CN110923572A - Rare earth weathering steel rich in alloying rare earth elements and manufacturing method thereof - Google Patents
Rare earth weathering steel rich in alloying rare earth elements and manufacturing method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
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Abstract
The rare earth weathering steel rich in alloying rare earth elements and the manufacturing method thereof, the rare earth elements are one or more of three elements of cerium Ce, lanthanum La and yttrium Y, the content of the alloying rare earth elements is controlled to be 0.005-0.045 by the process of feeding rare earth wires for steelmaking in percentage by weight, the yield strength grade is over 355MPa, and the atmospheric corrosion resistance (240-hour period infiltration test, corrosion rate is less than or equal to 1.2 g/(m) m2Hr)) is equivalent to Q355GNH in the national standard 'weather-resistant structural steel' GB/T4171-2008, has excellent mechanical property, cold formability and welding property, and can be widely applied to steel structure engineering such as vehicles, container manufacturing and buildings, bridges, tower mast structures and the like.
Description
Technical Field
The invention relates to a rare earth weathering steel technology, in particular to rare earth weathering steel rich in alloying rare earth elements and a manufacturing method thereof, wherein the rare earth elements are one or more of three elements of cerium Ce, lanthanum La and yttrium Y, the content of the alloying rare earth elements is controlled to be 0.005-0.045 in mass percent by weight percent through a process of feeding rare earth wires for steel making, and the rare earth weathering steel can provide a product with yield strength grade of over 355MPa and atmospheric corrosion resistance (the corrosion rate is less than or equal to 1.2 g/(m) in a 240-hour period infiltration test)2Hr)) is equivalent to Q355GNH in the national standard 'weather-resistant structural steel' GB/T4171-2008, has excellent mechanical property, cold formability and welding property, and can be widely applied to steel structure engineering such as vehicles, container manufacturing and buildings, bridges, tower mast structures and the like.
Background
In atmospheric environment, the surface of the metal material is inevitably oxidized and rusted. As the most widely used metal material in the world today, steel corrosion protection has been of constant interest and research. The surface coating is an important method for protecting the corrosion of other steel materials except stainless steel, and the flow comprises two steps of surface rust removal and coating. The surface rust removal is mainly carried out by sand blasting and shot blasting, a large amount of dust particles are generated in the operation process, and air dust pollution seriously harms the health of personnel. The surface coating, including spraying coating (various anti-corrosion paints), electroplating, hot galvanizing and zinc-aluminum composite materials, has serious pollution to soil and surface water, and particularly the steel structural member is gradually banned because the hot galvanizing pollution is more serious. On the other hand, since the beginning of the 20 th century, western countries including the united states have studied the corrosion resistance of steel materials themselves, and by adding a proper amount of elements such as P, Cu, Cr, and Ni, the corrosion rate of the steel material surface has been significantly reduced to 1/2 to 1/4 of plain carbon steel, and Cu, P, Cr, and Ni-based atmospheric corrosion resistant steel (i.e., weathering resistant steel) has been developed and used up to now and has been widely used in shipping containers, train body structural members, bridges, tower structures, and various guard rails. Currently the most widely used are ASTM A242(COR-TEN A, Japan SPA-H, China Q355GNH) and ASTMA588 steel (COR-TEN B, China Q355 NH). The elements for improving the weather resistance of the steel are Cu, P, Cr and Ni. China is a large rare earth resource country, heavy rare earth and medium rare earth elements are applied to special industries and become strategic resources, and a large amount of light rare earth represented by lanthanum (La) and cerium (Ce) is seriously surplus. Rare earth elements of lanthanum (La), cerium (Ce) and yttrium (Y) are added into the steel, so that the corrosion resistance of the steel can be improved. The invention relates to an economical weathering steel which is combined with the resource characteristics of China, adds rare earth into the steel on the premise of keeping the corrosion resistance of the existing weathering steel, reduces the using amount of Cu, Cr and Ni elements, and has great significance for changing surplus rare earth in China into valuable, reducing the alloy cost of the existing weathering steel and developing special steel products in China.
