WO2024149263A1 - 一种搪瓷用冷轧高强钢及其制造方法 - Google Patents

一种搪瓷用冷轧高强钢及其制造方法 Download PDF

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WO2024149263A1
WO2024149263A1 PCT/CN2024/071439 CN2024071439W WO2024149263A1 WO 2024149263 A1 WO2024149263 A1 WO 2024149263A1 CN 2024071439 W CN2024071439 W CN 2024071439W WO 2024149263 A1 WO2024149263 A1 WO 2024149263A1
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steel
enameling
enameled
temperature
enameled steel
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French (fr)
Inventor
魏娇
孙全社
郭亮亮
曲李能
王俊凯
王木
王金涛
蒋小明
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Baoshan Iron and Steel Co Ltd
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Baoshan Iron and Steel Co Ltd
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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
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0242—Flattening; Dressing; Flexing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • 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
    • 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
    • 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
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite

Definitions

  • the present disclosure relates to a metal material and a method for manufacturing the same, and in particular to a steel for enameling and a method for manufacturing the same.
  • Enamel products are a composite material formed by coating a layer of inorganic glass enamel on the surface of a formed steel plate and then sintering it at high temperature. Enamel products have good structural strength and corrosion resistance, wear resistance, high temperature resistance and other characteristics. They are widely used in light industrial appliances, building decoration, environmental protection, petrochemical, pharmaceutical and other industries. Mechanical strength, forming performance and enameling performance are the most critical technical indicators in the production process of enamel products.
  • high-strength steel can reduce the thickness of the steel plate and thus reduce the weight of the product, thereby achieving the goal of reducing material costs and saving enameling energy consumption;
  • the steel plate can maintain a high yield strength after enameling at a high temperature of 830-890°C, which can avoid the risk of large elastic deformation or plastic deformation of the product due to compressive stress, resulting in surface enamel peeling, thereby improving the safety performance and service life of the product.
  • the Chinese patent application with publication number CN112941418A and titled "A Cold-rolled High-strength Steel for Enameling and Its Preparation Method” discloses an enameling steel, whose element composition (wt%) is: C: 0.005-0.03%, Si ⁇ 0.03%, Mn: 0.2-0.5%, S ⁇ 0.006%, P ⁇ 0.012%, Alt ⁇ 0.05%, Nb: 0.01-0.03%, Ti: 0.05-0.20%, N: 0.005-0.012%; wherein Ti ⁇ 3.42N+4C, and the remainder is iron and unavoidable impurities.
  • the patent application mainly adopts the method of Nb and Ti composite microalloying to improve the strength and anti-scale explosion performance of the steel plate.
  • the Ti content in the enameling steel is relatively high (0.05-0.20%).
  • Ti oxides will continuously deposit on the inner wall of the nozzle during pouring to form nodules, which can easily cause nozzle blockage and reduce the number of continuous casting furnaces; on the other hand, the higher the Ti content, the easier it is to form TiO2 at high temperatures. This oxide adheres to the surface of the steel plate, hindering the infiltration and erosion of the enamel on the steel plate during high-temperature enameling, and reducing the adhesion strength of the enamel plate.
  • a Chinese patent application with publication number CN111945060A and titled "Method for Manufacturing Cold-Rolled High-Strength Heat-Resistant Enameled Steel” discloses a method for manufacturing cold-rolled high-strength heat-resistant enameled steel.
  • the element composition (wt%) of this enameled steel is: C: 0.04-0.07%, Si ⁇ 0.03%, Mn: 0.40-0.80%, P ⁇ 0.025%, S ⁇ 0.020%, Alt ⁇ 0.030%, Cr: 0.15-0.40%, Mo: 0.05-0.15%, N: 0.004-0.010%, and the balance is Fe and unavoidable trace elements.
  • one of the purposes of the present disclosure is to provide a low-carbon, rare earth element-containing cold-rolled enameling steel.
  • the enameling steel has certain strength and resistance to high-temperature enameling softening, good formability, anti-scale explosion performance and adhesion performance, and is low in cost, and is particularly suitable for the production of thin-gauge electric water heater tanks.
  • the present disclosure provides a steel for enameling, which contains, in addition to Fe and inevitable impurities, the following chemical elements in the following mass percentages:
  • the present disclosure also provides a steel for enamel, wherein the mass percentage content of each chemical element is as follows:
  • the mass percentage content of each chemical element also satisfies:
  • the unavoidable impurities include P and/or O.
  • the microstructure of the enameled steel disclosed in the present invention is ferrite+pearlite.
  • the pearlite is distributed at the triple grain boundary of the ferrite, and the volume phase ratio of the pearlite is less than 6%.
  • the ferrite matrix is also distributed with composite sulfides of Ti and RE and Ti precipitates.
  • the composite sulfides of Ti and RE are circular or elliptical (Ti, Mn)S and (RE, Mn)S, and the size of the composite sulfides is 2-20 ⁇ m, horizontal/vertical size ratio is 0.8-2.
  • the Ti precipitates include Ti(C, N), TiC and Ti 4 C 2 S 2 , and the size of the precipitates is 1-300 nm.
  • the grain size of ferrite is 9-10.
  • the enameling steel disclosed herein has a yield strength of ⁇ 280 MPa, a tensile strength of ⁇ 340 MPa, a fracture elongation of 30-40% at a gauge length of 50 mm, an anisotropy index ⁇ r ⁇ 0.45, and a hydrogen penetration value TH 2 ⁇ 7.0 min/mm 2 .
  • the yield strength is still maintained above 270 MPa.
