# Prediction of MAG Welding Formation Based on Fuzzy Interpolation Reasoning
## 4 Welding Formation Prediction
### Welding Process Parameter Model  
Metal active gas arc welding (MAG) is a common metal material connection process in industrial production. It is widely used in industrial fields such as machinery, shipbuilding, and chemical engineering due to its high production efficiency and strong welding process stability. The quality of a welding joint is determined by its mechanical properties, which are dependent both on its metallurgical properties and bead geometry, in which weld penetration is one of the important geometric parameters. For arc welding, the penetration of the welded joint depends on many input process parameters, such as welding current, welding speed, voltage, wire feeding speed, gas flow, nozzle plate distance, torch angle, and so on [32,33]. Therefore, the selection of the appropriate welding parameters is crucial for the welding process. The depth of a weld seam is an important index of welding quality. Two main technological parameters affect the weld depth Y: the welding current X\({}_{1}\) and welding speed X\({}_{2}\)[34]. In order to establish the relationship between welding depth Y and welding current X\({}_{1}\) and welding speed X\({}_{2}\), an experiment is used that employs the 85%Ar + 15%CO\({}_{2}\) mixed gas arc welding process that is widely used in metal connections [34]. The experimental equipment and conditions are shown in Table 3 and Figure 5, respectively. \begin{table}
\begin{tabular}{c c} \hline
**Type** & **Value** \\ \hline Material for test & Q235 low carbon steel \\ Welding power & AOTAI Pulse-500 RP \\ Welding position & Flat welding \\ Shielded gas & 85\%Ar + 15\%CO\({}_{2}\) \\ Groove gap (mm) & 2 \\ Gas flow (L/min) & 15 \\ Welding wire diameter (mm) & 1.2 \\ Wire elongation (mm) & 15 \\ Welding wire material & H08 Mn2 SiA \\ Measuring tools & JGX-2 Tool microscope \\ \hline \end{tabular}
\end{table} 
Table 3: Experimental conditions of MAG welding. Flat and fillet welds are commonly involved in the actual welding process, and in this paper, the experiment adopts commonly used butt-welding connection methods. The welded material is fixed on the welding workbench and the gap between the plates is adjusted to 2 mm before performing the welding operation, as shown in Figure 6.  
Then, the welding experiment is performed according to the present welding parameters. Subsequently, the weld penetration measurement is carried out by selecting qualified specimens through welding the appearance and forming the specimens. Due to the inability to measure weld penetration directly, it is necessary to cut the welded specimen. After cutting the welded specimen, the weld penetration can be measured by a JGX-2 Tool microscope. The welding formation and welding penetration are shown in Figure 7. The experimental sample data can be obtained through measurement, as shown in Table 4.  
Figure 5: Welding experimental equipment. Figure 6: Butt-weld connection. Figure 7: Actual welding formation and penetration measurement. Based on experimental sample data, the input domain of the welding current X\({}_{1}\) is set to [100, 120] and [170, 190], and the welding speed X\({}_{2}\) is set to [360, 390] and [470, 500]. Using fuzzy language to describe the input domain, fuzzy language variables are defined as small (S) and large (L), which are described by symmetric congruent triangular fuzzy sets, and the membership of welding current X\({}_{1}\) is shown in Figure 8a. The output domain of depth Y is set to [2.62, 3.6] and [4.31, 5.3], and fuzzy language variables defined as Small (S), Medium-small (MS), Medium-large (ML) and Large (L), which are described by symmetric congruent triangular fuzzy sets, and the membership of welding depth Y are shown in Figure 8b. By defining the fuzzy language of input variables, four fuzzy rules between welding penetration, welding current and welding speed are summarized, as shown in Table 5. Finally, a sparse rule base for the welding forming prediction model can be obtained.