### 1. Introduction

### 1.1 Heat affected zone (HAZ)

### 1.2 powder consumption

### 2. Research method

### 2.1 HAZ

##### Table 2

#### 2.1.1 Model development

*y*and surface expressed by

*f*(

*x*,

_{1}*x*

_{2},

*x*

_{3},…,

*x*) is known as response surface. The response can also be shown by graphical method in the contours plots or three-dimensional space that will help to anticipate shape of response surface.

_{n}##### Table 3

Parameters | Symbol | Levels | ||||
---|---|---|---|---|---|---|

-2 | -1 | 0 | 1 | 2 | ||

Direct Amp | I(DC) | 1000 | 1050 | 1100 | 1150 | 1200 |

Direct Volt | V(DC) | 28 | 31 | 34 | 37 | 40 |

Alternate Amp | I(AC) | 400 | 430 | 460 | 490 | 520 |

Alternate Volt | V(AC) | 28 | 31 | 34 | 37 | 40 |

##### Table 4

^{-3}I(DC) + 0.21389 × V(DC) + 1.25 × 10

^{-3}× I(AC) + 0.23056 × V(AC) + 0.97222 × 10

^{-3}× V(DC) × V(AC) (3)

^{2}and R

^{2}

_{adj}which is necessary for both of them to be close to each other and equal to 100% ideally. Also, predictability of a model to forecast new points in experimentation limits is described via R

^{2}

_{pre}that could be raised up to 100% theoretically. PRESS is a quantity that reveals the deviation between the fitted values via model and real observations. This deviation should be at minimum. Table 6 has summarized the adequacy statistics of the suggested models. These evidences imply that the presented models are acceptable reasonably.

##### Table 5

#### 2.1.2 Data Analyzing

#### 2.1.3 Optimization

_{i}. The values of d

_{i}generally alter from 0 to 1 where 0 denotes unacceptable case and 1 represents the ideal state. Composite desirability is the weighted geometrical mean of single desirability for each response in multi-response problems. When the total desirability is maximized, optimal conditions are reached17). Fig. 5 describes the conditional statements that have been adjusted to minimize HAZ length.

### 2.2 Powder consumption

#### 2.2.1 Model Development

##### Table 8

Parameters | Level 1 | Level 2 | Level 3 |
---|---|---|---|

Nozzles distance | 20 | 23 | 26 |

AC stick out | 18 | 22 | 26 |

DC stick out | 18 | 22 | 26 |

AC angle | 20 | 25 | 30 |

_{i}and n are the i

^{th}observed value of response and average value of observed response. “Smaller the better approach” (equation (6)) is followed for the response parameter which we desire to be minimum and “larger the better approach” (equation (7)) is followed for response parameter which we need to be maximum18).

##### Table 9

##### Table 10

##### Table 11

Level | Distance | AC stick out | AC angle |

1 | -37.43 | -38.56 | -37.6 |

2 | -38.58 | -38.55 | -38.65 |

3 | -39.19 | -38.1 | -38.95 |

Delta | 1.76 | 0.46 | 1.35 |

Rank | 1 | 3 | 2 |

#### 2.2.2 Data Analyzing

##### Table 12

Outside Weld | Speed (m/min) | ||||||
---|---|---|---|---|---|---|---|

DC | AC | Flux | Wire Dia. (mm) | 1.1 | |||

Amp. | Vol. | Amp. | Vol. | ||||

1100 | 32 | 460 | 35 | KJF 610 | 4 | 3 |

### 3. Conclusion

I(DC) is the most influential parameter as far as impact toughness and HAZ width are concerned; by increasing I(DC), HAZ width considerably increases while impact toughness tend to decrease.

There is a clear connection between HAZ width and impact toughness of HAZ; by increasing HAZ width, impact toughness decrease.

The most effective way to reduce I(DC) and consequently HAZ width would be using SAW wires with smaller diameters.

As can be seen, there is an interaction between V(DC) and V(AC) so that the effect of V(DC) on increasing the width of the HAZ is apparently higher at low level of V(AC).

Regarding the width of the HAZ, the influence of I(DC) is undoubtedly greater than I(AC). Conversely, V(AC) seems to be more influential in comparison with V(DC).

As can be expected, similar to single wire, current has no effect on the consumption of powder in the tandem method.