CN114507803B - Quenching distribution steel with gradient distribution of fault energy, preparation method and application - Google Patents

Abstract

The invention provides a preparation method of a fault energy gradient distribution quenching distribution steel, which comprises the steps of filling non-penetrating holes formed in the surface of a substrate with a quenching distribution steel plate as the substrate and fault energy regulating and controlling powder as an enhancement item, and then carrying out friction stir processing on the surface of the substrate filled with the fault energy regulating and controlling powder to obtain the fault energy gradient distribution quenching distribution steel. The invention also discloses the quenching distribution steel with the gradient distribution of the fault energy and application thereof. The invention prepares the quenching distribution steel with gradient distribution of the stacking fault energy by changing the deformation mechanism of the quenching distribution steel, introduces one or more of C powder, Mn powder or Al powder into a substrate through stirring friction processing to improve the stacking fault energy of the local area of the quenching distribution steel, so that the deformation mechanism of the quenching distribution steel is changed from single phase transformation into phase transformation and twinning, thereby achieving the purpose of high-strength plasticity, and the prepared quenching distribution steel has the characteristic of gradient stacking fault energy and is more suitable for being used under the condition of complex working conditions.

Description

A kind of stacking fault energy gradient distribution quenching partition steel, preparation method and application

technical field

The invention belongs to the technical field of iron and steel material processing, and in particular relates to a stacking fault energy gradient distribution quenching partition steel, a preparation method and an application.

Background technique

Compared with aluminum and magnesium alloys, steel not only has higher yield and tensile strength, but also has the advantages of light weight and corrosion resistance, and is widely used in the automobile body manufacturing industry. However, due to the complex application conditions of the car body, the performance requirements of the steel used in different parts of the car body are often very different. For example, the anti-collision beam of the car body requires better impact toughness, and the upper cover needs to be made of better and higher strength. . Therefore, in conventional manufacturing, different grades of steel plates are usually welded or riveted, and suitable and low-priced steel plates are assembled for use. Materials connected in this way often fail in the heat-affected zone of the weld during service, thereby reducing the service life of the material and causing inconvenience. Therefore, there is an urgent need for a quenched and partitioned steel that can prepare a stacking fault energy gradient distribution with different deformation mechanisms in different regions, so as to achieve the goal of different regional properties of the steel.

SUMMARY OF THE INVENTION

In view of the above technical requirements, the present invention proposes a stacking fault energy gradient distribution quenching and partitioning steel, a preparation method and an application. The lack of technical problems of steels with different regional properties.

In order to achieve the above object, the present invention adopts the following technical solutions to realize:

A method for preparing stacking fault energy gradient distribution quenching and partitioning steel. The quenching and partitioning steel plate is used as a base plate, and the stacking fault energy control powder is used as a reinforcement item, and the stacking fault energy control powder is filled in the non-penetrating holes opened on the surface of the base plate. Then, friction stir processing was performed on the surface of the substrate filled with stacking fault energy regulating powder to obtain a quenched and partitioned steel with a gradient distribution of stacking fault energy.

The present invention also has the following technical features:

Specifically, the stacking fault energy control powder includes one or more of C powder, Mn powder or Al powder.

Further, the particle size of the stacking fault energy control powder is 1 μm˜50 μm, and the purity of the stacking fault energy control powder is not less than 99%.

Further, the method includes the following specific steps:

Step 1. Determine the stacking fault energy of the substrate according to the chemical composition of the substrate; determine the stacking fault energy regulation range of the substrate according to the deformation mechanism of the substrate and the classification of the stacking fault energy; determine the stacking fault energy regulation range of the substrate according to the stacking fault energy regulation range of the substrate. The mass content in the quenched partitioned steel with dislocation energy gradient distribution;

Step 2: According to the stacking fault energy determined in step 1, the mass content of the powder in the stacking fault energy gradient distribution quenched and partitioned steel is regulated, and it is determined that when the transverse gradient stacking fault energy quenched partition steel or the longitudinal gradient stacking fault energy quenched partition steel is prepared, set at: The number and spacing of non-through holes on the substrate, and then complete the hole making on the pretreated substrate;

Step 3: Filling the reinforcing item in the non-penetrating holes on the surface of the substrate, and then performing friction stir processing on the surface of the substrate filled with the stacking fault energy regulating powder to obtain a quenched and partitioned steel with a gradient distribution of stacking fault energy.

