阅读说明：本技术 一种稀土处理提高含磷高强if钢轧制全过程有利织构的方法 (Method for improving texture of phosphorus-containing high-strength IF steel in whole rolling process by rare earth treatment ) 是由 王皓 段承轶 刘妍 路璐 张齐 敬鑫 刘成龙 李人杰 于 2020-05-18 设计创作，主要内容包括：本发明公开了一种稀土处理提高含磷高强IF钢轧制全过程有利织构的方法,包括：在RH精炼工序处理末期,在RH真空处理过程中加入Mn铁、Ti铁、Nb铁、硼铁进行合金化,在合金化结束后循环3min时添加稀土铈铁合金,使钢水Ce含量达到20ppm；将轧制工序试样进行抛光处理,通过XRD检测对比分析有利织构的含量及强度。本发明的目的是提供一种稀土处理提高含磷高强IF钢轧制全过程有利织构的方法,在钢中加入稀土Ce,有效增加P元素在钢中的固溶量,提高高强IF钢中P元素的固溶强化效果,得到较大比例的{111}有利织构,从而有利于提高成形性能指标r90值,使含磷高强IF钢具有更好的冲压性能。(The invention discloses a method for improving favorable texture of phosphorus-containing high-strength IF steel in the whole rolling process by rare earth treatment, which comprises the following steps: at the final stage of RH refining process, Mn iron, Ti iron, Nb iron and ferroboron are added in the RH vacuum treatment process for alloying, and rare earth cerium iron alloy is added when the circulation is performed for 3min after the alloying is finished, so that the Ce content of the molten steel reaches 20 ppm; and polishing the rolling procedure sample, and detecting and comparing and analyzing the content and the strength of the favorable texture through XRD. The invention aims to provide a method for improving favorable texture of phosphorus-containing high-strength IF steel in the whole rolling process by rare earth treatment, wherein rare earth Ce is added into steel, so that the solid solution amount of a P element in the steel is effectively increased, the solid solution strengthening effect of the P element in the high-strength IF steel is improved, and the favorable texture of {111} in a larger proportion is obtained, thereby being favorable for improving the forming performance index r90 value and enabling the phosphorus-containing high-strength IF steel to have better stamping performance.)

1. A method for improving favorable texture of phosphorus-containing high-strength IF steel in the whole rolling process by rare earth treatment is characterized by comprising the following steps:

at the final stage of RH refining process, Mn iron, Ti iron, Nb iron and ferroboron are added in the RH vacuum treatment process for alloying, and rare earth cerium iron alloy is added when the circulation is performed for 3min after the alloying is finished, so that the Ce content of the molten steel reaches 20 ppm;

and polishing the rolling procedure sample, and detecting and comparing and analyzing the content and the strength of the favorable texture through XRD.

2. The method for improving the favorable texture of the whole process of the phosphorus-containing high-strength IF steel rolling by rare earth treatment according to claim 1, further comprising the step of preventing nitrogen increase and oxygen increase by adopting strict protective casting measures for preventing secondary oxidation in the continuous casting process.

3. The method for improving favorable texture of the whole process of rolling the phosphorus-containing high-strength IF steel by rare earth treatment according to claim 1, wherein the Ce content of the rare earth cerium-iron alloy is 20%.

4. The method for improving favorable texture of phosphorus-containing high-strength IF steel in the whole rolling process by rare earth treatment according to claim 1, wherein the sedation time is more than 15min after RH treatment is finished so as to ensure that inclusions float sufficiently.

5. The method for improving favorable texture of the whole process of rolling the phosphorus-containing high-strength IF steel by rare earth treatment according to claim 1, wherein the size of the test sample is 20mm by 25 mm.

Technical Field

The invention relates to the field of steel rolling and product development, in particular to a method for improving favorable texture of phosphorus-containing high-strength IF steel in the whole rolling process by rare earth treatment.

Background

With the development of automobiles towards weight reduction and light weight, automobile plates with high strength and ultra-deep drawing performance are rapidly developed, and solid solution reinforced IF steel is one of the main directions for developing high-strength IF steel at home and abroad. Since the P element has a high strengthening effect and is inexpensive, the strength of the steel sheet is improved by adding an appropriate amount of the P element to the IF steel, adjusting the ratio of Si and Mn elements, and performing solid solution strengthening. The higher the favorable texture proportion is, the higher the plastic strain ratio r value is, the better the stamping performance of the strip steel is represented.

Disclosure of Invention

The invention aims to provide a method for improving favorable texture of phosphorus-containing high-strength IF steel in the whole rolling process by rare earth treatment.

In order to solve the technical problems, the invention adopts the following technical scheme:

a method for improving favorable texture of phosphorus-containing high-strength IF steel in the whole rolling process by rare earth treatment comprises the following steps:

at the final stage of RH refining process, adding Mn iron, Ti iron, Nb iron and ferroboron in sequence in the RH vacuum treatment process for alloying, and adding rare earth cerium iron alloy when the circulation is performed for 3min after the alloying is finished so that the Ce content of the molten steel reaches 20 ppm;

and polishing the rolling procedure sample, and detecting and comparing and analyzing the content and the strength of the favorable texture through XRD.

Furthermore, the continuous casting process adopts strict protective casting measures for preventing secondary oxidation, thereby preventing nitrogen increase and oxygen increase.

Further, the Ce content of the rare earth cerium-iron alloy is 20%.

Furthermore, the sedation time is more than 15min after the RH treatment is finished so as to ensure that the inclusion is fully floated.