  • the low-alloy cost enamel steel disclosed in the present invention adds a small amount of titanium and rare earth elements to low-carbon steel, and auxiliaryly adds copper, chromium, and nickel elements which improve the density of enamel, as well as trace amounts of calcium and zirconium elements which improve the plasticity of steel plates, thereby obtaining enamel steel with excellent anti-scale performance and yield strength.
  • the present disclosure also provides a method for manufacturing the enameled steel of the present disclosure, which comprises the following steps: (1) smelting, refining and continuous casting; (2) hot charging and hot feeding into a holding pit; (3) heating the ingot; (4) hot rolling and coiling; (5) pickling; (6) cold rolling, wherein the cold rolling reduction rate is 60-80%; (7) continuous annealing, wherein the soaking temperature is 750-860°C, the soaking time is 100-300s, the over-aging temperature is 300-420°C, and the over-aging time is 200-400s; and (8) leveling.
  • the heating temperature is 1120-1200° C.
  • the insulation time is ⁇ 240 min.
  • the final rolling temperature of hot rolling is 780-920°C, and the coiling temperature is 620-700°C.
  • the leveling reduction rate is 0.8-2.0%.
  • the present invention obtains a microstructure of fine and uniform ferrite + a small amount of pearlite through reasonable alloy element design and preferably further process control, realizes the dispersed distribution of the precipitated phase, ensures that the steel plate has high strength and plasticity, and has sufficient hydrogen traps, good adhesion and anti-pinhole properties.
  • the yield strength ReL the tensile strength Rm , and the elongation at break A50mm (elongation at break when the gauge length is 50 mm) are measured according to the tensile method standard GB/T 228.1, and the anisotropy index ⁇ r is measured according to GB/T 5027.
  • the grain size of ferrite is determined according to YB27-77.
  • the hydrogen penetration time of the steel plate is measured by the electrochemical method specified in BS EN10209, and then converted into the hydrogen penetration value TH 2 corresponding to the 1 mm thick steel plate.
  • overaging temperature and “overaging time” refer to the temperature and time when the aging temperature exceeds the normal aging temperature, that is, the temperature and time when the peak hardness is reached.
  • composition design principle of the enameled steel disclosed in the present invention is as follows:
  • C is the most basic strengthening element in steel. The higher the C content, the higher the strength of the steel plate, but the lower the plasticity and toughness. For enameled steel, in addition to affecting the mechanical properties, C is directly related to the steel plate's anti-scale burst performance and anti-pinhole defect ability.
  • the cementite and carbide dispersed in the steel plate are beneficial to the steel plate's anti-scale burst performance. However, if the cementite content is too high, it will decompose into a large amount of CO gas during high-temperature enameling. The bubble diameter is too large and it is very easy to form pinhole defects on the surface of the enamel layer, affecting the surface quality and anti-corrosion effect of the product. Therefore, the present disclosure controls the C content in enameled steel to 0.03-0.08%.
  • Si can play a role in solid solution strengthening in steel.
  • Si is an active element, and a certain thickness of SiO2 oxide film will inevitably exist on the surface of the steel plate in an air environment.
  • An appropriate amount of SiO2 oxide film promotes the adhesion between the steel plate and the enamel.
  • the present invention controls the Si content in the cold-rolled enameled steel to 0.01-0.04%.
  • Mn is also a common steel plate strengthening element, which plays a role in solid solution strengthening. Mn is also a good deoxidizer and desulfurizer, but the MnS inclusions formed are easily elongated and turned into spindle shapes at high temperatures, making the performance of the steel have obvious anisotropy. In addition, too high a Mn content will also affect the formability and adhesion of the steel. Therefore, the present disclosure controls the Mn content in the enamel steel to 0.15-0.35%.
  • S is a harmful element in common steels, usually existing in the form of MnS inclusions in steel, which can affect the transverse properties of steel.
  • a proper amount of strong sulfide-forming elements such as Ti and RE are added, and by controlling the element ratio, sulfides with suitable shapes and sizes are formed, while improving the toughness and anti-scale explosion performance of the steel plate. Therefore, the present invention controls the S content in the enameled steel to 0.002-0.012%.
  • Al is added to steel as a deoxidizer, reacting with O to form Al 2 O 3 , removing oxygen in steel during oxygen blowing smelting, avoiding the formation of a large number of other oxide inclusions, which is beneficial to grain refinement and improving the processing plasticity of steel.
  • Al can also fix N in steel and reduce the aging of steel plates.
  • the present disclosure controls the Al content in the enamel steel to 0.015-0.055%.
  • N solid solution in steel will cause aging and reduce the elongation at break of the steel plate. Therefore, in the enameled steel disclosed in the present invention, adding an appropriate amount of Ti can fix all the N into TiN particles, which is not only beneficial to the anti-scale performance of the steel plate, but also avoids the aging caused by solid solution N. Therefore, the N content needs to be strictly controlled.
  • the present invention controls the N content in the enameled steel to ⁇ 0.006%.
  • Titanium is an active element in steel, and forms corresponding compounds with O, N, S and C in order according to the affinity. These compounds are formed, dissolved and precipitated in steel to play their corresponding roles.
  • the content of Ti In the enameled steel disclosed in the present invention, in order to give full play to the promoting effect of Ti-containing compounds on the strength, anti-scale performance and adhesion performance of the steel plate, the content of Ti must be strictly controlled. This is because: at high temperatures, Ti first forms TiO2 with O, but the TiO2 precipitate should not be too much. On the one hand, too much TiO2 precipitate will lead to poor castability of molten steel and serious nozzle blockage.
  • Ti will also form dispersed TiN, TiS and TiC particles in the steel.