The Chinese patent application No. 200410061112.4 discloses a high-strength weathering steel with needle-shaped structure and a production method thereof. The main components and the mass percentage thereof are as follows: c: 0.01 to 0.04, Si: 0.15 to 0.30, Mn: 1.30-1.60, P: less than or equal to 0.060S: less than or equal to 0.010 percent, Ni: 0.10 to 0.24, Cr: 0.20 to 0.40, Cu: 0.15 to 0.20, Mo: 0.10 to 0.30 and, Als: less than or equal to 0.035, Ti: less than or equal to 0.030, Zr: less than or equal to 0.010 and added RE: not more than 0.40kg/t steel or Ca: more than or equal to 0.0050, the balance of iron and inevitable impurities, and the welding cold crack sensitivity index Pcm of C + Si/30+ (Mn + Cu + Cr)/20+ Mo/15+ Ni/60+ V/10+5B is less than or equal to 0.18%. The steel is low-alloy high-strength steel, is applied to engineering structures such as bridges, buildings, traffic, ocean oil extraction platforms and the like, and contains two or more of Ti, Als (Als represents the content of acid-soluble aluminum in the steel, and Alt represents the content of total aluminum in the steel), Zr, RE (rare earth) and Ca, namely REM (rare earth) is an optionally added component and is not an essential component. In addition, the steel does not have the content of the rare earth which is definitely required, and only the addition of the rare earth is given to be less than or equal to 0.40 kg/t. The invention is indicated in the specification, the effect of adding rare earth comprises: (1) the main function is sulfide spheroidization, the difference of longitudinal and transverse properties of the material is improved, and the Z-direction property is improved; (2) reducing the electrode potential difference between the sulfide and the surrounding matrix to improve the corrosion resistance; (3) a layer of rare earth protective film is formed on the surface layer of the steel plate, so that the weather resistance of the material is improved. (4) Meanwhile, the condition that the addition amount of the rare earth is too high, large-particle rare earth oxide inclusions are easily formed, the comprehensive performance of the steel is influenced, and the addition amount of the rare earth is required to be less than or equal to 0.40 kg/t. It should be pointed out that, if the rare earth is selectively added, the invention only gives the upper limit value of the addition amount, and does not give the specific content of the rare earth in the steel; the rare earth is added to improve the corrosion resistance, so that the rare earth reduces the electrode potential difference between the sulfide and the surrounding matrix; a dense rust protective film containing rare earth oxide is formed on the steel sheet instead of the rare earth protective film.
The document with Chinese patent application number 85108118 discloses rare earth-containing atmospheric corrosion resistant steel. The main components and the mass percentage thereof are as follows: c: less than or equal to 0.12, Si: 0.20 to 0.75, Mn: 0.20 to 0.70, P: 0.06-0.15, S: less than or equal to 0.04 and V: 0.02 to 0.12, Cu: 0.20-0.50, addition amount of REM (Rare Earth elements): less than or equal to 0.20 (namely less than or equal to 2 kg/ton); preferentially recommending the addition amount of the rare earth: 0.5 to 1kg per ton of steel. The steel is weather-resistant steel for railway vehicles in 1980 s in China, and steel ingots are manufactured by adopting open-hearth furnace or converter steelmaking and a die casting method. The method mainly utilizes the addition of rare earth to purify steel (remove harmful oxygen, sulfur and other elements) and spheroidize inclusions in the steel, thereby improving the toughness and the corrosion resistance of the steel. This patent only gives the rare earth addition and does not give the rare earth content in the steel, and this die casting method has been eliminated in the metallurgical production flow of large-scale production of plain carbon steel and low-alloy structural steel.
The Chinese patent application No. 200710119543.5 discloses Ca and REM composite modification treated high-strength weathering steel and a preparation method thereof. The main components and the mass percentage thereof are as follows: c: 0.04 to 0.07, Si: 0.2-0.4, Mn: 0.5-0.8, P: 0.08-0.10, S: less than or equal to 0.01, Nb: 0.02 to 0.03, Ti: 0.02-0.03, Ni: 0.3 to 0.4, Cu: 0.45-0.55, Ca: 0.002-0.006, REM (Rare Earth elements): 0.01 to 0.03, and the balance of iron and inevitable impurities. In REM, Ce accounts for 50% and La 50%. The steel is the technical field of weathering resistant steel, and is mainly applied to manufacturing of railway vehicles and containers. However, in the production method described in claim 3, there is no such a process in real circumstances, and the alloy of claim 4 is added in the same amount as the steel composition, i.e., the yield is 100%, which is almost impossible in actual smelting. Therefore, the feasibility of the preparation method of the invention is questionable.
