Abstract:Welding heat cycle computer software is developed successfully, bases on experiential
and practical mathematic model, uses LabVIEW7.1 to program, it can draw single or multi-process
welding heat cycle curve conveniently and quickly. This paper puts emphasize on explaining the
realization of multi-process heat cycle curve which is drawn by the same or different mathematic
model, and the research of heat cycle curve’ change which is caused by the change of parameters. It
introduces the comparison between practic… Show more
“…The welding HAZ thermal cycle simulation test was conducted on a Gleeble‐3800 thermal/mechanical simulator. The temperature profile for the thermal simulation was calculated by adopting the Rykalin mathematical model [ 33 ] for submerged arc welding with a heat input of 200 kJ cm −1 for 30 mm‐thick plates. The temperature curve of the simulation is plotted in Figure 1 .…”
It is frequently found in the literature that an acicular ferrite (AF) dominant microstructure has unsteady or even low‐impact toughness. It is necessary to analyze whether they are qualified for real AF. Herein, a Ti‐killed high strength low alloy steel is prepared and subjected to heat‐affected zones simulation tests to induce various AF‐like microstructures. The morphological differences of these microstructures are compared, and their crystallographic characteristics are analyzed. It is found that even within a single prior austenite grain, the transformed microstructure can be heterogeneous. Local areas having clear lath boundaries and a chaotic or interlocking morphology should be classified as AF. Adjacent laths in these areas are from different close‐packed plane and Bain groups. In contrast, local areas having vague lath boundaries and a granular‐bainite‐like morphology should be classified as granular bainite. Neighboring laths in these areas are from the same Bain group, and a relatively low density of high‐angle grain boundaries can be found. The heterogeneous microstructure consisting of granular bainite and AF has a wider grain size distribution and a higher area fraction occupied by large grains, which can lead to the scatter of Charpy impact energy. Criteria for the identification of AF are also proposed in this research.
“…The welding HAZ thermal cycle simulation test was conducted on a Gleeble‐3800 thermal/mechanical simulator. The temperature profile for the thermal simulation was calculated by adopting the Rykalin mathematical model [ 33 ] for submerged arc welding with a heat input of 200 kJ cm −1 for 30 mm‐thick plates. The temperature curve of the simulation is plotted in Figure 1 .…”
It is frequently found in the literature that an acicular ferrite (AF) dominant microstructure has unsteady or even low‐impact toughness. It is necessary to analyze whether they are qualified for real AF. Herein, a Ti‐killed high strength low alloy steel is prepared and subjected to heat‐affected zones simulation tests to induce various AF‐like microstructures. The morphological differences of these microstructures are compared, and their crystallographic characteristics are analyzed. It is found that even within a single prior austenite grain, the transformed microstructure can be heterogeneous. Local areas having clear lath boundaries and a chaotic or interlocking morphology should be classified as AF. Adjacent laths in these areas are from different close‐packed plane and Bain groups. In contrast, local areas having vague lath boundaries and a granular‐bainite‐like morphology should be classified as granular bainite. Neighboring laths in these areas are from the same Bain group, and a relatively low density of high‐angle grain boundaries can be found. The heterogeneous microstructure consisting of granular bainite and AF has a wider grain size distribution and a higher area fraction occupied by large grains, which can lead to the scatter of Charpy impact energy. Criteria for the identification of AF are also proposed in this research.
“…Samples were machined into a dimension of 10 mm10 mm55 mm so that the thermal cycle was loaded by the Gleeble-3500 thermal simulator. The Rykalin-3D program on the Gleeble-3500 thermal simulator was loaded in the experiment as described elsewhere [29]. A schematic illustration of the simulated thermal cycle is shown in Figure 1.…”
The effect of Zr addition on the impact energy at −20°C, the microstructure, and inclusions of hightitanium low-alloy steels in the simulated heat-affected zone was investigated. The impact energy of the steel without Zr addition was 25.7 J and increased to 242.9 J for the steel with the addition of 80 ppm Zr. When the heat input was 300 kJ cm−1, the impact energy of the steel without Zr addition was 17.5 J and increased to 140.9 J for the steel with 80 ppm Zr, the nucleation potential of AFs increased from 24.4 /mm2 to 76.7 /mm −2 , and the average nucleation potential of inclusions decreased from 2.02 to 1.67. The grain refinement by the formation of acicular ferrites stemmed from the increase of 1-3 μm Al-Ti-Zr-O inclusions was responsible for the toughness improvement in CGHAZ of the Zr-bearing steel.
“…The welding thermal cycle parameter is schematically presented in Figure 1. The heating rate for the thermal cycles was 100°C s −1 , the peak temperature is about 1350°C, and the holding time is 1 s. Times ( t 8/5 ) of 40, 85 and 137.5 s were used to simulate weld heat inputs of 54, 80 and 100 kJ cm −1 , respectively, according to the formula (1) [32], which is used to simulate the welding method with large heat input energy.where E is the input line energy, kJ cm −1 ; l is the thermal conductivity, W (cm °C) −1 ; c is the specific heat capacity, J (g °C) −1 ; ρ is the density, g cm −1 [3]; T 0 is the preheating temperature or the temperature between pass, °C; d is the plate thickness, cm. Figure 1. Schematic diagram of welding thermal cycle.…”
A critical investigation into the role of Mg on the toughness and microstructure of coarse grain heat-affected zone (CGHAZ) in low carbon steel has been investigated. In this research, the specimens (Mg-free and Mg-added) underwent weld thermal cycle with heat input of 54, 80, and 100 kJ cm −1 at 1350°C peak temperature using a thermal simulator. The typical inclusions characteristics were characterised by means of scanning electron microscopy and equilibrium calculations. The precipitates were characterised by transmission electron microscopy and energydispersive spectroscopy. It is revealed that the occurrence of Mg in steel mostly exists in the form of Mg-Al-O oxide inclusions, but a few in the form of solid solution state and (Nb,Ti)(C,N)+MgO precipitates when the concentration of Mg is 0.0026%. The improvement of CGHAZ toughness is obtained when the heat input is 80 and 100 kJ cm −1 . The possible reasons about the effects of Mg on the toughness of CGHAZ, including Mg-Al-O inclusions, precipitates, and soluble Mg, are discussed in detail.
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