CN113755762B - Low-V microalloyed ultra-fine dispersion precipitated phase high-strength steel and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of ultra-fine dispersion precipitated phase high-strength steel and a preparation method thereof, and particularly relates to low-V microalloyed ultra-fine dispersion precipitated phase high-strength steel and a preparation method thereof, which solve the technical problems in the background art. The method exerts the precipitation strengthening effect of the V (C, N) precipitated phase, so that the precipitated phase can be uniformly and dispersedly distributed in the matrix, the dispersion strengthening effect is achieved, and the high-strength and high-plasticity high-strength steel is prepared.

Description

A kind of low-V microalloyed ultra-fine disperse precipitation high-strength steel and preparation method thereof

technical field

The invention belongs to the technical field of ultrafine dispersed precipitation phase high-strength steel and a preparation method thereof, and relates to a low-V microalloyed precipitation phase, in particular to a low-V microalloyed ultrafine dispersed precipitation phase high-strength steel and a preparation method thereof.

Background technique

It is a relatively common process at this stage to improve the performance of steel by adding different alloying elements to the steel. Using the respective characteristics of different alloying elements enables them to play their respective roles in the steel, which can improve the performance of the steel. However, due to the different melting points of various elements, adding a certain amount of alloying elements to the steel may make it difficult for the alloying elements to dissolve in the steel. Due to the fact that some V does not reach the optimal melting temperature of V during smelting, all the added V cannot be melted back into the steel, and it is difficult to play the role of adding V during the smelting process. Generally speaking, after the steel is deformed, more nucleation sites will be generated, which will lead to deformation to induce nucleation and precipitation, and form ultra-fine and dispersed precipitation phases. The solid solubility of elements such as V is increased, and at the same time, the steel billet is normalized and reheated, so that the grains become finer and the influence of inclusions such as MnS can also be alleviated.

Through the review of existing literature and patents, it is found that the performance of steel is currently improved on the basis of the composition of carbon-manganese structural steel, by adding microalloying elements and using controlled rolling and controlled cooling technology or by changing the C content in the steel. However, there are some problems in these processes. For example, in some studies, by adding microalloying elements to improve the performance of steel, only Ti and Mo are added at the same time. The yield strength of the steel can reach the required value, which not only increases the cost of production, but also the addition of Mo element has a greater impact on the properties of the steel, which brings some problems to the smelting of the steel. In fact, how to make the dissolved alloy elements dispersable and finely precipitated through the heat treatment process is the key to the strengthening effect of the trace alloy elements. However, after the elements added during the smelting process are dissolved back into the steel, the relevant subsequent precipitation phase precipitation rules, In particular, there are few studies on the correlation between the precipitation temperature, the precipitation time, and the characteristics of the precipitation phase.

SUMMARY OF THE INVENTION

The present invention aims to solve the technical problems in the background technology, and provides a low-V microalloyed ultra-fine dispersed precipitation phase high-strength steel and a preparation method thereof. Through the scientific optimization design of the composition and subsequent heat treatment of the smelted steel billet, the alloying elements added in the steel can play their own role, and achieve the effect of fineness, dispersion and precipitation strengthening, and prepare a high-strength, The low-V microalloyed ultra-fine dispersed precipitation phase high-strength steel with high plasticity and other mechanical properties meets the mechanical properties requirements of the steel required in production, processing and application, reducing economic costs and improving safety factor.

The technical means adopted by the present invention to solve the technical problems are as follows: providing a low-V microalloyed ultra-fine dispersion precipitation phase high-strength steel, which is composed of the following elements by mass percentage: C: 0.03-0.35%, Si: 0.70-1.10% , Mn: 1.55-1.75%, V: 0.06-0.30%, N: 0.012-0.035%, Cr: 0.15-0.45%, P≤0.035%, S≤0.025%, the rest are Fe and inevitable impurities. The yield strength of the high-strength plastic and low-V micro-alloyed ultra-fine dispersed precipitation phase high-strength steel reaches over 750Mpa, the tensile strength is over 950Mpa, and the elongation is 15%-20%.