  • these particles themselves have a certain adsorption effect on hydrogen atoms, and after cold deformation, tiny holes will be generated around the particles, which can store the hydrogen generated during pickling and enameling; on the other hand, these particles play a role of precipitation strengthening, improving the yield strength and high temperature softening resistance of the steel plate; in addition, these particles can also prevent the coarsening of austenite grains in the overheating zone under the action of welding thermal cycles, and improve the mechanical strength of the welded joint.
  • the present disclosure controls the Ti content in the enameled steel to 0.02-0.05%, preferably 0.02-0.041%.
  • RE plays the following three beneficial roles: 1) RE has a greater affinity with S, reduces the number of harmful inclusions MnS and further deformation, plays a spheroidizing role, and can significantly weaken the anisotropy of the steel plate; 2) The addition of rare earth elements can increase the number of inclusions per unit volume without increasing the total amount of inclusions, that is, it plays a role in refining inclusions and improving the degree of dispersion of inclusions.
  • the finer and more dispersed the inclusions are, the more obvious the precipitation strengthening effect is, and the stronger the inhibitory effect on hydrogen diffusion is, which can effectively improve the anti-scale explosion effect of the steel plate; 3)
  • the addition of rare earth elements can also refine the grains and improve the strength and plasticity of the steel plate. Therefore, the present disclosure controls the RE content in the enameled steel to 0.005-0.015%.
  • Ca Trace amounts of Ca form stable high-melting-point inclusions CaO and CaS in steel. These inclusions are generally distributed in circular and polygonal shapes. Sulfides such as MnS nucleate and grow on these inclusions, and also have a morphology similar to these inclusions. Therefore, Ca plays a role in improving the morphology of inclusions, thereby improving the mechanical properties of the steel plate. If the Ca content is not properly controlled, not only will the expected metallurgical effect not be achieved, but the casting properties of the steel will be damaged. Therefore, the present invention controls the Ca content in enameled steel to 0 ⁇ Ca ⁇ 0.008%.
  • Copper, chromium and nickel When the content of these elements is controlled within a reasonable range, the chemical reaction and mutual diffusion of iron ions and enamel ions in the steel plate can be promoted, and the adhesion between the steel plate and the porcelain layer can be improved. In addition, Ni can also inhibit the diffusion of hydrogen and improve the anti-scale explosion performance. However, if the content of these elements is too high, the alloy cost will be increased and the adhesion performance will be unfavorable. Therefore, the present disclosure controls the Cu, Cr and Ni contents in the enamel steel to 0.01-0.06%, 0.01-0.05% and 0.005-0.05%, respectively.
  • a small amount of titanium added mainly forms dispersed second phase particles with carbon, nitrogen, sulfur, etc. These particles can serve as effective hydrogen traps to improve the fishscale resistance of the steel plate, and can also dissolve into the matrix during high-temperature enameling and precipitate as finer dispersed particles during the subsequent cooling process, so that the steel plate maintains a higher yield strength after high-temperature sintering.
  • Rare earth elements mainly combine with sulfur to form rare earth sulfides, which can not only improve the morphology of sulfides in steel and improve the lateral performance of steel plates, but also further improve the fishscale resistance of steel plates.
  • the inventors have found that the mass percentage of RE/S is very important for the formability of steel.
  • RE/S is less than 1, S mainly exists in the form of long and thin strips of MnS, which seriously damages the transverse properties of the steel plate.
  • RE/S is greater than 3, excessive rare earths will lead to an increase in the total amount of inclusions or excessive size, resulting in limited improvement in the plasticity and anti-scale performance of the steel plate. Therefore, in the enameled steel disclosed in the present invention, the ratio of RE to S elements (RE/S) is controlled to be 1-3.
  • RE/S When RE/S is within this range, it can play a metamorphic role in controlling the morphology of MnS, reduce the number of long and thin strips of MnS inclusions in the steel, generate beneficial rare earth complex sulfides, and reduce the anisotropy of the steel plate.
  • the inevitable impurities in the enameled steel disclosed in the present invention are mainly P and O. Among them:
  • Phosphorus increases the cold brittleness of steel, especially at low temperatures. Cold brittleness deteriorates processing and welding performance, so the lower the Phosphorus content, the better. Therefore, the present disclosure controls the Phosphorus content in the enameled steel to ⁇ 0.03%.
  • Oxygen blowing during smelting mainly plays a role in decarburization. Therefore, a certain amount of oxygen is inevitably left in the molten steel. The higher the content of O, the more titanium and rare earth oxide inclusions are formed, and the larger the size, which seriously damages the formability of the steel plate. Moreover, these oxides gather on the surface of the steel plate, changing the surface characteristics of the steel plate, thereby affecting the enameling performance of the steel plate. Therefore, the present disclosure limits the O content in the steel for enameling to ⁇ 0.005%.
  • the method for manufacturing the enameled steel of the present disclosure comprises the following steps:
  • the method disclosed herein controls the cold rolling reduction rate between 60-80% because the cold rolling reduction rate affects the size of the recrystallized grains.
  • the greater the reduction rate the more nucleation points of ferrite recrystallization, and the easier it is to form fine, uniform, equiaxed ferrite. If the reduction rate is too low, the above purpose cannot be achieved, and if it is too high, the degree of tissue hardening is high, which increases the load of the cold rolling equipment.
  • the method disclosed in the present invention through a reasonable annealing procedure, 1) ensures the recrystallization and growth of ferrite grains, obtains uniform and fine ferrite grains, and improves the strength and plasticity of the steel plate; 2) ensures the full development of the ⁇ 111 ⁇ recrystallization texture, thereby improving the stamping performance of the steel plate; 3) causes titanium compounds such as TiC, TiS and other particles to partially dissolve and then precipitate during annealing, which on the one hand plays a role of precipitation strengthening, and on the other hand can also improve the anti-scale explosion performance.
