Weathering steel and preparation method thereof

Abstract

The invention discloses a weathering steel and a preparation method thereof, which comprises, by weight percentage, C: 0.05% to 0.08%, Si: 0.10% to 0.18%, Mn: 1.06% to 1.45%, Cr: 0.46% to 0.57%, Ni: 0.32% to 0.78%, Cu: 0.26% to 0.31%, P: 0.06% to 0.010%, S: 0.06% to 0.010%, Ti: 0% to 0.12%, Mo: 0% to 0.63%, and the rest is Fe and unavoidable impurities. The invention adopts reasonable chemical composition design, and then uses a medium frequency induction furnace to smelt an ingot that meets the composition design range, and finally obtains a weathering steel with a ferrite and martensite structure. The weathering steel of the present invention has excellent comprehensive performance. The addition of microalloying elements such as Mo and Ti can not only meet the requirements of high weather resistance in the harsh service environment of high humidity and high salt fog in the ocean, but also meet the requirements of stable mechanical properties of steel. The present invention effectively improves the strength of weathering steel while ensuring good marine environmental corrosion resistance. The method is economical, efficient, simple and easy to promote.

Description

Technical Field

[0001] The invention belongs to the technical field of weathering steel, and specifically relates to weathering steel and a preparation method thereof. Background Art

[0002] Steel corrosion is widespread in all fields and is very harmful. According to statistics, the economic losses caused by steel structure corrosion account for 4% of GDP each year. The marine environment is relatively complex due to the humidity, heat and high chloride ion environment. Marine environmental corrosion can cause more serious failure behavior of steel materials. The corrosion of steel in the marine environment generally brings serious harm to the development of energy and shipbuilding industries and the development and utilization of marine resources. This has become increasingly important for the research and development of marine environment corrosion-resistant steel, namely weathering steel.

[0003] Weathering steel, that is, atmospheric corrosion-resistant steel, is made by adding a small amount of corrosion-resistant elements to ordinary carbon steel. Its weather resistance is 2 to 8 times that of ordinary carbon steel, and it has the characteristics of rust resistance and corrosion resistance. Weathering steel is generally used to manufacture structural parts such as containers, railway vehicles, oil derricks, port buildings, oil production platforms, and chemical and petroleum equipment. Especially in the marine atmospheric environment, facilities and equipment are exposed to high temperature, high humidity, high salt fog, and high radiation environment all year round. At present, ordinary weathering steel grades have shown shortened life, premature scrapping, frequent repairs and maintenance in this environment, which significantly reduces the integrity rate of facilities and equipment, and directly affects the reliability and service life of island and reef projects. Since weathering steel in the marine environment has more severe corrosion adverse conditions, it is necessary to develop new weathering steel grades to improve the steel's resistance to marine atmospheric corrosion while ensuring the service safety of steel, which is conducive to energy conservation and emission reduction and the reduction of steel service life. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a weathering steel and a preparation method thereof in view of the deficiencies in the above-mentioned prior art, so as to solve the technical problem that weathering steel causes serious failure behavior of steel materials in marine environment.

[0005] The present invention adopts the following technical solutions:

[0006] A weathering steel comprises, by weight percentage, 0.05%-0.08% C, 0.10%-0.18% Si, 1.06%-1.45% Mn, 0.46%-0.57% Cr, 0.32%-0.78% Ni, 0.26%-0.31% Cu, 0.06%-0.010% P, 0.06%-0.010% S, 0%-0.12% Ti, 0%-0.63% Mo, and the remainder is Fe and unavoidable impurities.

[0007] Specifically, the room temperature yield strength of the weathered steel is 580-592 MPa, the tensile strength is 655-669 MPa, and the elongation is 17%-21%.

[0008] Specifically, the corrosion weight gain of weathering steel is 9.42-9.55 mg / cm 2 , the corrosion rate is 0.0390~0.0403mg / cm 2 ·h.

[0009] Specifically, the metallographic structure of weathering steel is discretely distributed ferrite + Mahouti structure.

[0010] Another technical solution of the present invention is a method for preparing weathering steel, comprising the following steps:

[0011] Industrial pure iron, ferromanganese, low-carbon ferrochrome, pure copper, pure nickel, ferrotitanium, ferromolybdenum, pig iron and pure aluminum are added into a medium frequency induction furnace in turn for smelting until molten steel is obtained. Aluminum wire is fed into the molten steel for deoxidation treatment; then perlite is added, and the molten steel is poured at a controlled speed to obtain cast steel. After the cast steel is cooled, the required weathering steel material is obtained.