The Chinese patent application No. 200910180490.7 discloses a non-quenched and tempered acicular structure high-strength low-yield-ratio weathering steel and a production method thereof. The main components and the mass percentage thereof are as follows: c: 0.03 to 0.08, Si: 0.30-0.60, Mn: 1.30-1.80, P: less than or equal to 0.015, S: not more than 0.010 percent and Nb: 0.03 to 0.08, Ti: less than or equal to 0.04, Ni: 0.20 to 0.50, Cr: 0.40-0.80, Cu: 0.30 to 0.60, Mo: 0.10 to 0.40; optional ingredients, Als: RE is less than or equal to 0.04; (rare earth elements, RareEarth Metals): not more than 0.4 kg/ton steel, Ca: less than or equal to 0.005, and the balance of iron and inevitable impurities. The components and the mass percentage content of the material also meet the following formula: the cold crack sensitivity index Pcm is equal to C + Si/30+ (Mn + Cu + Cr)/20+ Mo/15+ Ni/60+ V/10+5B and is less than or equal to 0.20 percent; ASTM G101-01 has a corrosion resistance index > 6.0. The steel is low-yield-ratio high-strength weathering steel, the rare earth element RE is only added as a selection item, Ca treatment or rare earth addition is carried out after RH vacuum treatment, and the rare earth is only added per ton of steel without the content in the steel.
The document with Chinese patent application number 201010125410.7 discloses high-strength weathering steel and a manufacturing method thereof. The main components and the mass percentage thereof are as follows: c: 0.001-0.004, Si: 0.10 to 0.30, Mn: 0.40-0.70, P: less than or equal to 0.020 and S: less than or equal to 0.008, Al: 0.02 to 0.06, Nb: 0.01 to 0.03, Ti: 0.01 to 0.03, Ni: 0.20 to 0.40, Cr: 2.50 to 3.50, Cu: 0.25 to 0.50, REM (Rare Earth elements): 0.01-0.03, Ca: 0.001-0.004, [ N ]: 0.001 to 0.005 and the balance of iron and inevitable impurities. The steel is weather-resistant steel with the yield strength of 550MPa, and is applied to railway wagons, containers, bridges, communication and power towers and the like. The steel of the invention adopts an ultra-low carbon design, the carbon content is below 0.01, and the stable production difficulty is larger for most steel mills at present, no matter in an electric furnace flow or a converter steelmaking flow. The dephosphorization and decarburization operations are completed in one furnace, mainly the blowing end point C required by the converter blowing is very low, the tapping temperature is high, the lining of the converter is fast eroded, and the total number of the furnace in service is not high even if the most effective slag splashing furnace protection operation is adopted at present. In addition, the content of Cr in the composition is high, and the composition has great influence on welding performance. The design of ultra-low carbon and higher Cr content is adopted to meet the requirements of the patent steel in the use field, the smelting production cost is higher, and welding materials need to be redesigned. The economics of this patent are therefore questionable.
The Chinese patent application No. 201210262485.2 discloses a preparation method of vanadium-nitrogen microalloyed weathering steel with yield strength of above 650 MPa. The main components and the mass percentage thereof are as follows: c: 0.08 to 0.13, Si: 0.15 to 0.20, Mn: 1.55-2.00, P: less than or equal to 0.020 and S: less than or equal to 0.008 and V: 0.12 to 0.20, Ni: 0.20 to 0.30, Cr: 0.50 to 0.70, Cu: 0.25 to 0.50, REM (Rare Earth elements): 0.01 to 0.03, [ N ]: 0.031-0.045, and the balance of iron and inevitable impurities. The inventive steel is mainly precipitation strengthened by VN. The preparation method only gives a hot rolling process system and is deficient in steel-making-continuous casting processes.
The document with Chinese patent application number 201611077330.6 discloses a production method of rare earth treated weathering steel. The main components and the mass percentage thereof are as follows: c: 0.03 to 0.08, Si: 0.25 to 0.45, Mn: 0.25-0.60, P: less than or equal to 0.15, S: less than or equal to 0.035, Ni: less than or equal to 0.65, Cr: 0.30 to 1.25, Cu: 0.25 to 0.55, Ce: 0.0015 to 0.020, [ O ]: no more than 0.003, [ N ]: less than or equal to 0.004, and the balance of iron and inevitable impurities. The steel of the invention is added with rare earth Ce only, is mainly used for manufacturing structural components such as containers, railway vehicles and the like, the steel making-continuous casting process is described simply, no specific rare earth adding method is provided, and the thickness of a hot rolled product steel strip is less than or equal to 7 mm.
