# Multiparametric Investigation of Welding Techniques on Toe Radius of High Strength Steel at Low-Temperature Levels Using 3D-Scanning Techniques

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

_{2}) and “+” 100% CO

_{2}.

#### 2.1. Materials

#### 2.2. Varying Welding Techniques

- torch angle;
- number of cover passes;
- the length of electrode stick-out;
- the shielding gas.

#### 2.2.1. Torch Angle

#### 2.2.2. Number of Cover Passes

#### 2.2.3. Length of Electrode Stick-Out

#### 2.2.4. Shielding Gas

_{2}, while argon is the most commonly used inert gas. Over the recent times, mixtures of gases that have better characteristics than pure gases are used ever more frequently. The welding procedure is named after the type of gas used. Two shielding gases were used in this research, i.e., a mixture of gases (82% Ar and 18% CO

_{2}) and pure CO

_{2}.

## 3. Results

#### 3.1. D-Scanning and Methodology

^{6}pixels each. According to the instructions of GOM Inspect computational software (GOM GmbH, Braunschweig, Germany), the minimum distance between two points on the sample measured was 0.02 mm [35].

#### 3.2. Measurement of Geometries of the Welded Joint Cross-Section With the GOM Inspect Computational Software

_{2}) of shielding gas is used, marked with “A” in Figure 9a. This welding technique should be avoided.

## 4. Discussion

- (1)
- a new state-of-the-art method for scanning a welded joint surface and measuring the seam edge radius with a 3D scanner have been presented;
- (2)
- by analyzing the radius of the seam edge with a 3D scanner, new welding parameters were obtained which significantly affect the surface shape of the welded joint, thus preventing the initiation of surface cracks;
- (3)
- welding parameters have been obtained which should definitely be avoided during welding because if used, there is a high probability of surface cracks.

## 5. Conclusions

_{2}) the torch angle should be perpendicular, while with the pure CO

_{2}the torch has to be in the forehand position. In both cases, the electrode stick-out should be short, while the number of cover passes is not a parameter that significantly influences the stress concentration and can be independently selected.

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Appendix A

#### The Sensitivity Analysis of Expression for Calculation of Stress Concentration Factor in Butt Welding Joints

_{max}and nominal stress, σ

_{nom}, i.e.,

Geometric Quantity | Values in which the Sensitivity was Analyzed |
---|---|

Thickness of the base metal | 6, 10, and 20 mm |

Weld toe angle | 5°, 10°, 20°, and 50° |

Toe radius | 0,1, 0.5, 1, and 3 mm |

Reinforcement height | 1, 2, and 4 mm |

Weld width | 20, 25, and 30 mm |

- weld width

- base metal thickness;
- reinforcement height;
- weld toe angle with the toe radius bigger than 1 mm;
- toe radius with the radius bigger than 1 mm;

- weld toe angle with the toe radius of up to 1 mm;
- toe radius with the radius from 0.5 mm to 1 mm;
- Area of great influence:
- toe radius with the radius of up to 0.5 mm.

_{θ}in point “B” is 16.87. It is found in the Figure A1 that shows the influence of the change at the weld toe angle. The value is positive, which means that by increasing the weld toe angle, the stress concentration factor is increased. The value 16.87 is the coefficient of the direction of the tangent in the Equation (A2) in the point (φ = 0.1 mm, t = 10 mm, W = 20 mm, h = 4 mm, and θ = 5°).

**Figure A1.**Areas of significant and great influence of geometric quantities on the stress concentration factor; (

**a**) Influence of the weld toe radius on the stress concentration factor, (

**b**) Influence of the weld toe angle on the stress concentration factor

**Figure A2.**The analysis of the influence of geometric quantities (

**a**) thickness of base material, (

**b**) reinforcement height, (

**c**) weld width and (

**d**) weld toe angle on the geometric factor of stress concentration as function of toe radius after the expression suggested by Ushirokawa and Nakayama [28].

_{θ}= 4.14. This point is found in diagram b, which presents the influence of the weld toe angle on the stress concentration factor. The value is positive, which means that by lowering the weld toe angle, the stress concentration factor is increased. Value 4.14 is the coefficient of the tangent expression (A2) in point (φ = 0.1 mm, θ = 60°, t = 10 mm, h = 2 mm, and W = 18 mm).

**Figure A3.**(

**a**) Influence of the weld toe radius on the stress concentration factor, (

**b**) Influence of the weld toe angle on stress concentration factor.

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**Figure 4.**The sample: (

**a**) Generated in the GOM Inspect computational software; (

**b**) with marked bands.

**Figure 9.**Calculation of the toe radius as a function of the torch angle and the electrode stick-out for following welding techniques (

**a**) one cover pass; shielding gas 82% Ar + 18% CO

_{2}, (

**b**) three cover passes; shielding gas 82% Ar + 18% CO

_{2}, (

**c**) one cover pass; shielding gas 100% CO

_{2}and (

**d**) three cover passes; shielding gas 100 CO

_{2}.

