Ceramic Backing Research Articles

Research on the Influence of HMFI and PWHT Treatments on the Properties and Stress States of MAG-Welded S690QL Steel Joints.

The aim of this study was to analyze the effect of the HFMI (high-frequency mechanical impact) treatment of each weld bead on the properties of a butt joint with a ceramic backing welded by robotic method 135 (MAG-metal active gas welding method) and to determine the effect of HMFI on the stress level. This analysis was based on a comparison of three butt joints made of a S690QL plate, in the as-welded condition, with the HFMI of each bead and with the heat treatment carried out with PWHT stress relief annealing. The high-frequency (90 Hz) peening of each weld bead was linked with a stress reduction in the weld via the implementation of compressive stresses into the joint. The HFMI pneumatic hammer was used for this. The correctness of treatment was achieved when 100% of the surface of each bead including the face was treated. As part of the post-welding tests, basic tests were carried out based on the standards for the qualification of welding technology, and as a supplementary test, a stress state analysis using the Barkhausen effect was carried out. The tests carried out showed that the use of high-frequency peening after each pass did not affect the negative results of all the required tests when qualifying the welding technology of S690QL sheet metal compared to the test plates in the as-welded condition and after heat treatment-stress relief annealing. Inter-pass peening of the welded face and HAZ (heat-affected zone) resulted in a reduction in post-weld residual stresses at a distance of 12 mm from the joint axis compared to the stress measurement result for the sample in the as-welded condition. This allowed for a positive assessment of peening in the context of reducing the notch, which is the concentration of tensile stresses in the area of the fusion line and HAZ. The tests carried out showed that the peening process does not reduce the strength properties of welded joints, and the results obtained allow the technology to be qualified based on applicable standards.

Effect of Using Ceramic Backing Media on SMAW Welding on Value Reduction of Area on ASTM A36 Steel

ASTM A36 steel is a low-carbon steel often used as a general manufacturing material. Tensile testing is one of the most important and dominant mechanical properties in construction design and manufacturing. Each material or material has different properties (hardness, flexibility, etc.). A test is needed to determine a material's mechanical properties. One of the most frequently performed tests is the tensile test. This test has a function to determine the level of strength of a material and to identify the characteristics of the material. Therefore, this study aims to determine the effect of using ceramic backing media in SMAW welding on the value of area reduction in ASTM A36 steel. Based on the test results, the value of the area reduction varies in each specimen. The specimens that did not use ceramic backing had an average area reduction value of 53.51%, while the variation using ceramic backing had an average area reduction value of 61.17%.

Impact of Electrode Rotation on Aluminum GMAW Bead Shape

Aluminum gas metal arc welding (GMAW) uses inert shielding gas to minimize weld pool oxidation and reduce susceptibility to porosity and incomplete fusion defects. For aluminum shipbuilding, naval welding requirements highly recommend the use of helium-argon mixtures or pure helium shielding gas to provide a broader heat field and better weld toe fusion. Pure argon shielding gas can be used but has been susceptible to incomplete fusion and porosity defects, where argon’s lower thermal conductivity promotes a narrower arc heat field and shallow weld fusion depth. Using helium is a concern because it is a finite resource that costs approximately five times more than argon. The rotating electrode pulsed GMAW process was investigated to improve argon shielding fusion characteristics and reduce helium usage. Argon-shielded bead-on-plate tests were used to evaluate the relationship between ER5183 electrode rotation parameters and arc power on constant deposit area bead shape. These tests were compared to stringer beads (no oscillation) that were made with argon, helium, and helium-argon shielding gases. Electrode rotation improved underbead fusion depth width and toe fusion. With preferred rotation parameters, the bead width and incomplete fusion at weld toes were equivalent to helium-based welds. For weld reinforcement, electrode rotation promoted a nonsymmetric profile with deposit bias on the bead side, where rotation direction was aligned with travel direction. The bead-side deposit bias is an advantage based on preliminary horizontal V-groove welding procedures using ceramic backing. Electrode rotation can offset the effects of gravity, promoting a smoother bead and fusion profile.

