CN107557697A - A kind of sorbite stainless steel - Google Patents

Abstract

A kind of sorbite stainless steel, belongs to stainless steel technical field.The stainless steel main component is ferro element, and using 8 16% chromium, 1 5% nickel element as leading alloying element, other contain 0.01 0.1% P elements, and control carbon is less than 0.1%, and element sulphur is less than 0.04%, and oxygen element content is less than 30ppm.The sorbite stainless steel after electric furnace, converter smelting by AOD to be smelted, LF refining, and decarburization, deoxidation, desulfurization are carried out to molten steel.By the mechanical performance of Heat Treatment Control sorbite stainless steel, preferable performance can be being obtained in a big way.The problem of this stainless steel overcomes austenitic stainless steel, the intensity of ferritic stainless steel is not high；Overcome general structural steel corrosion problem；The high Cost Problems of two phase stainless steel are overcome, are a kind of structural steel with excellent machinability.

Description

A sorbite stainless steel

technical field

The invention relates to a stainless steel, in particular to a sorbite stainless steel, a preparation method of the sorbite stainless steel, and an industrial application of the sorbite stainless steel.

Background technique

The existing varieties of stainless steel include austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, duplex stainless steel, and 200 series stainless steel. Ferritic and austenitic stainless steels in these stainless steels are generally only used to make utensils and panels due to their low strength. When used as a structural material, due to its low strength, the dosage can only be increased, which greatly increases the cost. Duplex stainless steel has good comprehensive properties, but the heat treatment process is difficult and the cost is too high, which is 2-3 times that of austenitic stainless steel, which limits its application. 200 series stainless steel is widely used due to its low price, but also due to its low strength, its comprehensive mechanical properties cannot meet the requirements of being a structural material.

Prior Art 1 (CN201410177300A) discloses an austenitic stainless steel, and its chemical composition weight percentage is disclosed as follows: C<0.03%, Si: 0.75-1.0%, Mn: 6.5-8.0%, Cr: 16.0-17.5% , Ni: 3.0-4.5%, N: 0.15-0.25%, Cu: 0.5-1.0%, Ce: 0.02-0.05%, P: ≤0.040%, S: ≤0.03%, the rest are Fe and unavoidable impurities, However, this austenitic stainless steel has a problem that neither the yield strength nor the tensile strength is high.

Prior art 2 (CN201410177886A) discloses a ferritic stainless steel, and its chemical composition weight percentage is disclosed as follows: C: 0.01-0.07%, Si: 0.50-1.50%, Mn: 0.40-1.0%, Al: 0.5- 2.5%, S: 0.001～0.005, Cr: 12.0～20.0%, N: 0.01～0.07%, O: 0.002～0.008%, Tb: 0.15～0.7%, Y: 0.005～0.2%, Al+Si≥1.5% , Nb: ≥7×C%, Y>5×S%, and the rest are Fe and unavoidable impurities. However, the ferritic stainless steel also has the problem of low yield strength and tensile strength.

Prior art three (CN201410000448A) discloses a duplex stainless steel with the following composition and mass percentage: C≤0.03%, S≤0.03%, P≤0.03%, Cr: 19.0-21.0%, Mn: 8 ～12%, Ni: 0.1～0.5%, N: 0.15～0.35%, Si≤1.0%, B: 0.001～0.01%, rare earth Ce or Y: 0.005～0.20%, and the balance is iron. Although the strength of the duplex stainless steel is high, due to the high amount of alloying elements in the stainless steel, usually the Cr content is above 20%, and the duplex stainless steel has the defect that heat treatment is difficult, so there are production problems in actual production and application. The problem of high cost limits its wide application in industry.

Prior art 4 (CN201410104587A) discloses a high-strength structural steel, which discloses the following components calculated by weight percentage: carbon: 0.07-0.28%; silicon: 0.10-0.45%; manganese: 0.80-1.90% Copper≤0.55%; Phosphorus≤0.025%; Sulfur≤0.010%; Titanium: 0.018-0.040%; Boron: 0.0010-0.0035%; Molybdenum: 0.10-0.50%; Although the structural steel has sufficient strength, in practical applications, this type of structural steel has the technical problems of being prone to rust and poor corrosion resistance.