Preferably, it is composed of the following elements by mass percentage: C: 0.05-0.33%, Si: 0.70-0.95%, Mn: 1.60-1.75%, V: 0.11-0.18%, N: 0.018-0.030%, Cr: 0.15- 0.45%; P≤0.025%, S≤0.025%, the rest are Fe and inevitable impurities. Under the above ratio, the various properties of the high-strength steel obtained by mixing each element composition are better.

In order to solve the technical problem, the present invention also provides a method for preparing a low-V microalloyed ultra-fine dispersed precipitation phase high-strength steel. Then, the smelted steel billet is processed by the conventional heating furnace process or the direct rolling process. After the treatment, the steel ingot cooled to room temperature is heated and kept at a certain temperature for a certain period of time so that V can be completely dissolved into the steel ingot, and then at a certain temperature Under cooling and holding for a certain period of time, V can be completely precipitated to form V(C, N) uniformly dispersed fine precipitates, so as to provide low V microalloyed ultrafine dispersed precipitates high-strength steel. V(C,N) is vanadium carbonitride. The preparation method of the present invention adopts control of the content, size and distribution of the V(C,N) precipitation phase and refines the crystal grains by normalizing, so that it can obtain a A kind of high-strength plastic low-V micro-alloyed ultra-fine disperse precipitation high-strength steel with a yield strength of more than 750Mpa, a tensile strength of more than 950Mpa, and an elongation of 15% to 20%. Among them, mainly through the re-dissolution of V, the V element added in the nominal composition can be completely dissolved into the steel, and no inclusions and remaining V elements remain. In addition, the V (C, N ) The precipitation phase can be uniformly dispersed and precipitated, and the obtained precipitation phase is small and uniformly distributed near the grain boundary, exerting the precipitation strengthening effect of the V (C, N) precipitation phase, and improving the mechanical properties of the steel from the microstructure. .

The beneficial effects of the present invention are as follows: the present invention provides a high-strength plastic, low-V micro-alloyed ultra-fine dispersive precipitation high-strength steel with a yield strength of over 750 Mpa, a tensile strength of over 950 Mpa and an elongation of 15%-20%; The invention also provides a method for preparing low-V micro-alloyed ultra-fine dispersed precipitation phase high-strength steel, which exerts the precipitation strengthening effect of the V (C, N) precipitation phase, so that the precipitation phase can be uniformly dispersed in the matrix to achieve dispersion. The effect of strengthening is to prepare low-V micro-alloyed ultra-fine dispersed precipitation phase high-strength steel with high strength and high plasticity, with low application cost, simple heat treatment process and strong economic applicability.

Description of drawings

FIG. 1 is a metallographic structure diagram of the high-strength steel without heat treatment in Comparative Example 1 of the present invention.

FIG. 2 is a metallographic structure diagram of the low-V microalloyed ultra-fine disperse precipitation high-strength steel obtained in Example 1 of the present invention.

FIG. 3 is a metallographic structure diagram of the low-V microalloyed ultrafine disperse precipitation high-strength steel obtained in Example 2 of the present invention.

FIG. 4 is a metallographic structure diagram of the low-V microalloyed ultra-fine disperse precipitation high-strength steel obtained in Example 3 of the present invention.

FIG. 5 is a metallographic structure diagram of the low-V microalloyed ultra-fine disperse-precipitated high-strength steel obtained in Example 4 of the present invention.

Detailed ways

Referring to FIGS. 1 to 5 , a low-V microalloyed ultra-fine disperse precipitation high-strength steel according to the present invention and a preparation method thereof will be described in detail.

Comparative Example 1: According to the proportions, the components containing each element are mixed and then smelted, and then the slab is continuously cast into an ingot. The chemical composition weight ratio of each component is controlled as: C: 0.17%, Si: 0.81%, Mn: 1.64%, V: 0.145%, N: 0.0183%, Cr: 0.21%, S: 0.024%, P: 0.014%, and the rest is Fe; the billet is produced by the conventional heating furnace process, the heating temperature of the billet is 1197 ℃, and the discharge temperature of the billet is 1143 °C, the rolling temperature is 1093 °C, and the final rolling temperature is 1047 °C; in the direct rolling process, the billet rolling temperature is 1035 °C and the final rolling temperature is 1003 °C; The metallographic structure of the obtained steel ingot is shown in Figure 1.

