Revised Manuscript
Effect of Welding Heat Input on Microstructure and Toughness of Heated-Affected Zone in Steel Plate with Mg Deoxidation 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
Longyun Xu, Jian Yang,* Ruizhi Wang, Wanlin Wang, and Zhongmin Ren J. Yang, Professor, Shanghai University, State Key Laboratory of Advanced Special Steel, Shanghai, 200072, P.R. China E-mail:
[email protected] L. Xu, Doctoral candidate. W. Wang, Professor Central South University, School of Metallurgy and Environment, Changsha, 410083, P. R. China R. Wang, Researcher, Y. Wang, Researcher Steelmaking Research Department, Research Institute, Baoshan Iron and Steel Co., Ltd., Shanghai, 201999, P. R. China Z. Ren, Professor Shanghai University, State Key Laboratory of Advanced Special Steel, Shanghai, 200072, P.R. China
1
Keywords: oxide metallurgy; heat-affected zone; microstructure; toughness; Mg deoxidation 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
Effect of heat input on the microstructure and toughness of heat-affected zone (HAZ) in steel plate with Mg deoxidation has been investigated through welding thermal cycle simulation method. With the heat input increasing from 100 to 400 kJ cm-1, the average prior-austenite grain (PAG) size was increased from 43 to 56 and then to 173 μm, and the HAZ microstructure was changed from fine bainite lath to relative larger bainite lath and then to grain boundary ferrite (GBF) and intragranular acicular ferrite (IAF). With the heat input increasing up to 400 kJ cm-1, a great amount of IAF was nucleated by the MgO-MnS inclusions with the size about 2 μm. The Charpy impact values at 40 °C of HAZ were larger than 140 J, and excellent low temperature HAZ toughness was obtained for the 68 mm thickness steel plate with Mg deoxidation with the heat input in the range from 100 to 400 kJ cm-1.
2
1. Introduction 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
High strength thick steel plates have been widely used in the areas of architectural construction, shipbuilding and offshore structures.[1-3] From the viewpoint of improving the quality of weld joints and efficiency of welding process, many high-heat input welding (HHIW) technologies have been developed, such as submerged arc welding (SAW), electrical slag welding (ESW) and vertical electrical gas arc welding (EGW), in which welding is performed in single-pass.[4] The high-heat input generally refers to welding with the heat input greater than 100 kJ cm-1. During the thermal cycle of HHIW, the base metal near the fusion line, called as heat-affected zone (HAZ), is heated to a temperature of 1350 °C or higher and then is experienced a rather low cooling rate in the subsequent γ→α phase transformation. For conventional steel plate, the HAZ microstructure after HHIW becomes coarse to form a local brittle zone (LBZ). Therefore, the HAZ toughness is deteriorated. The initial austenite grain size before γ→α phase transformation and the cooling time from 800 to 500 °C (Δt8/5) affect the formation behavior of the HAZ microstructure during welding process. Zhang et al. reported that the volume fraction of intragranular acicular ferrite (IAF) was increased with the increase of austenite grain size.[5] In the steel with high Mg content, the austenite grains were with small sizes resulting in the ferrites nucleating preferentially from the austenite grain boundaries.[6] Shi et al.[7] found that the prior-austenite grain (PAG) size was increased due to longer holding time at high peak temperature (Tp) in the HHIW process. Besides, inclusion also plays a decisive role on the HAZ microstucture, which could induce the formation of IAF.[8] Nowadays, the most effective method to improve the HAZ toughness has been termed as oxide metallurgy, which utilizes the oxides formed during refining process as preferential precipitating sites of nitrides or sulfides.[9] These particles will induce the nucleation of IAF or prevent the growth of austenite grain during the welding process. Several kinds of deoxidizing elements, such as Ti, Zr, Mg and Ca, have been applied to the development of oxide metallurgy technology.[10-13]
3
Specially, a lot of research works regarding to the utilization of strong Mg deoxidizer to develop 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
advanced oxide metallurgy technology have been conducted. Chang et al.[14] and Kim et al.[15] have studied the effect of Mg addition on the variation of inclusions and microstructures during the solidification of steel after the molten steel was deoxidized by Mn-Si-Ti, and the results indicated that Mg further addition was beneficial for the heterogeneous nucleation of IAF. Zhu et al.
