Author Details

P460NH steels are extensively used in steel plants as ladle fabrication material. However, fusion welding of these steels leads to the problems such as cold cracking, residual stress, distortion and fatigue damage, these steels may require welding of the cracks that can develop during fabrication, handling and transportation stages, or during the service life of the plant. Present work explains repair welding procedure used for P460NH steel ladles welded by using shielded metal arc (SMA) welding and flux cored arc (FCW) welding processes and evaluation of its weld metal and heat affected area (HAZ) microstructure. Butter bead tempered bead technique followed to fill the joint groove and simulated repair welding of SMA and FCA welds was carried out at the weld/base metal interface, i.e. at the location at which cracks are usually reported to occur during fabrication. SMA repair welding procedure conforming to the ASME Boiler and pressure Vessel Code were used followed by post heating of welds at 300°C for 2 hours per 25mm thickness of the weld. Tensile properties, bend tests, hardness profiles, impact tests and metallography studies using scanning electron microscope (SEM) were determined for both SMA and FCA welds to evaluate simulated repair welds. Analysis of the test results showed that the cooling rate maintained by means of preheating, interpass and post heating plays an important role in repairing of P460NH steel weld cracks.

Keywords

Repair Welding, Ladles, Welding Procedure, P460NH Grade Steel, Microstructure.

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References

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A Comparative Study on Fatigue Performance of DP590 and DP780 Spot Welded and Weld Bonded Steel Sheets

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Authors

P. Banerjee ¹, T. K. Pal ¹, M. Shome ²

Affiliations
1 Welding Technology Centre, Metallurgical & Material Engineering Department, Jadavpur University, Kolkata - 700032, IN
2 Material Characterization and Joining, R & D, Tata Steel Ltd., Jamshedpur - 831001, IN

Source

Indian Welding Journal, Vol 46, No 4 (2013), Pagination: 45-58

Abstract

The automotive companies are quickly changing their material bill from low strength formable grades to advanced high strength steels (AHSS) in response to the global call for preserving a green environment and enhanced passenger safety. As compared to low carbon formable steels, the AHSS steels are relatively difficult to weld by the traditional processes and the joint performance is below expected levels. Thereby conventional manufacturing processes are being challenged, and new processes with improved service performance are being increasingly explored. Fatigue performance of material joints is a key design input and indicator of the performance of automobiles during service, particularly for AHSS. In this paper, primary joining process such as spot welding and emerging hybrid joining process such as weld-bonding were carried out on two commercially available AHS dual phase (DP590, DP780) automotive steels. Two dimensional spot welding lobes were developed for each of the steels following nugget diameter criteria of 4 √t to 5.5 √t, where t is the thickness of the sheets. By selecting two sets of parameters from the lobes, spot welding was carried out on shear-tension sheet samples with an AC type resistance spot welding machine. Weld-bonding was done by applying a thin layer of high strength epoxy based structural adhesive followed by spot welding on two overlapping sheet samples. Static shear tensile and fatigue properties under tension-tension mode for all the spot welded and weld-bonded joints of DP590 and DP780 steels were evaluated and compared.

Keywords

Weldability Lobe, DP Steels, Weld Bonding, Shear Tensile Strength, High Cycle Fatigue Performance.

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