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

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.

Autogenous Fiber Laser Welding of 316L Austenitic and 2304 Lean Duplex Stainless Steels.

This study presents results of experimental tests on quality of dissimilar welded joints between 316L austenitic and 2304 lean duplex stainless steels, welded without ceramic backing. Fiber laser welded butt joints at a thickness of 8 mm were subjected to non-destructive testing (visual and penetrant), destructive testing (static tensile test, bending test, and microhardness measurements) and structure observations (macro- and microscopic examinations, SEM, element distribution characteristics, and ferrite content measurements). Non-destructive tests and metallographic examinations showed that the welded joints meet the acceptance criteria for B level in accordance with EN ISO 13919–1 standard. Also the results of the destructive tests confirmed the high quality of the joints: specimens were fractured in base material with lower strength—316L austenitic stainless steel and a 180° bending angle was obtained confirming the high plasticity of the joints. Microscopic examination, SEM and EDS analysis showed the distribution of alloying elements in joints. The microhardness of the autogenous weld metal was higher by about 20 HV0.2 than that of the lean duplex steel. Ferrite content in the root was about 37% higher than in the face of the weld. The Schaeffler phase diagram was used to predict the phase composition of the welded joints and sufficient compliance with the magnetic method was found. The presented procedure can be used for welding of 316L–2304 stainless steels dissimilar welded joints of 8 mm thickness without ceramic backing.

Investigation of composite sandwich plates for ballistic armor application

Bullet proof vests or armours are the protective devices used to protect the individual from bullets or high speed projectiles. A variety of such vests is available currently and they offer bullet resistant for a particular level or grade of threat. The material used to produce the bullet proof armour offers protection. The requisite properties and various strength levels are obtained by different types of materials that can be used to for production. In addition to the contribution of the material in imparting strength, the quantity of material used also is an important factor for strength. Vests with least weight and thickness form the current trend in the market. The main focus of this research work was to develop bullet proof armour using a sandwich of epoxy composite and a ceramic backing material. When a bullet fired from handgun strikes the bullet proof armour, it is caught in a “web” of very strong reinforcing fibers. The impact energy transmitted to the bullet proof vest from the bullet causing the deformation of the bulle is absorbed and dispersed by these fibers. Most anti-ballistic materials, like bullet proof vests are made of Kevlar fibers, Twaron fibres, Dyneema fibres etc. in multiple layers. Kevlar fibers are used in the presented work. The effectiveness of the panels would be determined by ballistic testing for penetration.

Reduction in through put time of drum shell manufacturing by single-V welding configuration

The present work highlights the outcomes of the case study that investigate the reduction in through put time of drum shell manufacturing, which earlier employed a double-V butt welding configuration for joining the ends of the plates after rolling the plates into cylindrical form, while the proposed method makes use of single-V type configuration to fabricate the drum shells with ceramic backing strip arrangement. The proposed work eliminates some redundant operations like inside welding, back grinding and other side edge preparations thereby reducing the production time of drum shell manufacturing. 38% improvement in production rate of drum shells was observed by proposed method compared to the earlier method.

Effect of submerged arc welding process with one-side one-pass welding technique on distortion behavior of shipbuilding steel plate ASTM A131 grade A

Distortion induced by welding process is one of the major problems found in shipbuilding industries. Significant loss in time and cost to correct and repair this welding defect occurs whenever the distortion value exceeds the shipbuilding standard limitation. In addition, there is also a challenge to replace the common two-side welding with gouging technique currently used in Thai shipyards by the one-side one-pass welding technique to save time and cost during welding, flipping, and gouging steps. In this research, distortion and peak temperature during the one-side one-pass submerged arc welding of ASTM A131 Grade A steel plates were investigated by varying the effects of heat input levels (27 kJ/cm and 32 kJ/cm), joint design configurations (square butt joint and single 30° V-groove), and constraints (with and without fixtures). To prevent molten burn-through during welding with higher heat input, a ceramic backing was attached at the weld root. Based on the results, distortion varies with different joint types, heat input, and constraint conditions. The maximum distortion of 2.99 mm was found in the specimen welded with 32 kJ/cm and 30° V-groove without constraint. The proposed one-side one-pass welding technique using ceramic backing passes the distortion limitation enforced by the international shipbuilding standard, while improving the productivity for hull fabrication.