[16]
also
found that the toughness of HAZ was improved significantly by adding 0.005 mass% Mg to the Tibearing low carbon steel, since the pinning particles were formed during the welding processing. Yang et al.[12, 17] have obtained the excellent HAZ toughness of steel plate with Mg deoxidation after HHIW process. The relationship between microstructure and toughness in HAZ of steel with Mg deoxidation after welding with 400 kJ cm-1 has also been illustrated in our previous study[6]. Strong deoxidizing element Mg has been used successfully to produce the steel plate for HHIW in actual plant mill.[18] However, the relation of toughness and microstructure in coarse grain heat affected zone (CGHAZ) with HHIW process for steel plate with Mg deoxidation is seldom reported. The present work aims to provide an evidence of understanding the effect of welding heat input on the microstructures and toughness in HAZ of Mg deoxidized steel plate during HHIW process. The relations of PAG size and microstructure with welding heat input are discussed, and the role of inclusions on the HAZ microstructure is also investigated. 2. Experimental procedure 2.1. Materials Exprimental EH40 steel with 68 mm thickness was manufactured with 300 ton scale in the steelmaking plant of Baoshan Iron and Steel Cooperation limited, Shanghai, P. R. China. The steel plate was made through the production route of hot metal pretreatment, basic oxygen furnace (BOF) steelmaking, refining with ladle furnace (LF) and R-H vacuum degassing process, continuous casting (CC), and the slab was finally hot rolled with thermo-mechanical control process (TMCP). The slab with thickness of 300 mm was heating up to 1150 °C. Rough rolling was conducted at the temperature above 930 °C with the reduction ratio of 50%, and finish rolling was carried out at the temperature about 800 °C. Then, the steel plate with thickness of 68 mm was cooled down from 780 4
°C to 400 °C at the cooling rate of 6 °C s-1. The chemical composition of steel is: 0.073 C, 1.49 Mn, 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
0.2 Si, 0.0081 Ti, 0.0015 Mg, 0.002 Al, 0.0014 O, 0.0032 N and 0.005 S (mass%). The Mg in current steel was from Mg deoxidation, which was carried out after RH vacuum degassing process by feeding Mg alloy cored wire. And the mechanical properties of the hot rolled steel plate are as follows: yeld strength 446 MPa, tensile strength 556 MPa, elongation 28% and average impact toughness 251 J (-40 °C). 2.2. Welding thermal cycle simulation procedure In order to study microstructure evolution and impact toughness changes in the HAZ of the experimental steel plate, HHIW thermal cycle simulations were carried out on the Gleeble 3800 thermal simulation tester (Dynamic system INC., USA). The steel samples for welding thermal cycle simulation experiment were cut down from near the position which were 1/4 width and 1/4 length of steel plate from its edge. The welding thermal cycles were designed to simulate an EGW process of the HAZs with the heat inputs of 100, 200 and 400 kJ cm-1. The names of the samples were termed as M100, M200 and M400, respectively. The peak welding temperatures of M100 and M200 were both 1350 °C with holding time of 2 s and the peak welding temperatures of M400 was 1400 °C with holding time of 3 s. The Tp and holing time in present study were designed with referencing the previous reports.[6, 19, 20] The Δt8/5 of M100, M200 and M400 were 24, 96 and 383 s, respectively. The average cooling rate from 800 to 500 °C of M100, M200 and M400 were 12.50, 3.13 and 0.78 ̊C s-1, respectively. 2.3. Mechanical properties The specimens after welding thermal cycle simulation with different heat input were machined into standard Charpy V-norch samples with the sizes of 10×10×55 mm3, with the notch tip placed in the center of simulated HAZ. The Charpy impact tests were conducted at -40 °C. Then the fracture surfaces were examined by scanning electron microscopy (SEM, EVO MA10, Carl Zeiss, Germany) and the inclusions in the dimples were analyzed by energy dispersive spectrometer (EDS, Oxford Instruments, UK). 2.4. Characterization of inclusions and microstructures 5
The surfaces in parallel with the fracture cross-sections after Charpy impact test were polished and 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
prepared for the characterization of inclusions and microstructures. The inclusions in the polished cross section were analyzed through the inclusions automatic analyze system (IAAS). IAAS is consisited of SEM-EDS and inclusions analyze software, Feature (Oxford Instruments, UK), which can conduct the statistical analyses of the numbers, sizes, chemical compositions and morphologies of inclusions automatically. In present study the observed area of the sample was 38.1 mm2, and the inclusions with size less than 0.5 μm have not been counted. In order to observe the HAZ microstructure, these polished steel samples were etched with a 4 vol% nital solution. Then the characteristics of the microstructure in HAZ of the steel samples were investigated through optical microscope (OM, DM 2500M, Leica Microsystems, Germany) and SEM-EDS. These specimens were re-polished and then etched at 50 °C using mixed agent (saturated picric acid + detergent + distilled water) to reveal the PAG boundary. Then the size of PAG was measured with Image-Pro Plus software by the method of averaging the long axis and short axis in the grain from the OM observed micrographs. 3. Results 3.1. Characteristics of inclusions and microstructures
Figure 1. Size distribution of inclusions in the steel.
