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.

Effects of CNTs addition on the microstructure and microhardness of stainless steel alloy/carbon-manganese non-alloyed steel welding

In recent years some progress has been made about the addition of Carbon Nanotubes (CNTs) in the stainless steel metal matrix by pulsed Gas Tungsten Arc Welding (P-GTAW). Despite that, there is lack of information regarding to microstructural modifications induced by CNTs in dissimilar welding. In this sense, we present the welding of nanocomposite based on Nickel/Carbon Nanotubes-stainless steel 316L alloy (Ni/CNTs-SS 316L), as the welding metal, on carbon-manganese (C-Mn) non-alloyed structural steel, as the base metal. The microstructure of manufactured specimens with/without nanocomposite was characterized by: optical microscopy; Raman spectroscopy; scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and electron backscattering diffraction (EBSD). Moreover, Vickers tests were performed from the welding metal (WM) to the base metal (BM) before/after temper treatment in order to investigate the microhardness changes. The results show that dilution rate and grain size for specimen with nanocomposite was higher than without nanocomposite; the CNTs affected the misorientation angle and texture of the WM; the topside microhardness from WM with Ni-CNTs was on average 30.40% higher than BM; and, in transverse cross-section microhardness was 31% higher than control sample on average at fusion line zone. These results indicate that addition of CNTs in the metallic matrix by dissimilar welding is a fertile ground for new studies applicable to manufacturing industry.

Research on Carbide Characteristics and Their Influence on the Properties of Welding Joints for 2.25Cr1Mo0.25V Steel

The carbide characteristics of 2.25Cr1Mo0.25V steel have an extremely important influence on the mechanical properties of welding joints. In addition, hydrogen resistance behavior is crucial for steel applied in hydrogenation reactors. The carbide morphology was observed by scanning electron microscopy (SEM) and the carbide microstructure was characterized by transmission electron microscopy (TEM). Tensile and impact tests were carried out and the influence of carbides on properties was studied. A hydrogen diffusion test was carried out, and the hydrogen brittleness resistance of welding metal and base metal was studied by tensile testing of hydrogenated samples to evaluate the influence of hydrogen on the mechanical properties. The research results show that the strength of the welding metal was slightly higher and the Charpy impact value was significantly lower compared to the base metal. The hydrogen embrittlement resistance of the welding metal was stronger than that of the base metal. The presence of more carbides and inclusions was the main cause of the decreased impact property and hydrogen brittleness resistance of the welding metal. These conclusions have certain reference value for designing and manufacturing hydrogenation reactors.

Surface Galling Mechanism Analysis of Rotary Shouldered Thread Connection

In this paper, surface galling failure process and mechanism of drill pipe’s rotary shouldered thread connection (RSTC) was studied by means of full-scale make-up and break-out (M&B) testing. The results showed that surface galling damage mainly appearred at the positions of leading flank, bearing flank and make-up shoulder of RSTC. The galling damage of three different positions was a process of mutual independence and mutual promotion, and they might appear simultaneously, and also appear at different stage. The surface galling failure was mainly due to metal’s plastic deformation and peeling off under the effect of compressive stress caused by friction and compression effect among the contacting metal surface. During M&B testing, deformed and peeling metal accumulated continually and resulted in "cold welding" at local position. In the subsequent M&B process, "cold welding" metal was torn open and peeled off from metal matrix, and metal surface galling was getting serious gradually. M&B testing results showed that torque load and thread compound had decisive influence on surface galling damage, while the influence of RSTC’s surface wear, rearranging, torque fluctuations and tensile load was not obvious.

Development and Research of the Main Features of Joining Plastics and Metals

This work examines a method of ultrasonic pressing of metal parts into a thermoplastic part using thermoplastic rivets and screws installed into the threaded holes obtained by ultrasound forming, welding metal parts through a pre-applied plastic layer, and welding metal and plastic parts through an intermediate plastic insert. It is shown that the introduction of metal fittings into plastic products using ultrasound is a progressive method of obtaining permanent joints of products from plastics and metals. It leads to an increase in labor productivity and ensures production of consistently high-quality and durable connections. The dependence of the holding force of the metal reinforcement in thermoplastic on the tightness is determined. The possibility of obtaining a metal-plastic welded joint using ultrasound is established. It was previously impossible to obtain such joints using classical methods of welding due to specific features of the metal-plastic material. The main technological modes of joining metal materials with thermoplastics are determined, namely static force, duration of ultrasonic action, waveguide oscillation amplitude.