阅读说明：本技术 Hrb600高强钢筋的冷却方法 (Cooling method of HRB600 high-strength steel bar ) 是由 赵小军 杜芳芳 马正红 于 2020-05-25 设计创作，主要内容包括：本发明提供了一种HRB600高强钢筋的冷却方法,以10℃/s的加热速率升温到1150℃,保温5分钟后,以10℃/s的降温速率降温到1100℃,以开轧温度为1100℃,终轧温度为950℃,变形量为75％；热轧后以0.5℃/s-20℃/s的冷却速率冷却至600℃-760℃,再空冷自然冷却。在控制轧制的基础上,通过控冷工艺并结合微合金化技术可有效地控制钢中碳氮化物的析出以及过冷奥氏体的相变,同时获得细小铁素体+珠光体+少量贝氏体(0％-10％)的显微组织,以改善钢筋的强度和塑性。(The invention provides a cooling method of HRB600 high-strength steel bars, which comprises the steps of heating to 1150 ℃ at a heating rate of 10 ℃/s, preserving heat for 5 minutes, cooling to 1100 ℃ at a cooling rate of 10 ℃/s, rolling at 1100 ℃ at the beginning, rolling at 950 ℃ and deforming at 75%; after hot rolling, cooling to 600-760 ℃ at a cooling rate of 0.5-20 ℃/s, and then air cooling for natural cooling. On the basis of controlling rolling, the precipitation of carbonitride and the phase change of supercooled austenite in steel can be effectively controlled by a controlled cooling process and a microalloying technology, and a microstructure of fine ferrite, pearlite and a small amount of bainite (0-10%) is obtained at the same time so as to improve the strength and the plasticity of the steel bar.)

1. A cooling method of HRB600 high-strength steel bars is characterized in that the temperature is raised to 1150 ℃ at a heating rate of 10 ℃/s, the temperature is kept for 5 minutes, then the temperature is lowered to 1100 ℃ at a cooling rate of 10 ℃/s, the initial rolling temperature is 1100 ℃, the final rolling temperature is 950 ℃, and the deformation is 75%; after hot rolling, cooling to 600-760 ℃ at a cooling rate of 0.5-20 ℃/s, and then air cooling for natural cooling.

2. The method for cooling the HRB600 high-strength steel bar as claimed in claim 1, wherein the HRB600 high-strength steel bar is cooled to 600 ℃ -625 ℃ at a cooling rate of 0.5 ℃/s-3 ℃/s after hot rolling, and then is naturally cooled by air cooling.

3. The cooling method for the HRB600 high-strength steel bar as claimed in claim 1, wherein the HRB600 high-strength steel bar comprises the following chemical components: the steel plate is characterized by comprising 0.23-0.26 wt.% of C, 0.70-0.76 wt.% of Si, 1.44-1.56 wt.% of Mn, 0.006-0.007 wt.% of P, 0.004-0.005 wt.% of S, 0.06-0.23 wt.% of V, 0.009-0.043 wt.% of N and 3-23% of V: N.

4. The cooling method for the HRB600 high-strength steel bar as claimed in claim 1, wherein the HRB600 high-strength steel bar comprises the following chemical components: c content 0.23 wt.%, Si content 0.75 wt.%, Mn content 1.55 wt.%, P content 0.0075 wt.%, S content 0.0045 wt.%, V content 0.23 wt.%, N content 0.019 wt.%, V: N12.

5. The method for cooling the HRB600 high-strength steel bar as claimed in claim 1, wherein the rolling times are 3 times, namely three times of rolling at 1100 ℃, 1050 ℃ and 950 ℃.

Technical Field

The invention relates to the technical field of material processing, in particular to a cooling method of a HRB600 high-strength steel bar.

Background

The high-strength steel bar is a main reinforcing material of a reinforced concrete king building structure, and bears tensile stress, compressive stress and strain in the structure, and particularly with the development of national economy and the appearance of multifunctional building structures such as high-rise, large-span, earthquake-resistant, low-temperature-resistant and fire-resistant structures, the steel bar is required to have comprehensive properties such as higher strength, early plasticity, better welding performance and the like.

For 600MPa grade high-strength steel bars, the technological parameters such as soaking temperature before rolling, cooling rate after rolling, controlled cooling termination temperature and the like have great influence on the structure and performance of the steel bars. It is necessary to develop the HRB6000 high-strength steel bar by deeply researching the strengthening mechanism of the micro-alloy elements, the influence rule of the controlled rolling and controlled cooling process on the structure and the performance of the steel bar and adjusting the controlled rolling and controlled cooling technological parameters to fully play the strengthening effect of the micro-alloy elements. The method has important guiding significance for the production practice of the high-strength steel bars in China.

Disclosure of Invention

Aiming at the prior art, the invention provides a cooling method of HRB600 high-strength steel bars, which improves the India property of the steel bars, ensures that the plasticity is not reduced and obtains excellent comprehensive performance.

The present invention achieves the above-described object by the following technical means.

A cooling method of HRB600 high-strength steel bars is characterized in that the temperature is raised to 1150 ℃ at a heating rate of 10 ℃/s, the temperature is kept for 5 minutes, then the temperature is lowered to 1100 ℃ at a cooling rate of 10 ℃/s, the initial rolling temperature is 1100 ℃, the final rolling temperature is 950 ℃, and the deformation is 75%; after hot rolling, cooling to 600-760 ℃ at a cooling rate of 0.5-20 ℃/s, and then air cooling for natural cooling.

