Part Of Base Metal Research Articles

CRITICAL ANALYSIS OF MATERIAL BEHAVIOUR IN WELDED PLATES OF AISI 0.2%-C STEEL UNDER AS-WELDED, QUENCHED AND ANNEALED CONDITIONS

AISI 1020 grade of steel is well known for its good combination of high strength and fair ductility. Therefore, it is widely demanded in construction sectors. It possesses a good weldability too in both arc and gas welding conditions. In the present work four pairs of AISI 1020-0.2%C steel plates were welded by shielded arc welding method. Except one welded plate, other three were heat treated. Based on the heat treating, three different physical conditions were achieved- water quenched, oil quenched and annealed. All the samples were tested for tensile strength, hardness, and microstructure. The annealed specimen has showed a significantly improved tensile strength of 439 MPa which is 85% higher than as-welded specimen. Water and oil quenched specimens showed lesser strength than that of as-welded specimen. With regard to hardness, there were two different observations. The as-welded and annealed specimens indicated the highest hardness at welded joint whereas the lower values were reported in base metal part. In contrary, the water and oil quenched specimens were harder in base metal zone as compared to welded zone. Both, strength, and hardness were found in good correlation with microstructural appearance of the plates.

Microstructure, mechanical properties and fatigue behaviors of linear friction welded weathering steels

The weathering steels SMA490AW and SPA-H with a high phosphorus content were successfully joined by linear friction welding (LFW) without welding defects and heat affected zone (HAZ) softening. The residual stress of the welded joints was measured by X-ray diffraction (XRD) after the welding. The microstructure characteristics were observed using a scanning electron microscope (SEM) and analyzed corresponding to the microhardness distribution in different regions. The mechanical properties and fatigue behaviors were assessed using the digital image correlation (DIC). The results suggest that the bainites were crystallized in the weld center zone (WCZ), and the area fraction of bainites was obviously decreased at a small distance from the WCZ, which illustrated a large welding temperature gradient. The ductile fracture of LFW joints occurred at the base metal part of the specimens, resulting in a joint efficiency close to 100%. The fatigue strength of LFW joints was close to that of base metals and the proposed S-N curves showed a much higher fatigue strength compared to the design curve FAT112.

Estimation of Arc Welding Pressure Pipeline Weld Peaking Parameters Based on Data Prediction

Peaking parameter is the key content in the regular inspection of the pressure pipeline. Solving the problem of the peaking measurement method defined by a standard cannot be applied to a situation in which there exists a weld surface with reinforcement and misalignment. In this paper, a peaking estimation method based on data prediction was proposed to estimate the contour information of the base metal at the weld joint using the contour point set data of the base metal part of the weld. Herein, the longitudinal weld peaking estimation method based on a piecewise logistic regression (PLR) and the girth weld peaking estimation method based on a piecewise Bayesian linear regression (PBLR) were studied, and the midpoint of the two symmetrical points of the base metal on either side of the weld was used as a reference for calculating the peaking. Finally, we collected the surface profile data of longitudinal weld pressure pipes with diameters of 155 mm, 255 mm, 550 mm, and 600 mm and the surface profile data of girth weld pressure pipes with diameters of 120 mm, 130 mm, 140 mm, and 170 mm. This weld seam data used the data estimation method proposed in this article and traditional long short-term memory and fitting methods. The results showed that the proposed data prediction method could accurately predict the position of the base metal, and the theoretical mean absolute error of the peaking estimation based on the PBLR and PLR could attain 0.06 mm and 0.07 mm, respectively, which meets the parameter measurement requirements of related verification fields.

