method in order to provide the most suitable laser welding condition to weld this thin AZ31B. Welding as thin as 0.6 mm of AZ31B, laser welding by double fillet lap joint configuration is selected as it can produce lower heat input with high power due to the weld geometry of fillet lap joint which beam focused at the edge of upper sheet. It was preferred since the usage of laser was overwhelming especially in manufacturing industries. The first objective ofthis work is to optimize the laser welding parameters to weld double fillet lap joint on AZ31B. The second objective is to investigate the relation of microstructure changes on mechanical properties of this joint. According to design of experiment (DOE) generated by BBD, 15 samples are welded and their strength were tested using tensile-shear test. From the response, a mathematical model is constructed after the analysis of variance (ANOV A) has been performed. To discuss the relationship between the shear strength and microstructure, welded samples are cut at the stable weld's cross section and are prepared for the macro and microstructure observation. Sample 9 possesses the highest shear strength with 62.0 MPa and fracture load of 740 N. A mathematical model with quadratic equation was produced to calculate the tensile shear strength. For validation of mathematical model, percentage errors for all samples are less than 8 %. It shows a high accuracy of the model and it was accepted. Welding parameters then proceed to be optimized. The optimized parameters were; pulsed energy (EP): 2.2 J; welding speed (WS): 2.0 mm/s; and angle of irradiation (AOI): 2.0 °. The percentage error for the optimized sample was 0.79 %. Vickers hardness test was performed at the weld area for sample with highest and optimized parameter sample in order to compare the result. It was observed that most of the welded samples have the solidification crack at the weld centre area of the second weld and this defect contributed to the lower tensile shear strength as observed from macrograph. For microstructure, finer grain produced at the fusion zone (FZ) of upper sheet compared to the FZ near the transition line which produced coarser and medium grain. Optimized sample was fractured at the transition region of upper sheet, meanwhile sample 1 fractured at the weld due to the crack defect. It was observed that the fracture was brittle. The fine grain produced higher hardness values compared to the coarser grain with a value of 77 Hv for the optimized sample. Optimized sample has 80.5 MPa of tensile shear strength and fracture load of 800 N which could be applied in replacing AI and steel especially for the electronic parts since the strength was acceptable for a thin product

The Mechanical and Microstructural Study of Welded AA7075 Using Different Filler Metals

This paper discussed about the consequences of using different filer metal by metal inert gas (MIG) welding process on aluminium alloys Al 7075 sheet metal joint. Nowadays, Al 7075 is widely used in automobile and aviation industry due to its light weight, strong, and high hardness. Fusion welding, such as MIG and TIG were commonly used in joining the aluminium alloys due to its low cost. However, defects usually occurred using fusion welding because of the inaccurate welding parameters and types of filer metal used. The purpose of this study is to determine whether the filer metal with different elements and welding parameters affect the mechanical properties of welded Al 7075. Welding parameters used were current, voltage, welding speed, and Argon (Ar) as shielding gas. Two different types of filer metal were used which is Electrode Rod (ER) 4043 and ER5356 which is from Al-Si and Al-Mg based element, respectively. From microstructure analysis, fusion zone (FZ) of sample welded with ER4043 has a smaller grain size than that of with ER5356. Both filer produced equiaxed dendritic grain at FZ. Both samples welded with ER4043 and ER5356 has lower hardness value than heat affected zone (HAZ) and base metal(BM) due to the differences in their elements where ER4043 from Al-Si and ER5356 from Al-Mg group. The weld effiiency of sample welded using ER5356 was 61% which was higher compared to sample welded using ER4043 which at 43% and both sample was brittle fractured. Sample welded with ER5356 was fractured at HAZ due to porosity while sample welded with ER4043 fractured at FZ due to the oxide inclusion