6
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
Figure 2. Morphologies (a), (b) and EDS spectrums (c), (d), (e) of typical inclusions in HAZ.
Table 1. Average chemical compositions of inclusions (mass%). Elements Mass%
Mn
Si
Ti
Mg
Al
Ca
O
N
S
28.86 0.75 2.93 29.64 1.32 0.01 18.53 0.04 17.93
Figure 1 shows size distribution of inclusions in the experimental steel, based on the statistical analysis result of 4533 inclusions in the area of 38.1 mm2. It is seen in Figure 1 that 92% inclusions are with the size less than 3 μm. It has been reported that Mg deoxidation benefits the refining and even dispersion of inclusions in steel.[15, 17] Therefore, inclusions with size larger than 6 μm were hardly found in the steel sample. The number density and average size of inclusions are 119 mm-2 and 1.47 μm, respectively. The average chemical composition of these inclusions is shown in Table 1. It is indicated that the main compositions of inclusions in the experimental steel sample are Mg, Mn, O and S elements, as well as a little amount of Al and Ti elements. The morphologies and EDS results of typical inclusions in the steel with Mg deoxidation are shown in Figure 2. The typical 7
inclusions mainly comprise MgO or MgO-MnS, as well as a little amount of Al2O3 and Ti2O3. In 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
such complex inclusion, the central MgO oxide is covered by MnS layer. In addition, the size of the typical inclusion in the steel is around 2 μm. This type of inclusions is considered as effective nucleant of IAF in HAZ.[12]
Figure 3. HAZ microstructures of experimental steels after different welding thermal cycles. M100 (a), (b) and (c); M200 (d), (e) and (f); M400 (g), (h) and (i); 50× (a), (d) and (g); 200× (b), (e) and (h); 1000× (c), (f) and (i). The HAZ microstructures of experimental steels of M100, M200 and M400 in serial magnifications are shown in Figure 3. Grain boundary ferrites (GBFs) are hardly found in M100 and M200 as shown in Figures 3(a) and (d). In contrast, it is observed clearly and distributed evenly in M400 as shown in Figure 3(g). In the magnification of 200 shown in Figure 3(h), those well-developed IAFs are surrounded by GBFs. In the magnification of 1000 shown in Figures 3(c), (f) and (i), it is found that the HAZ microstructures are changed apparently with increasing welding heat input. In M100, the main microstructure consists of parallel fine bainite lathes. For M200, the bainite lathes 8
are finer than those in M100. When the welding heat input is as high as 400 kJ cm-1, well-developed 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
IAFs are formed within the austenite grains. It is clearly observed in M400 that five acicular ferrite laths are nucleated directly from the same inclusion, as shown in Figure 3(i).
Figure 4. SEM image and EDS analysis results of inclusions in HAZ microstructures. M100 (a) and (b); M200 (c) and (d); M400 (e) and (f). Figure 4 shows the SEM images and EDS analysis results of inclusions in HAZ microstructures of samples M100, M200 and M400. It is seen in Figure 4(a) that MgO-MnS inclusion is located within ferrite lathes. For M200, MgO-MnS inclusion is also located within ferrite lathes, as shown in Figure 4(c). In contrast, the typical MgO-MnS inclusion in M400 acts as the nucleant of acicular ferrites, which is located in the center of six ferrite emanations, as shown in Figure 4(e). Element mapping analysis has beeen subjected to further understand the structure of nucleant inclusion in HAZ microstructure of M400 as shown in Figure 5. It is seen in Figure 5 that the nucleant 9
inclusion is composed of central MgO, as well as a little amount of Al2O3 and Ti2O3, and the central 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
complex oxide compound is covered by the MnS layer.