Furthermore, the stacking fault energy regulation range is 12-18 mJ/m ² , and the mass content of the stacking fault energy regulation powder in the stacking fault energy quenched partition steel is 0.0218% to 6.69%.

Furthermore, when preparing the transverse gradient stacking fault energy quenched partition steel, the number of holes is calculated by the following formula:

In the formula, M is the mass content of the stacking fault energy control powder in the quenched partition steel with the gradient distribution of the stacking fault energy, M is the mass content of the corresponding element of the stacking fault energy control powder in the _substrate , a is the length of the substrate, the unit is mm, b is the inter-shaft diameter of the stirring needle in friction stir processing, in mm, c is the thickness of the substrate, in mm, d is the diameter of the hole, in mm, h is the depth of the hole, in mm, and L is the friction stir on the substrate The length of the processing area, the unit is mm, n is the number of holes, the unit is one, the ρ _powder is the stacking fault energy control powder density, the unit is g/cm ³ , the ρ _base is the substrate density, the unit is g/cm ³ .

Furthermore, when the longitudinal gradient stacking fault energy quenched partition steel is prepared, the spacing of the holes is calculated by the following formula:

In the formula, M is the mass content of the stacking fault energy-regulated powder in the quenched partition steel with the gradient distribution of the stacking fault energy, M is the mass content of the corresponding element of the stacking fault energy-regulated powder in the _substrate , f is the distance between the holes, the unit is mm, D ₀ is the diffusion constant of the powder controlled by the stacking fault energy, E is the diffusion activation energy of the powder controlled by the stacking fault energy, R is the thermodynamic constant, valued at 8.314J/mol, T is the welding temperature in the friction stir processing, the unit is °C, J is the mass flux in mol/m ² .

Further, the rotational speed of the stirring head of the friction stir processing is 400-2000 r/min, and the forward speed of the stirring head is 50-400 mm/min.

The invention also discloses the gradient quenching and distribution steel prepared by the above preparation method. The stacking fault energy gradient distribution quenching and partitioning steel takes the quenching and partitioning steel as the substrate, and the stacking fault energy regulation powder is used as the reinforcement item, and the stacking fault energy regulation powder is filled in the non-penetrating holes opened on the surface of the substrate, and then in the The surface of the substrate filled with stacking fault energy control powder is obtained by friction stir processing.

The invention also discloses the application of the stacking fault energy gradient distribution quenched partition steel prepared by the above preparation method for automobile body parts.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The method of the present invention prepares the gradient stacking fault energy quenched and divided steel by changing the deformation mechanism of the quenched and divided steel, and introduces one or more of C powder, Mn powder or Al powder into the quenched and divided steel by friction stir processing. As a stacking fault energy control powder, the deformation mechanism of the quenched partition steel is transformed from a single phase transformation to a phase transition and twinning, so as to improve the stacking fault energy in the local area of the existing quenched partition steel and achieve the purpose of high strength and plasticity. The prepared quenched partition steel Steel has the characteristics of stacking fault energy gradient, which is more suitable for use in complex working conditions.

(2) The existing stacking fault energy control method can only control the stacking fault energy of the entire sheet. Although the stacking fault energy can be changed, it does not improve the mechanical properties of the sheet by improving the deformation mechanism. It still relies on dislocation strengthening to improve the steel properties. . In this method, the stacking fault energy control powder is used as the enhancement item to achieve local precise control of the stacking fault energy, and the mechanical properties of the steel are improved by changing the deformation mechanism of the steel.

(3) The friction stir processing technology used in the method of the present invention belongs to the green solid-phase processing technology. Compared with the traditional metal material processing methods, that is, equal channel angular extrusion and high-pressure torsion, it has the advantages of simple operation, low cost, green environmental protection, fast and effective Etc.

(4) The mechanical properties of the stacking fault energy gradient distribution quenched partition steel prepared by the present invention are obviously improved compared with the strength-plastic product of the same kind of steels purchased in the market.

(5) The stacking fault energy gradient distribution quenched and partitioned steel prepared by the method of the present invention is especially suitable for the application of automobile body parts whose performance requirements are often very different, and has broader application prospects and strong promotion and use value.