Effect of weld line direction and paint orientation on corrosion and paint deterioration characteristics of welded part of steel

ABSTRACTOne thousand two hundred cycles of accelerated exposure experiment with combined salt water spray simulating atmospheric corrosion was performed for investigating the effect of weld line direction and paint orientation on the corrosion and paint deterioration characteristics of welded part of the steel. The corrosion depth of the weld toe of transverse weld line became 1.35 times as large as that of the base metal part because of the remained salt water on the weld toe. The coating thickness at the weld toe became thin by vertically painting on the transverse weld line. When the scribe line was installed at the thin painted weld toe under the transverse weld line, the paint blister area became 15% larger than that of the base metal part. The paint coating thickness at the weld toe in different weld line directions and paint orientations should be confirmed and ensured from the viewpoints of manufacturing and maintaining steel structures.

Microstructure, Composition, and Impact Toughness Across the Fusion Line of High-Strength Bainitic Steel Weldments

This paper analyzed the evolution of microstructure, composition, and impact toughness across the fusion line of high-strength bainitic steel weldments with different heat inputs. The main purpose was to develop a convenient method to evaluate the HAZ toughness quickly. The compositions of HAZ were insensitive to higher contents of alloy elements (e.g., Ni, Mo) in the weld metal because their diffusion distance is very short into the HAZ. The weld metal contained predominantly acicular ferrite at any a heat input, whereas the main microstructures in the HAZ changed from lath martensite/bainite to upper bainite with the increasing heat input. The evolution of HAZ toughness in relation to microstructural changes can be revealed clearly combined with the impact load curve and fracture morphology, although the results of impact tests do not show an obvious change with heat input because the position of Charpy V notch contains the weld metal, HAZ as well as a part of base metal. As a result, based on the bead-on-plate welding tests, the welding parameter affecting the HAZ toughness can be evaluated rapidly.

Residual stress measurement on the butt-welded area by electronic speckle pattern interferometry

Residual stress always exists on any kind of welded area. This residual stress can cause the welded material to crack or fracture. For many years, the hole-drilling method has been widely used for measuring residual stress. However, this method is destructive. Nowadays, electronic speckle pattern interferometry (ESPI) can be used to measure residual stress with or without the hole-drilling method. ESPI is an optical nondestructive testing methods that use the speckle effect. Mechanical properties can be measured by calculation of the phase difference by the variation of temperature, pressure, or loading force. In this paper, the residual stress on the butt-welded area is measured by using ESPI with a suggested numerical calculation. Two types of specimens are prepared. Type I is made of pure base metal part and type II has a welded part at the center. These specimens are tensile tested with a material test system. At the same time, the ESPI system was applied to this test. From the results of ESPI, the elastic modulus and the residual stress around the welded area can be calculated and estimated. With this result, it is confirmed that the residual stress on the welded area can be measured with high precision by ESPI.

酸化物分散強化白金合金の摩擦攪拌接合

The FSW of an oxide dispersion strengthened platinum alloy using an Ir-based alloy tool was performed. When the welding temperature during FSW was lower than the annealing temperature, abnormal grain growth was seen in the joint after annealing. On the other hand, the microstructure of the joint after annealing maintained finer grains when the welding temperature was higher than the annealing temperature. When the finer grain was maintained, the hardness of the joint after annealing was the same as before annealing and the tensile specimens fractured at the base metal part at room temperature. However, the tensile specimens fractured at stir zone with a large deformation during the high temperature tensile test at 1500°C.

Relation between Strength and Microstructure in Friction Stir Welded Joints of A383 and A5052 Aluminum Alloys

Friction stir welding (FSW) was applied to joints of ASTM-A383 (Al- 11 %Si- 3%Cu-0.3Mg alloy) die casting and 5052 (Al- 2.5%Mg alloy) rolled sheets. A tensile specimen of FSWed A383 and 5052-0 alloys was broken in the base metal part of the latter alloy. Its tensile strength was about 195MPa, which was equal to that of 5052-0. On the other hand, a tensile specimen of FSWed A383 and 5052-H34 alloys was broken in heat affected zone (HAZ) or thermo-mechanical affected zone (TMAZ) of FSWed 5052 side. The joint showed the tensile strength of 220MPa, which was somewhat lower than the latter alloy strength, 245MPa. Vickers hardness test result showed that tensile specimens were broken at a portion of the lowest strength in the joint.