Numerical analysis on temperature field in single-wire flux-aided backing-submerged arc welding

Single-wire flux-aided backing-submerged arc welding (FAB-SAW) technology has been widely used to weld thick steel plate due to its easy assembly and high heat input. The microstructure and property of welded joint are closely related to the thermal field of FAB-SAW process. In this research, the feature of thermal field for single-wire FAB-SAW was investigated. Based on the heat transfer mechanism, a three-dimensional transient model for thermal field was developed based on the influence of steel thickness, groove angle and ceramic backing. The temperature profile in single-wire FAB-SAW of D36 steel under different welding conditions was simulated by ANSYS. The characteristic of thermal field was analyzed and the influences of groove angle on temperature field for different plate thicknesses were discussed. The calculated geometries and dimensions of weld cross-section under different conditions show a good agreement with the experimental results. This newly built model can describe the thermal field accurately, which would be helpful to understanding the thermophysical mechanism of FAB-SAW and optimizing the welding process.

Development of ceramic backing for friction stir welding and processing

Usually, a workpiece is deformed during friction stir welding due to high applied loads. Consequently, fully and consolidated friction stir-welded joints as well as tool life time can be affected promoting unscheduled manufacturing stops, which favour decreasing the welding productivity. Furthermore, the workforce is dislocated to not predicted maintenance steps. This work proposes the development of a special ceramic backing to joining and processing material using FSW technologies. Four ceramic deposits were tested over a steel plate, which allowed selecting those with less porosity and, thus, better strength. This backing allowed us to obtain full penetration welds for duplex stainless steels, to high forces during engagement for high-strength low-alloy steels and to obtain consolidated aluminium–steel dissimilar joints. For the last one, there was not adherence of the soft material in the workpiece. In addition, the ceramic backing allowed us to confine the heat and plasticized metal, as well as develop established welding parameters.

Application of ceramic backing for singleside welding of 'V' welded joints

Zavarivanje jednostrano na suceonom V spoju uz pomoc keramike na brodskoj konstrukciji je moguce. Ovim postupkom dobija se na efikasnosti, kao i humanizaciji rada zavarivaca u zatvorenom prostoru Kao efikasna, ova tehnika zavarivanja može se vrlo siroko primenjivati u nasoj zavarivackoj praksi. Keramicke podloske su posebno podesne za zavarivanje u otežanim uslovima rada. Stoga je potrebno upoznati specificnosti njihove primene radi povecanja ekonomicnosti zavarivanja. Koreni zavar postavljen je u jednostranom V spoju, koji se zavaruje na keramickoj podloski, te je na taj nacin eliminisano žljebljenje i ponovo zavarivanje u nepovoljnim uslovima. Kvalitet zavarenih spojeva u kombinaciji u potpunosti zadovoljava traženi kvalitet zavarenih spojeva u brodskoj konstrukciji.

Study on fatigue experiment for transverse butt weldsunder 2G and 3G weld positions

Although the transverse butt weld method with ceramic backing strip has been widely used in various industrial fields for its fabricational convenience, it is rarely used in offshore industries since the fatigue strength of the weld joint has not been proved sufficiently. This study conducted fatigue tests for series of butt weld specimens with horizontal (2G) and vertical (3G) welding positions in order to verify the fatigue strength compared to S-N curve by DNV (Det Norske Veritas), IIW (International Institute of Welding) and Eurocode 3. The difference of the 2G specimens and the 3G specimens are investigated in terms of angular distortion and the effect on the fatigue strength are analyzed.

