Baoshan Iron & Steel Co., Ltd.

Houjun Pang

Hui Li

Chuanguo Zhang

Jian Ming Liu

Guodong Xu

Jian Liu

Lei Zheng

Leilei Sun

Xuyi Shan

Wenwang Meng

Zhiling Gao

Xingze Zhou

Konglin Zhu

Yong Zhang

Steel for coiled tubing with a low yield ratio and ultra-high strength and a preparation method thereof, wherein the chemical composition of the steel in mass percentage is: C: 0.05-0.16%, Si: 0.1-0.9%, Mn: 1.25-2.5%, P&#x2264;0.015%, S&#x2264;0.005%, Cr: 0.51-1.30%, Nb: 0.005-0.019%, V: 0.010-0.079%, Ti: 0.01-0.03%, Mo: 0.10-0.55%, Cu: 0.31-0.60%, Ni: 0.31-0.60%, Ca: 0.0010-0.0040%, Al: 0.01-0.05%, N&#x2264;0.008%, and the rest being Fe and inevitable impurity elements. The chemical composition combines the technologies of low temperature finishing rolling and low temperature coiling to obtain an MA constituent+bainite+ferrite multiphase structure. The steel has a low yield ratio and ultra-high strength with the following specific properties: yield strength&#x2265;620 MPa, tensile strength&#x2265;750 MPa, elongation&#x2265;11%, and yield ratio&#x2264;0.83, and is suitable for manufacturing coiled tubing with ultra-high strength having a grade of 110 ksi or higher.

Steel for coiled tubing with low yield ratio and ultra-high strength and preparation method thereof

The present invention relates to a method for producing hot rolled strip steel, especially the producing method of hot rolled strip steel with multiple target thicknesses in the longitudinal direction. It is a method to produce the strip steel with different target thicknesses in the longitudinal direction by using a hot continuous rolling mill. In this method, the first equal-thickness section of the strip steel is controlled with the conventional thickness control strategy, while other equal-thickness sections and the transition section between equal-thickness sections are controlled with the variable-thickness control strategy. Under the variable-thickness control strategy, the length of the first section of strip steel, the variation of thickness target value, the rolling stability and the spacing between stands are combined to determine the stand participating in the variable-thickness control, and calculate the roller gap value, as well as the time and speed of the variation of roller gap, thus achieving the producing control of strip steel with different target thicknesses in the longitudinal direction. The present invention utilizes the length of the first equal-thickness section and the variation of different target thicknesses and other related factors to determine the stands participating in the control, and then distributes the load variation among the stands, thus effectively avoiding the influence on the rolling stability due to imbalance of second flow, so that the produced strip with variable thickness in different sections in the longitudinal direction meet the user's requirements.

Method for producing band steel with different target thicknesses along longitudinal direction using hot continuous rolling mill set

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Shanghai, China

Houjun Pang