By HeidiK
Date 02-22-2019 06:57
Edited 02-22-2019 07:20
Hello,
Any suggestion how to decrease hardness?
Allowed maximum hardness: 210 HV10 (base material/HAZ/weld)
(Also impact requirements; -46C at least 27 J tranverse or 40 J longitudinal. (Values ar average of 3 tests with minimum values 21 J trans. and 30 J long.))
Material: SA333 Gr6
Welding process: GTAW (TIG)
Welding consumable: ER70S-3 (Böhler EML5)
Material thickness: 7,1 mm
Outside pipe diameter: 48,3 mm
Joint type: BW ss nb ml
Welding positions used during tests: PH, PC
Tungsten electrode type/size: WT 20 / 2,4 mm
PWHT: Temperature 620 C +/- 20 C; time 2 min/mm (at least 20 min); Heating rate 50 - (500/s) C/h, max 200 C/h; Cooling rate 7000/s C/h, max 275 C/h
Welding test No. 1:
After each run the material/weld were cooled under 200 C (in air) before welding next run.
PH 1, 2, 3... : 90-120 A, 8-12 V, DC-
PC (PB) 1, 2, 3... : 95-125 A, 8-12 V, DC-
Measured hardnesses:
- base: 1: 146-149 HV10; 2: 146-148 HV10
- HAZ: 1: 165-192 HV10; 2: 164-198 HV10
- weld: 1: 175-253 HV10
Welding test No. 2:
After each run temperature was kept over 200 C and top layer of weld was welded by using 2 runs.
PH 1, 2, 3... : 100-130 A, 15-18 V, DC-
PC (PB) 1, 2, 3... : 100-130 A, 15-20 V, DC-
Measured hardnesses:
- base: 1: 145-147 HV10; 2: 145-147 HV10
- HAZ: 1: 159-169 HV10; 2: 162-183 HV10
- weld: 1: 136-220 HV10
(question is also in Technical discussion section)