Further, after hot rolling, cooling to 600-625 ℃ at a cooling rate of 0.5-3 ℃/s, and then air-cooling and naturally cooling.

Further, the HRB600 high-strength steel bar comprises the following chemical components: the steel plate is characterized by comprising 0.23-0.26 wt.% of C, 0.70-0.76 wt.% of Si, 1.44-1.56 wt.% of Mn, 0.006-0.007 wt.% of P, 0.004-0.005 wt.% of S, 0.06-0.23 wt.% of V, 0.009-0.043 wt.% of N and 3-23 wt.% of V: N.

Further, the HRB600 high-strength steel bar comprises the following chemical components: c content 0.23 wt.%, Si content 0.75 wt.%, Mn content 1.55 wt.%, P content 0.0075 wt.%, S content 0.0045 wt.%, V content 0.23 wt.%, N content 0.019 wt.%, V: N12.

Further, the number of rolling passes was 3, and the three passes were 1100 ℃, 1050 ℃ and 950 ℃.

By controlling proper cooling rate and cooling process, the method adopts lower finish rolling temperature and lower cooling rate after rolling, is beneficial to precipitation of a precipitated phase, can promote V-N microalloying, can ensure that a large amount of fine and dispersed vanadium carbonitride particles are precipitated in steel to achieve the effect of precipitation strengthening, and simultaneously the dispersed vanadium carbonitride can pin austenite grain boundaries, inhibit the growth of austenite grains, and serve as nucleation cores of ferrite and refine ferrite grains, thereby playing the roles of fine grain strengthening and homogenization of tissues. On the basis of controlling rolling, the precipitation of carbon nitride in steel and the phase change of supercooled austenite can be effectively controlled by a controlled cooling process and a microalloying technology, and a required microstructure is obtained to improve the performance of the steel bar.

According to the invention, the micro-alloy elements in the steel are fully precipitated and precipitated by selecting a proper cooling rate after rolling, and meanwhile, a microstructure of fine ferrite, pearlite and a small amount of bainite (0-10%) is obtained, and when the room temperature structure of the steel bar contains no more than 10% of bainite, the strength of the steel bar can be obviously improved, the plasticity and yield platform of the steel bar cannot be influenced, and the strength and plasticity of the steel bar are improved.

Detailed Description

The present invention will be further described with reference to the following specific examples, but the scope of the present invention is not limited thereto.

The steel with the chemical components shown in the table 1 is heated to 1150 ℃ at the heating rate of 10 ℃/s, and is cooled to 1100 ℃ at the cooling rate of 10 ℃/s after being kept for 5 minutes, the initial rolling temperature is 1100 ℃, the final rolling temperature is 950 ℃, and the deformation is 75%; after hot rolling, cooling to 600-760 ℃ at a cooling rate of 0.5-20 ℃/s, and then air cooling for natural cooling.

TABLE 1

	C(wt.％)	Si(wt.％)	Mn(wt.％)	P(wt.％)	S(wt.％)	V(wt.％)	N(wt.％)	V：N
									1#	0.24	0.74	1.56	0.008	0.005	0.11	0.020	5.5
2#	0.23	0.75	1.55	0.007	0.004	0.23	0.019	12
									3#	0.23	0.72	1.54	0.007	0.004	0.22	0.024	9
4#	0.24	0.72	1.42	0.007	0.004	0.22	0.034	6.5

When the cooling speed is too high, the micro-alloy element V in the experimental steel is not ready for precipitation and precipitation, so that the precipitation strengthening and fine-grain strengthening effects of the micro-alloy element are weakened, and the waste of the alloy element is caused; meanwhile, as the solid solution amount of V in the steel is increased, the hardenability of the steel is improved, the content of bainite in the structure is greatly increased, and the plasticity of the steel is obviously reduced. If the cooling speed is too slow, ferrite grains obtained through phase change in the steel are gradually coarsened, vanadium carbonitride particles precipitated and separated in the cooling process are gradually grown, and the comprehensive performance of the steel is obviously reduced under the two conditions, so that a proper cooling speed needs to be selected, the precipitation strengthening and fine grain strengthening effects of micro-alloy elements are fully exerted, and the performance requirement of the 600MPa high-strength steel bar is further met.

The average values of microhardness of four experimental steels with different contents of vanadium and nitrogen under different cooling speed conditions are shown in table 2. Table experimental steels the average microhardness values increased with increasing cooling rate. As the cooling rate is increased, the supercooled austenite is mainly transformed from ferrite and pearlite phase transformation to bainite and martensite phase transformation, more hardening phases are generated, and different microstructures and contents thereof determine different microhardness.

TABLE 2

The 2# experimental steel has the Young modulus of 321.2GPa when the cooling speed is 0.5 ℃/s; when the cooling speed is 1 ℃/s, the Young modulus is 295.2 GPa; when the cooling rate was 3 ℃/s, the Young's modulus was 275.1 GPa. The Young modulus is obviously reduced along with the increase of the cooling speed from 0.5 ℃/s to 3 ℃/s. In order to ensure the strength and plasticity of the steel for the 600 MPa-grade high-strength steel bar, the cooling rate after hot rolling is controlled within the range of 0.5-3 ℃/s so as to obtain fine ferrite, pearlite and a small amount of bainite.

The present invention is not limited to the above-described embodiments, and any obvious improvements, substitutions or modifications can be made by those skilled in the art without departing from the spirit of the present invention.