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A technical reference library for welding engineers, supervisors and inspectors.
Introduction When welding procedures or welding performances (welders) are qualified, test pieces are prepared using a specific combination of parent material and consumables. To reduce the number of welding procedures to be qualified for production applications, codes and standards give provisions for a particular parent material and filler materials to cover a range of other … Read more
Distortion, Types and causes This article covers several key issues on distortion in arc welded fabrications, especially basic types of and factors affecting the degree of distortion. What causes distortion? Because welding involves highly localised heating of joint edges to fuse the material, non-uniform stresses are set up in the component because of expansion and … Read more
The MIG process is a versatile welding technique which is suitable for both thin sheet and thick section components. It is capable of high productivity but the quality of welds can be called into question. To achieve satisfactory welds, welders must have a good knowledge of equipment requirements and should also recognise fully the importance … Read more
Using an inert gas shield instead of a slag to protect the weld pool, this technology is a highly attractive alternative to gas and manual metal arc welding and has played a major role in the acceptance of high quality welding in critical applications. Essential equipment In TIG welding, the arc is formed between the … Read more
This article continues the fabrication defects series. The first part covers fusion and porosity. This part covers cracking: solidification cracking, reheat cracking and hydrogen cracking. Solidification Cracking Weld repair on a cast iron exhaust manifold A crack may be defined as a local discontinuity produced by a fracture which can arise from the stresses generated … Read more
In this instalment of the fabrication defects series, the AWI has brought you a further series of Job Knowledge articles. The following articles are all about typical fabrication defects, their possible causes and suggestions of remedies. Incomplete root fusion and penetration The SS Schenectady, an all welded tanker, broke in two while lying in dock … Read more
Best practice in design is not simply a matter of deciding on the appropriate weld size or component thickness capable of carrying the service loads; there are many aspects of designing a welded component that need to be considered in addition to calculating permissible stresses. Weldability and mechanical properties such as tensile strength, toughness and … Read more
Information and Guidance to FCAW Flux core arc welding (FCAW) was introduced in the 1950s as an alternative to shielded metal arc welding (SMAW). The advantage of FCAW over SMAW is that the use of the stick electrodes used in SMAW is unnecessary. This helped FCAW to overcome many of the restrictions associated with SMAW. … Read more
Choosing a career means weighing up skills, interests, working hours and the job market. Plenty of people in senior technical and management roles in this industry started in a welding trade. There is a misconception that a trade is a destination rather than a starting point. A trade gives you practical and problem solving skills … Read more
History The correct name for TIG welding is Gas Tungsten Arc Welding (GTAW). This is the name that most European and American Welding fabricators refer to on their welding procedures. When GTAW welding was introduced around the 1940s, Helium gas was the primary shielding gas used and the term Heliarc welding was in common use, … Read more
Earlier parts of this series cover cracks, lack of fusion, incompletely filled grooves and root concavity. This third and final instalment is all about the imperfections that occur with fillet welds and how to avoid them. This article will specifically focus on: Excessive convexity Oversized fillet welds Undersized fillet welds Asymmetric fillet welds Poor fit-up … Read more
In part one of this series, welding imperfections such as cracks, lack of fusion, penetration and porosity were discussed. This article looks at how common welding imperfections relate to the poor geometric shape of welds. This article will concentrate on the following: Incomplete filled groove Excessive penetration Root concavity Incomplete filled groove This is a … Read more
In the job knowledge series welding imperfections such as cracks, lack of fusion, penetration and porosity have been discussed. This article looks at those imperfections related to poor geometric shape and will concentrate on the following: Excess weld metal Undercut Overlap Linear misalignment Incompletely filled groove Such imperfections might be considered as anomalies in the … Read more
Heat treatment is an operation that is both time consuming and costly. It can affect the strength and toughness of a welded joint, its corrosion resistance and the level of residual stress but is also a mandatory operation specified in many application codes and standards. In addition it is an essential variable in welding procedure … Read more
Part 1 of this series of articles gave definitions of some of the heat treatments that may be applied to a welded joint and dealt with the operation of stress relieving a ferritic steel assembly. The temperature range within which stress relief takes place will also cause tempering of those regions in the HAZ’s where … Read more
When it is not possible to place the entire component in a furnace for heat treatment (because of the size of the fabrication, circumferential welds in a pipework system or when installing equipment on site, for example), then a local PWHT may be the only option. Local PWHT needs careful planning to ensure that heating … Read more
