In this study, Finite Element Method (FEM) was used to simulate the solidification process of a large blank (280 mm × 325 mm) under different technological conditions. The influence of casting speed and superheat on solidification process of bloom was analyzed. It was found that as the casting speed increases, the solidification position of the bloom moved backward by 3,68 m, and the time required for complete solidification increased by 1 min; When the superheat gradually increased, the position of complete solidification of 10B21 steel bloom moved by about 1,5 m

Xu, D.

Yang, X. K.

Yin, X.

Zheng, B.

English

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613METALURGIJA 61 (2022) 3-4, 613-615X. K. YANG, D. XU, B. ZHENG, X. YINEFFECT OF PROCESS FACTORS  ON SOLIDIFICATION PROCESS OF 10B21 STEEL BLOOMReceived – Primljeno: 2021-11-04Accepted – Prihvaćeno: 2022-03-10Original Scientific Paper – Izvorni znanstveni radIn this study, Finite Element Method (FEM) was used to simulate the solidification process of a large blank (280 mm × 325 mm) under different technological conditions. The influence of casting speed and superheat on solidification process of bloom was analyzed. It was found that as the casting speed increases, the solidification position of the bloom moved backward by 3,68 m, and the time required for complete solidification increased by 1 min; When the superheat gradually increased, the position of complete solidification of 10B21 steel bloom moved by about 1,5 m.Keywords: 10B21 steel, steel bloom, temperature field, solidification, FEM ISSN 0543-5846METABK 61(3-4) 613-615 (2022)UDC – UDK 669.15: 621.41 - 669.14.018: 536.5: 66.065: 518.5 = 111INTRODUCTIONCRS (Cold rolled steel) generally requires superb appearance and surface quality as well as stronger plas-ticity and flexibility in production and processing [1]. As a representative of boron bearing cold heading steel, 10B21 was mainly used to produce high strength stand-ard parts of grade 8,8 and above with complex section shape. It has good plasticity and cold heading perfor-mance, good hardenability, and small tendency of quenching deformation and cracking. The process con-trol of continuous casting solidification process directly affects the surface and internal quality of the bloom, due to mass, momentum and heat transfer in the solidifica-tion process of the bloom, and it can not be directly judged by measuring tools. The influence of continuous casting process parameters on solidification and heat transfer behavior of bloom shell can be analyzed by computer numerical simulation, which can provide the-oretical guidance for reasonable control of actual pro-duction process parameters [2]. Thermal stress, the con-tinuous casting process, is primarily caused by the une-ven temperature field in the continuous casting slab, which is the main factor leading to internal cracks in the generous slab [3,4]. Finite element method will be used to simulate the solidification process of 10B21 steel bloom, and analyze the influence of different techno-logical parameters on the solidification process, which provides a theoretical basis for determining the position of solidified end and formulating an appropriate soft-reduction.MODEL ESTABLISHMENT AND DESIGNThe selected object is the bow-type continuous cast-er with a cross-sectional size of 280 mm × 325 mm. 1/4 cross section was taken as the modeling area. Figure 1 shows the cross-section diagram after grid division.The cooling process of bloom is mainly carried out at the inlet-outlet of mold, the secondary cooling zone and the straightening part in the continuous casting pro-cess. The continuous casting bloom process system and heat transfer coefficient are determined by the refer-ences [5,6] and the data is provided by the enterprise.X. K. Yang, D. Xu (corresponding author), B. Zheng X. Yin Email: xudong_xyz@163.com Technology Innovation Center for High Quality Cold Heading Steel of Hebei Province, Hebei University of Engineer-ing, Handan 056038, China B. Zheng School of Materials and Metallurgy, University of Science and Technology Liaoning, Anshan 114051, China D. Xu Engineering Research Center for High Toughness Wind Tow-er Steel of Hebei Province, Hebei Puyang Iron and Steel Corp.Ltd, Handan 056305, ChinaFigure 1 Schematic diagram of cross sectionTHERMAL PHYSICAL  PROPERTY PARAMETERSAccording to the field data, the cooling rate of the strand in the secondary cooling zone was usually in the 614  METALURGIJA 61 (2022) 3-4, 613-615X.K. YANG et al.: EFFECT OF PROCESS FACTORS ON SOLIDIFICATION PROCESS OF 10B21 STEEL BLOOMrange of 0,3 °C ~ 1,0 °C/s, and the cooling rate was lower in the air cooling zone.The content of each element in steel was obtained by searching for information and input into JMatPro. In or-der to facilitate the simulation calculation, 1 °C/s was set as the cooling rate of the secondary cooling zone. The calculation results are shown in Figure 2. Accord-ing to the simulation calculation, the solid phase tem-perature of 10B21 steel is 1 472 °C, and the liquidus temperature is 1 515 °C.Figure 2  Thermal properties of 10B21 steel  (a) Young’s modulus and Poisson’s ratio distribution; (b) Density and specific heat capacity distribution;  (c) Thermal conductivity and yield stress distributionRESULTS AND DISCUSSIONComparison of the existing modeInfluence of casting speed on solidification process of bloomThe thermo-mechanical coupling module in ABAQUS software was