  • the heating temperature is 1120-1200°C
  • the holding time is ⁇ 240min.
  • the final rolling temperature of hot rolling is 780-920° C.
  • the coiling temperature is 620-700° C.
  • the steel plate after hot rolling, is cooled to between 620-700° C. by a laminar cooling system and then coiled, so as to ensure the formability of the steel plate and the full precipitation of the second phase particles.
  • the flattening reduction rate is 0.8-2.0%.
  • the yield platform of low alloy steel can be slowed down or eliminated, and the stamping performance of the steel plate can be improved; on the other hand, the roughness of the steel plate surface can be controlled, and the bonding degree between the steel plate and the enamel can be increased.
  • the present invention adopts low-cost alloy design and simple and easy-to-control manufacturing process to obtain enamel steel with excellent forming performance, excellent anti-scale performance and good adhesion performance, and solves the problem of low strength of steel plate for enamel tank of electric water heater. It meets the demand for higher rigidity of the enamel liner.
  • the disclosed enamel steel optimizes the morphology and distribution of harmful inclusions MnS by adding a small amount of rare earth elements, controlling the ratio of RE/S and the contents of Ca and Zr, thereby greatly improving the forming performance of the enamel steel, and improving the anti-scale performance, while reducing the amount of microalloying element Ti that plays an important role in the anti-scale performance.
  • the mass percentage of Ti is controlled at 0.02-0.05%, which can reduce the problems of poor castability of molten steel and poor adhesion of steel plates caused by excessive Ti content, and can also reduce the cost of the alloy.
  • the present invention makes full use of the formation, dissolution and precipitation characteristics of Ti compounds in high-temperature heating, high-temperature coiling and continuous high-temperature rapid annealing processes, and finally realizes the uniform precipitation of fine and dispersed Ti(C, N), TiC and Ti4C2S2 on the ferrite matrix, which not only plays a vital role as a hydrogen storage trap in anti-scale explosion performance, but also plays a role in precipitation strengthening and inhibiting grain growth during enameling, thereby improving the yield strength and high-temperature softening resistance of the steel plate, so that the strength change of the steel plate after high-temperature enameling is small, and it is suitable for preparing large-volume enamel liners with high requirements for anti-fatigue performance.
  • the enameled steel disclosed in the present invention achieves: yield strength ⁇ 280 MPa, tensile strength ⁇ 340 MPa, elongation at break of 30-40% at a gauge length of 50 mm, anisotropy index ⁇ r ⁇ 0.45, hydrogen penetration value TH 2 ⁇ 7.0 min/mm 2 . Moreover, after the enameled steel disclosed in the present invention is calcined at a high temperature of 850°C for 10 minutes, the yield strength is still maintained above 270 MPa.
  • FIG. 1 shows the metallographic microstructure of the enameling steel of Example A1.
  • FIG. 2 shows the metallographic microstructure of the enameling steel of Example A1 after simulated high-temperature enameling.
  • the following will further explain and illustrate the enameled steel and the manufacturing method thereof disclosed in the present invention in conjunction with specific embodiments and the drawings of the specification, but such explanation and description do not constitute an undue limitation on the technical solution disclosed in the present invention.
  • the reagents used in the embodiments can all be obtained through commercial channels.
  • the experimental methods in the embodiments without specifying the specific conditions are operated according to conventional conditions known in the art or according to the conditions recommended by the manufacturer.
  • Table 1 lists the mass percentages of the chemical elements in the enameled steels of Examples A1-A6 and Comparative Examples B1-B2.
  • the enameled steels of Examples A1-A6 and the steel sheets of Comparative Examples B1-B2 were prepared by the following steps:
  • Converter smelting Through top and bottom composite blowing, carbon reduction, dephosphorization, removal of harmful gases and inclusions, and adjustment of the basic composition of molten steel are achieved;
  • RH refining Under vacuum conditions, deep decarburization, deoxidation and desulfurization are carried out to further remove inclusions and harmful gases such as hydrogen and nitrogen in the molten steel, and to achieve precise control of the mass percentage of each chemical element in Table 1; to achieve morphological control of inclusions;
  • the slab heating temperature is 1120-1200°C, and the holding time is more than 240min;
  • Hot rolling The final rolling temperature is 780-920°C, and then the steel plate is cooled to the coiling temperature by a laminar cooling system for coiling, and the coiling temperature is 620-700°C;
  • Cold rolling The cold rolling reduction rate is 60-80%;
  • the soaking temperature is 750-860°C, the soaking time is 100-300s, and the over-aging temperature is 300-420°C, over-aging time is 200-400s;
  • Leveling The leveling reduction rate is 0.8-2.0%.
  • Table 2-1 and Table 2-2 list the specific process parameters of the enameled steels of Examples A1-A6 and the steel plates of Comparative Examples B1-B2.
  • the over-aging temperature in Table 2-2 is presented as a range of values rather than a point value in each embodiment and comparative example.
  • the enameled steels of Examples A1-A6 and the steel plates of Comparative Examples B1-B2 were tested for various properties. The results are listed in Table 3. Among them, the transverse mechanical properties of Examples A1-A6 and Comparative Examples B1-B2 at room temperature include yield strength ReL , tensile strength Rm , elongation at break A 50mm and anisotropy index ⁇ r.
  • Table 3 also lists the hydrogen penetration time of the steel plate measured by the electrochemical method specified in BS EN10209, which is then converted into the hydrogen penetration value TH 2 corresponding to the 1 mm thick steel plate.