The Chinese patent application No. 201710294446.3 discloses a high-strength fire-resistant weather-resistant steel and a production method thereof. The main components and the mass percentage thereof are as follows: c: 0.012 to 0.046, Si: 0.10 to 0.20, Mn: 0.60 to 1.10, P: less than or equal to 0.005, S: less than or equal to 0.002, Als: 0.015 to 0.025, Nb: 0.002-0.026, V: 0.041-0.072, Ti: and Ni: 0.28 to 0.45, Cr: 0.61-0.81, Cu: 0.18 to 0.48, Mo: 0.12 to 0.41, W: 0.15-0.32, REM (Rare Earth elements): 0.0010-0.0041, Ca: 0.0012 to 0.0025, and the balance of iron and inevitable impurities. The requirement of P is less than or equal to 0.005, the rough smelting difficulty is very large, the requirement of removing P by blowing in a converter is very high, namely, an ultralow P smelting process and equipment are needed, the increase of P is strictly controlled by external refining, and the smelting cost is obviously increased; in addition, the steel of the invention belongs to the category of high-strength low-alloy steel, W is not added in general, W is a precious alloy element, and the alloy cost is obviously reduced by adding W in the steel; in addition, the content of rare earth elements is low and is only 0.0010-0.0041, and the effect of enhancing the corrosion resistance is limited. Therefore, the invention has many points needing to be perfected in the aspect of component design, and has the characteristics of over-strict P content requirement, increased smelting difficulty and obviously increased process cost.
Disclosure of Invention
Aiming at the defects or shortcomings in the prior art, the invention provides rare earth weathering steel rich in alloying rare earth elements and a manufacturing method thereof, wherein the rare earth elements are one or more of three elements of cerium Ce, lanthanum La and yttrium Y, and the content of the alloying rare earth elements is controlled to be 0.005-0.045 in percentage by mass by a process of feeding rare earth wires for steel making, so that the rare earth weathering steel can provide a steel with yield strength grade of over 355MPa and atmospheric corrosion resistance (240-hour period infiltration test, corrosion rate of less than or equal to 1.2 g/(m)2Hr)) is equivalent to Q355GNH in the national standard 'weather-resistant structural steel' GB/T4171-2008, has excellent mechanical property, cold formability and welding property, and can be widely applied to steel structure engineering such as vehicles, container manufacturing and buildings, bridges, tower mast structures and the like.
The technical scheme of the invention is as follows:
the rare earth weathering steel rich in alloying rare earth elements comprises an iron-based structure, wherein alloying elements and inevitable impurity elements are distributed in the iron-based structure, and is characterized in that the alloying elements comprise alloying rare earth elements and other alloying elements, the alloying rare earth elements are one or more of cerium Ce, lanthanum La and yttrium Y, the other alloying elements comprise carbon C, silicon Si, phosphorus P, chromium Cr, copper Cu and calcium Ca in percentage by mass, the content of the alloying rare earth elements is controlled to be 0.005-0.045 through a steelmaking rare earth wire feeding process, the content of C is controlled to be less than or equal to 0.18 through a steelmaking decarburization process, the content of Si is controlled to be 0.05-0.80 through adding an iron alloy material in the steelmaking process, the content of Ca is controlled to be 0.0015-0.005 through a steelmaking Si-Ca wire feeding process, the P content is controlled to be less than or equal to 0.120, the Cr content is controlled to be 0.20-0.80 through an iron alloying process for steel making, the Cu content is controlled to be 0.15-0.55 through the iron alloying process for steel making, the inevitable impurity elements comprise sulfur S, the S content is controlled to be less than or equal to 0.020 through a steel making desulphurization process, and the rare earth elements are added into steel through a steel making feeding rare earth wire process according to 0.07-0.64 kg of rare earth per ton of molten steel.
The alloying rare earth elements are cerium Ce and lanthanum La, and the rare earth wire is La-Ce alloy rare earth wire.
The alloying rare earth element is yttrium Y, and the rare earth wire is a Y alloy rare earth wire.
The other alloying elements comprise Mn and Ni, wherein the Mn is less than or equal to 1.70, and the Ni is less than or equal to 0.65.
The other alloying elements comprise Mo and Zr, wherein Mo is less than or equal to 0.20, and Zr is less than or equal to 0.15.
The other alloying elements comprise one or more of the following in combination: nb is 0.015 to 0.110, V is 0.02 to 0.20, Ti is 0.02 to 0.20, and Alt is not less than 0.015.
