A Novel Ceramic Backing Strip from Metakaolin-Based Geopolymer with Gas Flow Holes for Welding Application

2020 ◽  
Vol 856 ◽  
pp. 309-316
Author(s):  
Songphop Plaichum ◽  
Attaphon Kaewvilai ◽  
Thammaros Pantongsuk ◽  
Duangrudee Chaysuwan ◽  
Chayanee Tippayasam

This research is firstly presented the thermal resistance of a ceramic backing made from metakaolin-based geopolymer for stainless steel welding. The general problems such as lack of fusion, hydrogen inclusion, porosity and corrosions of stainless steel welded specimens were found because, largely, stainless steel presents an affinity to gases as oxidation. Therefore, during welding, if these gases do not escape from the weld pool before solidification of weld metal, it results in porosities or hydrogen inclusions. In this case, it can be solved by properly using inert gas backing. The welder usually uses the steel backing plate with a gas release hole to support weld root and gas transmission for completed weld penetration and superior weld quality. Since the geopolymer shows a good property of thermal resistance, researchers are interested in using the ceramic backing made from geopolymer instead of the commercial ceramic backing. The ceramic backings from the geopolymer were designed merely in 3 types as follows: Narrow curved groove without gas release hole, narrow curved groove with gas release holes and wide curved groove with gas release holes. Consequently, two pieces of stainless steel were welded by gas tungsten arc welding and then the weld quality such as defects, porosity and root penetration of welded specimens was inspected. Moreover, the surface failure of ceramic backing after the welding process was also considered. The results revealed that ceramic backing from a geopolymer with wide curved groove and gas release holes gave completed penetration at the root when inspecting with non-destructive testing such as visual test, penetration test, and radiography test. It was concluded that the geopolymer could be used as ceramic backing in stainless steel welding by gas tungsten arc welding. Moreover, it could be used as backing for aluminum and steel welding as well.

2017 ◽  
Vol 50 (43) ◽  
pp. 43LT03 ◽  
Author(s):  
Hunkwan Park ◽  
Marcus Trautmann ◽  
Keigo Tanaka ◽  
Manabu Tanaka ◽  
Anthony B Murphy

Author(s):  
R Rajasekaran ◽  
AK Lakshminarayanan ◽  
M Vasudevan ◽  
P Vasantharaja

Nuclear grade 316LN austenitic stainless steel weld joints were fabricated using conventional gas tungsten arc welding (GTAW), activated flux gas tungsten arc welding (AGTAW), laser beam welding (LBW) and friction stir welding (FSW) processes. Assessment of weld beads was done by mechanical and metallurgical characterizations. Bead geometry and weld zones were studied by taking macrographs along the transverse side of the weld joints. Metallurgical features of different weld joints were carried out using optical microscopy and scanning electron microscopy. Microhardness distribution across four weld joints was recorded and hardness variations were compared. All weld zone, heat affected zone (HAZ) of GTAW and LBW, thermo-mechanically affected zone (TMAZ) of FSW processes, exhibited higher hardness values than the base metal. Reduced hardness was recorded at HAZ of AGTAW process. This was the result of a considerable grain growth. LBW joint showed the highest hardness value at the center of the fusion zone due to fine equiaxed dendrite morphology. Tensile and impact properties of different welding processes were evaluated and comparisons were made at room temperature. All weld samples displayed high yield strength (YS) and ultimate tensile strength (UTS) with a lower percentage of elongation compared to that of the base metal. FSW joint showed improved YS, UTS and impact toughness compared to other weld joints. This is attributed to the formation of strain-free fine equiaxed grains at stir zone around 5 µm in size with subgrains of 2 µm in size by severe dynamic recrystallization mechanism. Among the fusion welding techniques, AGTAW process exhibited improved toughness, besides almost equal toughness of the base metal due to low δ-Ferrite with high austenite content. Fractography studies of the base metal and different weld samples were carried out by SEM analysis and features were compared.


2011 ◽  
Vol 189-193 ◽  
pp. 3579-3582
Author(s):  
Jian Hao ◽  
Zhen Luo ◽  
Xian Zheng Bu ◽  
Jian Wu Zhang

In order to investigate the effect of active fluxes on weld penetration, angular distortion and weld morphology in gas tungsten arc welding (GTAW), three types of oxide fluxes-CaO, TiO2and Al2O3-were used in the welding of 5mm think stainless steel plates. Those powders were applied through a thin layer of the flux to produce a bead on plate welds. The results showed that compared with conventional TIG welding, increased weld penetration and reduced angular distortion of the weld piece were obtained with the application of active fluxes. However, the weld morphology was not changed significantly when the powders were coated on the surface of steel. It was also found that each of the powders has a fittest range in penetration increment. Whether the rate of the coating run out of the range, the effects of these active fluxes on the increased weld penetration were not obvious. The CaO flux has a narrow effective range for deep penetration, while the Al2O3powder does have no effect on A-TIG penetration. The mechanism of those different performances has not been found out. According to the investment, the mechanism of active fluxes for the increased weld penetration and reduced angular distortion is related to the contraction of the arc.


Sign in / Sign up

Export Citation Format

Share Document