In the manufacturing industry low-carbon and silicon-based steels are used for cold forming and/or application of various surface coatings. Due to the low carbon equivalent the weldability of these steels is very good, that is why they are also used for products where welding is a final or interphase operation, such as, for example, in the production of a cored wire for arc welding.
The purpose of the diploma thesis is the analysis of three types of low-carbon steels (DC01, DC04 and DC06) and butt welds on these steels, the conformity of steel strips with standards, and the influence of the composition of the strips on the microstructure and the properties of the laser weld. The following analyzes were carried out: chemical analysis, tensile test, hardness measurements, metallographic testing and calculation of the weldability of each type according to carbon equivalent equations.
The DC01 and DC04 steels are very similar in all analyzes, since they can even fall into the same class according to the chemical composition standard. After the chemical analysis, the DC06 steel differs from the first two, which also causes differences in the weld microstructures. Steels DC01 and DC04 have martensitic microstructure, which makes the weld hard and brittle and this is why soft annealing is necessary prior to the further reduction process in order to reduce the tension and hardness of the material. The DC06 welding microstructure is ferritic making it significantly lower in hardness in the welded area.
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