Welding Techniques | Level | ||
---|---|---|---|

Lower (Mark “−“) | Middle (Mark “0”) | Higher (Mark “+”) | |

Torch angle (A) | Forehand technique Group 1 | Vertical technique Group 2 | Backhand technique Group 3 |

Number of cover passes (B) | 1 pass | 3 passes | |

Length of electrode stick-out (C) | 5 mm | 15 mm | |

Shielding gas (D) | 82% Ar + 18% CO_{2} | 100% CO_{2} |

Input Factor | The Experiment Group and Label Level of Input Factor | |||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

1-1 | 1-2 | 1-3 | 1-4 | 1-5 | 1-6 | 1-7 | 1-8 | 2-1 | 2-2 | 2-3 | 2-4 | 2-5 | 2-6 | 2-7 | 2-8 | 3-1 | 3-2 | 3-3 | 3-4 | 3-5 | 3-6 | 3-7 | 3-8 | |

Group 1 | Group 2 | Group 3 | ||||||||||||||||||||||

Torch angle | − | − | − | − | − | − | − | − | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | + | + | + | + | + | + | + | + |

Number of cover passes | − | − | − | − | + | + | + | + | − | − | − | − | + | + | + | + | − | − | − | − | + | + | + | + |

Length of electrode stick-out | − | − | + | + | − | − | + | + | − | − | + | + | − | − | + | + | − | − | + | + | − | − | + | + |

Shielding gas | − | + | − | + | − | + | − | + | − | + | − | + | − | + | − | + | - | + | − | + | − | + | − | + |

Chemical Element (%) | C | Si | Mn | P | S | Cr | Mo | Ni | Al | Cu | Nb |
---|---|---|---|---|---|---|---|---|---|---|---|

Required (according to DNV GL Rules) [31] | ≤0.18 | ≤0.50 | 0.90–1.60 | ≤0.035 | ≤0035 | ≤0.20 | ≤0.08 | ≤0.40 | ≥0.020 | ≤0.35 | 0.02–0.05 |

Actual (according to factory certificate) [33] | 0.176 | 0.34 | 1.42 | 0.014 | 0.001 | 0.050 | 0.003 | 0.020 | 0.024 | 0.020 | 0.026 |

Sample | 1-1 | 1-2 | 1-3 | 1-4 | 1-5 | 1-6 | 1-7 | 1-8 | 2-1 | 2-2 | 2-3 | 2-4 |

Band A | 0.22 | 0.27 | 0.27 | 0.30 | 0.20 | 0.43 | 0.22 | 0.36 | 0.29 | 0.27 | 0.33 | 0.29 |

Band B | 0.21 | 0.41 | 0.29 | 0.30 | 0.29 | 0.39 | 0.26 | 0.31 | 0.27 | 0.40 | 0.26 | 0.26 |

Band C | 0.23 | 0.30 | 0.26 | 0.23 | 0.29 | 0.29 | 0.26 | 0.45 | 0.41 | 0.40 | 0.28 | 0.24 |

Sample | 2-5 | 2-6 | 2-7 | 2-8 | 3-1 | 3-2 | 3-3 | 3-4 | 3-5 | 3-6 | 3-7 | 3-8 |

Band A | 0.39 | 0.28 | 0.27 | 0.26 | 0.48 | 0.38 | 0.37 | 0.30 | 0.28 | 0.31 | 0.26 | 0.35 |

Band B | 0.39 | 0.24 | 0.28 | 0.33 | 0.29 | 0.33 | 0.25 | 0.29 | 0.27 | 0.29 | 0.21 | 0.25 |

Band C | 0.37 | 0.25 | 0.25 | 0.29 | 0.37 | 0.33 | 0.32 | 0.28 | 0.25 | 0.35 | 0.31 | 0.36 |

Main Effects and Interactions | p-Value | |
---|---|---|

A | Torch angle | 0.267 |

B | Number of cover passes | 0.783 |

C | Electrode stick-out | 0.036 |

D | Shielding gas | 0.053 |

AB | Torch angle—Number of cover passes | 0.016 |

AC | Torch angle—Length of electrode stick-out | 0.366 |

AD | Torch angle—Shielding gas | 0.027 |

BC | Number of cover passes—Length of electrode stick-out | 0.342 |

BD | Number of cover passes—Shielding gas | 0.247 |

CD | Length of electrode stick-out—Shielding gas | 0.882 |

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**MDPI and ACS Style**

Randić, M.; Pavletić, D.; Turkalj, G.
Multiparametric Investigation of Welding Techniques on Toe Radius of High Strength Steel at Low-Temperature Levels Using 3D-Scanning Techniques. *Metals* **2019**, *9*, 1355.
https://doi.org/10.3390/met9121355

**AMA Style**

Randić M, Pavletić D, Turkalj G.
Multiparametric Investigation of Welding Techniques on Toe Radius of High Strength Steel at Low-Temperature Levels Using 3D-Scanning Techniques. *Metals*. 2019; 9(12):1355.
https://doi.org/10.3390/met9121355

**Chicago/Turabian Style**

Randić, Miroslav, Duško Pavletić, and Goran Turkalj.
2019. "Multiparametric Investigation of Welding Techniques on Toe Radius of High Strength Steel at Low-Temperature Levels Using 3D-Scanning Techniques" *Metals* 9, no. 12: 1355.
https://doi.org/10.3390/met9121355