[0012] Specifically, by mass percentage: 1.75% to 1.81% ferromanganese, 0.87% to 0.94% low-carbon ferrochromium, 0.29% to 0.36% pure copper, 0.32% to 0.39% pure nickel, 0% to 0.78% to ferrotitanium, 0% to 1.16% to ferromolybdenum, 1.05% to 1.13% pig iron, and the remainder is industrial pure iron, wherein 2 to 3g of pure aluminum is used for deoxidation per kilogram of molten steel.

[0013] Specifically, before smelting in the medium frequency induction furnace, it is preheated to 1589-1628°C.

[0014] Specifically, 10 to 20 g of perlite is added each time during the smelting process, and the number of additions is 8 to 11 times.

[0015] Specifically, the temperature of the molten steel pouring is 1670-1720° C., and the holding time is 4-7 minutes.

[0016] Specifically, after the cast steel is cooled, the surface of the cast steel is finely polished to remove the oxide scale.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] A weathering steel is provided. The chemical composition of the experimental steel is rationally designed by optimizing the alloy composition, and metal elements such as Ti and Mo are added to obtain a cast weathering steel of good quality. Finally, a new type of high-strength weathering steel resistant to high salt fog marine atmosphere environment is provided. The low-carbon design helps to enhance the toughness of the steel on the one hand, and on the other hand, it can avoid the formation of carbides in the structure and improve the corrosion resistance. Si has a high solid solubility in steel, and deoxidizes the steel during the smelting process. The Mn element has the effect of expanding the austenite phase region and stabilizing austenite, improving the low-temperature toughness and fatigue resistance of the steel. Cr is an element that can improve the hardenability of steel, and can effectively improve the high-temperature oxidation resistance and creep resistance of steel. Ni plays the role of solid solution strengthening and improving hardenability in steel. Cu mainly plays the role of solid solution and precipitation strengthening in steel, while improving the hardenability of steel, and significantly improving the core strength of the steel plate and the uniformity of the structure in the thickness direction. S is a harmful element in steel. Sulfur in steel is easy to combine with Mn to form MnS inclusions, which has a great detrimental effect on the low-temperature toughness, fatigue resistance and corrosion resistance of steel, so it is controlled as an impurity element. Too high P content will segregate at the grain boundary, increase the cold brittleness of steel, and reduce the plasticity of steel, so it is controlled as an impurity element. Ti can refine austenite grains to achieve precipitation strengthening. Mo element is dissolved in ferrite, which is beneficial to strengthen the ferrite matrix and improve the corrosion resistance of steel.

[0019] Furthermore, the room temperature yield strength of weathering steel is 580-592 MPa, the tensile strength is 655-669 MPa, and the elongation is 17%-21%, and it has good marine atmospheric corrosion resistance and mechanical properties.

[0020] Furthermore, the corrosion weight gain of weathering steel is 9.42-9.55 mg / cm 2 , the corrosion rate is 0.0390~0.0403mg / cm 2 h. The experimental steel has a smaller unit corrosion weight gain, a lower corrosion rate, and better corrosion resistance.

[0021] Furthermore, the metallographic structure of weathering steel is discretely distributed ferrite + Mahō Island structure. The experimental steel with this structure has excellent strength, toughness and corrosion resistance.

[0022] Furthermore, the entire weathering steel preparation method ultimately provides a weathering steel having excellent mechanical properties and good corrosion resistance, which is suitable for use in a high-humidity and high-salt fog marine atmospheric environment.

[0023] Furthermore, 2 to 3 g of pure aluminum is required for deoxidation per kilogram of molten steel so that the oxygen in the molten steel can be fully reacted to achieve the purpose of sufficient deoxidation.

[0024] Furthermore, preheating to 1589-1628°C before smelting in the medium frequency induction furnace is to melt the raw materials quickly.

[0025] Furthermore, 10 to 20 g of perlite is added each time during the smelting process, and the addition is 8 to 11 times to fully remove impurities.

[0026] Furthermore, the temperature of the molten steel pouring is 1670-1720° C. and the holding time is 4-7 minutes in order to fully melt the raw materials and obtain a uniform steel structure.

[0027] Furthermore, the surface of the cast steel is carefully polished to remove the oxide scale in order to accurately characterize the structure of the weathering steel and thus conduct accurate performance analysis.

