*2.1.3 Welding speed*

Welding speed is the linear speed at which the arc moves with respect to the plate, along with the weld joint. The heat input and cooling rate increase with decreasing welding speed. Welding speed is calculated by Eq. (2) [13]:

$$\text{Welding Speed} \left( \text{mm}/\text{min} \right) = \text{Electrode Travel}/\text{Arc Time} \tag{2}$$

Moreover, optimization of AISI 316 weld sample characteristics was studied [14] by Taguchi method (ANOVA). Besides, the effect of welding variables as welding speed and current, filler metal and root gap on UTS and bend strength was studied. Travel speed (46.51% contribution) has a greater influence on toughness (bend

#### **Figure 7.**

*Comparison between FN of welding procedures using shielding gas pure and 2% N/98%Ar.*

**Figure 8.**

*Comparison between ductility of welding procedures using shielding gas pure Ar and 2%N/98%Ar.*

#### **Figure 9.**

*Hardness values for PNo.1 (0.395 Kj/mm), PNo.2 (0.79 Kj/mm) and PNo.3 (0.998 Kj/mm) all with using shielding gas of pure argon.*

*Effect of Welding Variables on the Quality of Weldments DOI: http://dx.doi.org/10.5772/intechopen.103175*

#### **Figure 10.**

*Hardness values for PNo.4 (0.411 Kj/mm), PNo.5 (0.822 Kj/mm) and PNo.6 (1.053 Kj/mm) all with using shielding gas of (2%N/98% Ar).*

**Figure 11.**

*Comparison between impact toughness of PNo.3 versus PNo.4.*

strength) and welding current (96.75%) has maximum influences on UTS. The root gap has some effect on both tensile and bend strengths.

#### *2.1.4 Effect of heat input*

Heat input is a relative measure of the energy transferred per unit length of weld. It is an important characteristic because, like preheat and interpass temperature, it influences the cooling rate, which may affect the mechanical properties and metallurgical structure of weld region and HAZ [15]. It is calculated by Eq. (3).

$$\text{HI} \, (\text{K} \text{/mm}) = \eta \ast (\text{V} \ast \text{I} \ast \text{60}) / (\text{S} \ast \text{1000}) \tag{3}$$

where HI is the heat input (in KJ/mm*)*, η is welding efficiency (ηTIG = 70%), V is arc voltage (in volt), I is welding current (in Amp) and S is welding speed (in mm/min)*.*

The effect of heat input on microstructure and mechanical properties have been extensively investigated. For example, Movahedi and Ozlati [16] studied the influence of heat input on mechanical properties of dissimilar welds AISI 410 MSS and 2209 DSS rods. The heat input, UTS and %EL increase with increasing welding current. Best results of *UTS* and %EL are obtained at a welding current of 3.5 kA. Whereas the lowest results of UTS and %EL are obtained at a welding current of 2 kA (**Figure 12**). Moreover, Sergei Yu et al. [17] analyzed the influence of *Hnet* on residual strain and phase content in AISI 304 stainless steel welds using different heat input values. The ferrite content increased with increasing heat input from 0.225 to 0.247 kJ/mm, while the austenite content decreased.

Singh and Kumar [18] investigated the characteristics of 304 stainless steel joints using SMAW-GTAW hybrid welding and different filler metals. The joint with 90A

#### **Figure 12.**

*(a) Hardness profile across the weld interface. (b) Stress-strain curves and (c) values of tensile strength and elongation for all samples [16].*

## *Effect of Welding Variables on the Quality of Weldments DOI: http://dx.doi.org/10.5772/intechopen.103175*

has the highest hardness value and lowest toughness value. The toughness value of weld metal and HAZ increases with increasing heat input. Welding width and depth (penetration) increase with increasing heat input. It can be seen that root reinforcement deposited at 0.93 kJ/mm is wider than that deposited at 0.68 kJ/mm. Whereas, D. Bahar [19] studied the effect of welding parameters as; welding current, gas flow rate and welding speed on bending strength and weld geometry of dissimilar welds of SS 304 and mild steel 1018. The welding width, depth of penetration and bending strength increased with increasing welding current, gas flow rate and welding speed. Additionally, Bodude and Momohjimoh [20] explained the influence of welding variables on mechanical properties of low carbon steel welded by SMAW. Highest ultimate tensile strength and hardness were realized for samples welded at low current. Moreover, best results of weld toughness were obtained at welding current of 150A. HV and UTS increased with decreasing heat input, while the impact toughness increased with increasing heat input. Gupta et al. [21] studied the influence of *Hnet* on the mechanical behavior of FSS 409 plate using two different filler metals (ER304L and ER308 L). Best *UTS* result, yield strength, hardness value and grain size is obtained using medium heat input '4 kj/mm', irrespective of the used filler metal. The mechanical behavior is also infl uenced by grain size of weld metal and heat input. Generally, the joints welded using 304 filler metal showed better results than using 308 filler wire. Moreover, the effect of heat input on the mechanical properties and fatigue life of AA6061 alloy welded by MIG welding was reported [22]. The weld penetration increased linearly with increasing the weld current and arc voltage, but with decreasing the welding speed. On the other hand, the fatigue life decreased with increasing the welding current and arc voltage, whereas, the fatigue life increased with increasing the welding speed. The impact toughness increased slightly with increasing heat input (**Table 1**). Swami et al. [23] studied the influence of MIG welding current, gas flow rate and shielding gas on UTS of 12 mm thick mild steel plates. MIG welding process variables affect UTS value of the weld metal. Best *UTS* result was recorded at 190 A, 15 (L/min) and 50% CO2. Bansod et al. [24] investigated the change of mechanical properties of low-nickel ASS 304 welds using SMAW technique at various heat input values. Highest UTS and HV were obtained using low heat input values (**Table 2**). Hardness of the weld zone was lower than that of the heat affected zone and base metal (**Figures 13**–**15**). The ferrite number of weld region increased with decreasing the heat input (**Table 3**). Furthermore, Bansod et al. [25] studied the influence of heat input on physical metallurgy, mechanical behavior and corrosion rate of Cr-Mn ASS and low nickel ASS specimens. The width of HAZ increased with increasing heat input, while the FN and volume fraction of delta ferrite in weld region decreased. On the other hand, the hardness and tensile strength increased with decreasing heat input. Besides, the pitting resistance was improved with increasing delta ferrite. Ahmed et al. [26] studied the change of weld strength of ASS 316 welds using GTAW technique at various heat input values and filler metals. Using ERNiCrMo-3 as filler rod produced weldments with higher ultimate tensile strength and yield stress than using ER309L or ER316 L. The ultimate tensile strength, yield stress and elongation percent decrease with increasing heat input. Highest values are obtained using ERNiCrMo-3 filler rod at comparatively low welding current (80 A). The hardness is lower in weld zone than that of in heat affected zone and base metal. In general, it decreases with increasing heat input (welding current). Highest values are obtained using ERNiCrMo-3 filler with low heat input (80 A) (**Figures 16**–**18**).


 298.98 296 90.55 2.932 256.26 408 77.21 2.802 405.6 101 63.25 2.941 337.98 264 94.32 2.970 289.68 372 84.62 2.872 360 136 77.84 2.983 300 272 91.01 3.020 257.1 390 78.68 2.911 414 98 61.17 3.078 345 258 85.65 3.101 295.68 366 88.61 3.001 468 85 58.64 3.150 390 246 71.91 3.202

334.26 353 93.65 3.120

358.8 157 81.41 2.860

**Table 1.**

*Life, impact energy and penetration of weld with respect to the weld parameters [22].*