The effect of laser surface hardening on surface hardness of mild steel

Laser surface hardening (LSH) has become the most vital process to increase the hardness of a mild steel surface, especially to overcome the wear issues in machining parts, where mild steel was hugely applied due to its advantages such as less air pollution, low cost of maintenance and easy to handle compare to other conventional surface hardening process. The laser surface hardening of mild steel has been performed using fiber laser machine which is having a maximum peak power of 30 watts, with 1060 nm of a wavelength above the surface of mild steel having the dimension of 15 × 15 × 6 mm. The Vickers hardness test on the laser hardened surface of this metal was measured with a load of 0.5 kgf and 10 seconds dwell time for ten indention points, randomly. It was found that the highest average microhardness value was 281.72 HV on the surface of sample hardened by a laser power of 21 Watt and 40 mm/s scanning speed. Across the cross-section area, the affected hardened depth was measured at 19 ± 2.5 µm from the surface. At this region, fine martensitic grain structure was observed which contributes to the higher microhardness value. Higher laser power produced higher surface hardness, meanwhile higher scanning speed lead to lower surface hardness

Effect of Fiber Laser Parameters on Laser Welded AZ31B Magnesium Alloys

Recently, the usage of Magnesium (Mg) alloys has been hugely applied in the industrial application such as in automotive, marine, and electronic due to its advantages of recyclability and lightweight. This alloys required low heat input to be weld since it is easily evaporated due to the Magnesium Oxide (MgO) at the surface and it also possesses lower melting point compared to steel. Laser welding is more convenient to weld Mg alloys due to its high power and lower heat input. AZ31B was selected since it has strong mechanical properties among others Mg alloys due to the major alloying elements; Aluminium (Al) and Zinc (Zn). Low power fiber laser machine with wavelength of 900 nm was used in this experiment. The intention of this work was to investigate the effect of low power fiber laser parameters and effect of shielding gas on weld penetration and microstructure. Another aim in this work was to produce the joint for this thin sheets metal. Penetration depth and microstructure evaluation were emphasized in the analysis section. Bead-on-Plate (BOP) and laser lap welding was conducted on AZ31B with thicknesses of 1.0mm and 0.6 mm for feasibility study using pulsed wave (PW) mode. Defocusing features was used in order to find better focal position, which has less occurrence of evaporation (underfill). The effect of different angle of irradiation was also investigated. Two types of shielding gases, Argon (Ar) and Nitrogen (N2) were used in order to study the effect of shielding gas. Lastly, the effect of pulsed energy on penetration types and depth of BOP welded samples was investigated. Focus point was found at focal length of 156 mm with 393.75 µm. For BOP experiment, higher pulsed energy used contributes to melt through defect. Meanwhile, Ns shielding gas proved to be better shielding gas in laser welding the AZ31B. Higher angle of irradiation could reduce the underfill defect. Fillet Lap joint of similar metal was successfully done where 2.0 J of pulsed energy reveals better weld joint compared to 2.4 J

A Study on Bead-on-Plate Welding of AA7075 using Low Power Fiber Laser

Laser welding promises the best method to produce higher strength of aluminium joints compared to conventional arc welding process. Arc welding usually produces a large heat affected zone (HAZ), which leads to lower joint strength on aluminium alloys. AA7075 aluminium alloy has many advantages due to its light weight, low density, high corrosion resistance, and high alloy strength as compared to steel. This paper presents a weld feasibility studies on AA7075 surface using low power fiber laser with two different modes; continuous wave (CW) and pulse wave (PW) modes. The intention of this research work is to investigate the effect of laser welding modes with different focal position on penetration depth, type of weld penetration, and microstructure of bead on plate welded AA 7075 using low power fiber laser. The bead-on-plate (BOP) welding was carried out by heating the surface of AA7075 with a thickness of 2 mm using both CW and PW modes with focal lengths that ranged from 60 to 200 mm. 90 % power was used for both welding modes with the same welding speed, 2 mm/s. The macrostructure of the welded line was captured using an optical microscope, and the beam width and penetration were measured. The smallest bead was observed at 120 mm focal length with 570 µm diameter. Pulse wave (PW) welding with keyhole profile produced optimum penetration depth, which was approximately 1.0 mm. However, continuous mode (CW) welding produced 0.153 mm penetration depth. To conclude, AA 7075 could be joined using the low power fiber laser welding method since the half weld penetration with keyhole profile was produced. For better welding joint with fewer defects, shielding gas and incident angle of laser beam could be applie