Shielded metal arc welding

About: Shielded metal arc welding is a research topic. Over the lifetime, 4462 publications have been published within this topic receiving 40560 citations. The topic is also known as: manual metal arc welding & flux shielded arc welding.

Electric metallic arc welding

Abstract: This invention relates to new and useful improvements in electric metallic arc welding, in which the metal of the electrode is fused by the arc struck between it and the work to deposit the fused metal in a continuous seam being welded. The greatest speed heretofore achieved with this type...

Prevention of weld metal hydrogen cracking in high-strength multipass welds

Abstract: Welding modern high-strength steel with low carbon and impurity contents, preheat may be dictated by cracking sensitivity of the weld metal instead of the HAZ. Standard EN 1011 does not provide the user with any unified methodology for the calculation of safe preheat for weld metal. The few calculation formulae that apply to multipass welds can give greatly varying predictions. This article studies controlling factors that govern transverse hydrogen cracking in high-strength multipass weld metal. The experiments comprised heavily restrained Y- and U-groove multipass cracking tests of SMAW and SAW welds. The objectives were the assessment of hydrogen cracking risk by defining the Crack — No Crack boundaries in terms of safe line description giving the desired lower-bound estimates, and to derive predictive equations capable of giving reliable estimates of the required preheat/interpass temperature T 0/T i for the avoidance of cracking. Equations were derived to assess the weld critical hydrogen content H cr corresponding to the Crack — No Crack conditions as a function of either weld metal P cm, yield strength R p0.2 or maximum hardness HV 5(max). For the calculation of safe T 0/T i estimates, a formula incorporating weld metal strength as linear functions of either CET or weld HV 5(max), weld build-up thickness a w in the form of tanh expression and weld diffusible hydrogen H d in terms of combined [In / powerlaw] expression, was found descriptive.

Improvement of Weld Characteristics by Variation in Welding Processes and Parameters in Joining of Thick Wall 304LN Stainless Steel Pipe

Abstract: Nitrogen added austenitic stainless steel is a prospective material for the reactor vessels and piping systems primarily due to its good inter granular corrosion resistance along with desired mechanical and fracture mechanics properties. The use of such a material may provide comparatively longer life with enhanced safety of any component requiring higher stress for a rapid crack propagation indicating more resistance to brittle fracture. The austenitic stainless steel being a readily weldable material, the fabrication of its components and structures in various applications is largely carried out by using different welding processes and procedures. However, the quality of weld joints of this class of steel primarily depends upon thermal behavior of the welding processes employed with or without involvement of fluxes. The weld joint is a mechanically heterogeneous body composed of base metal, weld metal and heat affected zone (HAZ). These different regions of the weld joint leads to heterogeneous mechanical and metallurgical properties of the material along with considerable development of harmful tensile residual stresses. These difficulties resulting from heterogeneity of weld get further compounded in case of heat-sensitive materials like austenitic stainless steel (ASS), especially of thick sections, due to its lower thermal conductivity and higher coefficient of thermal expansion in comparison to those observed in structural steel. The considerably low thermal conductivity makes the HAZ of arc weld of ASS more prone to sensitization while its significantly high coefficient of thermal expansion develops considerable stresses in the weld. Hence the proper selection of welding process and procedure by considering efficient energy distribution in the welding arc leading to comparatively low heat built-up in the weld pool is imperative to reduce the amount of damage produced in different zones of weld joint due to heterogeneity in their properties. Such a control in arc characteristics can be primarily achieved by using gas metal arc welding (GMAW) and possibly more appropriately by employing pulsed current gas metal arc welding (P-GMAW) processes. This is because the use of P-GMAW with proper selection of its simultaneously interactive pulse current parameters that includes pulsed current (Ip), base current (Ib), pulse time (tp), pulse off time (tb) and pulse frequency ( f ) may provide a comparatively low heating welding process. The criticality of selection of pulse parameters in this regard is well addressed by considering its summarized influence defined by a hypothetical factor f [(Ib/Ip) f · tb] where, tb [(1/f ) tp]. But hardly any systematic work is reported so far considering the influence of welding processes on characteristics of the weld joint of thick wall pipe of 304LN

Cancer risk assessment for occupational exposure to chromium and nickel in welding fumes from pipeline construction, pressure container manufacturing, and shipyard building in Taiwan.

Abstract: OBJECTIVE We assessed the cancer risks resulting from the exposure to chromium, hexavalent chromium (Cr (VI) ), oxidic nickel (Ni), and soluble Ni in welding fumes during pipeline and shipyard construction and pressure container manufacturing in Taiwan. We also determined the roles of welding performance and demographic characteristics during the exposure to Cr and Ni. METHODS Personal air samples were collected for the analysis of Cr and Ni, and the concentrations of Cr (VI), oxidic Ni, and soluble Ni were quantified. We assessed cancer slope factors for Cr, Cr (VI), oxidic Ni, and soluble Ni, and we used the Incremental Lifetime Cancer Risk model proposed by the United States Environmental Protection Agency to calculate excess risk. RESULTS The risks of exposure to Cr and Cr (VI) in welding fumes exceeded the acceptable level of occupational exposure (10-3). We ranked the excess cancer risk in three industries in decreasing order as follows: pipeline construction, shipyard construction, and pressure container manufacturing. The most sensitive parameters for the risk assessment were Cr and Ni concentrations. Statistically significant determinants of Cr (VI), oxidic Ni, and soluble Ni concentrations were the following: stainless steel as the base metal and the filler metals of shielded metal arc welding (SMAW) and of gas tungsten arc welding (GTAW). CONCLUSION The study revealed that welders belong to a high cancer-risk group. Furthermore, we demonstrated the roles of filler metals and stainless steel in exposure to Cr and Ni.