Preparation method of ultrahigh-strength high-plasticity high-temperature-oxidation-resistant steel through hot stamping forming

A technology of hot stamping and high temperature oxidation resistance, which is applied in heat treatment equipment, heat treatment furnaces, manufacturing tools, etc., and can solve problems such as oxidation and strong plasticity

Active Publication Date: 2021-07-13

UNIV OF SCI & TECH BEIJING

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AI-Extracted Technical Summary

Problems solved by technology

[0007] In view of the above technical problems, the purpose of the present invention is to improve the oxidation problem and the low plasticity problem in the heating and heat preservation process of the current hot-formed steel, and provide a method for preparing an ultra-high-strength, high-plasticity, high-tempe...

Abstract

The invention discloses a preparation method of ultrahigh-strength high-plasticity high-temperature-oxidation-resistant steel through hot stamping forming. The steel comprises the following components of, in percentage by mass, 0.25%-0.45% of C, 1.0%-3.0% of Si, 3.0%-5.5% of Mn, less than or equal to 2.5% of Ni, 0.8%-2.0% of Al, 0.04%-0.10% of Nb, less than or equal to 0.5% of Mo, less than or equal to 0.005% of B, less than or equal to 0.04% of Ti, less than or equal to 0.1% of RE, less than or equal to 0.015% of P, less than or equal to 0.015% of S, less than or equal to 1.5% of Cu or less than or equal to 0.08% of V or less than or equal to 0.5% of W, or a combination of a plurality of components, and the balance Fe, wherein Si/Al satisfies 1.2-2.2, Si + Al is greater than 2.5, and Mn is greater than Al + Si. The hot-formed steel is obtained through smelting, pouring, forging, hot rolling, air cooling or simulated curling, acid pickling, cold rolling, annealing and hot forming. The preparation process of the hot-formed steel is simple, after component optimization and hot stamping forming, the structure comprises a martensite matrix and 2.0%-10.0% residual austenite, it can be guaranteed that the tensile strength is larger than or equal to 1900 MPa, the yield strength is larger than or equal to 1200 MPa, the total ductility is larger than or equal to 9.5%, meanwhile, the high-temperature oxidation resistance is remarkably improved, it can be guaranteed that after a steel plate is heated to a temperature smaller than or equal to 950 DEG C in air, and subjected to heat preservation for shorter than or equal to 5 min, and after hot stamping forming, the thickness of an oxide layer is smaller than or equal to 4.2 micrometer, and an expensive AlSi coating can be omitted, so that the cost is reduced, and the production efficiency is improved.

Application Domain

Furnace typesHeat treatment furnaces

Technology Topic

Plastic propertyPost oxidation +14

Image

Examples

Experimental program(3)

Example Embodiment

[0084] Example 5: Si / Al = 1.2 to 2.2, and Si + Al <2.5, the average thickness of the oxide layer was 5.5 μm after the thermal stamping process of the corresponding steel in Table 2.

Example Embodiment

[0085] Example 6: Si / AL <1.2, and Si + Al> 2.5, the average thickness of the oxide layer was 5.1 μm after the thermal stamping process of the corresponding steel in Table 2;

Example Embodiment

[0086] Example 7: Si / Al <2.5, and Si + Al <2.5, the average thickness of the oxide layer was 5.8 μm after the thermal stamping process of the corresponding steel in Table 2. figure 2 (c) Example 7 The oxide layer typical SEM picture is given.

[0087] The thickness of the oxide layer in Examples 4, 5, 6 and 7 is found to reduce the Si / AL ratio and Si + Al content reduce oxidation resistance, and the thickness of the oxide layer of steel is the thinnest, and the oxidation resistance is optimal. It is necessary to make Si / Al = 1.2 to 2.2, and Si + Al> 2.5 is necessary. In summary, steel (satisfying: Si / Al = 1.2 ~ 2.2, and Si + Al> 2.5) After ≤ 950 ° C holding ≤ 5min, the oxide layer thickness is ≤4.2.2 μm.

[0088] Example 1-7 After the steel sheet is described in Table 2, the heat treatment and thermal punching process are performed by standard tensile test, and the tensile strength and total elongation of the steel are detected by standard tensile test, and the results are shown in Table 3, and 22MNB5 is compared.

[0089] Table 3 Mechanical properties of steel plate after thermal stamping process

[0090]

[0091] Embodiments of the present invention (Examples 2 and 3) and the engine stress after the 22MNB5 thermal punch - engineering strain curve, image 3 Shown

[0092] From the tensile performance data of Table 3, a steel sheet having the components of the present invention has a stamping steel sheet having a particularly excellent intensity and elongation comprehensivity by the thermal punching forming process of the present invention. Specifically, the tensile strength is ≥1900 MPa, the yield strength is ≥1200 MPa, the total elongation is ≥9.5%. Compared to the intensity and elongation of 22MNB5 steel (tensile strength = 1550 MPa, total elongation = 7.5%) compared to the commercial application, the tensile strength increased by 400 MPa, and the total elongation also increased greater than 2%. Further, the present invention preferably has excellent anti-high temperature oxidation resistance. Specifically, the thickness of the steel plate oxide layer is ≤4.2 μm after thermoforming of ≤ 950 ° C, and the resistance to high temperature oxidation resistance compared to steel (22Mnb5). Significantly improved, the thickness of the oxide layer is only 1/12 of the contrast steel, and can be replaced by the AlSi coating.

PUM

Property	Measurement	Unit
Thickness	5.5	µm
Thickness	5.1	µm
Thickness	<= 4.2	µm

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