Description of drawings

Fig. 1 is the engineering stress-strain curve of 2 prepared in Example 1, Comparative Example 1 and Comparative Example 2;

Fig. 2 is the preparation schematic diagram of the transverse gradient stacking fault energy quenched partition steel in Example 1;

FIG. 3 is a schematic diagram of the preparation of the longitudinal gradient stacking fault energy quenched partition steel in Example 2. FIG.

Detailed ways

In the following, only certain exemplary embodiments are briefly described. As those skilled in the art would realize, the described embodiments may be modified in various different ways, with additions, deletions, modifications, etc., all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive.

The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, but not to limit the present invention.

The technical terms involved in the present invention are explained below:

Stacking fault energy gradient: refers to the phenomenon that a material exhibits a gradient distribution in stacking fault energy along a certain direction.

Quenched partitioned steel: refers to quenched-carbon partitioned steel. The mechanical properties that quenched partitioned steel can usually achieve are in the range of tensile strength of 800 to 1500 MPa and elongation of 15% to 40%.

Transverse gradient: The transverse direction in this scheme refers to the direction perpendicular to the rolling direction of the quenched and partitioned steel plate. The stacking fault energy of each processing pass along the transverse direction of the quenched and partitioned steel plate presents a gradient distribution. At this time, the hole spacing is fixed. In the same processing time, the diffusion amount of the reinforcing element is the same, and the content of the reinforcing element is uniform under the same processing pass. Therefore, the overall mass ratio is used to calculate the number of voids in the preparation of the transverse gradient stacking fault energy quenched partition steel.

Longitudinal gradient: The longitudinal direction in this scheme refers to the rolling direction of the quenched and partitioned steel plate. At this time, the stacking fault energy of each longitudinal processing pass on the quenched and partitioned steel plate is distributed in a gradient, and the hole spacing is not constant. Stacking faults can control the diffusivity of powder elements at different distances and at the same processing time. Under the same processing pass, stacking faults can control the element content of powders to be non-uniform. Therefore, in the preparation of longitudinally graded stacking fault energy quenched partition steel, the overall mass ratio cannot be used, but the diffusion rate formula is used to calculate the pore spacing.

It should be noted that the hole spacing in the present invention refers to the distance between the centers of the holes.

The performance of steel is closely related to its deformation mechanism, and the deformation mechanism is divided into four types according to the stacking fault energy: 1. The stacking fault energy is less than 12mJ/m ² , and the deformation mechanism of the material is mainly phase transformation; 2. The stacking fault energy is in In the range of ^12-18mJ /m2, the deformation mechanism is mainly phase transition and twinning; 3. The stacking fault energy is in the range of ^18-35mJ /m2, mainly due to the twinning mechanism; 4. The stacking fault energy is above 35mJ/ ^m2 , The main deformation mechanism is dislocation slip. Phase transformation can increase the work hardening rate, and twinning is beneficial to plasticity. The stacking fault energy of quenched partition steel is below 12mJ/m ² , and the deformation mechanism is a single phase transformation. Therefore, the plasticity of quenched partition steel is far less than that of twin-induced plasticity steel with twin deformation mechanism. In this scheme, the element content will be used to increase the stacking fault energy, and the stacking fault energy of the quenched and partitioned steel will be increased to the range of 12-18 mJ/m ² , thereby improving the strength and plasticity of the steel.

The invention discloses a preparation method of a quenched and distributed steel with a gradient distribution of stacking fault energy. The quenched and distributed steel plate is used as a base plate, and the stacking fault energy control powder is used as a reinforcing item, and the stacking fault energy control powder is filled in the openings opened on the surface of the base plate. Then, friction stir processing is performed on the surface of the substrate filled with the stacking fault energy control powder in the non-penetrating holes, and the quenched partition steel with the stacking fault energy gradient distribution is obtained.

Preferably, the stacking fault energy control powder includes one of C powder, Mn powder or Al powder.

Preferably, the particle size of the stacking fault energy regulated powder is 1 μm˜50 μm, and the purity of the stacking fault energy regulated powder is not less than 99%.