[0028] In summary, the present invention adopts the idea of ​​alloying to improve the toughness and corrosion resistance through reasonable chemical composition design, and smelts ingots that meet the composition design range through a medium-frequency induction furnace, and finally obtains weathering steel with ferrite and Maho Island structures; the prepared weathering steel has excellent comprehensive performance, which can not only meet the requirements of high weather resistance in the harsh service environment of high humidity and high salt fog in the ocean, but also meet the requirements of stable mechanical properties of steel. The present invention effectively improves the strength of weathering steel while ensuring good resistance to marine environment corrosion, and is economical, efficient, simple and easy to promote.

[0029] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the microstructure diagram of the steel in Example 1;

[0031] Figure 2 This is the surface rust layer morphology of the steel in Example 1. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] In the present invention, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0034] In the present invention, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0035] In the present invention, unless otherwise specified, percentage (%) or part refers to the weight percentage or weight part relative to the composition.

[0036] In the present invention, unless otherwise specified, the components or preferred components involved can be combined with each other to form a new technical solution.

[0037] In the present invention, unless otherwise specified, the numerical range "a-b" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "6-22" means that all real numbers between "6-22" have been listed in this document, and "6-22" is just an abbreviation of these numerical combinations.

[0038] The “range” disclosed in the present invention is in the form of a lower limit and an upper limit, which can be one or more lower limits, and one or more upper limits, respectively.

[0039] In the present invention, the term "and / or" used herein refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0040] In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in accordance with the sequence. Preferably, the reaction method herein is carried out sequentially.

[0041] Unless otherwise specified, the professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content may also be applied to the present invention.

[0042] The present invention provides a weathering steel and a preparation method thereof. In view of the problem that ordinary weathering steel may cause serious failure of steel materials in the ocean, a new type of weathering steel with a new composition is designed. Through the effect of Ti and Mo elements in steel, alloying is adopted to improve the toughness and corrosion resistance engineering idea, and a new weathering steel is designed and developed. The metallographic structure of the experimental steel is analyzed, and corrosion experiments are carried out through mechanical property tests and salt spray corrosion simulating marine environments to explore the differences in mechanical properties and corrosion resistance of the experimental steel, and obtain a weathering steel with excellent comprehensive mechanical properties and corrosion resistance.

[0043] The present invention uses a reasonable chemical composition design, and then uses a medium frequency induction furnace to smelt an ingot that meets the composition design range, and finally obtains a weathering steel with a structure of ferrite and martensite; the prepared weathering steel has excellent comprehensive performance, and the addition of microalloying elements such as Mo and Ti can not only meet the high weather resistance requirements of the harsh service environment of high humidity and high salt fog in the ocean, but also meet the stable mechanical property requirements of the steel. The present invention effectively improves the strength of the weathering steel while ensuring good marine environmental corrosion resistance. The method is economical, efficient, simple and easy to promote.

[0044] The invention discloses a weathering steel, which comprises, by weight percentage, 0.05%-0.08% of C, 0.10%-0.18% of Si, 1.06%-1.45% of Mn, 0.46%-0.57% of Cr, 0.32%-0.78% of Ni, 0.26%-0.31% of Cu, 0.06%-0.010% of P, 0.06%-0.010% of S, 0%-0.12% of Ti, 0%-0.63% of Mo, and the rest is Fe and unavoidable impurities.

[0045] The metallographic structure of weathering steel is discretely distributed ferrite + martensite; the room temperature yield strength is 586MPa, the tensile strength is 661MPa, and the elongation is 19%.

[0046] The corrosion weight gain of weathering steel is 9.48 mg / cm 2 , the corrosion rate is 0.0395mg / cm 2 ·h.

[0047] C: The composition of the present invention adopts a low-carbon design. The C element is the most basic and economical strengthening element in steel. The strength of the steel is improved by solid solution strengthening and precipitation strengthening. The strength level of the steel is determined by the C content, that is, the higher the C content, the higher the strength level of the experimental steel. However, too high a C content will lead to interstitial solid solution or precipitation of carbon, and the plasticity and toughness of the steel will be significantly reduced. Therefore, the C content cannot be too high, and the strength of the steel is compensated by appropriately adding alloying elements. On the one hand, the low-carbon design helps to enhance the toughness of the steel. On the other hand, it can avoid the formation of carbides in the structure, avoid the formation of micro-galvanic couples between carbides and the steel matrix, and improve corrosion resistance. Therefore, the carbon content in the present invention is controlled at 0.05-0.08%.

[0048] Si: Silicon has a high solid solubility in steel, which can improve the purity of steel and deoxidize the steel during the smelting process. The increase in silicon content can increase the ferrite content, improve the tensile strength of steel, refine the grains, and when Si is combined with Cu, Cr, and P, it can improve the corrosion resistance of steel. However, a higher Si content in steel will damage the low-temperature toughness and weldability of the steel plate, so its mass percentage is controlled at 0.10-0.18%.