Prior art five (CN20151061991A) discloses a martensitic stainless steel, and discloses that the mass percentage of its chemical composition is: C≤0.06%, Si≤1.00%, Mn≤1.00%, P≤0.030%, S≤ 0.015%, Cr15.00%～17.00%, Ni4.50%～5.50%, Mo0.80%～1.20%, H≤0.00025%, N≥0.020%, the balance is Fe and unavoidable impurities. However, due to its own structural characteristics, martensitic stainless steel cannot be used as a structural steel in practice.

Therefore, in view of the increasing requirements for the long life, high strength, easy welding and acceptable cost of steel structure materials, it has become one of the main directions of invention in the field of steel materials.

Contents of the invention

In view of the technical problems mentioned in the prior art, this application provides the following technical solutions.

A stainless steel whose main components include: Cr, Ni and P, and whose structure is a sorbite structure.

A stainless steel, the main components of which include: Cr content 8-15%, Ni content 1-5%, P content 0.03-1%, and its structure is sorbite structure.

A stainless steel, the main components of which include: Cr content 8-15%, Ni content 1-5%, P content 0.03-1%, and the stainless steel is a sorbite structure.

A stainless steel consisting of the following elements: Cr, Ni, P, C, S, O and Fe, and its structure is a sorbite structure.

A stainless steel, the composition and content of the stainless steel are: Cr content 8-15%, Ni content 1-5%, P content 0.03-1%, C content less than 0.1%, S content less than 0.04%, O content less than 30ppm, The balance is Fe, and its organization is a sorbite structure.

A stainless steel, the composition and content of the stainless steel are: Cr content 8-15%, Ni content 1-5%, P content 0.03-1%, C content less than 0.1%, S content less than 0.04%, O content less than 30ppm, The balance is Fe, and the above-mentioned stainless steel has a sorbite structure.

A stainless steel, the composition and content of the stainless steel are: Cr content 12-15%, Ni content 3-5%, P content 0.03-0.08%, C content less than 0.08%, S content less than 0.03%, O content less than 25ppm. , the balance is Fe, and the above-mentioned stainless steel has a sorbite structure.

A stainless steel, the composition and content of the stainless steel are: Cr content 13%, Ni content 3.5%, P content 0.08%, C content less than 0.05%, S content less than 0.02%, O content less than 20ppm. , the balance is Fe, and the above-mentioned stainless steel has a sorbite structure.

A stainless steel whose microstructure is a sorbite structure, and whose mechanical properties are: the tensile strength is not less than 750MPa, the non-proportional elongation strength R _P 0.2 is not less than 500MPa, and the elongation % after fracture is not less than 14 %.

A stainless steel whose microstructure is a sorbite structure, and whose mechanical properties are: the tensile strength is not less than 800MPa, the non-proportional elongation strength R _P 0.2 is not less than 550MPa, and the elongation % after fracture is not less than 16 %.

A stainless steel, the composition and content of the stainless steel are: Cr content 13%, Ni content 3.5%, P content 0.08%, C content less than 0.05%, S content less than 0.02%, O content less than 20ppm. , the balance is Fe, and the above-mentioned stainless steel has a sorbite structure. The mechanical properties of the stainless steel are: the tensile strength is not less than 750MPa, the specified non-proportional elongation strength R _P 0.2 is not less than 500MPa, and the elongation % after fracture is not less than 14%.

A stainless steel, the composition and content of the stainless steel are: Cr content 13%, Ni content 3.5%, P content 0.08%, C content less than 0.05%, S content less than 0.02%, O content less than 20ppm. , the balance is Fe, and the above-mentioned stainless steel has a sorbite structure. The mechanical properties of the stainless steel are: the tensile strength is not less than 800MPa, the specified non-proportional elongation strength R _P 0.2 is not less than 550MPa, and the elongation % after fracture is not less than 16%.

The function of each element is explained in detail below.

For the element Cr: Cr is an essential component element to improve the carbon dioxide corrosion resistance of steel, and it is also a key component element for the formation of a surface protective film at high temperature. In general, the level of Cr content is directly proportional to the corrosion resistance of steel, low content leads to low corrosion resistance, although high content increases corrosion resistance, it will increase the cost and reduce the hot workability. In the present application, within the scope of controlling the Cr content, the synergistic effect is achieved by adjusting the element P, thereby ensuring the corrosion resistance of the stainless steel.

