African Fusion November 2018

Modified GMAW-P on Q&T steel

C Cr 0.17 0.018 1.37 0.21 0.004 0.017 0.2 Mo Cu Al Sn Ti B CE (IIW) 0.2 0.026 0.035 0.002 0.019 0.0017 0.4812 Table 3: Chemical Composition of Q&T Steel (% by weight from the manufacturer). The parent plate sections were then sandblasted using a ToolTec Sandblast SB-350 with glass beads with a diameter of up to 305 μ m, which removed any mill scale and/or surface contaminants. The groove surfaces of the test specimen and 25 mm either side of the weld centreline was polished down with ISO 80 grit (201 μ m) emery paper and degreased with acetone. The entire specimenwas degaussed prior towelding. The parent plates and electrodes chemical compositions are given in Table 3, Table 4 and Table 5 P Mn Si S Ni metallographically prepared weldment cross-sections, pol- ished to 1.0 μ mdiamondpaste and etched in 2%nital solution. Welding parameter selection and control Weldability testing was carried out on a uni-directional, mechanised cradle (Lorch Track RL Pro) with the test specimen in a fixed horizontal position. For GMAW-P, the welding torch was secured in the cradle and the trigger was manually oper- ated to initiate and extinguish the welding arc (Figure 5). For SMAW, the electrode holder was manually manipulated. The arm of the mechanised cradle was used as a guide to govern travel speed (Figure 6). Thewelding parameters employed during testing are sum- marised in Table 1 and Table 2. A Lorch S3 Speed XT was used as the welding power source. Material specification The MWIC tests and procedure qualification test coupons were fabricated from AS/NZS 3597 Grade 700 (EN 10137-2 Grade S690Q) steel for the parent plate. Parent plate sections were cut from a single steel plate using the Techni INTEC- G2 1612 water jet cutting system. The cutting direction was oriented such that the prepared welding joint would remain perpendicular to the rolling direction of the plate, emulating field conditions.

Figure 5: Set up of weldability test cradle. The specimen racks were adopted to hold, 150 mm length coupons for productivity testing. MWIC weldability tests for HACC testing and 400 mm length sections for procedure qualification testing.

C

Mn 1.6

Si

Ni

Cr

Mo

V

Figure 6: Procedure qualification testing, using non-mechanised deposition.

0.09

0.5

1.4

0.3

0.25 0.09

Welding Specifications

Welding Parameters

Table 4: Electrode Batch Chemical Composition of AWS A5.28, ER110S-G (% by weight from the manufacturer).

Direction

Current Voltage

Flat (1G)

135-225 A

Diameter of Wire 1.2 mm

21-30 V

AWS Class

Travel speed

A5.28

170- 400 mm/min

C Mn Si Mo V 0.06 1.5 0.4 0.015 0.01 2.2 <0.15 0.4 0.08 Table 5: Electrode Batch Chemical Composition of AWS 5.5 E11018M-H4 (% by weight from the manufacturer). P S Ni Cr

Specification

Heat input range 0.48-2.19 kJ/mm

ER 110S-G

Polarity

Pre-heat range

DC+

250 °C

Shielding gas

Deposition mode GMAW-P [ISO 857 (Process No. 13)]

Ar 18% CO 2 (15-20 ℓ/min)

Results and Discussion Speed trials

Table 1: Welding Parameters -GMAW-P.

Speeds trials were conducted at three target heat inputs – 0.5, 1.5 and 2.0 kJ/mm – to simulate the widest practical range of heat inputs that would be encountered during the fabrication of safety-critical structures. As illustrated in Figure 7, a maxi- mum variation of ±0.2 kJ/mm was noted between the target heat input and the actual measured heat input over the range tested. Additionally, between welding processes a maximum variation of 4.26%was noted at the 0.5 kJ/mm target.

Welding Specifications

Welding Parameters

Direction

Current

Flat (1G)

130-180 A

Size of electrode 3.2 & 4.0 mm Voltage

21-25 V

AWS class

Travel speed

A5.5

80-290 mm/min 0.41-2.22 kJ/mm

Specification

Heat input range Pre heat range

E11018M-H4

Polarity

DC+

250 °C

Table 2: Welding Parameters -SMAW

18

November 2018

AFRICAN FUSION