  • Examples A1-A6 and Comparative Examples B1-B2 were placed in a resistance heating furnace at 850°C for 10 minutes to simulate high temperature sintering test, then taken out and air cooled to room temperature. The yield strength of the high temperature sintered samples was tested, and the results are also listed in Table 3.
  • Figure 1 shows the metallographic microstructure of Example A1. It can be seen that the microstructure of the steel plate is uniform ferrite. Grains + a small amount of pearlite, the pearlite is located at the triple boundary of the ferrite grains, and the complex sulfides of Ti and RE and Ti precipitates are also distributed on the ferrite matrix.
  • the ferrite is fine, and the grain size of the ferrite is 9-10.
  • the composite sulfides of Ti and RE are round or elliptical (Ti, Mn)S and (RE, Mn)S, with a size of 2-20 ⁇ m and a horizontal/vertical size ratio of 0.8 to 2.
  • Ti precipitates include Ti(C, N), TiC and Ti 4 C 2 S 2 , and the sizes of these precipitates are between 1-300 nm.
  • Figure 2 shows the metallographic microstructure of Example A1 after simulated high-temperature sintering. It can be seen that the ferrite grains grew uniformly, with the average grain size increasing from 12.0 ⁇ m to 14.0 ⁇ m, and no abnormal growth occurred.

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Abstract

一种搪瓷用钢及该搪瓷用钢的制造方法，其含有Fe和不可避免的杂质，还含有质量百分比如下的下述化学元素：C：0.03-0.08％，Si：0.01-0.04％，Mn：0.15-0.35％，S：0.002-0.012％，Al：0.015-0.055％，N≤0.006％，Ti：0.02-0.05％，RE：0.005-0.015％，0＜Ca≤0.008％，0＜Zr≤0.008％，以及选自Cu：0.01-0.06％、Cr：0.01-0.05％和Ni：0.005-0.05％中的至少一种；所述搪瓷用钢不含Nb和B元素。通过合理的合金元素设计，优选进一步进行工艺控制，获得了细小均匀铁素体+少量珠光体的显微组织，实现了析出相的弥散分布，确保钢板具有较高的强度和塑性，同时具有足够的氢陷阱、良好的密着性能和抗针孔性能。

Description

一种搪瓷用冷轧高强钢及其制造方法 技术领域
本公开涉及一种金属材料及其制造方法，尤其涉及一种搪瓷用钢及其制造方法。
背景技术
搪瓷制品是在成型后的钢板表面涂覆一层无机玻璃质瓷釉，然后经过高温烧结形成的一种复合材料。搪瓷制品具有良好的结构强度和耐腐蚀、耐磨、耐高温等特性，在轻工家电、建筑装饰、环保、石化、制药等行业得到广泛应用。机械强度、成型性能和涂搪性能是搪瓷制品生产过程中最为关键的技术指标。
在经济成本、节能环保和高安全性能的驱动下，搪瓷用冷轧高强钢越来越受到搪瓷行业的关注与重视。一方面，高强钢的应用可以减少钢板的厚度进而减轻制品自重，从而实现降低材料成本、节约搪烧能耗的目标；另一方面，钢板在830-890℃的高温下搪烧后可以保持较高的屈服强度，可以避免制品因受到承压应力而发生较大的弹性变形或塑性变形导致表面搪瓷剥落的风险，从而提高制品的安全性能和使用寿命。
