African Fusion August 2018

– Italy, was the first fabricator to evaluate and apply this new technique on a real- life project. After carrying out several trials under industrial conditions, twowelding procedures for SS 347 cladding onCr-Mobasema- terial were successfully qualified: using 60×0.5 mm strip with two 1.6mmMCWwires; and 90×0.5mmstripwith three 1.6mm MCWwires. The procedureswere qualified tomeet ASME Sec IX requirements as well as other licensor specifications. The test coupon was subjected to the following tests in minimum PWHT conditions (690 ±50 °C for six hours), as well as maximum PWHT conditions (690 ±50°C for 3×6 hours). All of the test results listed below were satisfactory: • Chemical analysis at all 0.5 mm depths meet undiluted SS347 chemistry requirements. • 1 800 mm side bend test as per ASME Sec IX. • Macroscopic examination at 10× magnification as per ASTM E 340-15. • Microscopic examination at 100× magnification as per ASTM E 407-07. • Hardness surveys (Hv10) on theweldmetal (WM), HAZ and base material as per NACE MR0175-09. • Corrosion tests as per ASTM A 262 Practice E. • Hydrogen disbonding test as per ASTM G-146 (Test tem- perature: 4 500°C; H2 Partial pressure: 175 bar; Holding time: 48 hours; Cooling rate: 1 500°C/hr). The tests deter- mined zero disbonding. Subsequent to the successful qualification of awelding proce- dure, this new technique was applied on several CrMo vessels using a ‘step overlay’ technique. The entire claddingworkwas completed at Walter Tosto workshop very smoothly without any interruption (Figure 11(a) and (b)). The H-ESC technique brings the following benefits over other cladding techniques: • Much better flexibility in terms of chemistry and delta fer- rite control bymeans of easy adjustment of MCWcomposi- tionwithout any need to change the strip compositions or the neutral flux type. • Offers a single layer cladding solution. This not only saves overall weld metal costs and cladding time, it also elimi- nates all associated NDE cost and the time required for additional layers. • Much higher welding speed – typically 27 to 32 cm/min for Ni Alloys and 33 to 40 cm/min for austenitic stainless steels: as compared to 16 to 18 cm/min for conventional ESC cladding methods. Higher speed not only helps fabri- cators to reduce their labour cost, it allows them to utilise those hours effectively in producing more components, thereby raising their throughput. • Significantly higher deposition rates – typically 38 to 44 kg/hr as compared to 22 to 24 kg/hr for conventional ESW cladding using 60×0.5 mm strip. The deposition rate for 90×0.5 mm strip with three 1.6 mm metal-cored wires is about 50 to 58 kg/hr. • In the case of all major austenitic stainless steel cladding, working capital costs for fabricators is reduced substan- tially due to shorter delivery times for using standard strip and flux consumables for multiple stainless grades. Conclusions The following can be concluded: • Weld cladding remains one of the major areas in fabrica- tion of CPEs.

Figure 9(a): Cladding of SS347 on a 2.25Cr-1Mo vessel using the H-ESC technique – 60×0.5 mm strip and two 1.6 mm MCWs at Walter Tosto.

Figure 9(b): Cladding of SS347 on a 1.25Cr-0.5Mo vessel using the H-ESC technique – 90×0.5 mm strip with three 1.6 mm MCW wires at Walter Tosto.

• Weld cladding for Ni alloys and austenitic stainless steel using the ESWcladding process is preferred by fabricators as compared to SAW cladding. • ESW offers single layer and/or high-speed solutions for many of the commonly used alloys. However, it has limi- tations on higher speeds as well as single layer solutions for materials such as Ni-625, where reaching the required chemistry of Fe content <5% in single layer is not possible using Neutral flux under production condition. • TheH-ESC innovative introducesmultiple hotmetal-cored wires into the arcless molten electro-slag weld pool. As a result, this solution offers much better dilution control, much faster welding speeds and the highest deposition rates. • H-ESCmakes it possible to reach stringent undiluted clad- ding chemistry in a single layer for all commonly used Ni and stainless steel alloys. It is possible to reach Fe <5% in single layer Ni-625 alloy deposit at a welding speed of 27 cm/min or to reach a minimum 40% Ni content in Ni-825 alloy in single 4.0 mm deposit layer with higher welding speeds. • H-ESC requires only one single strip composition and a neutral flux for all major austenitic stainless steel grades to achieve the different alloy chemistries of, for example, SS316L, 308L, 347 and 317L – also in a single layer and at welding speeds above 33 cm/min. • H-ESChas been successfully applied on an industrial scale. Acknowledgements: The authors would like to offer special thanks to the management and technical personnel of their industrial partner, Walter Tosto SpA – Italy, for excellent support and cooperation during the development and industrialisation of the H-ESC technique. Extracted from the proceedings of the 71st IIWAnnual Assembly & International Conference, 15 to 20 July 2018, Bali, Indonesia. ©IIW 2018.

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August 2018

AFRICAN FUSION