A welding engineer needs the knowledge of welding metallurgy in order to control : — the chemistry and soundness of weldmetal. — the micro-structure of the weldmetal and heat-affected-zones (HAZs). Metallurgy consists of two parts: — Process metallurgy (e. g.) convertion of ore to metals, refining and alloying, shaping through casting, forging and rolling etc.). […]

All electrode standards describe in great detail the procedures for executing all-weld tensile and impact test. Some of them also describe methods for determining weld deposition effi­ciency and hydrogen in the weld deposit. The tensile strength, yield strength and elongation values obtained in the tensile test, and the values obtained in the other two tests […]

AWS-A5.1 — 81 Specification for Carbon Steel Covered Arc Welding Electrodes The American Coding System starts with a prefix E which means an electrode. Then comes a two digit number 60 or 70 designating tensile strength in ksi (60 ksi or 70 ksi). The actual stipulated minimum tensile strength values and the associated yield strength […]

DIN 1913 (Jan. 1976) Coated Electrodes for the Welding of Unalloyed and Low-alloy Steels The German coding system is also based on ISO : 2560 with some modifications as in BS 639. It starts with prefix E followed by two digits 43 or 51 indicating the range of tensile strengths as in ISO, with the […]

Various systems of electrode specifications are used in different countries. Most important ones are from: 1. International Organisation for Standardisation (ISO) 2. American Welding Society 3. Indian Standards Institution 4. British Standards Institution 5. Deutsches Institut Fur Normung (DIN). They cover some or all of the following groups of electrodes 1. Mild steel electrodes 2. […]

According to AWS A5.1—81, the core wire for the electrodes in this specification is usually a rimmed or capped steel having a typical composition of 0.1% C, 0.45% Mn, 0.03% S, 0.02% P, and 0.01% Si. IS : 2879-1975 recommends rimming quality steel with the following composi­tion (maximum percent) 0.1% C, 0.38—0.62% Mn, 0.03% S, […]

Depending upon the welding situational requirements a number of chemical compounds are used in formulating a flux. In Table 4.1 these compounds are listed with their major functions and secondary benefits for the welding of steels. The electrode flux covering performs the following functions: 1. Provide a protecting atmosphere 2. Forms slag of suitable characteristics […]

• Flux melts with the core wire and covers the surface of the molten metal drops and the weld-pool (see Fig. 4.3), excluding oxygen and nitrogen to come in their contact. As the weld-pool progressively solidifies, the flux forms a slag blanket over the weld — bead and continues to protect it from oxidation till […]

Electrode size and type and thickness of coating on it determine the arc voltage require­ment (overall range 16—40 V) and current requirement (within an overall range of 20—550 A). The current could be direct of alternating depending upon the electrode being used. Almost all electrodes work well on d. c. but only a few flux […]

• Shielded Metal Arc Welding (SMAW) is a welding process in which coalescence of metals is produced by heat from an electric arc maintained between the tip of a con­sumable electrode and the surface of the base metal in the joint being welded. • This is the most commonly used arc welding process, the equipment […]