The rare earth weathering steel is economic weathering steel with yield strength grade of more than 355MPa, and the mechanical properties of the steel are as follows: tensile strength Rm490-610 MPa, yield strength ReLMore than or equal to 355MPa, elongation A after fracture more than or equal to 22 percent and yield ratio less than or equal to 0.80.
The corrosion rate of the rare earth weathering steel is less than or equal to 1.2 g/(m) after 240-hour periodic infiltration test2*hr)。
The manufacturing method of the rare earth weathering steel rich in alloying rare earth elements is characterized by comprising the following steps of 1, smelting in a converter/electric furnace; step 2, slag stopping, tapping, deoxidizing and alloying; step 3, LF refining; step 4, soft blowing molten steel for sedation; step 5, continuous casting; the converter blowing in the step 1 comprises decarburization and dephosphorization, wherein decarburization is mainly performed, and a certain phosphorus content is reserved in dephosphorization; the LF refining in the step 3 mainly comprises deoxidation and desulfurization, a certain phosphorus content is reserved by molten steel rephosphorization or dephosphorization, and the Ca/Al ratio of the molten steel reaches 0.05-0.14 after the refining is finished; and the pouring temperature of the continuous casting tundish in the step 5 is 1520-1550 ℃.
The invention has the following technical effects: the invention relates to rare earth weathering steel rich in alloying rare earth elements and a manufacturing method thereof, which can provide economic weathering steel with yield strength grade of more than 355MPa, have excellent mechanical property, cold forming property and welding property, the corrosion resistance thereof is equivalent to the prior weathering steel (ASTM A242(COR-TEN A, Japanese SPA-H, China Q355GNH), the corrosion rate is less than or equal to 1.2g/(m & ltm & gt) in a 240-hour period infiltration test2Hr). The steel can be widely applied to steel structure engineering such as vehicle, container manufacturing and building, bridge, tower mast structure and the like.
The invention has the following characteristics: based on the components of the weathering resistant steel in the existing national standard 'weathering resistant structural steel' GB/T4171-2008; the contents of Cu, Cr and Ni elements are reduced, the physical and chemical properties of Rare Earth elements in steel and the property of being beneficial to enhancing the corrosion resistance of steel are fully utilized by adding Rare Earth elements (REM, Rare Earth Metals) La, Ce, Y and the like, the atmospheric corrosion resistance of the invented steel can still reach the level equivalent to that of the existing weathering steel (ASTM A242(COR-TEN A, Japanese SPA-H, China Q355GNH), and simultaneously has excellent mechanical property and process property. From the anticorrosion perspective, the operations of sand blasting and rust removal, anticorrosive coating spraying or hot dipping can be omitted in the structure processing and installation process, the anticorrosive operation in the use process is not needed after the structure is installed, and coating-free, less maintenance and even maintenance-free are realized during application. Except for marine environment and industrial heavy corrosion environment, the steel can replace the existing anticorrosive operation of Q355 series steel and components thereof, is an economic and environment-friendly steel, and has obvious economic significance, environmental protection significance and social benefit.
Detailed Description
The present invention will be described with reference to examples.
The invention aims to provide economical rare earth weathering steel with yield strength grade of more than 355MPa and atmospheric corrosion resistance equivalent to Q355GNH in national standard 'weathering structural steel' GB/T4171-2008 and a manufacturing method thereof.
The invention provides economic weathering steel with yield strength grade of more than 355MPa, which comprises the following chemical components (in percentage by mass, in wt%): c: less than or equal to 0.18, Si: 0.05-0.80, Mn: less than or equal to 1.70, P: less than or equal to 0.120, S: less than or equal to 0.020, Ni: less than or equal to 0.65, Cr: 0.20 to 0.80, Cu: 0.15-0.55, REM (Rare Earth elements): 0.005-0.045, Ca: 0.0015 to 0.005 and the balance of iron and other inevitable impurity elements. In order to improve the performance of the steel, one or more than one trace alloy elements can be added: nb 0.015-0.110, V0.02-0.20, Ti 0.02-0.20, Alt is more than or equal to 0.015(Als represents the content of acid-soluble aluminum in steel, and Alt represents the content of total aluminum in steel), if the elements are used in combination, at least one element is ensured to reach the lower limit of the chemical composition. The following alloying elements may be added: mo is less than or equal to 0.20, and Zr is less than or equal to 0.15. Wherein, the REM rare earth element is preferably added with one or more of three elements of cerium Ce, lanthanum La and yttrium Y, the single element pure rare earth can be singly added, and the mixed rare earth composed of the elements can also be added compositely.
