Influence of Heat Treatment on Structure and Durometric Properties of Coatings Obtained by Surfacing with CSR-04СR27NI7MO3CU2Т Cast Rods

The effect of heat treatment modes on the structure and durometric properties of coatings obtained by surfacing with CSR-04СR27NI7MO3CU2Т cast rods, is considered. It is found that the temperature of 800°С and soaking time of 5 hours are optimal to increase the deposited metal hardness. It is shown that such a phenomenon results from the formation of the austenitic structure hardened by the precipitates of the σ-phase (FeCr), chromium carbides (Cr3C2) and titanium carbides (TiC). The heat treatment modes proposed can be applied in the wear-resistant surfacing technology of chemical equipment parts.

Tensile Behaviour of Friction Stir Welded Joints of Different Aluminium Alloys

This paper investigates the outcome of base metals and their temper condition on tensile and fracture behavior of friction stir welds of various work and precipitation hardening aluminium alloys in different tempers (AA1100-O, 5052-H, AA5086-O & H25, AA2024-O & T6, and AA6061-T651). The type and temper of aluminium alloys affected the tensile, and fracture behavior of weld joints. The extent of improvement in tensile properties of welded joints increased with a decrease in hardness (i.e., from T6 or H to O) of base metals. Softening was not observed for welded joints when base metal was in an annealed temper and an opposite trend was observed for hardened tempers ‘H’ and ‘T6’. Fracture location moved towards the weld centre with the change in temper from ‘O’ to ‘H’ and ‘T6’, hardness minima were closer to base metal hardness in the first case than later. The mode of fracture was ductile for all the weld joints except AA2024-T6 and AA 6061-T651. Except for AA2024-T6 and AA 6061-T651, all weld joints had ductile fracture mode.

Influence of Residual Stresses on the Weld Metal Hardness of 5V Titanium Alloy

Influence of residual welding stresses on the hardness values of the weld metal is studied. The investigations were carried out on 5V titanium alloy welded joints, obtained by electron-beam welding and argon-arc welding (TIG-welding). It is shown that the nature of the residual stresses distribution depends on the parameters of welding and affects the hardness values of the weld metal. It is shown, that the difference between the hardness values of the metal after welding and the metal after partial relief of residual stresses on the investigated alloy is up to 90 MPa, which is about 3% of the weld metal hardness level.

Numerical Studies on Temperature and Material Flow During Friction Stir Welding using Different Tool Pin Profiles

A three dimensional computational fluid dynamics (CFD) model has been developed to study the effect of tool pin profile on the material flow and temperature development in friction stir welding (FSW) of high specific strength AA 7068 alloy. Numerical simulations were carried out using a RNG k-e turbulence model. Three tool pin profiles, viz. cylindrical, conical and straight cylindrical threaded were considered for the simulation. The temperature distribution and material flow pattern obtained from the simulation were compared for different pin profiles. Simulation results predicted Temperature distribution and material maxing was better in straight cylindrical tapered thread pin welds. Weld joints were fabricated using the straight cylindrical threaded pin with the same parametric combinations as in the simulation. Peak temperature measured in the experiment was less than that obtained by simulation. Hardness measurements taken at different weld regions has showed that about 71% of that of the base metal hardness is obtained with the threaded tool pin. The microstructure study revealed a defect free weld joint. Precipitates distributed in the microstructure indicate sufficient heat input to join the material without dissolving precipitates. The developed numerical model is helpful in optimising FSW process parameters.

PENGARUH PENGGUNAAN PASIR BALIKPAPAN TERHADAP KEKERASAN DAN FLUIDITAS LOGAM CORAN PADUAN Al-Si

The use of sand as a mold in the casting process is very common. In this study, Balikpapan sand used as casting sand then analyzed its effect on hardness and fluidity of the Al-Si alloy. The research method used in this research is quantitative research methods using pre-experimental design, especially the one-shot case study model. The final results of this study will be obtained (1) the value of metal hardness from casting using the Micro Vickers Hardness Tester with a Hardness Vickers (HV) scale, (2) fluidity testing is carried out using the Birmingham method in order to determine the length of the cast metal flow (mm) on the final result of casting.

The Effect Of Addition Of Limestone Powder And Gypsum As Isolator Media On Low Carbon Steel SMAW Welding

Metal connection due to heat with or without the influence of pressure or metallurgical bonds caused by attractive forces between atoms. DIN (Deutsche Industrie Normen) state that metallurgical bonding of metal or guide metal joints in a melted or liquid state. This study aims to determine the effect of limestone powder and gypsum as an insulating medium in SMAW (Shielded metal arc welding) welding. This study using experimental methods with SMAW welding. Welding metal cooled with limestone media has a harder hardness than gypsum and air media, which is limestone has a thermal conductivity value of 3.897 W / mºC. In comparison, gypsum has a thermal conductivity value of 1.39 W/mºC, and air has a thermal conductivity value of 0.023 J/msºC, so limestone is a better insulator than gypsum and air. The greater the conductivity value of the object, the better the thermal conductivity of the metal and the more complicated the weld metal and the lower the thermal conductivity value, the softer the metal hardness, limestone has a thermal conductivity value of 3.897 W / mºC while gypsum has a thermal conductivity value of 1, 39 W / mºC and air have a thermal conductivity value of 0.023 J / msºC, proving that the lower the conductivity value, the hardness of the weld metal is getting softer, but in the HAZ section it proves that the lower the conductivity value, the more complex the hardness in the HAZ section.