Figure 5. Element mapping analysis results of nucleant inclusion in HAZ microstructure of sample M400. 3.2. Prior-austenite grain sizes Figure 6 shows the change of PAG sizes of experiment steels with the heat input after welding thermal cycle simulation process. The numbers of PAGs measured in M100, M200 and M400 were 466, 242 and 207, respectively. It is seen that the average PAG size of M100 is slightly smaller than that in M200, with the former of 43 μm and the latter of 56 μm. When the welding heat input is increased up to 400 kJ cm-1, the average PAG size in M400 is increased sharply to 173 μm, which is 10
two times larger than those in M100 and M200. It indicates that the PAG sizes are increased greatly 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
with increasing welding heat input from 100 to 400 kJ cm-1. It is also found that the standard deviation (STDEV) of PAG sizes is increased with increasing welding heat input, which is 15, 17 and 55 μm in M100, M200 and M400, respectively.
Figure 6. Change of prior-austenite grain sizes of experiment steels with heat input in the welding thermal cycle simulation process.
Figure 7. Charpy impact toughness of HAZ at different heat input.
11
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
Figure 8. Macro fractographs and SEM images of fracture surfaces of HAZ. M100 (a), (b) and (c); M200 (d), (e) and (f); M400 (g), (h) and (i). 3.3. Charpy impact toughness of HAZ Figure 7 shows charpy absorbed energy values at -40 °C for HAZ after different HHIW thermal cycles. The average charpy absorbed energy values for specimens of M100, M200 and M400 are 159, 207 and 205 J, respectively. Figure 8 shows the macro fractographs and SEM images of the fracture surfaces of the HAZs for M100, M200 and M400. The fractographs of all three samples show the obvious transverse deformation as indicated by the lateral expansion or notch contraction as shown in Figures 8(a), (d) and (g), respectively. Fibrous zones are apparently observed in all three samples as shown in Figures 8(c), (f) and (i), indicating that those samples with high toughness. The sizes of fracture facts in radical zone are decreased in the order of M100, M200 and M400, as shown in Figures 8(b), 12
(e) and (h), respectively. As a result, the HAZ toughness of M100 is not as excellent as those in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
M200 and M400.
Figure 9. SEM images of fibrous zones on fracture surface and EDS analysis result of inclusion in steel sample M400. (a) dimples and (b) EDS spectrum. Figure 9 shows the magnified SEM images of the fibrous zone on the fracture surfaces and the EDS analysis results of inclusions in the HAZ of specimen M400. The inclusions in the dimples of M400 are essentially spherical in shape and around 2 μm in size as shown in Figure 9(a). In Figure 9(b), the EDS analysis result indicates that the inclusions in M400 is mainly consisted of MgO-MnS. 4. Discussion 4.1. Effect of welding heat input on the austenite grain size Generally, during the welding thermal cycle simulation process, the heat input above 100 kJ cm-1 is called as high-heat input, which has a high Tp in the austenitizing temperature. In present study, the heat inputs have been designed as 100, 200 and 400 kJ cm-1 with the Tp of 1350, 1350, and 1400 °C, respectively. For M100 and M200, the Tp and the holding time were the same, being 1350 °C and 2 s, respectively. Due to the relatively low Tp, the growth of austenite grain during the welding 13
process is effectively prohibited by the pinning effect of TiN particles.[21] Therefore, the average 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
