Strain ageing embrittlement behaviour of X80 self-shielded flux-cored girth weld metal

Figures & data

Figure 1. Schematic of through thickness plate tensile specimen for prestrain and CVN sample position.

Figure 2. Microstructure of X80 FCAW weld metal. (a, c) Cap pass; (b, d) Filling passes.

Figure 3. Microstructure of filling passes of X80 FCAW girth weld metal at different strain ageing conditions. (a) No strain ageing (a); (b) 1% prestrain and 150°C for 3-h ageing; (c) 100°C for 6-h ageing; and (d) 80°C for 30-day ageing (d).

Figure 4. Strain ageing embrittlement behaviour of FCAW girth weld metal. Charpy absorbed energy; (b) strain ageing sensitivity (C_V).

Table 1. CVN absorbed energy and strain-ageing sensitivity (C_V) of X80 FCAW weld metal before and after strain ageing treatment.

Prestrain	Ageing Temp. & Period	Akv/J			$\overline{{\mathrm{A}}_{\mathrm{k}\mathrm{v}}}$/J	Cv/%
-	-	153.8	128.8	193.8	158.8	-
1%	-	71.3	141.2	133.8	115.4	27.3
-	150°C + 1 h	120	142.5	72.5	111.7	29.7
	150°C + 3 h	109.3	115	91	105.1	33.8
1%	150°C + 1 h	85	41.3	60	62.1	60.9
	150°C + 3 h	46.7	67	65	59.6	62.5
	100°C + 1 h	115	65	86.3	88.8	44.1
	100°C + 3 h	62.5	90	78.5	77.0	51.5
	100°C + 6 h	61	75	53.5	63.2	60.2
	80°C + 1 day	168.7	71.3	121.2	120.4	24.2
	80°C + 3 days	76.2	78.8	87.5	80.8	49.1
	80°C + 7 days	77.5	88	70.6	78.7	50.4
	80°C + 15 days	58	80.5	64	67.5	57.5
	80°C + 30 days	53.5	72	55.8	60.4	62.0

Figure 5. (a–h) Fracture surfaces of the CVN samples at different strain ageing conditions characterized by stereo microscope.

Figure 6. (a–h) Fracture surfaces of the CVN samples at different strain ageing conditions characterized by SEM.

Figure 7. (a–c) Fracture surfaces of the CVN samples strain aged at 80°C for different periods.