Development of method to remove weld scallop and ceramic backing material of wedge type and its application

The weld scallop has been used for joining T-bars. There are a lot of weld scallops in shipbuilding. It is difficult to perform scallop welding due to the inconvenient welding position. This results in many problems such as porosity, slag inclusion, etc. In this study, a new method is devised to remove weld scallops by incorporating a Ceramic Backing Material (CBM). The weld scallop is removed by an elongation of the v groove. In order to insert a CBM into the groove without a weld scallop, a wedge-shaped CBM is developed. The top side of the developed CBM is similar to the shape of a general back bead. The bottom surface has a saw-toothed shape for cutting at a suitable length. This can be attached to the root side of a face plate using adhesive tape, just like a general CBM. Welding experiments in normal and abnormal conditions are carried out and the possibility of burn-through is examined. This CBM’s applicability to shipbuilding is verified.

High Temperature Ultrasonic Transducer for Real-time Inspection

A broadband ultrasonic transducer with a novel porous ceramic backing layer is introduced to operate at 700°C. 36° Y-cut lithium niobate (LiNbO3) single crystal was selected for the piezoelectric element. By appropriate choice of constituent materials, porosity and pore size, the acoustic impedance and attenuation of a zirconia-based backing layer were optimized. An active brazing alloy with high temperature and chemical stability was selected to bond the transducer layers together. Prototype transducers have been tested at temperatures up to 700°C. The experiments confirmed that transducer integrity was maintained.

논-스캘럽 블록 조인트 용접법 개발

Abstract A weld scallop is a small quadrant or half circle type hole installed in the weld line cross area for easy welding operation. Many types of T-bars with a scallop can be welded in a block assembly stage in shipbuilding. The difficulties arise from the fact that scallops are to be filled by build-up welding after welding of the cross line is complete. In this study, a non-scallop block joint welding method was developed using special type CBM (ceramicbacking material). The wedge shaped CBM was devised to insert a CBM into just the V groove of weld line crossarea without weld scallop. A saw-toothed shape was adopted for easy cutting of the unnecessary part in the CBMfitting process. The applicability of the developed method was verified through welding experiments based on the yardwelding conditions. Key Words : Weld scallop, Build-up welding, Block assembly stage, CBM(ceramic backing material) 이 논문은 2014학년도 동의대학교 교내연구비에 의해 연구되었음(2014AA007). * Corresponding Author : Dae-Eun Ko(Dong-Eui Univ.)Tel: +82-51-890-2594 email: deko@deu.ac.krReceived May 8, 2014 Revised June 17, 2014 Accepted September 11, 2014

Effect of Backing Plate Thermal Property on Friction Stir Welding of 25-mm-Thick AA6061

By using backing plates made out of materials with widely varying thermal diffusivity this work seeks to elucidate the effects of the root side thermal boundary condition on weld process variables and resulting joint properties. Welds were made in 25.4-mm-thick AA6061 using ceramic, titanium, steel, and aluminum as backing plate (BP) material. Welds were also made using a “composite backing plate” consisting of longitudinal narrow strip of low diffusivity material at the center and two side plates of high diffusivity aluminum. Stir zone temperature during the welding was measured using two thermocouples spot welded at the core of the probe: one at the midplane height and another near the tip of the probe corresponding to the root of the weld. Steady state midplane probe temperatures for all the BPs used were found to be very similar. Near root peak temperature, however, varied significantly among weld made with different BPs all other things being equal. Whereas the near root and midplane temperature were the same in the case of ceramic backing plate, the root peak temperature was 318 K (45 °C) less than the midplane temperature in the case of aluminum BP. The trends of nugget hardness and grain size in through thickness direction were in agreement with the measured probe temperatures. Hardness and tensile test results show that the use of composite BP results in stronger joint compared to monolithic steel BP.