PAG sizes are both about 50 μm, as shown in Figure 6. When the Tp is higher than 1350 °C, pinning particles, such as TiN, are partly dissolved and the pinning force for preventing the movement of austenite grain boundary is decreased.[22, 23] In M400, the Tp was 1400 °C holing for 3 s. In the steel containing low level Mg content, it is difficult to form large quantity of pinning particles with sizes ranging from tens to hundreds nanometers and with high thermal stability, such as MgO and MgO-TiN particles.[24] For the experimental steel in the present study, MgO particles are with the sizes of several micrometers, as shown in Figure 2. Thus, the pinning effect in the steel with relative low level Mg content is limited.[6] As a result, the austenite grains are grown up apparently during welding thermal cycle simulation process with the heat input of 400 kJ cm-1. The average PAG size of M400 is three times larger than that of M100, as shown in Figure 6. Shi et al.[7] reported the similar tendency of change in austenite grain size with the welding heat input increasing from 100 to 400 kJ cm-1. 4.2. Effect of welding heat input on the microstructures The PAG size and cooling rate from 800 to 500 °C are important factors to determine the HAZ microstructure after welding process. The former is increased with increasing welding heat input as shown in Figure 6. Austenite grain boundary acts as preferential nucleating site for ferrite during γ→α phase transformation resulting from low energy barrier.[25] A smaller austenite grain size provides larger surface area for ferrite nucleation from austenite grain boundary.[26] In the steel containing high level Mg content of 99 ppm reported in our previous paper, the PAG sizes were about 100 μm and the γ→α transformation was firstly take place at the boundary triple points to form polygonal ferrites (PFs) during welding thermal cycle simulation process with Δt8/5 of 383 s.[6] The PAG sizes in M100 and M200 are smaller than 100 μm. IAF is quite less in these two samples because of the small size of PAGs. However, the HAZ microstructures in M100 and M200 are both consisted of fine bainite laths, as shown in Figures 3(c) and (f). The Δt8/5 of M100 and M200 are 24
14
and 96 s, respectively. There is no enough time to form PFs in M100 and M200 instead of bainite 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
lathes. In M400, the HAZ was heated to 1400 °C for holding 3 s and was experienced a rather low cooling rate of 0.78 °C /s in the subsequent phase transformation temperature zone. Thus, the coarse GBFs were formed along the austenite grain boundaries. Due to the relative larger austenite grain sizes and a lot of intragranular inclusions acting as the effectively nucleating sites for acicular ferrites, a great amount of IAFs were formed within the austenite grain in M400. Consequently, the main HAZ microstructures are consisted of well-developed IAFs and GBFs, as shown in Figures 3(g-i). 4.3. Effect of welding heat input on the HAZ toughness Although the PAG sizes and microstructures in HAZ are changed with increasing heat input from 100 to 400 kJ cm-1 during the welding thermal cycle simulation process, LBZ, which is comprising coarse GBFs, ferrite side plate (FSP) and upper bainite (Bu), has not been formed within the HAZs of all three steel samples. In addition, the HAZ microstructures in M100 and M200 mainly compose of bainite lathes are beneficial to obtain excellent toughness.[27] In addition, the well-developed IAF in the HAZ microstructure of M400 brings the excellent HAZ toughness. Thus, the HAZ toughness of all three steel samples has not been deteriorated. Excellent HAZ toughness has been achieved for the 68 mm thickness steel plates with Mg deoxidation after welding with the heat input in the range from 100 to 400 kJ cm-1. 5. Conclusions The microstructural evolution and low temperature impact toughness of heat-affected zone (HAZ) in steel plate with Mg deoxidation after the welding thermal cycle simulation process with different heat input were investigated. The following results were obtained: (1) The prior-austenite grain (PAG) size was increased from 43 to 56 and then to 173 μm with increasing heat input from 100 to 200 and then to 400 kJ cm-1 during the welding process. (2) The HAZ microstructure was changed from fine bainite lath to relative larger bainite lath and then to grain boundary ferrite (GBF) and intragranular acicular ferrite (IAF) with increasing heat input from 100 to 200 and then to 400 kJ cm-1 during the welding process. 15