[0049] Mn: Mn element has the function of expanding austenite phase area and stabilizing austenite, which is beneficial to stabilizing supercooled austenite. Under faster cooling rate, bainite, martensite and other structures can be obtained, which improves the low-temperature toughness and fatigue resistance of steel, promotes the formation of low-temperature phase transformation structure, and thus improves the strength of steel plate, achieving a two-way improvement in strength and toughness; however, Mn is easy to form Mn segregation and MnS inclusions during the solidification of molten steel, especially high Mn content will aggravate the segregation and looseness of the center of the ingot, causing difficulties in casting operation, which will not only affect the toughness of the steel, but also cause corrosion cracking. Therefore, the reasonable range of Mn content is 1.06-1.45%.

[0050] Cr: An element that improves the hardenability of steel. It can effectively improve the high-temperature oxidation resistance and creep resistance of steel. Cr is a typical ferrite-forming element, which can increase the bainite transformation temperature and make the steel structure more uniform. Another main function of Cr is to improve the weather resistance of steel. It can form a dense oxide film on the surface of steel to improve the passivation ability of the steel plate. A chromium content greater than 0.2% can improve the corrosion resistance of steel, while enhancing the liquid permeability of steel and increasing the strength of steel. However, too high a Cr content will deteriorate the welding performance of steel and reduce the plasticity and toughness of steel. In order to ensure the coordination of corrosion resistance and strength and toughness, the chromium content is controlled at 0.46% to 0.57% in the present invention.

[0051] Ni: It plays a role in solid solution strengthening and improving hardenability in steel. At the same time, Ni can refine ferrite grains, improve the toughness of steel plates, increase the stability of steel plates, improve the corrosion resistance of steel plates, refine the grains of the inner rust layer, increase the density of the inner rust layer, and improve the weather resistance of steel plates. Considering the comprehensive cost, the appropriate amount of Ni added is 0.32% to 0.78%.

[0052] Cu: It mainly plays the role of solid solution and precipitation strengthening in steel, while improving the hardenability of steel, significantly improving the core strength of the steel plate and the uniformity of the structure in the thickness direction. Cu is also an element that improves weather resistance. During atmospheric corrosion, it is mainly distributed in the outer corrosion product film in the form of CuS, which prevents the penetration of corrosive gases into the inner layer and passivates the matrix. The enrichment of Cu in the inner rust layer of weathering steel can reduce the accelerated corrosion effect of Cl ions on steel, and at the same time increase the polarization resistance of the entire system during the electrochemical process of steel corrosion, thereby enhancing the protection of the rust layer on the steel matrix and improving the marine atmospheric corrosion resistance of weathering steel. However, Cu has a low melting point, and too high a content can easily lead to the occurrence of the "copper brittleness" phenomenon. Therefore, the present invention controls Cu: 0.26% to 0.31%.

[0053] S: S is a harmful element in steel. Sulfur in steel is easy to combine with Mn to form MnS inclusions. MnS inclusions have a great damaging effect on the low-temperature toughness, weldability, fatigue resistance and corrosion resistance of steel. Therefore, in the present invention, S is controlled as an impurity element, and its content is in the range of 0.06% to 0.010%.

[0054] P: Too high P content will cause segregation at the grain boundary, increase the cold brittleness of steel, reduce the plasticity of steel, and deteriorate the cold bending performance of steel. However, a small amount of phosphorus can improve the corrosion resistance of steel. P element as an anode depolarizer can significantly improve the atmospheric corrosion resistance of steel. The phosphorus content is controlled at 0.06% to 0.010%.

[0055] Ti: Ti is relatively active in steel and can form carbonitrides with C and N, which can refine austenite grains and achieve precipitation strengthening. The presence of TiN can inhibit the coarsening of grains in the heat-affected zone of welding. At the same time, Ti will also form compounds with S in steel and precipitate at high temperatures to avoid the formation of MnS and reduce corrosion resistance. In addition, Ti will also reduce the size of α-FeOOH crystals in the corrosion rust layer and improve the corrosion resistance of steel. And Ti is cheap and has low cost. Therefore, its content is controlled at 0% to 0.12%.