Precipitation or age hardening There are several methods that may be used to increase the strength of a metal; alloying, quenching of steel, work hardening, and one very specific form of heat treatment, that of precipitation or age hardening (the two terms are synonymous). Many ferrous and non-ferrous alloys are capable of being age hardened … Read more
Hot gas welding of plastics Part 1, The basics Process background Hot gas welding is a fabrication process for thermoplastic materials. The process, invented in the mid 20th century, uses a stream of heated gas, usually air, to heat and melt both the thermoplastic substrate material and the thermoplastic welding rod. The substrate and the … Read more
Introduction Hot gas welding is a fabrication process for thermoplastic materials. The process uses a stream of heated gas, usually air, to heat and melt both the thermoplastic substrate and the thermoplastic welding rod. The substrate and the rod fuse together to produce a weld. To ensure that welding takes place, adequate temperature and pressure … Read more
Notched bar or impact testing, Part 1 Before looking at impact testing let us first define what is meant by ‘toughness’ since the impact test is only one method by which this material property is measured. Toughness is, broadly, a measure of the amount of energy required to cause an item, a test piece or … Read more
Induction heating is the process of heating an electrically conducting object (usually a metal) by electromagnetic induction, through heat generated in the object by eddy currents. An induction heater consists of an electromagnet, and an electronic oscillator that passes a high-frequency alternating current (AC) through the electromagnet. The rapidly alternating magnetic field penetrates the object, … Read more
Non-destructive Examination (NDE) Part 1 Liquid Penetrant and Magnetic Particle Inspection In achieving high quality defect free welds there is no substitute for experienced and qualified welders and competent supervision. However, no matter how skilled the welder, during the process of depositing weld metal, imperfections of various types may be formed. It is therefore necessary … Read more
There is a misconception in the repair industry that materials that are deployed in the mining industry are basic in specification, metallurgical composition and heat-treated status; nothing could be further from the truth. Another misconception is to draw conclusions from Australian Standards as to the materials specification, and from there to run inadequate weld procedures … Read more
To confirm that a weld has been made to specification it is usually required to measure and often document the parameters that have been used. For arc welding the main parameters are as follows: Welding current Arc voltage Travel speed These parameters can be used to calculate the heat input, which is derived from the … Read more
Mechanical testing, Tensile testing, Part 1 Mechanical testing is carried out to produce data that may be used for design purposes or as part of a material joining procedure or operator acceptance scheme. The most important function may be that of providing design data since it is essential that the limiting values that a structure … Read more
Low alloy steels are used extensively for high-temperature applications in power plants and the petrochemical industries but, while they have good weldability, they also present distinct challenges when they have been aged through service. This is because these steels, when service aged, are particularly susceptible to embrittlement and cracking. Repair welding generally requires the use … Read more
Post weld cleaning using pickling pastes Introduction Pickling pastes contain a combination of hydrofluoric acid and nitric acid which can cause serious burn injuries. They are primarily used to post weld clean stainless steels and can be applied by brush or by a spray on process. Their use is relatively widespread amongst stainless steel fabricators … Read more
The precipitation hardening (PH) stainless steels are a family of corrosion resistant alloys some of which can be heat treated to provide tensile strengths of 850MPa to 1700MPa and yield strengths of 520MPA to over 1500MPa, some three or four times that of austenitic stainless steel such as type 304 or type 316. They are … Read more
Radiography is one of the best known processes for reliably detecting buried imperfections, a so-called volumetric detection method. The first such method to be used in manufacturing to determine the quality of fabricated components is radiography. X-rays generated from a cathode ray tube were discovered in the late 1890s, soon followed by the discovery of … Read more
Types of electrodes and their compositions Many types of manual metal arc (MMA) electrodes are available on the market. Depending on the main constituent of their flux, they are grouped into three categories: cellulosic, rutile and basic. All electrodes consist of a core wire (typically 2.5 to 6mm diameter) coated by a flux. The core … Read more
Defects are common in any type of manufacturing, welding included. In the process, there can be deviations in the shape and size of the metal structure. It can be caused by the use of the incorrect welding process or the wrong welding technique. Learn about the 7 most common welding defects, their types, causes and … Read more
Shielded metal arc welding (SMAW), also known as manual metal arc welding (MMA or MMAW), or regularly as stick welding is a manual arc welding process that uses a consumable electrode covered with a flux to produce the weld. An electric current, in the form of either alternating current or direct current from a welding … Read more