Example 1: Take each element component according to the nominal composition ratio, the mass percentage of each element component is: C: 0.03%, Si: 0.70%, Mn: 1.5%, V: 0.06%, N: 0.012%, Cr : 0.15%, P: 0.035%, S: 0.025%, and the rest is Fe. After mixing each element component, the steel smelting process is used to smelt the billet, and then the smelted billet is processed by the conventional heating furnace process. The conventional heating furnace The process is to preheat the smelted billet, and then cool it to room temperature in the air; in the conventional heating furnace process, the heating temperature of the billet is 1150 °C, the billet discharge temperature is 1100 °C, the rolling temperature is 1000 °C, and the final rolling temperature is 950℃; after the treatment, heat the steel ingot cooled to room temperature, at 960℃, hold for 2h so that V can be completely dissolved into the steel ingot, and then at 500℃, hold for 3h, so that V can be completely precipitated, forming V(C, N) uniform The finely dispersed precipitates are dispersed to provide a low-V microalloyed ultra-fine dispersed precipitated high-strength steel. The metallographic structure of the high-strength steel prepared in Example 1 is shown in FIG. 2 .

Example 2: Take each element component according to the nominal composition ratio, the mass percentage of each element component is: C: 0.032%, Si: 0.8%, Mn: 1.60%, V: 0.08%, N: 0.020%, Cr : 0.25%, P: 0.030%, S: 0.020%, and the rest is Fe. After mixing each element component, the steel smelting process is used to smelt the billet, and then the smelted billet is processed by the conventional heating furnace process. The conventional heating furnace The process is to preheat the smelted billet, and then cool it to room temperature in the air; in the conventional heating furnace process, the heating temperature of the billet is 1170 °C, the billet discharge temperature is 1110 °C, the rolling temperature is 1050 °C, and the final rolling temperature is 980℃; after the treatment, heat the steel ingot cooled to room temperature, at 1030℃, holding for 1h so that V can be completely dissolved into the steel ingot, and then at 530℃, holding for 1h, so that V can be completely precipitated, forming V(C, N) uniform The finely dispersed precipitates are dispersed to provide a low-V microalloyed ultra-fine dispersed precipitated high-strength steel. The metallographic structure of the high-strength steel prepared in Example 2 is shown in FIG. 3 .

Example 3: Take each element component according to the nominal composition ratio, the mass percentage of each element component is: C: 0.033%, Si: 0.9%, Mn: 1.70%, V: 0.10%, N: 0.030%, Cr : 0.35%, P: 0.025%, S: 0.015%, and the rest is Fe. After mixing each element component, the steel smelting process is used to smelt the billet, and then the smelted billet is processed by the conventional heating furnace process. The conventional heating furnace The process is to preheat the smelted billet, and then cool it to room temperature in the air; in the conventional heating furnace process, the heating temperature of the billet is 1180 °C, the billet discharge temperature is 1130 °C, the rolling temperature is 1080 °C, and the final rolling temperature is 1000°C; after treatment, heat the steel ingot cooled to room temperature, at 1060°C for 0.5h, V can be completely dissolved into the steel ingot, and then at 600°C for 0.5h, V can be completely precipitated to form V(C,N ) uniformly disperse the fine precipitation phase to provide a low-V microalloyed ultra-fine dispersed precipitation phase high-strength steel. The metallographic structure of the high-strength steel prepared in Example 3 is shown in FIG. 4 .

Example 4: Take each element component according to the nominal composition ratio, the mass percentage of each element component is: C: 0.35%, Si: 1.10%, Mn: 1.75%, V: 0.30%, N: 0.035%, Cr : 0.45%, P: 0.015%, S: 0.010%, and the rest is Fe. After mixing each element component, the steel smelting process is used to smelt the billet, and then the smelted billet is processed by the conventional heating furnace process. The conventional heating furnace The process is to preheat the smelted billet, and then cool it to room temperature in the air; in the conventional heating furnace process, the heating temperature of the billet is 1200 °C, the billet discharge temperature is 1150 °C, the rolling temperature is 1100 °C, and the final rolling temperature is 1050℃; after the treatment, heat the steel ingot cooled to room temperature, at 1000℃, holding for 1.5h so that V can be completely dissolved into the steel ingot, and then at 570℃ and holding for 2h, V can be completely precipitated to form V(C,N) The fine precipitation phases are uniformly dispersed to provide a low-V microalloyed ultra-fine dispersed precipitation phase high-strength steel. The metallographic structure of the high-strength steel prepared in Example 4 is shown in FIG. 5 .