Including the following specific steps,

Step 1. Determine the stacking fault energy of the substrate according to the chemical composition of the substrate; determine the stacking fault energy regulation range of the substrate according to the deformation mechanism of the substrate and the classification of the stacking fault energy; determine the stacking fault energy regulation range of the substrate according to the stacking fault energy regulation range of the substrate. The mass content in the quenched partitioned steel with dislocation energy gradient distribution;

Step 2. According to the stacking fault energy determined in step 1, the mass content of the powder in the stacking fault energy gradient distribution quenching and partitioning steel is regulated, and after determining the preparation of the transverse gradient stacking fault energy quenching and partitioning steel or the longitudinal gradient stacking fault energy quenching and partitioning steel, it is determined to open. The number and spacing of non-through holes on the substrate, and then complete the hole making on the pretreated substrate;

Substrate pretreatment specifically refers to grinding the surface of the quenched and distributed steel substrate with sandpaper before processing to make the surface roughness of the substrate Ra ≤ 10 μm, and then cleaning the polished surface with acetone to remove oil and oxides on the surface of the metal plate. and impurities, and finally dried.

Preferably, when preparing the transverse gradient stacking fault energy quenched partition steel, the number of holes is calculated by the following formula:

In the formula, M is the mass content of the stacking fault energy control powder in the stacking fault energy quenched partition steel, M is the mass content of the corresponding element of the stacking fault energy control powder in the _substrate , a is the length of the substrate, in mm, and b is The inter-shaft diameter of the stirring needle in friction stir processing, in mm, c is the thickness of the substrate, in mm, d is the diameter of the hole, in mm, h is the depth of the hole, in mm, and L is the friction stir processing area on the substrate The length of , in mm, n is the number of holes, in units, ρ _powder is the stacking fault energy control powder density, in g/cm ³ , ρ _base is the substrate density, in g/cm ³ .

The stacking fault energy regulation range is 12-18 mJ/m ² , and the mass content of the stacking fault energy regulation powder in the stacking fault energy quenched partition steel is 0.0218% to 6.69%.

Using the existing thermodynamic model and regular solid solution model, the mass content of the stacking fault energy control powder in the stacking fault energy quenched partition steel can be determined through the control range of the stacking fault energy. Among them, the control range of the stacking fault energy on the substrate is determined to be 12-18mJ/m ² , because the quenched partition steel is a low-alloy high-strength steel, and the mass proportion of each element in the alloy will not exceed the proportion of the C element content of the steel material, so The lowest C content in the steel material is 0.0218% as the stacking fault energy to control the lower limit of the mass content of the powder in the stacking fault energy quenched partitioned steel, and the highest C content of 6.69% is used as the stacking fault energy to control the powder in the stacking fault energy quenched partition steel. To limit the initial range of the mass content of the stacking fault energy control powder in the stacking fault energy quenched partition steel.

Preferably, when preparing the longitudinal gradient stacking fault energy quenched partition steel, the spacing of the holes is calculated by the following formula:

In the formula, M is the mass content of the stacking fault energy regulated powder in the stacking fault energy quenched and partitioned steel, M is the mass content of the corresponding element of the stacking fault energy regulated powder in the _substrate , f is the hole spacing, in mm, D ₀ is the stacking fault energy to control the diffusion constant of the powder, E is the stacking fault energy to control the diffusion activation energy of the powder, R is the thermodynamic constant, the value is 8.314J/mol, T is the welding temperature in friction stir processing, the unit is °C, and J is Mass flux, in mol/m ² .

Preferably, the thickness of the substrate is 1-3 mm, the diameter of the hole is 1-2.5 mm, and the depth of the hole is 0.5-1.2 mm.

Step 3: Filling the reinforcing item in the non-penetrating holes on the surface of the substrate, and then performing friction stir processing on the surface of the substrate filled with the stacking fault energy regulating powder to obtain a quenched and partitioned steel with a gradient distribution of stacking fault energy.

The friction stir processing device adopts existing equipment, including a shaft shoulder and a stirring needle connected in sequence, wherein the shaft shoulder is cylindrical, and the diameter of the shaft shoulder is 12-18 mm; the stirring needle is cylindrical, conical or truncated; cylindrical The diameter of the stirring needle is 4 to 8 mm and the length is 0.5 to 4 mm; the diameter of the root of the conical stirring needle is 2 to 6 mm and the length of 1.5 to 10 mm; the diameter of the root of the circular cone-shaped stirring needle is 4 to 8 mm, and the diameter of the top is 2 to 6 mm. , the length is 1 ~ 15mm.