The first patent on the submerged-arc welding (SAW) process was taken out in 1935 and covered an electric arc beneath a bed of granulated flux. Developed by the E O Paton Electric Welding Institute, Russia, during the Second World War, SAW’s most famous application was on the T34 tank. Process features Similar to MIG welding, … Read more
The goal of any Australian welding and fabrication company is to create quality products for their customers, while also managing costs and maintaining the desired levels of productivity and quality. Missed or defective welds can severely affect costs, productivity and quality levels of the company and defects in the welds could also lead to potential … Read more
Ultrasonic examination uses the same principles as the sonar used for the detection of submarines, a sound wave is emitted from a transmitter, bounces off any objects in its path and is reflected back to a receiver, somewhat similar to shining the beam of a torch at a mirror. Knowing the speed of sound in … Read more
The previous article explained the basic principles of ultrasonic examination. As to determine accurately the size and position of a feature it is necessary, with any measuring equipment, to calibrate the ultrasonic examination system. The type of calibration blocks (there are varying shapes and sizes to be used), depend on the application and the form … Read more
Part 2 dealt with the manual scanning method of ultrasonic examination stating that accurate determination of weld flaw size and position, to within ±2mm, was difficult, if not impossible, in most circumstances. Methods developed now enable flaw sizes to be determined with accuracy better than ±1mm. This article will look at two of these techniques; … Read more
Introduction A shortage of skilled welders and a need for welds of a consistently high quality is fuelling an increasing demand for automated welding systems. As well as delivering consistency and quality, these systems have the added benefit of removing the operator from the hazardous welding environment, satisfying increasingly stringent health and safety regulations. However, … Read more
Corrosion and fatigue Corrosion: nature’s great destroyer, and the bane of any offshore operator’s business. In 2016, NACE International released its report on global corrosion, “International Measures of Prevention, Application and Economics of Corrosion Technology (IMPACT)”. Put together over two years, the study came to some staggering conclusions about the price of corrosion, and the … Read more
A common claim on the shop floor is that every weld needs deep or maximum penetration into the base plate to be strong, that shallow penetration means a weaker weld, and that the deepest possible penetration is always best. None of those three statements is reliably true, and this article sets out why. Fig 1 … Read more
Cast irons are iron based alloys containing more than 2% carbon, 1 to 3% silicon and up to 1% manganese. As cast irons are relatively inexpensive, very easily cast into complex shapes and readily machined, they are an important engineering and structural group of materials. Unfortunately not all grades are weldable and special precautions are … Read more
In arc welding, as the weld metal needs mechanical properties to match the parent metal, the welder must avoid forming defects in the weld. Imperfections are principally caused by: poor welder technique; insufficient measures to accommodate the material or welding process; high stress in the component. Techniques to avoid imperfections such as lack of fusion … Read more
Job Knowledge · Written for AWI · Published 4 August 2026 · Free to read Welder qualification and procedure qualification are not the same thing Two completely different things get called a welding qualification. One qualifies a person. One qualifies a method. Confusing them is the most common reason welding documentation gets rejected on an … Read more
Welding of austenitic stainless steel, Part 1 There are a number of different types of steels that may be referred to as ‘stainless’; previous articles have considered ferritic and precipitation hardening steels for example. It is therefore advisable to be specific and to refer to the group to which the steel belongs in order to … Read more
Welding of austenitic stainless steel, Part 1, dealt with the metallurgy of austenitic stainless steels and some of the welding problems that may be encountered. Austenitic stainless steels can be welded with all the commercially available welding processes. There are matching filler metals available for most of the austenitic range of alloys, the exceptions being … Read more
A previous article from the TWI (number 95), dealt with the methods of determining the weight of deposited weld metal in a joint, enabling the cost of welding consumables to be calculated. This is obviously the first step towards calculating the cost of actually making a welded joint but there are many other factors that … Read more
Flux cored arc welding The previous two articles dealt with the mechanics of costing a weld: how to calculate the weld volume and how to calculate the amount of welding consumables required to fill a weld preparation. The final step in costing a weld is to determine the length of time to deposit this weight … Read more
Fumes are airborne particles small enough to be inhaled and are produced in all welding and cutting operations. They are a mixture of: gases from the surrounding air, shielding gas, metallic elements, from parent metals, coatings and welding fluxes, which are vaporised in the welding arc. Fume concentration decides the risk. Where the concentration is … Read more