One-sided welding with cordierite ceramic backing

This paper presents an evaluation of welded joints using ceramic backing produced in the laboratory. The one-sided welding technique was used to weld A-36 steel plate with 6.4 and 15.8 mm thicknesses by employing the GMAW process. With the 6.4 mm steel plate, only the root bead welded over the ceramic backing was evaluated. With the 15.8 mm steel plate, a multipass welded joint was made. After welding, the welded joints were submitted to visual inspection, dye penetrant, macrograph, Vickers microhardness, optical microscopy, bending and tensile testing and chemical analysis using non-destructive test. The results show that the root pass made over the ceramic backing presented adequate shape, free from discontinuities, with adequate penetration in the edges of the groove and adequate reinforcement. With regard to the welded joint, the microstructure of the fusion zone presented predominance of primary ferrite, consisting of grain boundary ferrite and polygonal ferrite, and ferrite with an aligned second phase. The Vickers microhardness obtained mean values below 180 VH both in the heat affected zone and the fusion zone. Bending tests did not show discontinuities greater than 3 mm and in the tensile tests, the rupture occurred in the base metal, indicating that the welding procedure was adequate. The chemical composition of the inclusions both in the root pass and in the last weld bead have the same constituents, despite different proportions, indicating that there was no contamination of the ceramic backing material into the weld bead.

On the Design of Bi-Layer Armor Materials

A modified Florence model to predict ballistic limit velocity (BLV) for bi-layer armor systems comprising ceramic front and metallic backing plate is proposed based on energy conservation. Maximization of the BLV for a given AD or TT is studied. Comparison between the maximum BLV obtained from new model, two other available models in the literature and experiments is performed. It is shown that the new model, Energy model compares well to the experimental data. Keywords: Impact; perforation; optimization; bi-layer armor system

Study of formulations and the manufacturing variables of a ceramic weld backing

This paper presents a methodology for the in-lab manufacturing of a ceramic backing for the one-sided steel welds. Formulations were prepared using cordierite, bauxite, and magnesite as refractory minerals. Bentonite and sodium silicate were used as additives for the ceramic blend. The manufacturing process included dry mixture, compressing, drying, and sintering of the specimens. The weld backings were characterized by X-ray diffraction, optical microscopy of the surface, water absorption, and flexible voltage. They were also submitted to the welding of the root pass with the MIG–MAG process. The results show that the conventional ceramic manufacturing process is adequate for the production of the ceramic weld backing. Among the tested formulations, cordierite showed better integrity both during its manufacturing and during the welding operation, producing well-shaped weld beads, free from discontinuities. Manufacturing variables were evaluated such as compacting pressure, sintering temperature, and the amount of water added to the ceramic mass.

Preparation and characterisation of ceramic-faced metal–ceramic interpenetrating composites for impact applications

This article accesses the impact performance of ceramic-faced, metal–ceramic interpenetrating composites (IPCs) produced in situ from infiltrating ceramic foams with a molten aluminium–magnesium alloy. The approach had two variations, viz., the production of a metal bond between a ceramic front face and backing IPC and the creation of a ceramic bond. The impact performance of metal-bonded IPCs was evaluated using both split Hopkinson’s pressure bar (SHPB) and depth of penetration (DoP) techniques. With a 4-mm thick Al2O3 front face and an 8-mm thick IPC backing, the DoP was zero. In one case, a sample survived fundamentally intact with only spall damage to the dense Al2O3 front face. The resulting damage was thoroughly assessed using a range of techniques, including polarized light microscopy, scanning electron microscopy (SEM), 3D MicroCT and transmission electron microscopy (TEM). The metal phase deformed as a result of the formation of large numbers of dislocations, whilst the ceramic phase accommodated the deformation via localised cracking. Metal bridges across the cracks formed, increasing the damage tolerance of the IPCs. The metal bond between the ceramic front face and the IPC was also observed to withstand the impact of the armour piercing rounds without any sign of debonding occurring.