Further, the sample size was 20mm 25 mm.

Compared with the prior art, the invention has the beneficial technical effects that:

rare earth Ce is added at the final stage of RH refining process treatment, the Ce content in the molten steel reaches 20ppm, the Ce is combined with the activity O in the steel to have lower Gibbs free energy, and the CeAlO is easy to generate₃、Ce₂O₂S、Ce₂O₃Rare earth oxides, rare earth aluminates, rare earth oxysulfides. The rare earth Ce inhibits the precipitation of P element and Fe (Nb + Ti) P phase, can effectively increase the solid solution amount of the P element in the steel, is beneficial to improving the solid solution strengthening effect of the P element in the high-strength IF steel, and can obtain {111} favorable texture with a larger proportion, thereby being beneficial to improving the forming performance index r90 value and leading the phosphorus-containing high-strength IF steel to have better stamping performance. Provides a new idea for improving the control of the favorable texture content of the phosphorus-containing high-strength IF steel.

Drawings

The invention is further illustrated in the following description with reference to the drawings.

FIG. 1 is a diagram illustrating a specific adding time of a cerium-iron alloy in a smelting process;

FIG. 2 shows ODF sectional views (phi 2 is 45 degrees) of the steel strip detected in each rolling process, and the contents of (1# non-rare earth, (a) hot rolled plate, (b) cold rolled plate, (c) continuous annealing plate, (2 # rare earth, (d) hot rolled plate, (e) cold rolled plate and (f) continuous annealing plate) are counted;

FIG. 3 is a scatter plot comparing r-values with and without rare earth addition.

Detailed Description

The phosphorus-containing reinforced IF steel production test of the adjacent furnaces in the same casting time is carried out on the hot continuous rolling production line, and the production process flow and the rare earth adding time are shown in figure 1. When RH vacuum treatment is carried out, the ultimate vacuum degree is less than or equal to 0.106Kpa, and the total vacuum treatment time is 30 min. Because rare earth has stronger oxidability, in order to avoid oxidation by oxygen brought by other alloys in the alloying process and simultaneously ensure the effective boron content in steel, after aluminum deoxidation, the adding sequence of the alloys in the RH vacuum treatment process is Mn iron, Ti iron, Nb iron and boron iron. 48kg of rare earth cerium-iron alloy (the Ce content is 020%) is added when the circulation is carried out for 3min after the alloying is finished. The sedation time is more than 15min after the RH treatment is finished so as to ensure that the inclusion is fully floated. The yield of the rare earth Ce is 56%, the final components of the test steel are shown in Table 1, and the content of the rare earth is 20 ppm.

The continuous casting process adopts strict protective casting measures for preventing secondary oxidation, and prevents nitrogen increase and oxygen increase. The selected steel grade and the middle ladle components are shown in the table I, the specific processes of all the procedures in the casting and rolling process are shown in the table 1, the processes are completely the same except for adding rare earth in the whole production process, the definition of a whole series sample without adding rare earth is 1#, and the definition of a whole series sample with adding rare earth is 2 #. The chemical compositions of the rare earth addition and the rare earth non-addition are shown in Table 1.

And cutting the sample size of the rolling procedure into 20mm by 25mm, polishing the sample, and analyzing the content and strength of the favorable texture by XRD detection contrast.

TABLE 1 Process schemes for the execution of the various rolling sequences

TABLE 2 test Steel chemistry (Wt%)

The excellent deep drawing performance of IF steel is mainly derived from the fact that IF steel has a large proportion of 111 texture. Table 3 shows the statistics of the favorable texture content of the strip detected in each rolling step, and it can be seen that the percentage contents of the favorable texture {110} <001> in the hot rolling step, and the percentage contents of the favorable texture {111} (<110> + <112>) in the cold rolling and continuous annealing step in the sample group # 2 are respectively 5.78%, 22.7% and 24.16%, which are all greater than the percentage contents in the corresponding steps 3.79%, 18.8% and 21.62% in the sample group # 1. Fig. 2 shows the ODF sectional view (Φ 2 is 45 °) content statistics of the strip detected in each step of rolling (1# no rare earth addition, (a) hot rolled sheet, (b) cold rolled sheet, (c) continuous annealing sheet, (2 # rare earth addition, (d) hot rolled sheet, (e) cold rolled sheet, and (f) continuous annealing sheet), and it can be seen that Max values of hot rolling, cold rolling, and continuous annealing steps in 2# sample are 4.1, 13.3, and 7.9, respectively, and are all greater than corresponding steps 2.9, 12.4, and 6.5 in 1# sample group. The body-centered cubic metal has the highest tensile strength in the <111> crystal direction, i.e. the largest deformation resistance in the <111> direction of crystal grains, and the <111> direction of the {111} texture is perpendicular to the plate surface, so the texture causes the thick direction of the steel plate to be not easy to deform during stamping, and the r value is larger. The higher the {111} texture content, the higher the strength, and the higher the plastic strain ratio r value. Therefore, the sample No. 2 has better annealing structure and deep drawing performance.

TABLE 3 statistics of advantageous texture content of each rolling pass

After the rare earth Ce is added, the solid solution strengthening effect of the P element in the high-strength IF steel is improved, a {111} favorable texture with a large proportion is obtained, the r90 value of the product is improved, and the r90 value of the 2# sample group strip steel added with the rare earth shown in figure 3 is obviously larger than that of the 1# sample group strip steel without the rare earth.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.