The functions of the above elements are as follows.
The content of C is controlled below 0.18, so that the strengthening effect of C is fully exerted on the premise that the material meets the mechanical property and the process property, and the economical efficiency is reflected. In addition, steel products have different shapes, different specifications and different production equipment, and the C content control range can be flexibly selected by combining with actual conditions. The content of Si is controlled to be 0.05-0.80, the solid solution strengthening capability of Si is strong, the corrosion resistance of the material is improved, the welding performance is reduced due to overhigh content, and oxide skin on the surface of the material is not easy to remove. However, practice proves that the weldability of the medium plate steel with the Si content of 0.40-0.60 is still good, and non-preheating submerged arc welding can be carried out. For the corrosion-free coated weathering steel, the compact high-temperature oxide skin generated during hot rolling can play the role of an early-stage protective film and can delay the corrosion of materials. Therefore, the invention recommends that the Si content is between 0.05 and 0.40 for the structure which needs surface rust removal coating from the aesthetic point of view; for the structure without surface coating, the Si content is between 0.40 and 0.60. The Mn content is controlled to be less than 1.70, for example, 0.60 to 1.70. Mn has a solid solution strengthening effect, can improve the tensile strength of the material, can reduce the austenite phase transition starting temperature Ar3, moderately improves the hardenability, and reduces the hot brittleness and the cold brittleness caused by sulfur.
The sulfur S is controlled to be less than 0.020. S forms sulfide inclusions in the steel, and reduces the toughness of the material. The lower the better in structural steel, the upper limit requirements are given by the present invention. The phosphorus P is controlled below 0.120. P improves the cold brittleness and weldability of the material, and has obvious effects of solid solution strengthening and corrosion resistance improvement. In addition, rare earth elements are segregated to grain boundaries, and it is possible to offset some of the material embrittlement effects caused by P. Therefore, compared with the carbon manganese steel Q355, the upper limit of P in the invention is obviously improved so as to be suitable for the conditions with different toughness requirements.
The rare earth element REM is controlled to be between 0.005 and 0.045, and the rare earth content refers to the rare earth content in steel materials, but not the addition amount, one or more of Ce, La and Y are preferably added, the single element pure rare earth can be independently added, and mixed rare earth consisting of the elements can also be added in a composite manner.
The content of calcium Ca is controlled between 0.0015 and 0.005, and the Ca/Al ratio of the molten steel reaches 0.05 to 0.14 after refining. MnS inclusions in the steel deform and elongate in the thermal deformation process, have serious negative effects on the transverse and longitudinal impact property ratio of the steel plate, and can aggravate the anisotropy of the material and deteriorate the performance of the plate. Ca treatment is performed to form CaS inclusions in steel, which are hard to deform during hot working, and the effect of MnS is weakened to improve the anisotropy of the material. In addition, most of the plate production at present, Al is selected as a deoxidizer in molten steel, and Al in the molten steel is selected as a deoxidizer2O3The high-melting-point compound with high content is easy to block a tundish nozzle in the continuous casting process, and can form calcium aluminate with lower melting point by Ca treatment, thereby ensuring the smooth continuous casting process. Therefore, for slab continuous casting production, it is necessary that the molten steel contains a certain amount of Ca for Ca treatment after refining.
