Influence of welding interpass temperature on Charpy V-notch impact energy of coarse-grain heat-affected zone of AISI 4130 steel pipe

Welding thermal cycle of SMA490BW corrosion resistance steel with different heat inputs were simulated by using Gleeble-3500 thermo-mechanical simulator to investigate the microstructure and impact toughness of the heat-affected zone (HAZ). The results shows that the microstructure of the coarse-grain heat affected zone(CGHAZ) is mainly composed of lath bainites and the surpass critical coarse-grain heat affected zone(SCCGHAZ) consists mainly of granular bainites with a small content of ferrites. The grain size increased with the heat input increasing, Besides, the impact energy of the surpass critical coarse-grain heat affected zone(SCCGHAZ) is higher than that of the coarse-grain heat affected zone(CGHAZ), when the heat input energy is 15kJ/cm after twice thermal cycle, the impact energy is highest.

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Continuous Cooling Transformation Diagram, Microstructures, and Properties of the Simulated Coarse-Grain Heat-Affected Zone in a Low-Carbon Bainite E550 Steel

Metals ◽

10.3390/met9090939 ◽

2019 ◽

Vol 9 (9) ◽

pp. 939 ◽

Cited By ~ 1

Author(s):

Yun Zong ◽

Chun-Ming Liu

Keyword(s):

Impact Toughness ◽

Cooling Rate ◽

Vickers Hardness ◽

Heat Affected Zone ◽

Granular Bainite ◽

Coarse Grain ◽

Low Carbon ◽

Transformation Diagram ◽

Lath Bainite ◽

Continuous Cooling Transformation Diagram

In order to provide important guidance for controlling and obtaining the optimal microstructures and mechanical properties of a welded joint, the continuous cooling transformation diagram of a new low-carbon Nb-microalloyed bainite E550 steel in a simulated coarse-grain heat-affected zone (CGHAZ) has been constructed by thermal dilatation method in this paper. The welding thermal simulation experiments were conducted on a Gleeble-3800 thermo-mechanical simulator. The corresponding microstructure was observed by a LEICA DM2700M. The Vickers hardness (HV) and the impact toughness at −40 °C were measured according to the ASTM E384 standard and the ASTM E2298 standard, respectively. The experimental results may indicate that the intermediate temperature phase transformation of the whole bainite can occur in a wide range of cooling rates of 2–20 °C/s. In the scope of cooling rates 2–20 °C/s, the microstructure of the heat-affected zone (HAZ) mainly consists of lath bainite and granular bainite. Moreover, the proportion of lath bainite increased and granular bainite decreased as the cooling rate increasing. There is a spot of lath martensite in the microstructure of HAZ when the cooling rate is above 20 °C/s. The Vickers hardness increases gradually with the increasing of the cooling rate, and the maximum hardness is 323 HV10. When the cooling time from 800 °C to 500 °C (t8/5) is 5–15 s, it presents excellent −40 °C impact toughness (273–286 J) of the CGHAZ beyond the base material (163 J).

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Influence of Ni and Mn on Microstructure and Mechanical Properties of Coarse Grain Heat Affected Zone in Low Carbon Microalloyed Steel

Energy Materials 2014 ◽

10.1007/978-3-319-48765-6_76 ◽

2014 ◽

pp. 629-637

Author(s):

Xuelin Wang ◽

Xueda Li ◽

Xuemin Wang ◽

Chengjia Shang

Keyword(s):

Mechanical Properties ◽

Heat Affected Zone ◽

Microalloyed Steel ◽

Coarse Grain ◽

Low Carbon ◽

Microstructure And Mechanical Properties ◽

Carbon Microalloyed

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Microstructure and Mechanical Properties of Heat-Affected Zone of Repeated Welding AISI 304N Austenitic Stainless Steel by Gleeble Simulator

Metals ◽

10.3390/met8100773 ◽

2018 ◽

Vol 8 (10) ◽

pp. 773

Author(s):

Y.H. Guo ◽

Li Lin ◽

Donghui Zhang ◽

Lili Liu ◽

M.K. Lei

Keyword(s):

Mechanical Properties ◽

Stainless Steel ◽

Austenitic Stainless Steel ◽

Impact Energy ◽

Heat Affected Zone ◽

Ferrite Content ◽

Equipment Safety ◽

Microstructure And Mechanical Properties ◽

Δ Ferrite ◽

The Impact

Heat-affected zone (HAZ) of welding joints critical to the equipment safety service are commonly repeatedly welded in industries. Thus, the effects of repeated welding up to six times on the microstructure and mechanical properties of HAZ for AISI 304N austenitic stainless steel specimens were investigated by a Gleeble simulator. The temperature field of HAZ was measured by in situ thermocouples. The as-welded and one to five times repeated welding were assigned as-welded (AW) and repeated welding 1–5 times (RW1–RW5), respectively. The austenitic matrices with the δ-ferrite were observed in all specimens by the metallography. The δ-ferrite content was also determined using magnetic and metallography methods. The δ-ferrite had a lathy structure with a content of 0.69–3.13 vol.%. The austenitic grains were equiaxial with an average size of 41.4–47.3 μm. The ultimate tensile strength (UTS) and yield strength (YS) mainly depended on the δ-ferrite content; otherwise, the impact energy mainly depended on both the austenitic grain size and the δ-ferrite content. The UTS of the RW1–RW3 specimens was above 550 MPa following the American Society of Mechanical Engineers (ASME) standard. The impact energy of all specimens was higher than that in ASME standard at about 56 J. The repeated welding up to three times could still meet the requirements for strength and toughness of welding specifications.

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Research on Brittle Fracture of X70/X80 Line Pipes with Big Wall Thickness at Low Temperature

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.795.3 ◽

2019 ◽

Vol 795 ◽

pp. 3-8

Author(s):

Hai Tao Wang ◽

Shi Li Li ◽

Yan Long Luo ◽

Jun Qiang Wang ◽

Hai Bin Zhang ◽

...

Keyword(s):

Low Temperature ◽

Brittle Fracture ◽

Wall Thickness ◽

Impact Energy ◽

Charpy Impact ◽

High Rate ◽

Steel Pipe ◽

Thickness Effect ◽

Structural Factors ◽

Charpy Impact Energy

Based on research of the low temperature fracture property of high grade steel pipe, it shows that X70, X80 steel pipe and X80 tee have high Charpy impact toughness. However, as the wall thickness increases, the shear area of DWTT decreases rapidly, and the thickness effect is significant. The research results show that the original wall thickness impact specimen fracture of steel pipe may not be ductile, for design temperature less than -30°C and wall thickness greater than 40mm. The brittle fracture was caused by structural factors. The Charpy impact energy, which just reflects the toughness of materials, does not show the fracture appearance as it would occur in service, because of the different specimen geometry and high rate of impact. The brittle fracture can occur at low temperature and low stress even with a high Charpy impact energy, the conditions of brittle fracture should be established under combination of the wall thickness, temperature and other factors. In this work, it is clarified that measurement of the fracture toughness under service temperature should be used to control low stress brittle fracture, besides the Charpy impact energy to ensure the material toughness.

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