[0056] Mo: Mo element is dissolved in ferrite, which is beneficial to strengthen the ferrite matrix. The dissolved Mo is easy to be concentrated on the grain boundary, which plays a role in improving the high temperature strength of steel. Mo can also increase the stability of supercooled austenite. After adding Mo, the volume fraction of bainite in steel increases. The bainite structure with high dislocation density enables fire-resistant and weathering steel to obtain good high temperature performance. Mo precipitates in steel to form carbides, which improves its high temperature strength. Mo4 can be formed in the rust layer. 2- On the one hand, Mo4 2- It has corrosion inhibition effect. On the other hand, Mo4 2- The presence of can make the inner rust layer have cation selectivity, thus electrically inhibiting Cl - The intrusion of Mo4 2- with Fe 2+ It will also form water-insoluble compounds, forming a stable protective layer and improving the corrosion resistance of steel. However, too high Mo content will increase the hardenability of steel, which is not good for welding, so its content is controlled at 0% to 0.63%.

[0057] The present invention provides a method for preparing weathering steel, comprising the following steps:

[0058] S1. Material composition

[0059] The raw materials include industrial pure iron, ferromanganese, low-carbon ferrochrome, pure copper, pure nickel, ferrotitanium, ferromolybdenum, pig iron and pure aluminum for deoxidation. The proportions of the raw materials are as follows: ferromanganese 1.75% to 1.81%, low-carbon ferrochrome 0.87% to 0.94%, pure copper 0.29% to 0.36%, pure nickel 0.32% to 0.39%, ferrotitanium 0% to 0.78%, ferromolybdenum 0% to 1.16%, pig iron 1.05% to 1.13%, and pure iron as the remainder. Among them, 2 to 3g of pure aluminum is used for deoxidation per kilogram of molten steel. The raw material component percentages include carbon, silicon, manganese, sulfur, phosphorus, copper, chromium, nickel, titanium and molybdenum.

[0060] S2. Raw material smelting

[0061] A medium frequency induction furnace is used for smelting, and the medium frequency induction furnace is started for heating, and the medium frequency induction furnace is heated to 1589-1628°C, and the different materials obtained in step S1 are added to the medium frequency induction furnace in sequence, and the materials are smelted according to conventional processes by the medium frequency induction furnace until all the added furnace materials are melted into molten steel.

[0062] S3, deoxidation treatment

[0063] The charge is melted into molten steel at 1650℃~1720℃ and aluminum wire is fed into the molten steel for deoxidation treatment.

[0064] S4. Impurity removal

[0065] During the smelting process of the medium frequency induction furnace, 10 to 20 grams of perlite is added each time, and this is done 8 to 11 times. The perlite can not only remove non-metallic inclusions but also keep the induction furnace warm.

[0066] S5. Molten steel pouring

[0067] When the temperature reaches 1670-1720℃, keep it warm for 5-8 minutes, slowly pour the molten steel into the prepared sand mold. The pouring speed should be steady and pay attention to slag blocking. After the riser slag is discharged, cool it to room temperature.

[0068] S6, made of weathering steel

[0069] Wait for the cast steel to cool down, and then use an angle grinder to carefully grind the surface of the cast steel to remove the oxide scale to obtain the required weathering steel material.

[0070] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0071] Table 1 Chemical composition of implementation cases 1 to 5 (wt%)

[0072]

[0073]

[0074] Example 1

[0075] S1. Material composition

[0076] The raw materials include industrial pure iron, ferromanganese, low-carbon ferrochrome, pure copper, pure nickel, ferrotitanium, ferromolybdenum, pig iron and pure aluminum for deoxidation, wherein the proportions of the raw materials are: ferromanganese 1.75%, low-carbon ferrochrome 0.87%, pure copper 0.29%, pure nickel 0.32%, ferrotitanium 0%, ferromolybdenum 0%, pig iron 1.05%, pure iron balance, and 20g of pure aluminum for deoxidation. The raw material composition percentages include carbon, silicon, manganese, sulfur, phosphorus, copper, chromium and nickel.

[0077] S2. Raw material smelting

[0078] A medium frequency induction furnace is used for smelting, and the medium frequency induction furnace is started for heating, and the medium frequency induction furnace is heated to 1589°C, and the different materials obtained in step S1 are added to the medium frequency induction furnace in sequence, and the materials are smelted according to conventional processes by the medium frequency induction furnace until all the added furnace materials are melted into molten steel.

[0079] S3, deoxidation treatment

[0080] The charge is melted into molten steel at 1650℃, and aluminum wire is fed into the molten steel for deoxidation treatment.

[0081] S4. Impurity removal

[0082] During the smelting process of the medium frequency induction furnace, 10g of perlite is added each time, and this is done 8 times. The perlite can not only remove non-metallic inclusions but also keep the induction furnace warm.

