There is so much theory about metallurgy which would be impossible to learn it all in a 2-year course. That is why the industry you’re in will be a lifelong learning process, you know about welding, but the metallurgical issues, well it can be an issue.
There is no need to become a metallurgical engineer; but awareness of the basic theory of metallurgy, the knowledgeability about the chemical compound, the physical properties of various materials, and improving your range of knowledge, how it applies to the integrity and industrial specification and standards, linking to the approval of welding procedures, may be of benefit to you.
A welder uses various data in codebooks, customer specifications and materials inspection standards which state the yield and tensile strength. The welder will also often have to be aware of the metal’s chemical composition, the heat and electrical conductivity information. These charts do not always provide adequate information to attain the perfect weld, so the educational metallurgical theory and its industrial application are all too important to acquire by chance.
Carbon, alloy and stainless steels are all affected by the carbon and alloying elements. It is also important the welder knows the possible consequences of hydrogen entrapment of the material at pre-heat temperature. To understand the reasons that cause cracking in the weld it is important to analyse the material's appearance and structure of metals as they are heated.
The specifications and standards can provide information on what can be undertaken after welding to reduce cracking, but how can hydrogen be minimised before and after the process? Metallurgical principals can help!
Welders should be able to read the material test report (MTR) and be aware of which metals need to be re-inspected a day or two after completion. Again, all important to achieve the perfect weld.
If elongation, or the reduction area of the material, impacts the value of tensile and yield results there is a need to determine the specific type of welding material and the type of pre/post-heating procedures required.
A welder should be aware of the strength of metals and other properties like ductility, brittleness, toughness and resistance to failure by the fatigue of rapid impact.
Observing the material and understanding the MTR to ascertain the correct mechanical properties and the atmospheric corrosion properties. Knowing the properties of metals and their susceptibility to cracking, the welder can achieve crack-free welds successfully.
These useful graphic representations are possibly simplified, describe what is present in both solid and liquid form at differing temperatures. Changes in the composition of heat treatment make them suitable for different applications.
Although welders can find resources online and in books to assist, it is advantageous to have the correct technical information and knowledge to assess the probabilities of the material.
Cracking in some alloy and stainless steels is down to different phases in the metals and issues of stress - corrosion cracking can be a major factor linking to phase diagrams.
Chemical composition at grain or crystal boundaries are affected by the chemical composition of the welded material.
Heat and electrical conductivity are different in materials such as copper, aluminium and their alloys. Having technical knowledge of the material characteristics will determine their hardness, hardenability by heat treatment, corrosion resistance as all these metals can be welded etc.
Often these materials have different characteristics to other metals ie stainless steel and other alloys. Welders should be aware of the stresses obtained by fabrication or bending the material, its hardness, sensitivity and the deformations likely to be caused by the joining processes.
Knowing the physical metallurgy of the ferrous and non-ferrous metals and alloys, along with the effects on metals concerning welding will enhance your understanding of metallurgy. Developing written procedures to comply with the correct standards and specifications, inspection and industrial welding procedure approval criteria, will contribute to additional benefits of quality control and assurance to gain customer confidence and repeat business.