LOTHERMAL XL WELDING ALLOYS

INTRODUCTION TO MAINTENANCE WELDING”

Advances in technology have their counter effects too good or bad. Increasing automation leads to arduous demands from an engineering component and the cost of downtime is mind boggling. Particularly tor core sector industry power, cement, sugar, paper, mining, petrochemicals etc. the consequences of wear of part or breakage directly affect the bottom line. Since the investment in this sector is phenomenal the prolongment of machine availability or reduced downtime is critical for the maintenance Engineers. This is because the value of the output per hour in these instances is as enormous as is the toll with every hour of breakdown. An hour of downtime in some industries may cost cost rupees. The OEM’s of late have been designing components with a average ifa before failure. This enables the user to plan the replacement of the same before that period. However, by accepting the ways of OEM’s the user can do we with his profitability and productivity. To rely on spare parts or resort to cannibalism proves very costly to the industry. Heavy inventory cost and the machine cost due to cannibalism cuts down on profits.

However, clever manager do not rely on these techniques but actively endeavors to use his engineering skills to either prolong the life of the component or resort to maintenance and repair welding. Maintenance welding is unlike production welding wherein the parameters and conditions are all known. For example the base materials are known, required equipment is provided for, parameters are controlled from tests because repetitive jobs have to be carried out. The prototypes developed before commencing main line production are subi subjected to all sort of destructive and non-destructive tests to confirm required properties in the welds. However, in maintenance welding the Engineer comes across a variety of unpredictable factors, limitations and doubts. The consumables should possess special features to overcome handicaps like welding temperature, warping, cracking, bond strength, weldability and solidification rate.

Maintenance welding may come across applications wherein the part is poor designed or else may involve improvement in design by strengthening.

reinforcing etc. as also fatigued component which have been overworked in capacity to satisfy the production needs. Identifying these difficulties special coatings have been developed for stick electrodes and gas rods to aid the maintenance welders. Special additives are developed to provide better weldability to result into proper orientation of weld constituents/grain refinement. Some electrodes have a low melting core wire and the alloys ad through the flux. This results in a circumferential are where are heat is not concentrated on the base metal. Infact most of the heat is utilised in meltin alloys in the flux thereby a minimal energy goes into the base material. The metallurgy is thus not affected much.

WELDING ALLOYS FOR LOW HIGM CARBON AND ALLOY STEEL INTRODUCTION TO THE WEDDING OF MILESTONES AN LOW HIGH ALLOY STEEL

MILD STEEL The welding of so called mild steel generally present in problems to welder Mild steel consists of an alloy containing Carbon, Score and Manganese. the carbon content being up to 0. and Basic eonted mild steel the job being decided by the size and section of the work place, the position in which it has to be welded, and whether a deep penetrating normal arc or touch type electrode is preferred or required. Material containing up to 0.2carbon are littie affected by heat and so preheat and post heat are not normally required except in the case of heavy sections or highly stressed weldments where post- weld stress relieving is sometimes called for the weld deposit does not harden in response to heat treatment. Such types can be welded with Future coated electrodes. The selection of the north electrode for

MEDIUM CARBON STEELS

These steels usually contain an increase in carbon above 0.2% and it should be noted that the increase in carbon allows to be hardened by healing and quenching, Quenching can be brought about by cooling in water, forced alt, oil, tc. Therefore, caution should be taken when cooling a work piece after welding

arge section that have been welded may also cool rapidly due to heat, ssipation. It is, therefore, recommended that heavier sections is first given me preheat to minimize this effect and to allow a slower cooling rate. These her carbon steels are generally used where high tensile, yield strength, hardness and impact values are required and a detrimental element against aining some of these higher values is hydrogen. During welding hydrogen be absorbed in and around the weld pool and during cooling this hydrogen be trapped, leaving pockets of trapped gas, some of which then forces its out to the surface, causing cracks to open up. This can still occur hours or days later resulting in surface and underbead cracks. The remaining ped hydrogen leaves fissures and pockets inside the metal. It is most rtant, therefore, to select. Basic coated electrodes for welding fine grain

1. Basic coated electrodes are designed specifically for this purpose and e relied upon to give the required results.