The rotational speed of the stirring head of the friction stir processing is 400-2000 r/min, and the forward speed of the stirring head is 50-400 mm/min.

Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent transformations made on the basis of the technical solutions of the present application fall into the protection scope of the present invention.

Example 1

Following the above technical solution, a method for preparing a quenched and partitioned steel with a gradient distribution of stacking fault energy is provided in this embodiment. The quenched and partitioned steel plate is used as the substrate, and the stacking fault energy regulation powder is used as the enhancement item. The powder is filled in the non-penetrating holes opened on the surface of the substrate, and then friction stir processing is performed on the surface of the substrate filled with the stacking fault energy regulating powder to obtain a quenched and partitioned steel with a gradient distribution of the stacking fault energy.

In this embodiment, QP1180 quenched and distributed steel plate with a thickness of 1.5 mm is used as the substrate, and the stacking fault energy control powder is 6-layer graphene powder with a purity of 99.9%. The chemical composition of the substrate and the mass content of the chemical composition are: C: 0.19% , Si: 1.7%, Mn: 2.7%, P: 0.015%, Fe: 95.39%.

First, a QP1180 quenched and distributed steel substrate with a size of 210mm×96mm×1.5mm was prepared and pretreated. Pretreatment refers to mechanical grinding to remove rust and cleaning the surface with acetone to remove oil.

Set the hole diameter to 2mm, the hole depth to 0.5mm, and the hole length to 200mm.

Then, according to the chemical composition of the substrate, the existing regular solution thermodynamic model is used to determine the stacking fault energy of the substrate to be ^-15.8mJ /m ² . For the deformation mechanism, the control range of the substrate stacking fault energy is 12-18 mJ/m ² .

The above parameters are brought into the existing thermodynamic model and regular solid solution model to determine the corresponding element of carbon powder, that is, the mass content of carbon element in the prepared stacking fault energy gradient distribution quenching partition steel is 2.71-2.91%.

In this embodiment, the transverse gradient stacking fault energy quenching and partitioning steel is prepared by the preparation method of the present invention, and the mass content of carbon powder in the prepared stacking fault energy gradient distribution quenching and partitioning steel is 2.71-2.91%. The mass content of carbon in the substrate is 0.19%, the density of the substrate is 7.86g/cm ³ , the diameter of the hole is 2mm, the length of the friction stir processing area on the substrate is 200mm, and the density of the powder controlled by stacking fault energy is 3.7g/cm ³ . The number of holes is 5 to 6.

As shown in Figure 2, the number of rows of non-penetrating holes prepared on the substrate is 8, thus forming 8-pass processing areas, the width of each processing area is 12mm, and the processing of the 1st, 3rd, 5th and 7th rows The number of holes in each column in the area is 5, and the hole spacing is 42mm. In the processing area of the 2nd, 4th, 6th, and 8th columns, the number of holes in each column is 6, and the hole spacing is 35mm.

Finally, the carbon powder is filled in the non-penetrating holes opened on the surface of the substrate, and then friction stir processing is performed on the surface of the substrate filled with the stacking fault energy regulating powder to obtain a transverse gradient stacking fault energy quenching partition steel.

The specific friction stir processing parameters include: the rotation speed of the stirring head is 800 r/min, the forward speed of the stirring head is 300 mm/min, the diameter of the stirring needle is 6 mm, and the diameter between the shafts is 12 mm.

Experimental results:

Tensile specimens with a size of 32 mm × 6 mm were taken from the transverse gradient stacking fault energy quenched and partitioned steel plate prepared in this example, and then the overall properties of the steel plate were tested, and the first row of processing zones with a size of 4 mm × 2 mm were prepared. The local tensile specimens and the local tensile specimens in the processing area of the second column were tested for performance respectively. The results are shown in the following table:

Table 1: Performance comparison of transverse gradient stacking fault energy quenched partition steels

tensile strength Yield Strength Elongation stacking fault energy first row 1521MPa 1085MPa 24.4% 15.3mJ/m² the second list 1543MPa 1141MPa 23.5% 14.3mJ/m²

The experimental results show that the stacking fault energy of the first column with 5 holes on the prepared transverse gradient stacking fault energy quenched partition steel plate is 15.3 mJ/m ² , the tensile strength and yield strength are low, but the plasticity is high; The stacking fault energy of the second row with 6 holes is 14.3 mJ/m ² , the tensile strength and yield strength are high, and the plasticity is slightly poor. The whole plate realizes the gradient of stacking fault energy along the transverse direction, and the performance also achieves the gradient effect.