In Examples 1 to 4, the conventional heating furnace process can also be replaced by a direct rolling process; in the direct rolling process, the billet rolling temperature is 950°C to 1050°C, and the final rolling temperature is 900°C to 1050°C.

It can be seen from the comparison between Fig. 1 and Fig. 2 to Fig. 5 that the microstructure after heat treatment has changed greatly, and the ferrite and pearlite are obviously refined, indicating that V can be completely dissolved into the ingot after treatment, and then cooled at a certain temperature. And keep for a certain time so that V can be completely precipitated, forming V(C, N) uniformly dispersed fine precipitates to pin the grain boundaries, so as to provide low V microalloyed ultrafine dispersed precipitates high strength steel.

The above specific structure is a specific description of the preferred embodiment of the present invention, but the invention is not limited to the embodiment, and those skilled in the art can make various equivalents without departing from the spirit of the present invention. Modifications or substitutions, and these equivalent modifications or substitutions are all included within the scope defined by the claims of the present application.

Claims (5)

1. a preparation method of a low-V micro-alloyed ultra-fine dispersion precipitation phase high-strength steel, is characterized in that, the low-V micro-alloyed ultra-fine dispersion precipitation phase high-strength steel is made up of the following mass percentage elements: C: 0.03～0.35% , Si: 0.70～1.10%, Mn: 1.55～1.75%, V: 0.06～0.30%, N: 0.012～0.035%, Cr: 0.15～0.45%, P≦0.035%, S≦0.025%, the rest are Fe and Inevitable impurities; take each element component according to the nominal composition ratio, mix each element component and smelt to obtain a billet, and then process the smelted billet through a conventional heating furnace process or a direct rolling process. The conventional heating furnace process is: The smelted billet is preheated, and then cooled to room temperature in the air; the heating temperature of the billet in the conventional heating furnace process is 1150 ℃ ~ 1200 ℃, the billet discharge temperature is 1100 ℃ ~ 1150 ℃, and the rolling temperature is 1000 ℃ ~ 1100 ℃, the final rolling temperature is 950 ℃ ~ 1050 ℃; in the direct rolling process, the billet rolling temperature is 950 ℃ ~ 1050 ℃, and the final rolling temperature is 900 ℃ ~ 1050 ℃; At 960℃～1060℃ for 0.5h～2h, V can be completely dissolved into the steel ingot, and then at 500℃～600℃ and kept for 0.5h～3h, V can be completely precipitated to form V(C,N ) uniformly disperse the fine precipitates to provide low-V microalloyed ultra-fine disperse precipitates high-strength steel. 2. The preparation method of a low-V microalloyed ultrafine disperse-precipitated phase high-strength steel according to claim 1, characterized in that, it is composed of the following elements by mass percentage: C: 0.05-0.33%, Si: 0.70- 0.95%, Mn: 1.60-1.75%, V: 0.11-0.18%, N: 0.018-0.030%, Cr: 0.15-0.45%; P≤0.025%, S≤0.025%, the rest are Fe and inevitable impurities. 3. the preparation method of a kind of low-V micro-alloyed ultra-fine disperse precipitation phase high-strength steel according to claim 1, is characterized in that, the temperature that V can all dissolve in the steel ingot is 960 ℃～1030 ℃, the holding time is 960 ℃～1030 ℃. 0.5h～1h. 4 . The method for preparing a low-V microalloyed ultra-fine dispersed precipitation phase high-strength steel according to claim 1 , wherein V can be completely precipitated and form V(C, N) uniformly dispersed and finely dispersed precipitation phase. 5 . The temperature is 530℃～570℃, and the holding time is 0.5h～1h. 5. the preparation method of a kind of low-V microalloyed ultrafine disperse precipitation phase high-strength steel according to claim 1, is characterized in that, what is adopted is the steel smelting process when smelting the billet.

Images