[0083] S5. Molten steel pouring

[0084] When the temperature reaches 1670℃, keep it warm for 5 minutes, then slowly pour the molten steel into the prepared sand mold. The pouring speed should be steady and pay attention to slag blocking. After the riser slag is discharged, cool it to room temperature.

[0085] S6, made of weathering steel

[0086] Wait for the cast steel to cool down, and then use an angle grinder to carefully grind the surface of the cast steel to remove the oxide scale to obtain the required weathering steel material.

[0087] Example 2

[0088] S1. Material composition

[0089] The raw materials include industrial pure iron, ferromanganese, low-carbon ferrochrome, pure copper, pure nickel, ferrotitanium, ferromolybdenum, pig iron and pure aluminum for deoxidation, wherein the proportions of the raw materials are: ferromanganese 1.77%, low-carbon ferrochrome 0.91%, pure copper 0.32%, pure nickel 0.36%, ferrotitanium 0.73%, ferromolybdenum 0%, pig iron 1.09%, pure iron balance, and 22g of pure aluminum for deoxidation. The raw material composition percentages include carbon, silicon, manganese, sulfur, phosphorus, copper, chromium, nickel and titanium.

[0090] S2. Raw material smelting

[0091] A medium frequency induction furnace is used for smelting, and the medium frequency induction furnace is started for heating, and the medium frequency induction furnace is heated to 1594°C, and the different materials obtained in step S1 are added to the medium frequency induction furnace in sequence, and the materials are smelted by the medium frequency induction furnace according to conventional processes until all the added furnace materials are melted into molten steel.

[0092] S3, deoxidation treatment

[0093] The charge is melted into molten steel at 1670℃, and aluminum wire is fed into the molten steel for deoxidation.

[0094] S4. Impurity removal

[0095] During the smelting process of the medium frequency induction furnace, 12g of perlite is added each time, and this is done 9 times. The perlite can not only remove non-metallic inclusions but also keep the induction furnace warm.

[0096] S5. Molten steel pouring

[0097] When the temperature reaches 1680℃, keep it warm for 5 minutes, then slowly pour the molten steel into the prepared sand mold. The pouring speed should be steady and attention should be paid to slag blocking. After the riser slag is discharged, cool it to room temperature.

[0098] S6, made of weathering steel

[0099] Wait for the cast steel to cool down, and then use an angle grinder to carefully grind the surface of the cast steel to remove the oxide scale to obtain the required weathering steel material.

[0100] Example 3

[0101] S1. Material composition

[0102] The raw materials include industrial pure iron, ferromanganese, low-carbon ferrochrome, pure copper, pure nickel, ferrotitanium, ferromolybdenum, pig iron and pure aluminum for deoxidation, wherein the proportions of the raw materials are: 1.80% ferromanganese, 0.91% low-carbon ferrochrome, 0.32% pure copper, 0.35% pure nickel, 0.76% ferrotitanium, 0.45% ferromolybdenum, 1.08% pig iron, the balance of pure iron, and 24g of pure aluminum for deoxidation. The raw material composition percentages include carbon, silicon, manganese, sulfur, phosphorus, copper, chromium, nickel, titanium and molybdenum.

[0103] S2. Raw material smelting

[0104] A medium frequency induction furnace is used for smelting, and the medium frequency induction furnace is started for heating, and the medium frequency induction furnace is heated to 1600°C, and the different materials obtained in step S1 are added to the medium frequency induction furnace in sequence, and the materials are smelted according to conventional processes by the medium frequency induction furnace until all the added furnace materials are melted into molten steel.

[0105] S3, deoxidation treatment

[0106] The charge is melted into molten steel at 1690℃, and aluminum wire is fed into the molten steel for deoxidation treatment.

[0107] S4. Impurity removal

[0108] During the smelting process of the medium frequency induction furnace, 14g of perlite is added each time, and this is done 10 times. The perlite can not only remove non-metallic inclusions but also keep the induction furnace warm.

[0109] S5. Molten steel pouring

[0110] When the temperature reaches 1700℃, keep it warm for 6 minutes, and slowly pour the molten steel into the prepared sand mold. The pouring speed should be steady and pay attention to slag blocking. After the riser slag is discharged, cool it to room temperature.

[0111] S6, made of weathering steel

[0112] Wait for the cast steel to cool down, and then use an angle grinder to carefully grind the surface of the cast steel to remove the oxide scale to obtain the required weathering steel material.