公开号为CN112941418A，名称为“一种冷轧搪瓷用高强钢及其制备方法”的中国专利申请公开了一种搪瓷用钢，其各元素成分(wt％)为：C：0.005-0.03％，Si≤0.03％，Mn：0.2-0.5％，S≤0.006％，P≤0.012％，Alt≤0.05％，Nb：0.01-0.03％，Ti：0.05-0.20％，N：0.005-0.012％；其中，Ti≥3.42N+4C，余量为铁和不可避免的杂质。该专利申请主要采用Nb、Ti复合微合金化的方法，提高钢板的强度和抗鳞爆性能。然而，该搪瓷用钢中Ti含量较高(0.05-0.20％)。一方面，Ti的氧化物在浇注时会不断在水口内壁沉积形成结瘤，容易造成水口堵塞，减少连浇炉数；另一方面，Ti含量越高越容易在高温下形成TiO2，这种氧化物附着于钢板表面，阻碍高温搪烧时瓷釉对钢板的浸润和侵蚀，降低搪瓷板的密着强度。
公开号为CN111945060A，名称为“冷轧高强度耐热搪瓷钢的制造方法”的中国专利申请公开了一种冷轧高强度耐热搪瓷钢的制造方法。这种搪瓷用钢的元素成分(wt％)为：C：0.04-0.07％，Si≤0.03％，Mn：0.40-0.80％，P≤0.025％，S≤0.020％，Alt≤0.030％，Cr：0.15-0.40％，Mo：0.05-0.15％，N：0.004-0.010％，余量为Fe和不可避免的微量元素。然而，为了提高钢板强度，该搪瓷用钢中加入了较高含量的Cr、Mo等贵重合金元素，不仅增加了钢板的成本， 同时增加了裂纹敏感性，不利于焊接性能，而且容易在钢板表面形成致密的氧化膜，影响搪瓷密着性能。
发明内容
鉴于现有技术的上述不足，本公开的目的之一在于提供一种低碳、含稀土元素的冷轧搪瓷用钢。该搪瓷用钢具有一定的强度和抗高温搪烧软化能力、良好的成形性、抗鳞爆性能和密着性能，并且成本低廉，特别适用于生产薄规格电热水器内胆。
为了实现上述目的，本公开提供了一种搪瓷用钢，除含有Fe和不可避免的杂质之外，该搪瓷用钢还含有质量百分比如下的下述化学元素：
C：0.03-0.08％，Si：0.01-0.04％，Mn：0.15-0.35％，S：0.002-0.012％，Al：0.015-0.055％，N≤0.006％，Ti：0.02-0.05％，RE：0.005-0.015％，0＜Ca≤0.008％，0＜Zr≤0.008％，以及选自Cu：0.01-0.06％，Cr：0.01-0.05％和Ni：0.005-0.05％中的至少一种；并且，所述搪瓷用钢不含Nb和B元素。
另一方面，本公开还提供了一种搪瓷用钢，其各化学元素的质量百分比含量如下：
C：0.03-0.08％，Si：0.01-0.04％，Mn：0.15-0.35％，S：0.002-0.012％，Al：0.015-0.055％，N≤0.006％，Ti：0.02-0.05％，RE：0.005-0.015％，0＜Ca≤0.008％，0＜Zr≤0.008％，以及选自Cu：0.01-0.06％，Cr：0.01-0.05％和Ni：0.005-0.05％中的至少一种；余量为Fe和不可避免的杂质。
优选地，在本公开的搪瓷用钢中，RE和S元素的质量百分比含量满足：RE/S＝1-3。
优选地，在本公开的搪瓷用钢中，各化学元素的质量百分比含量还满足：
6×Ti/(3.43×N+1.5×S-0.32×RE+4×C)≤1，式中各化学元素代入其质量百分比含量百分号前的数值。
优选地，在本公开的搪瓷用钢中，不可避免的杂质包括P和/或O。优选地，P≤0.03％和/或O≤0.005％。
优选地，本公开的搪瓷用钢的微观组织为铁素体+珠光体。优选地，珠光体分布在铁素体的三叉晶界处，珠光体的体积相比例低于6％。
在本公开的搪瓷用钢中，加入适量的RE和Ti元素，形成了具有较强抗塑性变形能力的稀土和钛的复合硫化物，能够明显改善钢的横向力学性能。
优选地，铁素体基体上还分布有Ti和RE的复合硫化物、Ti的析出物。优选地，Ti和RE的复合硫化物为圆形或椭圆形的(Ti，Mn)S和(RE，Mn)S，所述复合硫化物的尺寸为 2-20μm，横/纵尺寸比为0.8-2。
优选地，Ti的析出物包括Ti(C，N)、TiC和Ti4C2S2，所述析出物的尺寸为1-300nm。
优选地，铁素体的晶粒度为9-10级。
优选地，本公开的搪瓷用钢的屈服强度≥280MPa，抗拉强度≥340MPa，标距为50mm时的断裂延伸率为30-40％，各向异性指数Δr≤0.45，氢穿透值TH2≥7.0min/mm2。
优选地，本公开的搪瓷用钢在850℃的高温下搪烧10min后，屈服强度仍保持在270MPa以上。
不同于现有技术通常采用Nb和B合金化的技术路线，本公开的低合金成本的搪瓷用钢在低碳钢的基础上，添加少量的钛元素和稀土元素，并辅助添加对搪瓷密性能有提升的铜、铬、镍元素，以及对钢板塑性有提升的微量钙、锆元素，获得了抗鳞爆性能和屈服强度优异的搪瓷用钢。
另一方面，本公开还提供了一种制造本公开的搪瓷用钢的方法，其包括如下步骤：(1)冶炼、精炼和连铸；(2)热装热送进保温坑；(3)铸坯加热；(4)热轧和卷取；(5)酸洗；(6)冷轧，其中冷轧压下率为60-80％；(7)连续退火，其中均热温度为750-860℃，均热时间为100-300s，过时效温度为300-420℃，过时效时间为200-400s；(8)平整。
优选地，在步骤(3)中，加热温度为1120-1200℃，保温时间≥240min。
优选地，在步骤(4)中，热轧的终轧温度为780-920℃，卷取温度为620-700℃。
优选地，在步骤(8)中，平整压下率为0.8-2.0％。
本公开通过合理的合金元素设计，优选进一步进行工艺控制，获得了细小均匀铁素体+少量珠光体的显微组织，实现了析出相的弥散分布，确保钢板具有较高的强度和塑性，同时具有足够的氢陷阱、良好的密着性能和抗针孔性能。
