Experimental Study On Droplet Transfer And Welding Spatter Of Self-shielded Flux Cored Wire

The researches on the droplet transfer of welding materials, spatter and the arc parameter are always the hot issues of arc physical characteristic research of welding materials. The research of this topic mainly focuses on analyzing the droplet transfer types and stability applying the welding current and arc voltage. That is to say, the research of this topic analyzes the stability of droplet transfer and then assesses the stability of the welding process through studying the droplet transfer mechanism and the wave form of welding current and arc voltage, and calculating the mathematical statistics of arc parameter.Through the high speed photography, hanover analyzer, the welding wire dissect test end and the spatter rate test, this thesis, taking self-shielded flux cored wire as the subject, analyzes the model, the mechanism and the arc parameter characteristic of bridging transfer without arc interruption based on the same self-shielded flux cored wire of two different parameters. Furthermore, the present study assesses the droplet transfer form of self-shielded flux cored wire under different welding conditions and the stability of bridging transfer without arc interruption. In addition, the present study tests the spatter of three self-shielded flux cored wires under the same welding condition and assesses the degree of spatter.The results reveal that bridging transfer without arc interruption is a droplet transfer model which the liquid bridge constantly exists and the arc keeps burning. Meanwhile,it is also one of the main transfer models of self-shielded flux cored wire. The arc voltage and the welding current waveform of self-shielded flux cored wire have no signs of short-circuit transfer, characterized by small-scope fluctuation within certain premises and according with the characteristic of bridging transfer without arc interruption. The density distribution curve of voltage probability and current probability do not support the characteristic of short-circuit transfer.The liquid bridge of bridging transfer without arc interruption is the mixture of the smelting reduction and the liquid metal, and its characteristic of distribution is that the smelting reduction encloses the surface of the liquid metal. The structural characteristic of the liquid bridge is formed under the interaction of the surface tension of metal, smelting reduction and the interface of the reduction and the metal. Bridging transfer without arc interruption of self-shielded flux cored wire is that the special structure of the liquid bridge leads to the partly conducting of the current, and it is completed through the interaction of the surface tension of the liquid bridge and the electromagnetic retractile power.Through analyzing the arc voltage wave form, welding current wave form and voltage current rate density distribution curve of the same self-shielded flux cored wire under different welding standards, it shows that the droplet transfer form of self-shielded flux cored wire varies with the pre-set voltage. That is, when the pre-set voltage is 17V-21V, it mainly represents short-circuit transfer; when the pre-set voltage is 21V-28V, it mainly represents bridging transfer without arc interruption; when the pre-set voltage is 21 V, there will be either short-circuit transfer or the bridging transfer without arc interruption. Through the statistical analysis of the arc parameters, it unfolds that the approximate entropy of arc voltage can be used to assess the stability of the bridging transfer without arc interruption process of the self-shielded flux cored wire and the quantity the of the bridging transfer without arc interruption of. The higher the average approximate entropy of arc voltage is, the lower the approximate entropy standard deviation will be. That is to say, under such condition, the quantity is directly proportional to the stability of bridging transfer without arc interruption.Droplet transfer form of self-shielded flux cored wire ha closed relationship with the degree of spatter. The explosive spatter and arc exclusion spatter forms. Judged by the high voltage rate of more than 30V and∑n(UB), spatter degree of self-shielded flux cored wire can be assessed quantificationally. The lower the is, the slighter the spatter degree will be; the higher the∑n(UB) is, the more serious the spatter degree will be.The partial least squares regression analysis of the three spatter rates of self-shielded flux cored wire reveals that the lower the average voltage is, the higher the∑n(UB) will be;the higher the∑n(Is) and the coefpilient of variation of voltage are, the more serious the spatter of self-shielded flux cored wire will be. Furthermore, the effects of the high voltage probability density are the biggest, the effects of high current probability density comes next, whereas the effects of average voltage and the coefpilient of variation of voltage is relatively small.