For the element Ni: Ni can increase the solubility of carbon in stainless steel, enhance the tendency of carbide precipitation, avoid the formation of δ-ferrite, and ensure the machinability of stainless steel.

For element P: P is generally regarded as an inevitable impurity element in steel, which is a harmful element. High content of P can reduce the strength between grain boundaries, but in the sorbite stainless steel of this application, element P is used to increase strength and increase corrosion resistance. A reasonable content range of alloying elements is necessary.

Regarding the content of C: C, as an interstitial solute element, is beneficial to improve the strength of steel, but because high Cr content in stainless steel will lead to the formation of CrC compounds in steel, such as Cr ₂₃ C ₆ , thereby reducing the corrosion resistance of stainless steel, so this The application limits the C content to a lower range.

Regarding the content of S: S, as a common impurity element in steel, detrimentally reduces the strength and toughness of steel, so the application needs to strictly control the range of S content to improve the comprehensive performance of steel.

For the content of O: low content of O is beneficial to the combination of sufficient toughness and good mechanical properties of stainless steel. Preferably, the O content of the stainless steel of the present application is lower than 20 ppm.

The present application also provides the preparation methods of the above-mentioned various stainless steels: after smelting by electric furnace and converter, alloying treatment, then AOD smelting, composition adjustment, ladle refining furnace (LF furnace) refining, and decarburization and deoxidation of molten steel , desulfurization, continuous casting and rolling, and finally tempering heat treatment.

Specifically, the smelting process of stainless steel is as follows:

(1) Converter or electric furnace smelting: molten steel is smelted in a converter or electric furnace using conventional processes.

(2) Alloying treatment: Alloying the molten steel obtained by smelting by adding an intermediate alloy.

(3) Refining: Refining and decarburizing the obtained alloy by feeding argon-oxygen mixed gas, that is, AOD decarburization treatment.

(4) Adjusting the composition: tap the molten steel obtained by the AOD decarburization treatment to the ladle, and adjust the alloy composition at the same time.

(5) Refining: Refining is carried out in the ladle refining furnace (ie LF furnace), and deoxidation treatment is carried out to control the oxygen content within the specified range.

(6) Continuous casting: Continuous casting into slab, round billet or square billet by conventional technology.

(7) Rolling: The continuous casting slab or round billet or square billet is rolled into plate or bar or seamless pipe by conventional technology.

(8) Heat treatment: adopt tempering process to heat-treat the rolled product. While controlling the composition, the tempering treatment can ensure that the structure has a fine sorbite structure without obvious growth.

Metallographic analysis of the stainless steel obtained above shows that the metallographic structure of the stainless steel is sorbite, and through grading determination, the sorbite grain size is controlled to be above grade 8, preferably grade 9 or 9 above grade.

The beneficial effects of the present application will be described below.

For the stainless steel satisfying the above composition and the stainless steel prepared by the above method, it has a typical sorbite structure and is a kind of structural steel with good processability.

The stainless steel obtained in this application overcomes the corrosion problem of ordinary structural steel, and the comparative corrosion rate under neutral salt spray corrosion conditions is 30-80 times that of Q345, and has good corrosion resistance.

At the same time, the stainless steel obtained in the present application has the characteristics of high strength and easy welding, and overcomes the problem of low strength of austenitic stainless steel and ferritic stainless steel.

In addition, compared with the duplex stainless steel, the present application reduces the amount of alloying elements and greatly reduces the production cost.

Compared with martensitic stainless steel, although martensitic stainless steel has the advantages of high strength and high corrosion resistance, due to its structural characteristics, it cannot be used as a structural steel in practice, especially as a high-strength steel that meets the requirements of seismic performance. . The sorbite stainless steel obtained in the present application expands the application range of stainless steel and enriches the types of stainless steel.

Description of drawings

Fig. 1 is one of the metallographic structure diagrams of the sorbite stainless steel of the present invention.

Fig. 2 is the second diagram of the metallographic structure of the sorbite stainless steel of the present invention.

Fig. 3 is the third metallographic structure diagram of the sorbite stainless steel of the present invention.

Fig. 4 is the fourth metallographic structure diagram of the sorbite stainless steel of the present invention.

detailed description

In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the specific implementation manners of the sorbite stainless steel of the present application and the implementation manners of the preparation method of the sorbite stainless steel are described below.