具体实施方式
除非另有定义，否则本文使用的所有技术和科学术语具有与本公开所属领域的普通技术人员的通常理解相同的含义。在本公开的描述中使用的术语仅用于描述特定实施方案的目的，而不旨在限制本发明。
在本文中，屈服强度ReL、抗拉强度Rm、断裂延伸率A50mm(标距为50mm时的断裂延伸率)依据拉伸方法标准GB/T 228.1测定，各向异性指数Δr依据GB/T 5027测定。
在本文中，珠光体的体积相比例采用Image J软件计算。。
在本文中，铁素体的晶粒度依据YB27-77测定。
在本文中，参照BS EN10209规定的电化学方法测得钢板的氢穿透时间，然后换算成1mm厚钢板所对应的氢渗透值TH2。
在本文中，“三叉晶界”是指三条晶界相遇时形成的线缺陷。
在本文中，“过时效温度”和“过时效时间”是指当时效温度超过正常时效温度，也就是达到峰值硬度时的温度及时间。
具体来说，本公开的搪瓷用钢的成分设计原理如下：
碳：C是钢中最基本的强化元素。C含量越高，钢板的强度越高，但塑性和韧性越低。对搪瓷用钢而言，C除了影响力学性能外，与钢板的抗鳞爆性能和抗针孔缺陷能力有直接关系。钢板中弥散的渗碳体、碳化物有益于钢板的抗鳞爆性能。但是，渗碳体含量太高，在高温搪烧时会分解为大量的CO气体，气泡直径过大极易在搪瓷层表面形成针孔缺陷，影响制品的表面质量和防腐作用。因此，本公开将搪瓷用钢中的C含量控制在0.03-0.08％。
硅：Si在钢中能起到固溶强化的作用。Si属于活泼元素，在空气环境中钢板表面不可避免会存在一定厚度的SiO2氧化膜。适量的SiO2氧化膜对钢板与瓷釉之间的密着起到促进作用。但是SiO2氧化膜过厚会阻碍金属铁离子与瓷釉离子的相互交换。因此，本公开将冷轧搪瓷用钢中的Si含量控制在0.01-0.04％。
锰：Mn也是常见的钢板强化元素，起到固溶强化作用。Mn还是良好的脱氧剂和脱硫剂，但形成的MnS夹杂物在高温时易被拉长而变成纺锤形状，使钢的性能有明显的各向异性。并且，Mn含量过高还会影响钢的成形性和密着性能。因此，本公开将搪瓷用钢中的Mn含量控制在0.15-0.35％。
硫：S在普通用途的钢中是有害元素，通常在钢中以MnS夹杂物的形式存在，这种夹杂物会影响钢的横向性能。在本公开的搪瓷用钢中，加入适量的Ti和RE等强硫化物形成元素，通过控制元素比例，形成形态和尺寸合适的硫化物，同时改善钢板的韧性和抗鳞爆性能。因此，本公开将搪瓷用钢中的S含量控制在0.002-0.012％。
铝：Al在钢中作为脱氧剂加入，与O反应生成Al2O3，去除吹氧冶炼时钢中的氧，避免形成大量的其他氧化物夹杂，有利于细化晶粒，提高钢的加工塑性。Al还能固定钢中的N，降低钢板的时效。然而，若Al含量过高，钢板上的搪瓷易出现鳞爆缺陷和密着强度下降的现象。因此，本公开将搪瓷用钢中的Al含量控制在0.015-0.055％。
氮：N固溶在钢中会引起时效，降低钢板的断裂延伸率。因此，在本公开的搪瓷用钢中，加入适量的Ti，可以将N全部固定为TiN颗粒，不仅有利于钢板的抗鳞爆性能，还避免了固溶N引起的时效。因此，N含量需严格控制，本公开将搪瓷用钢中的N含量控制在≤0.006％。
钛：Ti在钢中属于活泼元素，按照亲和力大小依次与O、N、S和C形成相应的化合物。这些化合物在钢中的形成、溶解和析出，发挥其相应作用。在本公开的搪瓷用钢中，为充分发挥含Ti化合物对钢板的强度、抗鳞爆性能和密着性能等的促进作用，必须严格控制Ti的含量。这是因为：高温时Ti最先与O形成TiO2，但TiO2析出物不宜过多，一方面TiO2析出物过多会导致钢水的可浇性变差，水口堵塞现象严重，另一方面，过多的TiO2会阻碍高温搪烧时瓷釉对钢板的浸润，降低密着强度。此外，Ti在钢中还会形成弥散的TiN、TiS和TiC颗粒，一方面，这些颗粒本身对氢原子有一定的吸附作用，且经过冷变形后颗粒周围会产生微小孔洞，可以贮存酸洗和搪烧时产生的氢；另一方面，这些颗粒起到析出强化的作用，提高钢板的屈服强度和抗高温软化能力；此外，这些颗粒还可以阻止焊接热循环作用下过热区奥氏体晶粒的粗化，改善焊接接头的机械强度。然而，Ti的含量过多会形成粗大的TiN、TiS和TiC颗粒，不仅损害钢板的成形性，而且对钢板的强度、抗鳞爆性能和焊接性能的提高有限。因此，本公开将搪瓷用钢中的Ti含量控制在0.02-0.05％，优选0.02-0.041％。
稀土：作为本公开的搪瓷用钢中必须添加的元素，RE起到以下三方面的有利作用：1)RE与S有较大的亲和力，减少了有害夹杂MnS的数量和进一步变形，起到了球化作用，可以明显削弱钢板的各向异性；2)稀土元素的加入可以在不增加夹杂物总量的前提下，使单位体积内夹杂物的个数增加，即起到了细化夹杂物、提高夹杂物分散程度的作用，夹杂物越细小弥散，析出强化作用越明显，同时对氢扩散的抑制作用越强，可有效改善钢板的抗鳞爆作用；3)稀土元素的加入还可以细化晶粒，同时提高钢板的强度和塑性。因此，本公开将搪瓷用钢中的RE含量控制在0.005-0.015％。
钙：微量Ca在钢中形成稳定的高熔点夹杂物CaO和CaS。这些夹杂物一般成圆形和多边形分布。MnS等硫化物则依附于这些夹杂物上形核、生长，也呈与这些夹杂物类似的形态。因此，Ca起到了改善夹杂物形态的作用，从而提高了钢板的力学性能。如果Ca含量控制不当，不仅达不到预期的冶金效果，反而会破坏钢的浇铸性能。因此，本公开将搪瓷用钢中的Ca含量控制在0＜Ca≤0.008％。