The invention provides a manufacturing method of economical weathering steel, which comprises the following steps: the smelting process comprises converter/electric Furnace smelting, slag-stopping tapping and deoxidation alloying, LF (Ladle refining Furnace) refining, optional Vacuum treatment (RH: Ruhrstahl-Heraeus-Vacuum refining or VD: Vacuum refining) soft blowing molten steel sedation and slab continuous casting. The hot rolling comprises a hot rolling division continuous rolling process and a wide and thick plate production process, wherein the hot rolling continuous rolling process comprises slab reheating, high-pressure water descaling, rough rolling, finish rolling continuous rolling, controlled cooling and reeling; the wide and thick plate process comprises plate blank reheating, high-pressure water descaling, rough rolling (high-temperature single-pass large reduction), intermediate blank temperature waiting, finish rolling (controlled rolling, namely controlled rolling temperature, single-pass reduction and accumulated reduction), controlled cooling, hot straightening, cooling bed cooling, shearing, nondestructive testing and the like, and the extra-thick plate and the steel plate with special requirements also comprise normalizing treatment and subsequent straightening procedures after rolling. The method is characterized in that: (1) converter blowing mainly comprises decarburization without pursuing dephosphorization (P) intentionally, and molten steel keeps proper phosphorus content according to the product requirement; (2) the LF refining mainly comprises deoxidation and desulfurization, molten steel rephosphorization is not controlled intentionally, and even phosphorus needs to be added according to the requirements of finished products; (3) feeding Si-Ca wires before the ladle is ready to be hung and continuously cast after refining, wherein the Ca/Al ratio of molten steel reaches 0.05-0.14 after refining, and the content of calcium (Ca) in the steel is 0.0015-0.005; (4) determining an economical and reasonable LF refining and vacuum treatment process according to the requirements of steel quality grades (impact test temperature, impact power and shearing area), steel thickness specifications and nondestructive testing internal quality; (5) the pouring temperature of the continuous casting tundish is 1520-1565 ℃; (6) the rare earth alloy is added according to the equipment and the process flow of a steel-making workshop, and the addition amount of the rare earth is 0.07-0.64 kg/ton of molten steel; (7) the reheating temperature of the plate blank is 1160-1250 ℃; (8) the two-stage controlled rolling is adopted, for the steel plate with the quality grade of C-F, the thickness ratio of the intermediate blank to the finished product is more than or equal to 3.0, and for the steel plate with the quality grade of A, B, the thickness ratio of the intermediate blank to the finished product is more than or equal to 2.0; (9) the rough rolling finishing temperature is 1100-950 ℃; (10) the finish rolling temperature is 900-780 ℃; (11) the cooling rate after rolling is determined according to the product structure, performance requirements and thickness specification, and is generally 8-20 ℃/second; (12) the coiling temperature of the hot continuous rolling plate coil or the hot straightening temperature of the wide and thick plate is 560-660 ℃.
Example (b): according to the component requirements of the steel, the manufacturing method of the economical rare earth weathering steel provided by the invention has the smelting processes of converter blowing, LF refining, slab continuous casting, slab hot delivery, slab heating, controlled rolling, controlled cooling, reeling and finishing. The steel-making-continuous casting process comprises molten iron desulphurization and slagging-off pretreatment, top-bottom combined blowing converter blowing, steel tapping alloying, LF refining and slab continuous casting. The lime powder is blown into the ladle for desulfurization, and then, a slag removing vehicle is used for mechanically removing slag, wherein the temperature of molten iron is more than or equal to 1300 ℃, and S is less than or equal to 0.006 percent. After the converter is splashed and protected, the converter is shaken to firstly load scrap steel and then add molten iron. Converting in a converter, removing P and C, wherein the converting end point is 0.06C and 0.012P, the molten steel temperature is 1650 ℃, and the sliding plate blocks slag and taps. Adding aluminum particles for deoxidation in the tapping process, mixing and flushing steel slag, adding ferroalloy materials for alloying, adding a small amount of refined reducing slag to cover the surface of molten steel after tapping, blowing argon, stirring and hanging to an LF furnace. In the LF refining process, top slag is melted and heated, and then temperature measurement and sampling are carried out; then according to the test result, the slag condition and the molten steel temperature, alloy is added, slag is added and the temperature is raised respectively. The whole LF refining process continuously adjusts components, slag and temperature to meet the target requirements. And after LF refining is finished, feeding Si-Ca wires for impurity modification treatment according to the Al content in the molten steel, wherein the Ca/Al content in the molten steel reaches 0.12. And then the molten steel is softly blown and kept stand for 15 minutes, and the ladle is put on a continuous casting table for casting. In the production process, a rare earth wire feeding method is adopted, rare earth elements are added into steel, the adding amount of Si-Ca wires and the rare earth wires is shown in table 1, and the chemical components of the steel are shown in table 2. Cutting the plate blank into a fixed length, directly hot charging, entering a hot rolling process, heating the plate blank for about 3 hours, discharging, removing phosphorus by high-pressure water, rough rolling, finish rolling, controlled cooling after rolling, coiling and finishing to obtain a finished hot rolled plate coil, wherein the hot rolling process parameters are shown in table 3. The mechanical properties of the finished product are shown in Table 4, and the corrosion resistance test results are shown in Table 5.
