Manual metal arc

Matczak W, Chmielnicka J. 1993. Relation between various chromium compounds and some other elements in fumes from manual metal arc stainless steel welding. Br J Ind Med 50 244-251. 

Jarvisalo J, Olkinuora M, Kiilunen M, et al. 1992. Urinary and blood manganese in occupationally nonexposed populations and in manual metal arc welders of mild steel. Int Arch Occup Environ Health 63 495-501. 

Jelmert O, Hansteen IL and Langard S (1994) Chromosome damage in lymphocytes of stainless steel welders related to past and current exposure to manual metal arc welding fumes. Mutat Res 320 223-233. 

Weld metal hydrogen cracks in (a) single-run manual metal-arc fillet weld, (b) root bead of Y groove welding test, (c) submerged-arc weld (longitudinal section). 

Moisture in the coating of manual metal-arc electrodes, in the flux used in submerged-arc welding or in flux-cored wires. 

Minimum leg length for single run fillet weld Manual metal-arc welding Tubular cored arc welding... 

Manual metal-arc electrodes with other than basic coverings... 

Manual metal-arc electrodes of hydrogen controlled type unless established as low or very low... 

Care must be taken to measure the arc voltage, which is likely to be lower than the voltage indicated on the welding set because of potential drop along leads, etc. The scale of heat input on the weldability diagrams relates to the manual metal-arc process with an assumed arc efficiency of 80%. Other processes are included by comparing their arc efficiencies with that of the manual metal-arc process. Some typical approximate figures are ... 

Manual metal arc, gas-shielded metal arc with hydrogen potential ... 

Guide to preheat temperatures when using austenitic manual metal-arc electrodes at about l-2kj/mm a) low restraint, e. g. material thickness <30 mm b) high restraint, e-g material thickness >30 mm. 

Consumables to be tested shall be prepared according to the information wanted from the results of the test. For example, manual metal arc electrodes or submerged-arc flux would normally be dried... 

British Standard BS 6693, Part 1 1986, Method for determination of hydrogen in manual metal arc weld metal using 3 day collection. 

The amount of heat introduced by the welding process per unit length of weld, defined (for manual metal-arc welding with covered electrodes) ... 

Speed and Quality of Welding. The primed plates are cut and welded by a number of techniques (plasma, submerged arc, inert gas, manual metal arc, laser). The primers must not interfere with the speed and quality of welding. The principal defects of the previous generation of materials was their high organic content, which yielded porous welds. 

The most common arc-welding methods are manual metal arc welding, tungsten arc gas-shielded welding and metal arc gas-shielded welding. 

At this point in the fabrication process for the later RPVs, the welds were given a hot UT inspection to assure compliance with a pre-service examination. The shell course was then placed in a furnace and given a post-weld heat treatment (PWHT). The welds were then ground smooth on the external and internal surfaces. The ASME Code-required radiographic (RT) and MT inspections were then performed. Any required repairs of unacceptable indications were made at this point using manual metal arc (MMA) welding and a repeat of the preheat-post-weld heat treatment. 

In manual metal arc and shielding gas welding fumes nickel is dissolved in the iron oxide fume particles and in small amounts it exists as separate nickel oxide particles. 

The most common process is a.c. manual metal arc welding where flux-coated stick electrodes are used and the power source is a transformer with inductive control of the welding current between about 50 and 600 A. The secondary windings of the transformer are isolated from the casing and hence from earth, as shown in Fig. 16.1. The standard open circuit voltage is 80 V, falling on load to some 20 to 40 V depending on the load current. 

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