Controlled rolling and cooling process for low carbon cold forging steel

Abstract

Effect of controlled rolling and cooling process on the mechanical properties of low carbon cold forging steel was investigated for different processing parameters of a laboratory hot rolling mill. The results show that the specimens with fast cooling after hot rolling exhibit very good mechanical properties, and the improvement of the mechanical properties can be attributed mainly to the ferrite-grain refinement. The mechanical properties increase with decreasing final cooling temperature within the range from 670 °C to 570 °C due to the finer interlamellar spacing of pearlite colony. The specimen with fast cooling after low temperature rolling shows the highest values of the mechanical properties. The effect of the ferrite grain size on the mechanical properties was greater than that of pearlite morphology in the present study. The mechanical properties of specimens by controlled rolling and cooling process without thermal treatment were greatly superior to that of the same specimens by the conventional rolling, and their tensile strength reached 490 MPa grade even in the case of low temperature rolling without controlled rolling. It might be expected to realize the substitution medium-carbon by low-carbon for 490 MPa grade cold forging steel with controlled rolling and cooling process.

Keywords

controlled rolling and cooling process / low carbon cold forging steel / fast cooling / low temperature rolling / the ferrite-grain refineme

References

[1] Kirby B. R. The Behaviour of High-strength Grade 8.8 Bolts in Fire[J]. J. Construct Steel Research, 1995, 33: 3-38.

[2] Arno B., Hendrik J. Theoretical and Experimental Damage Prediction in Cold and Semi-Hot Bulk Forming of Ductile Steels[J]. Steel Res. Int., 2005, 76(2–3): 210-218.

[3] Park K. S., Park K. T., Lee L. D., . Comparison of Cold Formability of Cold Drawn Non-heat-treated Steels Having Similar Strength[J]. ISIJ Int., 2005, 45(9): 1 352-1 357.

[4] Xue X. H., Shan Y. Y., Zheng L., . Microstructural Characteristic of Low Carbon Microalloyed Steels Produced by Thermo-mechanical Controlled Process[J]. Materials Science & Engineering A, 2006, 438–440: 285-287.

[5] Liu Y., Zhu F., Li Y., . Effect of TMCP Parameters on the Microstructure and Properties of an Nb-Ti Microalloyed Steel[J]. ISIJ Int., 2005, 45(6): 851-857.

[6] Li Z., Wu D. Influence of Hot Rolling Conditions on the Mechanical Properties of Hot Rolled TRIP Steel[J]. J. Wuhan University of Technology-Mater. Sci. Ed., 2008, 23(1): 74-79.

[7] Hickson M. R., Hurley P. J., Gibbs R. K., . The Production of Ultrafine Ferrite in Low-Carbon Steel by Strain-Induced Transformation[J]. Metall. Trans., 2002, 33A(4): 1 019-1 026.

[8] Li Z., Wu D. Study of the High Strength and Low Yield Ratio Cold Forging Steel[J]. Materials Science & Engineering A, 2007, 452–453(4): 142-148.

[9] Luo H., Zhao L., Kruijver S. O. Effect of Intercritical Deformation on Bainite Formation in Al-containing TRIP Steel[J]. ISIJ Int., 2003, 43(8): 1 219-1 227.

[10] Weng Y. Q., Sun X. J., Dong H., . Overview on the Theory of Deformation Induced Ferrite Transformation[J]. Iron & Steel, 2005, 40(S1): 9-15.

[11] Wu D., Li Z. Study of Controlled Rolling and Cooling of 490 MPa Grade Low Carbon Cold Heading Steel[J]. Iron & Steel, 2008, 43(4): 61-65.

[12] Werner O. Microstructure-strength Relationship for LC and HSLA Steels[J]. Steel Research, 1994, 65(8): 338-344.

[13] Hong S. C., Lee K. S. Influence of Deformation Induced Ferrite Transformation on Grain Refinement of Dual Phase Steel[J]. Materials Science and Engineering A, 2002, 323(1–2): 148-159.

[14] Beladi H., Kelly G. L., Hodgson P. D. Ultrafine Grained Structure Formation in Steels Using Dynamic Strain Induced Transformation Processing[J]. International Materials Reviews, 2007, 52(1): 14-28.

[15] Ministry of Metallurgical Industry of the People’s Republic of China. Cole Heading Steel Technical Requirements[S], 1986 Beijing Metallurgical Industry Press 368-373.