(3) In the HAZ of steel plate with heat input less than 200 kJ cm-1, typical MgO-MnS inclusions 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
were located within the ferrite laths. With the heat input increasing up to 400 kJ cm-1, a great amount of IAF was nucleated by the MgO-MnS inclusions with the size about 2 μm. (4) With the heat input in the range from 100 to 400 kJ cm-1, the Charpy impact values at -40 °C of HAZ were larger than 140 J and excellent low temperature HAZ toughness was obtained for the 68 mm thickness steel plate with Mg deoxidation. Acknowledgements The financial support from Baosteel Group Corporation is great appreciated. References [1] A. Kojima, K. I. Yoshii, T. Hada, O. Saeki, K. Ichikawa, Y. Yoshida, Y. Shimura,K. Azuma, Nippon Steel Tech. Rep. 2004, 39. [2] N. Koichi, H. Kazukuni,E. Taiki, JFE Tech. Rep. 2015, 8. [3] I. Katsuyuki, F. Takaki, S. Shinichi, JFE Tech. Rep. 2015, 20. [4] S. Ohita,H. Oikawa, Nippon Steel Tech. Rep. 2007, 2. [5] D. Zhang, H. Terasaki, Y. I. Komizo, Acta Mater. 2010, 58, 1369. [6] L. Y. Xu, J. Yang, R. Z. Wang, Y. N. Wang,W. L. Wang, Metall. Mater. Trans. A 2016, 47, 3354. [7] M. H. Shi, P. Y. Zhang, F. X. Zhu, ISIJ Int. 2014, 54, 188. [8] D. S. Sarma, A. V. Karasev,P. G. Jönsson, ISIJ Int. 2009, 49, 1063. [9] S. Ogibayashi, Nippon Steel Tech. Rep. 1994, 70. [10] W. Shu, X. M. Wang, S. R. Li,X. L. He, Acta Metall. Sin. 2010, 46, 997. [11] X. B. Li, Y. Min, C. J. Liu,M. F. Jiang, Mater. Sci. Tech. 2016, 32, 507. [12] J. Yang, K. Zhu, R. Z. Wang,J. G. Shen, Steel Res. Int. 2011, 82, 552. [13] T. Kato, S. Sato, H. Ohta,T. Shiwaku, Kobe Steel Tech. Rep. 2011, 61, 32. [14] C. H. Chang, I. H. Jung, S. C. Park, H. S. Kim, H. G. Lee, Ironmak. Steelmak. 2005, 32, 251. [15] H. S. Kim, C. H. Chang, H. G. Lee, Scripta Mater. 2005, 53, 1253. [16] K. Zhu, J. Yang, R. Z. Wang,Z. G. Yang, J. Iron Steel Res. Int. 2011, 18, 60. 16
[17] J. Yang, L. Y. Xu, K. Zhu, R. Z. Wang, L. J. Zhou, W. L. Wang, Steel Res. Int. 2015, 86, 619. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
[18] J. Yang, Z. G. Ma, K. Zhu, R. Z. Wang,Q. Zheng, Baosteel Tech. Res. 2012, 9, 41. [19] Y. Q. Zhang, H. Q. Zhang, J. F. Li,W. M. Liu, J. Iron Steel Res. Int. 2009, 16, 73. [20] F. Chai, C. F. Yang, H. Su, Y. Q. Zhang,Z. Xu, J. Iron Steel Res. Int. 2009, 16, 69. [21] Y. Tomita, N. Saito, T. Tsuzuki, Y. Tokunaga,K. Okamoto, ISIJ Int. 1994, 34, 829. [22] S. MUKAE, K. NISHIO, M. KATOH, Trans. Jpn. Weld. Soc. 1987, 18, 148. [23] J. Moon, C. Lee, S. Uhm,J. Lee, Acta Mater. 2006, 54, 1053. [24] K. Zhu,Z. G. Yang, Metall. Mater. Trans. A 2011, 42, 2207. [25] R. A. Ricks, P. R. Howell,G. S. Barritte, J. Mater. Sci. 1982, 17, 732. [26] T. Koseki,G. Thewlis, Mater. Sci. Technol. 2005, 21, 867. [27] W. Zhao, W. Wang, S. Chen,J. Qu, Mater. Sci. Eng. A 2011, 528, 7417.
17
1
68 mm thickness steel plate with Mg deoxidation is manufactured with 300 ton scale. Effect of
12 2 3 3 4 5 64 7 85 9 10 11 6 12 7 13 14 8 15 16 9 1710 18 19 20 21 22 23 24 25 26 27 28 29 30 3111 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
welding heat input on the microstructure and toughness of HAZ in the steel plate has been investigated. The results reveal that excellent low temperature toughness is obtained for the steel plate with the heat input in the range from 100 to 400 kJ cm-1.
Longyun Xu, Jian Yang,* Ruizhi Wang, Wanlin Wang, and Zhongmin Ren
Effect of Welding Heat Input on Microstructure and Toughness of Heated-Affected Zone in Steel Plate with Mg Deoxidation
18
Production Data
Click here to access/download
Production Data Figures.ppt