Example 2

As shown in FIG. 2 , the difference between this embodiment and Embodiment 1 is that this embodiment adopts the preparation method of the present invention to prepare a longitudinally gradient stacking fault energy quenched partition steel.

The mass content of carbon element in the prepared quenched and partitioned steel with stacking fault energy gradient distribution is 2.71-2.91%. The mass content of carbon element in the substrate is 0.19%, the length, width and thickness of the substrate are 210mm, 96mm and 1.5mm respectively, the hole diameter is 1mm, R is 8.314J/mol, T is 700℃, E is 140J/mol, J is 1.9 mol/m ² , D ₀ is 2.0×10 ^-4 m ² /s, and t is 15s. Then according to the method of the present invention, the calculated result of the hole spacing is 14-16, and the hole spacing after rounding is 10mm or 20mm. Sample for performance testing.

Table 2: Comparison of properties of longitudinal gradient stacking fault energy quenched partition steels

Hole spacing tensile strength Yield Strength Elongation stacking fault energy 1mm 1192MPa 1047MPa 8% 18mJ/m² 2mm 1532MPa 858MPa 28% 14.5mJ/m²

Experimental results:

As shown in Table 3 and Table 4, it is found through testing that the longitudinal carbon content in the local area of the sample is different, and the quenched partition steel has high yield strength, poor tensile and plasticity in the longitudinal 10mm spacing area, and 20mm longitudinal spacing area. The yield strength is low, and the tensile strength and plasticity are high, indicating that the longitudinal gradient stacking fault energy quenched partition steel prepared in this example presents a gradient change in properties.

Table 3: The distribution table of the element content distribution table of regional energy spectrum analysis detection at the hole spacing 2mm in Example 2;

element name Percentage (%) mean squared error Fe 93.7 0.6 Mn 2.7 0.4 C 2.1 0.5 Si 1.5 0.1 P 0.0 0.1

Table 4: is the distribution table of element content detected by regional energy spectrum analysis at the hole spacing of 2 mm in Example 1.

element name Percentage (%) mean squared error Fe 89.8 0.8 Mn 2.7 0.4 C 4.9 0.5 Si 1.7 0.2 S 0.1 0.1

Example 3

The difference between this example and Example 1 is that: the substrate selects 980 quenched and partitioned steel with a thickness of 2 mm, and the distance between the non-penetrating holes on the substrate is 10 mm. The uniform quenched and partitioned steel is prepared, and the performance test results are as follows:

tensile strength Yield Strength Elongation stacking fault energy 1016MPa 997MPa 14% 19mJ/m²

Comparative Example 1

The difference between this comparative example and Example 1 is that no non-penetrating holes are formed on the quenched and partitioned steel substrate, no stacking fault energy control powder is filled, friction stir processing is directly performed on the substrate, and then the performance of the processed substrate is tested. , the engineering stress-strain curve shown in Figure 1 is obtained.

Comparative Example 2

The difference between this comparative example and Example 1 is that the steel used in this comparative example is a quenched and partitioned steel substrate prepared by a conventional quenching and partitioning process, and the quenched and partitioned steel substrate is directly tested for performance without friction stir processing, as shown in Figure 1. The engineering stress-strain curve shown.

It can be seen from Figure 1 that the strength and ductility of the transverse gradient stacking fault energy quenched partition steel prepared in Example 1 are much higher than those of the processed steel obtained in Comparative Example 1 without element-controlled stacking faults, and are also much higher. Regarding the strength of the commercially available metallurgically prepared quenched and partitioned steel used in Comparative Example 2, it is shown that the strength of the transverse gradient stacking fault energy quenched and partitioned steel prepared in Example 1 is much higher than that of the same kind of steel plate prepared by metallurgical methods, and the strength and plasticity are even higher. For steel plates prepared by single friction stir processing without stacking fault energy regulation.

Comparative Example 3

The difference between this comparative example and Example 1 is that the hole diameter is 2.8 mm, the hole depth is 1 mm, and the number of punched holes is 10.