[0113] Example 4

[0114] S1. Material composition

[0115] The raw materials include industrial pure iron, ferromanganese, low carbon ferrochrome, pure copper, pure nickel, ferrotitanium, ferromolybdenum, pig iron and pure aluminum for deoxidation, wherein the proportions of the raw materials are: ferromanganese 1.79%, low carbon ferrochrome 0.91%, pure copper 0.33%, pure nickel 0.34%, ferrotitanium 0.74%, ferromolybdenum 0.79%, pig iron 1.12%, pure iron balance, and 26g of pure aluminum for deoxidation. The raw material composition percentages include carbon, silicon, manganese, sulfur, phosphorus, copper, chromium, nickel, titanium and molybdenum.

[0116] S2. Raw material smelting

[0117] A medium frequency induction furnace is used for smelting, and the medium frequency induction furnace is started for heating, and the medium frequency induction furnace is heated to 1610°C, and the different materials obtained in step S1 are added to the medium frequency induction furnace in sequence, and the materials are smelted according to conventional processes by the medium frequency induction furnace until all the added furnace materials are melted into molten steel.

[0118] S3, deoxidation treatment

[0119] The charge is melted into molten steel at 1700℃, and aluminum wire is fed into the molten steel for deoxidation treatment.

[0120] S4. Impurity removal

[0121] During the smelting process of the medium frequency induction furnace, 16g of perlite is added each time, and this is done 10 times. The perlite can not only remove non-metallic inclusions but also keep the induction furnace warm.

[0122] S5. Molten steel pouring

[0123] When the temperature reaches 1710℃, keep it warm for 7 minutes, then slowly pour the molten steel into the prepared sand mold. The pouring speed should be steady and pay attention to slag blocking. After the riser slag is discharged, cool it to room temperature.

[0124] S6, made of weathering steel

[0125] Wait for the cast steel to cool down, and then use an angle grinder to carefully grind the surface of the cast steel to remove the oxide scale to obtain the required weathering steel material.

[0126] Example 5

[0127] S1. Material composition

[0128] The raw materials include industrial pure iron, ferromanganese, low-carbon ferrochrome, pure copper, pure nickel, ferrotitanium, ferromolybdenum, pig iron and pure aluminum for deoxidation, wherein the proportions of the raw materials are: ferromanganese 1.81%, low-carbon ferrochrome 0.94%, pure copper 0.36%, pure nickel 0.39%, ferrotitanium 0.78%, ferromolybdenum 1.16%, pig iron 1.13%, pure iron balance, and 30g of pure aluminum for deoxidation. The raw material composition percentages include carbon, silicon, manganese, sulfur, phosphorus, copper, chromium, nickel, titanium and molybdenum.

[0129] S2. Raw material smelting

[0130] A medium frequency induction furnace is used for smelting, and the medium frequency induction furnace is started for heating, and the medium frequency induction furnace is heated to 1628°C, and the different materials obtained in step S1 are added to the medium frequency induction furnace in sequence, and the materials are smelted according to conventional processes by the medium frequency induction furnace until all the added furnace materials are melted into molten steel.

[0131] S3, deoxidation treatment

[0132] The charge is melted into molten steel at 1720℃, and aluminum wire is fed into the molten steel for deoxidation treatment.

[0133] S4. Impurity removal

[0134] During the smelting process of the medium frequency induction furnace, 20g of perlite is added each time, and this is done 11 times. The perlite can not only remove non-metallic inclusions but also keep the induction furnace warm.

[0135] S5. Molten steel pouring

[0136] When the temperature reaches 1720℃, keep it warm for 8 minutes, then slowly pour the molten steel into the prepared sand mold. The pouring speed should be steady and attention should be paid to slag blocking. After the riser slag is discharged, cool it to room temperature.

[0137] S6, made of weathering steel

[0138] Wait for the cast steel to cool down, and then use an angle grinder to carefully grind the surface of the cast steel to remove the oxide scale to obtain the required weathering steel material.

[0139] Table 2 Mechanical properties of implementation cases 1 to 5

[0140]

[0141] Table 2 is a table of mechanical properties of five embodiments. Compared with Example 1, the yield strength and tensile strength of the steel in Example 2 are improved after adding Ti, but the elongation is reduced. Compared with Example 2, due to the addition of Mo, the strength of the steel in Example 3 is improved, but the elongation is reduced. Compared with Example 3, the strength of the steel in Example 4 is improved, but the elongation is reduced. The yield strength, tensile strength and elongation of the steel shown in Example 5 are significantly increased. The comprehensive mechanical properties of Example 5 are the best.

[0142] Immersion experiments of different cycles were carried out. The immersion solution was a simulated solution of Xisha atmosphere: 0.1% wtNaCl, 0.05% wtNa2SO4, 0.05% wt CaCl2. The experimental temperature was room temperature. The test cycle nodes were set to 7d, 15d, 30d, 60d, and 90d. With the extension of corrosion time, the corrosion rate of weathering steel gradually decreased and the corrosion resistance improved.