INVESTIGATION OF TIRE CRUSHING KNIFE RESTORATION TECHNOLOGY

The paper investigates the quality of a steel welded joint of a tire shredding knife. Defects occurring during restoration are analyzed. In order to determine the mechanical properties of the welded joint, the following tests and tests were carried out: visual inspection, magnetic particle tests, metal hardness tests and chemical analysis of the parent and weld metal.

Effects of particulate reinforcements on the hardness, impact and tensile strengths of AA 6061-T6 friction stir weldments

Due to loss of structural strengthening at temperatures beyond 250°C, heat-treated aluminium alloys (e.g. AA 6061-T6) weldments are usually characterized with poor mechanical properties including hardness, tensile and impact strengths. In this work, friction stir weldments of AA 6061-T6 reinforced with the additions of SiC, B4C and Al2O3 particles at the joints were produced and investigated for improved hardness, tensile strength and impact strength over the unreinforced weldment. The results showed that the entire reinforced welded joint exhibited improved hardness because of the enhanced metal matrix grain refinement and inherent high hardness of the reinforcement particles. B4C particle addition produced hardest joint of about 81% of the base metal hardness (∼114 HV0.3). The impact energies of the SiC (16.9 J), B4C (16.5) and Al2O3 (12.2 J) reinforced weldments are closer to that of the base metal (18.6 J) compared with the unreinforced weldment (9.6 J). The reinforced weldments showed no significant improvement over the tensile strength of the unreinforced weldment. B4C and SiC reinforcements produced the highest improvements in the hardness (at the joint) and impact strength of the AA 6061-T6 friction stir weldments, respectively.

Badania nad technologią wybranych zabytków żelaznych

The extensive programme of research on artefacts recovered from the Przeworsk culture cemetery in Żelazna Nowa, Comm. Magnuszew, included performing a series of metallographic analyses. Only three objects were subjected to the analyses due to their good preservation: two knives and a shield grip fragment. The aim was to determine the technology of manufacture of particular objects and to identify the raw materials from which they were forged. Microstructure was examined using a Leica DMLM metallurgical microscope, and the observed metal structures were photographed. In addition, metal hardness was measured using the Vickers method, with a load of 10 kG (98N). Carbon content of steel was determined based on microscopic observation. As demonstrated by the analyses, the artefacts were made from metal obtained through the bloomery process from bog iron with a significant admixture of phosphorus. The technology used for manufacture of the analysed artefacts was not particularly sophisticated. They were forged from single pieces of bloomery iron. The only exception is a knife (inv. no. CCLII/15), which was forged from two different pieces of metal welded together, namely from a piece of high phosphorus iron and a piece of soft steel. This made the knife more flexible, while rendering its blade sufficiently hard and more resistant to abrasion. One cannot rule out that the blades of both knives were originally hardened by local carburisation, in connection with later thermal processing (quenching). The results of metallographic research seem to support our assumptions. The two knives and the shield grip were manufactured in local Przeworsk culture workshops, perhaps from iron originating from the centre of metallurgy in the Mazowsze (Mazovia) region.

Study of wear resistance of railway rails welded joint

Welding joints of rails are a weak point of a jointless railway line, which stipulates actuality of studies on increasing their operational resistance. Microstructures of welded joints made by existing at present welding technology and by a new one were compared. Existing (base) technology comprises further thermal treatment of the welded joint, while the new technology comprises welding followed by a short-time electric current impact during the rail joint cooling. To study the microstructures of welded joints, samples were cut out the welded seam zone and heat affected zone, as well as out of the base metal. The study was carried out in the depth of 5 mm from the surface, after thin section etching by 4% solution of nitric acid in alcohol. In the macro-structure of the metal of welded joint, made by the base technology, an uneven heat affected zone was detected. The zone had the following dimensions: 51 mm – in the head, from 45 mm to 62 mm – in the neck and 64 mm – in the bottom (by each of the seal side). In the longitudinal mac- ro-template of sample Б (the new welding method), the heat affected zone was even and along the whole joint had the width of 22 mm (in each of the joint side). It was shown, that the new welding method of railway rails enables to decrease the extension of zone with sorbitic and granular pearlite at various stage of coagulation. A short-time impact of electric current during rail joint cooling ensures obtaining a zone with a decreased hardness of 15 mm extension and decrease of welded seam metal hardness relatively the lower border of base metal hardness by less than 15%. Application an additional local thermal treatment by a separate induction heating during base technology results in forming zones of 30 mm extension in the area of welded joint, which wear resistance is 4.5 times lower comparing with wear resistance of the rail base metal. At the new welding method application, the extension of the abovementioned zone does not exceed 10 mm and wear resistance was decreased by less than 2 times.