The test results are as follows

tensile strength Yield Strength Elongation stacking fault energy 1203MPa 839MPa 3.8% 37mJ/m²

Since the diameter of the holes in this comparative example is greater than 2 mm, the stacking fault energy is beyond the range of 12-18 mJ/m ² . Therefore, compared with the transverse gradient stacking fault energy quenched partition steel prepared in Example 1, the The strength and plasticity of the transverse gradient stacking fault energy quenched partition steel are poor.

Comparative Example 4

The difference between this comparative example and Example 1 is that the added stacking fault energy control powder is Si powder. Then, the properties of the quenched and partitioned steel obtained after processing are tested, and the test results are as follows:

tensile strength Yield Strength Elongation stacking fault energy 796MPa 736MPa 2.5% -11.2mJ/m²

The Si powder used in this comparative example cannot increase the stacking fault energy, and the transverse gradient stacking fault energy quenching partition steel cannot be prepared, and the properties of the prepared sheet are far lower than the transverse gradient stacking fault energy quenching partition obtained in Example 1. properties of steel.

Comparative Example 5

In order to better verify the effectiveness of the method, in Comparative Example 5, referring to the scheme of heat treatment to control the bainite stacking fault energy in the published patent application CN 112280941A, heat treatment was performed on the quenched partition steel, and the chemical composition and size of the quenched partition steel were the same as the implementation. example 1.

The steps of heat treatment are:

1. Heat to 950℃ for 180s;

2. Cool down to 200℃ and keep warm for 30s;

3. Reheat to 380℃ for 300s;

4. Finally, cool down to room temperature with the furnace.

Then, the properties of the quenched and partitioned steel obtained after heat treatment are tested, and the test results are as follows:

tensile strength Yield Strength Elongation stacking fault energy Before heat treatment 1084MPa 710MPa twenty two% -15.8mJ/m² After heat treatment 697MPa 453MPa 26% 20mJ/m²

In this comparative example, the heat treatment process was used to try to adjust the stacking fault energy to prepare the quenched partition steel with gradient distribution of the stacking fault energy. The properties of quenched and partitioned steel cannot achieve the goal of property gradient.

To sum up, conventional heat treatment and only friction stir welding cannot accurately control the stacking fault energy of quenched and partitioned steel plates, resulting in poor performance of the steel plate; while using an excessively large hole diameter or adding non-improving stacking fault energy powder will also As a result, the stacking fault energy control fails, and the prepared steel sheet has poor performance. The method can prepare stacking fault energy gradient distribution quenched partition steel, and the properties are distributed in gradient on the whole steel plate. As in Example 1, the first pass has low yield and good plasticity; the second pass has higher strength and slightly poorer plasticity.

Therefore, the quenched and partitioned steel prepared by this method can be better applied to the position where the strong plasticity requirements of the automobile body are greatly different, such as the connection between the anti-collision beam and the frame, so that the area with higher strength is located at the frame, and the plasticity is higher. The area is located at the crash beam.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above-mentioned embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, These simple modifications all belong to the protection scope of the present invention.

In addition, the various embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the spirit of the present invention, they should also be regarded as the contents disclosed in the present invention.

[1] Lin Zhangguo, Chen Jiayong, Tang Di, Jiang Haitao, Duan Xiaoge. Study on the deformation mechanism of medium manganese Q&P steel based on stacking fault energy [J]. Journal of South China University of Technology (Natural Science Edition), 2016,44 (02): 140-146.

Claims (6)

1. A preparation method of a quenching distribution steel with gradient distribution of fault energy is characterized in that a quenching distribution steel plate is used as a substrate, a fault energy regulating powder is used as an enhancement item, the fault energy regulating powder is filled in a non-through hole formed in the surface of the substrate, and then stirring friction processing is carried out on the surface of the substrate filled with the fault energy regulating powder to obtain the quenching distribution steel with gradient distribution of fault energy;

the stacking fault energy regulating powder comprises one or more of C powder, Mn powder or Al powder;

the particle size of the stacking fault energy regulation powder is 1-50 mu m, and the purity of the stacking fault energy regulation powder is not less than 99%;

the method comprises the following specific steps:

step 1, determining the stacking fault energy of a substrate according to the chemical components of the substrate by using a quenching distribution steel plate as the substrate; determining the adjustment and control range of the stacking fault energy of the substrate according to the deformation mechanism and the stacking fault energy classification of the substrate; determining the mass content of the stacking fault energy regulating powder in the stacking fault energy gradient distribution quenching distribution steel according to the stacking fault energy regulating range of the substrate;

step 2, regulating and controlling the mass content of the powder in the quenching distribution steel with the gradient distribution of the stacking fault energy according to the stacking fault energy determined in the step 1, determining the number and the intervals of non-penetrating holes formed in the substrate when preparing the transverse gradient stacking fault energy quenching distribution steel or the longitudinal gradient stacking fault energy quenching distribution steel, and then finishing hole making on the pretreated substrate;

when the transverse gradient fault energy quenching distribution steel is prepared, the number of the non-penetrating holes arranged on the base plate is in gradient distribution along the vertical rolling direction, so that when the longitudinal gradient fault energy quenching distribution steel is prepared, the spacing of the non-penetrating holes arranged on the base plate is in gradient distribution along the rolling direction;

step 3, filling the reinforcing item into a non-penetrating hole formed in the surface of the substrate, and then performing friction stir processing on the surface of the substrate filled with the stacking fault energy regulating powder to obtain stacking fault energy gradient distribution quenching distribution steel;

the adjustment and control range of the stacking fault energy is 12-18mJ/m ² The mass content of the fault energy regulating powder in the fault energy quenching distribution steel is 0.0218-6.69%.

2. The method for producing a transverse gradient fault energy gradient distribution quenched distribution steel as claimed in claim 1, wherein the number of holes is calculated by the following formula:

wherein M is the mass content of the stacking fault energy regulating and controlling powder in the quenching distribution steel with stacking fault energy gradient distribution, and M is _{Base of} Regulating the mass content of corresponding elements of the powder in a substrate for the purpose of stacking fault energy, wherein a is the length of the substrate and is expressed in mm, b is the diameter between shafts of a stirring pin in stirring friction processing and is expressed in mm, c is the thickness of the substrate and is expressed in mm, d is the diameter of a hole and is expressed in mm, h is the depth of the hole and is expressed in mm, L is the length of a stirring friction processing area on the substrate and is expressed in mm, n is the number of the holes and is expressed in unit, rho _Powder The density of the powder is regulated and controlled by the stacking fault energy, and the unit is g/cm ³ ，ρ _{Base of} Is the substrate density in g/cm ³ 。

3. The method for producing a fault energy gradient distribution quenched distribution steel as claimed in claim 1, wherein the pitch of the holes is calculated by the following formula when producing the longitudinal gradient fault energy quenched distribution steel:

wherein M is the mass content of the stacking fault energy regulating and controlling powder in the quenching distribution steel with stacking fault energy gradient distribution, and M is _{Base of} The mass content of corresponding elements of the powder in the substrate is regulated and controlled by the stacking fault energy, f is the space between holes and has the unit of mm, D ₀ Regulating the diffusion constant of the powder by using the stacking fault energy, regulating the diffusion activation energy of the powder by using the stacking fault energy, wherein R is a thermodynamic constant and takes the value of 8.314J/mol, T is the welding temperature in friction stir processing, the unit is K, J is the material flux and the unit is mol/m ² 。

4. The method for preparing the fault energy gradient distribution quenched distribution steel as claimed in claim 1, wherein the rotation speed of the stirring head in the friction stir processing is 400-2000 r/min, and the advancing speed of the stirring head is 50-400 mm/min.

5. The quenching distribution steel with the gradient distribution of the stacking fault energy, which is prepared by the preparation method of the quenching distribution steel with the gradient distribution of the stacking fault energy as claimed in any one of claims 1 to 4, is characterized in that the quenching distribution steel with the gradient distribution of the stacking fault energy takes quenching distribution steel as a substrate, stacking fault energy regulating powder as an enhancement item, the stacking fault energy regulating powder is filled in a non-through hole formed in the surface of the substrate, and then the surface of the substrate filled with the stacking fault energy regulating powder is subjected to stirring friction processing to obtain the quenching distribution steel with the gradient distribution of the stacking fault energy.

6. The application of the quenching distribution steel with the gradient distribution of the fault energy, prepared by the preparation method of the quenching distribution steel with the gradient distribution of the fault energy according to any one of claims 1 to 4, in automobile body parts.

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