TABLE 1 Si-Ca lines and rare earth additions
| Si-Ca powder core (kg/ton) | Rare earth REM (kg/ton) | Remarks for note | |
| Example 1 | 0.73 | 0.21 | La-Ce alloy wire |
| Example 2 | 1.20 | 0.36 | La-Ce alloy wire |
| Example 3 | 1.05 | 0.40 | Y alloy wire |
TABLE 2 chemical composition of the steels
TABLE 3 Hot Rolling Process parameters
TABLE 4 mechanical Properties of the steels
TABLE 5 test results of atmospheric corrosion resistance
It is pointed out here that the above description is helpful for the person skilled in the art to understand the invention, but does not limit the scope of protection of the invention. Any such equivalents, modifications and/or omissions as may be made without departing from the spirit and scope of the invention may be resorted to.
Claims (9)
1. The rare earth weathering steel rich in alloying rare earth elements comprises an iron-based structure, wherein alloying elements and inevitable impurity elements are distributed in the iron-based structure, and is characterized in that the alloying elements comprise alloying rare earth elements and other alloying elements, the alloying rare earth elements are one or more of cerium Ce, lanthanum La and yttrium Y, the other alloying elements comprise carbon C, silicon Si, phosphorus P, chromium Cr, copper Cu and calcium Ca in percentage by mass, the content of the alloying rare earth elements is controlled to be 0.005-0.045 through a steelmaking rare earth wire feeding process, the content of C is controlled to be less than or equal to 0.18 through a steelmaking decarburization process, the content of Si is controlled to be 0.05-0.80 through adding an iron alloy material in the steelmaking process, the content of Ca is controlled to be 0.0015-0.005 through a steelmaking Si-Ca wire feeding process, the P content is controlled to be less than or equal to 0.120, the Cr content is controlled to be 0.20-0.80 through an iron alloying process for steel making, the Cu content is controlled to be 0.15-0.55 through the iron alloying process for steel making, the inevitable impurity elements comprise sulfur S, the S content is controlled to be less than or equal to 0.020 through a steel making desulphurization process, and the rare earth elements are added into steel through a steel making feeding rare earth wire process according to 0.07-0.64 kg of rare earth per ton of molten steel.
2. The rare earth weathering steel rich in alloyed rare earth elements according to claim 1, characterized in that the alloyed rare earth elements are cerium Ce and lanthanum La, and the rare earth wires are La-Ce alloyed rare earth wires.
3. The rare earth weathering steel rich in alloyed rare earth elements according to claim 1 wherein the alloyed rare earth element is yttrium Y and the rare earth wire is a Y-alloy rare earth wire.
4. The rare earth weathering steel rich in alloying rare earth elements of claim 1 wherein the other alloying elements include Mn and Ni, the Mn ≦ 1.70, the Ni ≦ 0.65.
5. The rare earth weathering steel rich in alloying rare earth elements of claim 1 wherein the other alloying elements include Mo ≦ 0.20 and Zr ≦ 0.15.
6. The rare earth weathering steel rich in alloying rare earth elements of claim 1 wherein the other alloying elements include one or a combination of more than one of the following: nb is 0.015 to 0.110, V is 0.02 to 0.20, Ti is 0.02 to 0.20, and Alt is not less than 0.015.
7. Rare earth weathering steel rich in alloyed rare earth elements according to claim 1 characterized in that it is an economical weathering steel with yield strength grade above 355MPa, which has mechanical properties: tensile strength Rm490-610 MPa, yield strength ReLMore than or equal to 355MPa, elongation A after fracture more than or equal to 22 percent and yield ratio less than or equal to 0.80.
8. The rare earth weathering steel rich in alloying rare earth elements according to claim 1, characterized in that the corrosion rate of the rare earth weathering steel is not more than 1.2 g/(m) after 240-hour periodic infiltration test2*hr)。
9. The manufacturing method of the rare earth weathering steel rich in alloying rare earth elements is characterized by comprising the following steps of 1, smelting in a converter/electric furnace; step 2, slag stopping, tapping, deoxidizing and alloying; step 3, LF refining; step 4, soft blowing molten steel for sedation; step 5, continuous casting; the converter blowing in the step 1 comprises decarburization and dephosphorization, wherein decarburization is mainly performed, and a certain phosphorus content is reserved in dephosphorization; the LF refining in the step 3 mainly comprises deoxidation and desulfurization, a certain phosphorus content is reserved by molten steel rephosphorization or dephosphorization, and the Ca/Al ratio of the molten steel reaches 0.05-0.14 after the refining is finished; and the pouring temperature of the continuous casting tundish in the step 5 is 1520-1550 ℃.
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