Comparative analyses of the mechanical and microstructural properties of the weld region of LPG cylinder materials

Figures & data

Table 1. Chemical composition of cylinder source materials

Steel	C	Si	Mn	S	P	Nb	Ti	V
LPG-C1	0.21	0.05	0.80	0.01	0.02	0.03	0.001	0.004
LPG-C2	0.08	0.26	0.52	0.02	0.04	0.04	0.001	0.000
LPG-C3	0.22	0.27	0.75	0.01	0.06	0.04	0.002	0.006
LPG-C4)	0.20	0.16	0.35	0.01	0.04	0.03	0.002	0.004
LPG-C5	0.15	0.53	0.81	0.02	0.01	0.03	0.002	0.005
ISO 9809–1	0.3–0.37	≤0.4	0.60–0.90	≤0.35	≤0.035	0.9–1.2	<0.15	<0.30

Table 2. Material property used for modeling

Type of steel	E (GPa)	Poisson’s ratio
Low Carbon Steel	230	0.3

Figure 1. Optical micrographs of the samples (a) LPG-C1, (b) LPG-C2, (c), LPG-C3, (d) LPG-C4 and (e) LPG-C5.

Figure 2. SEM micrographs of the fractured surface showing the ductile behavior of all the samples (a) LPG-C1 (b) LPG-C2, (c) LPG-C3, (d) LPG-C4 and (e) LPG-C5.

Figure 3. Stress-strain curves for various cylinder material sources.

Table 3. Mechanical test results for cylinder sources

Sample	Tensile strength/MPa	Yield strength/MPa	Modulus/GPa	Elongation/%	Hardness/HV
LPG-C1	583.8 ± 65	376 ± 42	311.5 ± 23	17 ± 4	189.9 ± 8.7
LPG-C2	578.3 ± 58	389 ± 46	253.6 ± 21	14 ± 3	200.1 ± 10.5
LPG-C3	611.3 ± 66	418 ± 54	232.4 ± 18	9 ± 2	201.7 ± 13.5
LPG-C4	558.6 ± 45	392 ± 45	217.1 ± 16	15 ± 3	181.4 ± 10.6
LPG-C5	525.6 ± 60	352 ± 40	162.9 ± 12	23 ± 6	165.9 ± 7
ISO 22,991	241–2450	140–2400	183–213	3.00–48.0	22.0–661

Figure 4. Shows the burst testing technique (a) and position of crack relative to welded region in the LPG-C1-LPG-C5 ((b)-(e)).

Table 4. Burst test results

Sample	Burst Pressure (MPa)	Volumetric Expansion (%)	Crack Initiation
LPG-C1	12.4	11.3	Fracture did not initiate in the weld
LPG-C2	12.2	6.3	Fracture did not initiate in the weld
LPG-C3	11.8	13.8	Fracture did not initiate in the weld
LPG-C4	11.5	6.5	Fracture did not initiate in the weld
LPG-C5	12.2	19.48	Fracture did not initiate in the weld

Figure 5. Tensile test models for various cylinder materials (a) LPG-C1 (b) LPG-C2 (c) LPG-C3 (d) LPG-C4 and (e) LPG-C5.

Figure 6. Burst test results for various cylinder material sources (a) LPG-C1, (b) LPG-C2 (c) LPG-C3, (d) LPG-C4 and (e) LPG-C5.

Figure 7. Shows the mechanical properties of samples; (a) fracture toughness and (b) Energy release rate curves.

Figure 8. Progression of crack during tensile test of cracked specimen (Models).