[0143] Table 3 Average corrosion rate

[0144]

[0145] Table 3 is a table of average corrosion rates of five embodiments. After 2 days of corrosion, the corrosion conditions of the five embodiments are consistent. The corrosion rate is the fastest and the corrosion resistance is the worst at 4 days. The corrosion rate drops significantly at 6 days. At this time, the corrosion products on the steel surface have a protective effect. The overall corrosion rate continues to decrease at 8 days, and the corrosion resistance is improved. The corrosion rate of each embodiment reaches the lowest at 10 days. A stable rust layer is formed on the surface of the weathering steel, and the steel has the best corrosion resistance.

[0146] See also Figure 1 , which is the microstructure morphology of Example 5, and its structure is discretely distributed ferrite + Mahō Island structure. The experimental steel shown by this structure has excellent strength, toughness and corrosion resistance.

[0147] See also Figure 2 , which is the microscopic morphology of the corrosion surface of Example 5. There are no obvious cracks or holes on the surface, the surface rust layer is relatively dense, and the corrosion resistance is good.

[0148] In summary, the present invention provides a weathering steel and a preparation method thereof. Through reasonable chemical composition design, alloying is adopted to improve the toughness and corrosion resistance engineering idea. Ingots that meet the composition design range are smelted by a medium-frequency induction furnace, and finally a weathering steel with a ferrite and Maho Island structure is obtained. The prepared weathering steel has excellent comprehensive performance, which can not only meet the requirements of high weather resistance in the harsh service environment of high humidity and high salt fog in the ocean, but also meet the requirements of stable mechanical properties of steel. The present invention effectively improves the strength of weathering steel while ensuring good resistance to marine environment corrosion. It is economical and efficient, and the method is simple and easy to promote.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A weathering steel, characterized in that: Calculated by weight percentage, it includes: C: 0.05% ~ 0.08%, Si: 0.10% ~ 0.18%, Mn: 1.06% ~ 1.45%, Cr: 0.46% ~ 0.57%, Ni: 0.32% ~ 0.78%, Cu: 0.26% ~ 0.31%, P: 0.06% ~ 0.010%, S: 0.06% ~ 0.010%, Ti: 0% ~ 0.12%, Mo: 0% ~ 0.63%, the rest is Fe and unavoidable impurities. The metallographic structure of weathering steel is discretely distributed ferrite + Maho Island structure. The room temperature yield strength of weathering steel is 580 ~ 592MPa, the tensile strength is 655 ~ 669MPa, the elongation is 17% ~ 21%, and the corrosion weight gain of weathering steel is 9.42 ~ 9.55mg / cm 2 , the corrosion rate is 0.0390~0.0403mg / cm 2 ·h.

2. A method for preparing the weathering steel according to claim 1, characterized in that: The following steps are involved: Industrial pure iron, ferromanganese, low-carbon ferrochrome, pure copper, pure nickel, ferrotitanium, ferromolybdenum, pig iron and pure aluminum are added into a medium frequency induction furnace in turn for smelting until molten steel is obtained. Aluminum wire is fed into the molten steel for deoxidation treatment; then perlite is added, and the molten steel is poured at a controlled speed to obtain cast steel. After the cast steel is cooled, the required weathering steel material is obtained.

3. The method for preparing weathering steel according to claim 2, characterized in that: Calculated by mass percentage: ferromanganese 1.75%~1.81%, low carbon ferrochromium 0.87%~0.94%, pure copper 0.29%~0.36%, pure nickel 0.32%~0.39%, ferrotitanium 0%~0.78%, ferromolybdenum 0%~1.16%, pig iron 1.05%~1.13%, and the remainder is industrial pure iron, among which 2~3g pure aluminum is used for deoxidation per kilogram of molten steel.

4. The method for preparing weathering steel according to claim 3, characterized in that: Before smelting in the medium frequency induction furnace, preheat to 1589~1628℃.

5. The method for preparing weathering steel according to claim 3, characterized in that: During the smelting process, 10 to 20 g of perlite is added each time, and the number of additions is 8 to 11 times.

6. The method for preparing weathering steel according to claim 3, characterized in that: The pouring temperature of molten steel is 1670~1720℃ and the holding time is 4~7 minutes.

7. The method for preparing weathering steel according to claim 3, characterized in that: After the cast steel has cooled, the surface is finely polished to remove the oxide scale.

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