used to simulate the tempera-ture field of bloom.Under the condition of superheat of 25 °C, the heat transfer coefficient was obtained by reference [7]. Moreover, the effect of casting speed on the solidifica-tion process of bloom was investigated with other un-Figure 3  Interval distribution of two-phase region  (a) Exit of crystallizer, 0,6 m/min; (b) Liquid terminal,  0,6 m/min;(c) Mould outlet, 0,76 m/min; (d) Liquid terminal, 0,76 m/min(a) (b)(c) (d)Table 1  Influence of different casting speed on 10B21 steel bloomCasting speed / m/min 0,6 0,76Thickness of bloom shell at exit of mould / mm 29 26,5Distance between liquid end and crystallizer liquid level / m5,35 6,99Time required for complete solidication / s 1 075 1 139Complete solidication distance   from crystallizer interface / m10,75 14,43transformed parameters. Figure 3 shows the distribution of two phases in solidification process, and Table 1 shows the influence of different casting speed on the bloom.Typically, the position of the solidification end is about 10,75 m when the casting speed is 0,6 m/min and the position of the solidification end is about 14,43 m when the casting speed is 0,76 m/min, the solidification end moves back 3,68 m. The time required for complete solidification of bloom increases by 1 min.Influence of superheat on solidification processConsidering the influence of superheat on the solidi-fication process, the casting speed of 0,76 m/min was adopted and other parameters were unchanged to simu-late the influence of superheat of molten steel at 15 °C, 25 °C and 50 °C on the solidification process of the bloom shell, as shown in Figure 4.Figure 4 Influence of superheat on Solid-liquid ratioAccording to the simulation calculation, the time re-quired for complete solidification of continuous casting billet is 19,3 min, 20,0 min and 21,2 min when the su-perheat is 15 °C, 25 °C and 50 °C. The time required for solidification increases with the increase of superheat, and the position of complete solidification of the bloom moves backward. The position of complete solidifica-tion of bloom is 14,7 m away from the mould liquid when the superheat is 15 °C; Similarly, the position of complete solidification of bloom is 15,2 m away from the mould liquid when the superheat is 25 °C and the position of complete solidification of bloom is 16,2 m away from the mould liquid when the superheat is 50 °C. In addition, when the superheat increased from 15 °C to 50 °C, the temperature of each part of the bloom transformed little, the time required for complete solidi-fication of the bloom increased.615X.K. YANG et al.: EFFECT OF PROCESS FACTORS ON SOLIDIFICATION PROCESS OF 10B21 STEEL BLOOMMETALURGIJA 61 (2022) 3-4, 613-615CONCLUSIONThis work is based on 280 mm × 325 mm generous billet of 10B21 steel and takes 1/4 cross section as the modeling area, in which a relatively accurate tempera-ture field model is obtained through reverse calculation. The main conclusions are as follows:(1) When the casting speed increases from 0,6 m/min to 0,76 m/min, the solidification end moves back 3,68 m, the time required for complete solidification of bloom increases by 1min.(2) The position of complete solidification of the bloom was shifted backward by 1,5 m, the time required for complete solidification of bloom is increased by 1,9 min when the superheat increases from 15 °C to 50 °C.(3) The casting speed has an important influence on the thickness of solidified bloom shell. The change of the casting speed affect the position of the soft reduc-tion. If the position of the soft reduction deviates from the appropriate area, it may cause internal cracks and cannot reduce the segregation of the bloom.AcknowledgmentsThe authors gratefully acknowledge the help and support of the Iron and Steel Joint Foundation of Hebei Province (E2020402016), and Open Topic of Key Lab-oratory of Material Forming and Structure Property Control from University of Science and Technology Li-aoning (USTLKFSY201708).REFERENCES[1] E.Z. Cao, S.G. Song, Z.J. Chen, X.Q. Yang, W. Li, J. Shi, Production of 10B21 cold heading steel for high strength fasteners, Henan metallurgy 28 (2020) 04, 32-34+37.[2] J.Y Zhang, G.L. Zhu, Mathematical simulation of thermo-mechanical coupling of solidified billet shell in mould of medium carbon steel billet continuous casting [J], Casting technology 38 (2017) 06, 1376-1380.[3] A.G. Dang, C. Juan, Y.C. Li, Generation and control of subcutaneous cracks in continuous casting process [J], Journal of Iron and Steel Research 33 (2021) 06, 217-223.[4] X.Z. Gao, S.F. Yang, J.S. Li, Q.Y. Zhang, H.Y. Chen, Nu-merical simulation of solidification process in thick slab continuous casting [J], Casting technology 36 (2015) 03, 678-683.[5] D. Xu, H.Y. Zhao, Y.Q. Lu, Numerical simulation of soli-dification process of continuous casting slab [J], Materials science and technology 19 (2011) 5, 106-110.[6] D. Xu, H.Y. Liu, C. Peng, Z.P. Pei, Effect of Casting Tem-perature on Continuously-Cast Bearing Steel GCr15 Billet Structure Formation, Metallurgist 61 (2017) 1, 19-25.[7] Z.Z. Cai ,M.Y. Zhu, Thermal behavior of steel during soli-dification in slab continuous casting mould I Mathematical Model [J], Acta Metall sin 47 (2011) 06, 669-675.Note:  Dong Xu is the responsible translator and the corresponding author, Handan, Hebei, China.

Effect of process factors on solidification process of 10B21 steel bloom

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