阅读说明：本技术 一种解决含铌螺纹钢产生贝氏体的生产工艺 (Production process for solving bainite generation of niobium-containing deformed steel bar ) 是由 谢锦官 谢吉祥 曾锦 刁承民 闻树春 谢碧松 黄彦飞 赵根社 于 2019-10-14 设计创作，主要内容包括：本发明涉及冶金技术领域,尤其涉及一种解决含铌螺纹钢产生贝氏体的生产工艺,其包括如下操作：控制碳含量在0.21～0.25％,铌含量在0.015-0.025％；控制钢水锰含量低于1.35-1.45％；控制开轧温度900-950℃；通过中间自动控温控轧确保进精轧机温度850-900℃；控制上冷床温度830-850℃；低温终轧压下量30％,产生亚晶粒铁素体组织。本发明提供的控轧控冷轧制工艺,炼钢控制合适钢水成分,削弱过冷奥氏体稳定性；轧钢过程控制冷却速度和上冷床温度,避免贝氏体形成；双相区轧制产生亚晶界铁素体,提高螺纹钢的屈服强度,达到国家Ⅲ螺纹钢标准性能要求。(The invention relates to the technical field of metallurgy, in particular to a production process for solving the problem of bainite generation of niobium-containing deformed steel, which comprises the following operations: controlling the carbon content to be 0.21-0.25% and the niobium content to be 0.015-0.025%; controlling the manganese content of the molten steel to be lower than 1.35-1.45%; controlling the initial rolling temperature to be 900 ℃ and 950 ℃; the temperature of the finishing mill is ensured to be 850-900 ℃ by automatic temperature control and rolling in the middle; controlling the temperature of an upper cooling bed to 830-850 ℃; the low-temperature finish rolling reduction is 30%, and a sub-grain ferrite structure is generated. According to the controlled rolling and controlled cooling rolling process provided by the invention, proper molten steel components are controlled in steel making, and the stability of super-cooled austenite is weakened; the cooling speed and the temperature of an upper cooling bed are controlled in the steel rolling process, so that bainite is prevented from being formed; and the double-phase region rolling generates sub-crystal boundary ferrite, so that the yield strength of the deformed steel bar is improved, and the national III deformed steel bar standard performance requirements are met.)

1. A production process for solving the problem of bainite generation of niobium-containing deformed steel bars is characterized by comprising the following operations:

controlling the carbon content to be 0.21-0.25%;

controlling the content of niobium to be 0.015-0.025%;

controlling the manganese content of the molten steel to be lower than 1.35-1.45%;

controlling the initial rolling temperature to be 900 ℃ and 950 ℃;

the temperature of the finishing mill is ensured to be 850-900 ℃ by automatic temperature control and rolling in the middle;

controlling the temperature of an upper cooling bed to 830-850 ℃;

the low-temperature finish rolling reduction is 30%, and a sub-grain ferrite structure is generated.

2. The production process for solving the problem of generating bainite in the niobium-containing deformed steel bar according to claim 1,

controlling the carbon content to be 0.21%;

controlling the content of niobium to be 0.015 percent;

controlling the manganese content of the molten steel to be lower than 1.35 percent;

controlling the initial rolling temperature to be 900 ℃;

the temperature of the finishing mill is ensured to be 850 ℃ through automatic temperature control and rolling control in the middle;

controlling the temperature of an upper cooling bed to be 830 ℃;

the low-temperature finish rolling reduction is 30%, and a sub-grain ferrite structure is generated.

3. The production process for solving the problem of generating bainite in the niobium-containing deformed steel bar according to claim 1,

controlling the carbon content to be 0.25%;

controlling the content of niobium to be 0.025 percent;

controlling the manganese content of the molten steel to be lower than 1.45 percent;

controlling the initial rolling temperature to 950 ℃;

the temperature of the finishing mill is ensured to be 900 ℃ through automatic temperature control and rolling control in the middle;

controlling the temperature of an upper cooling bed to be 850 ℃;

the low-temperature finish rolling reduction is 30%, and a sub-grain ferrite structure is generated.

4. The production process for solving the problem of generating bainite in the niobium-containing deformed steel bar according to claim 1,

controlling the carbon content to be 0.23%;

controlling the content of niobium to be 0.02 percent;

controlling the manganese content of the molten steel to be lower than 1.4 percent;

controlling the initial rolling temperature to be 900 ℃;

ensuring the temperature of the finishing mill to be 875 ℃ through automatic temperature control and rolling control in the middle;

controlling the temperature of the upper cooling bed to be 840 ℃;

the low-temperature finish rolling reduction is 30%, and a sub-grain ferrite structure is generated.

Technical Field

The invention relates to the technical field of metallurgy, in particular to a production process for solving the problem of bainite generation of niobium-containing deformed steel.

Background

In order to ensure the yield strength and the processability of the building material deformed steel bar, the national relevant standards stipulate that the metallographic structure of the normal deformed steel bar is ferrite + pearlite, and other abnormal structures (such as bainite, martensite and the like) cannot appear. Bainite structures are detected in internal structures of HRB400 threads formed by microalloying niobium developed by a plurality of domestic steel mills, so that the yield of the deformed steel is not obvious, the toughness and the plasticity are poor, and the national standard requirements cannot be met. Most of niobium-containing deformed steel bars developed by a plurality of domestic steel mills improve the strength of the deformed steel bars by improving the niobium content, performing strong cooling after rolling and utilizing the solid solution strengthening and the fine grain strengthening of niobium. The process method has the following defects:

1. the solid solution strengthening has high niobium content which is generally controlled to be 0.03-0.04 percent, the stability of super-cooled austenite is improved, and a bainite structure is easy to generate;

2. after rolling, strong cooling is carried out, although the growth of austenite after rolling is inhibited, bainite tissues are easy to generate because the cooling speed is close to or reaches the critical transformation speed of bainite;

disclosure of Invention

The invention aims to solve the technical problem of providing a production process for solving the problem of bainite generation of niobium-containing deformed steel, which has low cost, poor stability of super-cooled austenite and difficult bainite generation.

The invention is realized by the following technical scheme:

a production process for solving the problem of bainite generation of niobium-containing deformed steel bars comprises the following operations:

controlling the carbon content to be 0.21-0.25%;

controlling the content of niobium to be 0.015-0.025%;

controlling the manganese content of the molten steel to be lower than 1.35-1.45%;

controlling the initial rolling temperature to be 900 ℃ and 950 ℃;

the temperature of the finishing mill is ensured to be 850-900 ℃ by automatic temperature control and rolling in the middle;

controlling the temperature of an upper cooling bed to 830-850 ℃;

the low-temperature finish rolling reduction is 30%, and a sub-grain ferrite structure is generated.

In the first concrete embodiment, a production process for solving the problem of bainite generation of the niobium-containing deformed steel bar,

controlling the carbon content to be 0.21%;

controlling the content of niobium to be 0.015 percent;

controlling the manganese content of the molten steel to be lower than 1.35 percent;

controlling the initial rolling temperature to be 900 ℃;

the temperature of the finishing mill is ensured to be 850 ℃ through automatic temperature control and rolling control in the middle;

controlling the temperature of an upper cooling bed to be 830 ℃;

the low-temperature finish rolling reduction is 30%, and a sub-grain ferrite structure is generated.