As mentioned above, it is necessary to control the composition of stainless steel, in which Cr and Ni are used as the main alloying elements, and P is used as the alloying element at the same time, and the composition is Cr content 8-15%, Ni content 1-5%, P content 0.03-1%.

For the preparation process, when smelting molten iron, either converter smelting or electric furnace smelting can be selected; then the obtained molten iron is alloyed, and intermediate alloys are added to meet the requirements for the dominant alloying elements and alloying elements; then AOD decarburization Refining treatment to control the C content; then pour the molten steel obtained from the AOD treatment into the ladle for tapping, and then adjust the alloy composition; enter and refine in the ladle refining furnace, perform deoxidation treatment, and control the O content; then perform continuous casting and rolling respectively and heat treatment. Among them, for the continuous casting step, it can be cast into slab, round billet or square billet; for rolling, it can be rolled into plate, bar or seamless pipe; for heat treatment, tempering process is adopted to ensure fine and dense sorbite structure.

Preferred solution: For the above stainless steel, it is necessary to control the C content to be less than 0.1%, the S content to be less than 0.04%, and the O content to be less than 30ppm.

More preferred solution: for the above stainless steel, control Cr content to 12-15%, Ni content to 3-5%, P content to 0.03-0.08%, C content to less than 0.08%, S content to less than 0.03%, and O content to less than 25ppm. , the balance being Fe.

The most preferred scheme: for the above stainless steel, control the Cr content to 13%, the Ni content to 3.5%, the P content to 0.08%, the C content to less than 0.05%, the S content to less than 0.02%, and the O content to less than 20ppm. , the balance being Fe.

The mechanical properties of the resulting sorbite stainless steels are listed below. The range of mechanical properties of the prepared sorbite stainless steel is: breaking strength>750MPa, yield strength>500MPa, elongation not less than 14%. And the sorbite grain size is controlled above grade 8. The metallographic structure of the sorbite stainless steel produced in the test is shown in Figure 1-4. It can be seen that the metallographic structure is sorbite, and the grain size is 9 grades.

The following tempering heat treatment is carried out for different types of sorbite stainless steel, and the experimental results are shown in Table 1 below.

Table 1 Tempering heat treatment process of different types of sorbite stainless steel

As above, the sorbite stainless steel of the present application and the preparation method of the sorbite stainless steel have been described, but the application is not limited by the embodiments and examples, and can be appropriately changed within the scope of the gist of the present invention. Implementation, these are included in the technical scope of the present invention.

Although the application was described in detail with reference to the specific embodiment, it will be clear to those skilled in the art that various changes and modifications can be added without departing from the spirit and scope of the application.

Regarding the industrial applicability of the sorbite stainless steel obtained in this application, according to the structural characteristics and performance characteristics of the material itself, it can be used as a structural material in industry, and can also be used as a high-strength steel that requires seismic performance.

Claims (6)

1. A stainless steel, the main components of which include: Cr content 8-15%, Ni content 1-5%, P content 0.03-1%, and the stainless steel is a sorbite structure. 2. A stainless steel whose composition and content are: Cr content 8-15%, Ni content 1-5%, P content 0.03-1%, C content less than 0.1%, S content less than 0.04%, O content less than 30ppm, the balance is Fe, and the above-mentioned stainless steel has a sorbite structure. 3. A stainless steel whose microstructure is a sorbite structure, and whose mechanical properties are: the tensile strength is not less than 750MPa, the specified non-proportional elongation strength R _P 0.2 is not less than 500MPa, and the percent elongation after fracture is not less than 500MPa. Less than 14%. 4. according to the preparation method of the item stainless steel of claim 1-3: after being smelted by electric furnace, converter, through alloying treatment, then through AOD smelting, adjusting composition, ladle refining furnace (LF furnace) refining, molten steel is carried out decarburization, Deoxidation, desulfurization, continuous casting and rolling, and finally tempering heat treatment. 5. The stainless steel according to claims 1-3, and the application of the stainless steel obtained by the preparation method according to claim 14 as structural steel. 6. The stainless steel according to claims 1-3, and the application of the stainless steel obtained by the preparation method according to claim 4 as high-strength steel required for anti-seismic performance.