锆：微量Zr同样在钢中起到将细长条状的MnS转变为几乎没有延性的球形硫化物的作用，从而提高钢板的塑性和韧性。本公开将搪瓷用钢中的Zr含量控制在0＜Zr≤0.008％。
铜、铬和镍：当这些元素的含量控制在合理范围时，能促进钢板中铁离子与瓷釉离子的化学反应和相互扩散，改善钢板与瓷层之间的密着。另外，Ni还可以抑制氢的扩散，提高抗鳞爆性能。然而，若这些元素的含量过高，则会提高合金成本，且对密着性能不利。因此，本公开将搪瓷用钢中的Cu、Cr和Ni含量分别控制在0.01-0.06％、0.01-0.05％和0.005-0.05％。
在本公开的搪瓷用钢中，少量添加的钛主要和碳、氮、硫等形成弥散分布的第二相粒子。这些粒子一方面可以作为有效氢陷阱，提高钢板的抗鳞爆性能，另一方面还能在高温搪烧时溶入基体，在后续冷却过程中以更细小弥散的颗粒析出，使钢板高温烧结后保持较高的屈服强度。稀土元素主要与硫结合形成稀土硫化物，不仅可以改善钢中硫化物的形态，提高钢板的横向性能，而且可以进一步提高钢板的抗鳞爆性能。
在一个优选实施方式中，在本公开的搪瓷用钢中，RE和S元素的质量百分比含量满足：RE/S＝1-3。
本发明人发现，RE/S的质量百分比对钢的成形性很重要。当RE/S＜1时，S主要以细长条状MnS的形式存在，严重损害钢板的横向性能。当RE/S＞3时，过量的稀土会导致夹杂物总量的增加或尺寸过大，从而使得钢板的塑性和抗鳞爆性能提升有限。因此，在本公开的搪瓷用钢中，将RE与S元素的比例(RE/S)控制在1-3。当RE/S在该范围内时，可以起到控制MnS形态的变质作用，使钢中的细长条状MnS夹杂物的数量减少，生成有益的稀土的复合硫化物，降低钢板的各向异性。
在一个优选实施方式中，在本公开的搪瓷用钢中，各化学元素的质量百分比含量还满足：6×Ti/(3.43×N+1.5×S-0.32×RE+4×C)≤1；式中各化学元素代入其质量百分比含量百分号前的数值。当各化学元素的含量满足该公式限定的范围时，能够保证含钛化合物呈细小弥散的状态分布，从而提高钢板的抗鳞爆性能、强度和塑性。
本公开的搪瓷用钢中的不可避免的杂质主要是P和O。其中：
磷：P特别在低温时，会增加钢的冷脆性。冷脆使加工和焊接性能变差，因此P的含量越低越好。因此，本公开将搪瓷用钢中的P含量控制在≤0.03％。
氧：在冶炼时吹氧主要起到脱碳的作用。因此，钢水中不可避免地残留一定的氧。O的含量越高，形成的钛和稀土氧化物夹杂的数量越多，尺寸越大，严重损害钢板的成形性。而且这些氧化物聚集在钢板表面，改变钢板的表面特性，从而影响钢板的涂搪性能。因此，本公开将搪瓷用钢中的O含量限定在≤0.005％。
在一个实施方式中，制造本公开的搪瓷用钢的方法包括如下步骤：
(1)冶炼、精炼和连铸；
(2)热装热送进保温坑，以减少铸坯加热时间和能源消耗，简化生产流程和提高生产节奏；
(3)铸坯加热；
(4)热轧和卷取；
(5)酸洗；
(6)冷轧，其中冷轧压下率为60-80％；
(7)连续退火，其中均热温度为750-860℃，均热时间为100-300s，过时效温度为300-420℃，过时效时间为200-400s；
(8)平整。
本公开的方法将冷轧压下率控制在60-80％之间，是因为冷轧压下率会影响再结晶晶粒的尺寸，压下率越大，则铁素体再结晶的形核质点越多，越容易形成细小、均匀的等轴状铁素体。压下量过低则达不到上述目的，过高则造成组织硬化程度高，增加冷轧设备负荷。
此外，本公开的方法通过合理的退火程序，1)确保了铁素体晶粒的再结晶和长大，得到均匀细小的铁素体晶粒，同时提高了钢板的强度和塑性；2)保证了{111}再结晶织构充分发展，从而提高了钢板的冲压性能；3)使钛的化合物如TiC、TiS等颗粒在退火时部分溶解再析出，一方面起到析出强化的作用，另一方面也可以提高抗鳞爆性能。
在一个优选实施方式中，在本公开的方法的步骤(3)中，加热温度为1120-1200℃，保温时间≥240min。通过使连铸坯的加热温度和保温时间在上述范围内，可以保证连铸坯的合金成分和碳氮化物等充分固溶、扩散，获得成分均匀的、细小的奥氏体组织。若温度过低或时间过短，奥氏体成分不均匀性会遗传至成品组织，导致成品组织偏析严重、力学性能受损。若温度过高或时间过长，则连铸坯会发生脱碳或氧化，奥氏体晶粒粗大，浪费能源、材料，且不利于钢板成品的性能。
在一个优选实施方式中，在本公开的方法的步骤(4)中，热轧的终轧温度为780-920℃，卷取温度为620-700℃。当热轧的终轧温度控制在780-920℃之间时，可以在奥氏体未再结晶区获得足够多的变形量，为细化晶粒做准备，同时避免在两相区轧制成为混晶组织，造成热轧板的力学性能不均匀。
在一个优选实施方式中，热轧结束后，钢板经层流冷却系统冷至620-700℃之间，然后进行卷取。这样可以保证钢板的成形性和第二相粒子的充分析出。
在一个优选实施方式中，在本公开的方法的步骤(8)中，平整压下率为0.8-2.0％。通过将平整压下率控制在0.8-2.0％，一方面可以减缓或消除低合金钢的屈服平台，提高钢板的压冲性能；另一方面可以控制钢板表面的粗糙度，增加钢板与瓷釉的结合度。
本公开的搪瓷用钢具有以下特点和有益效果：
本公开采用了低成本的合金设计和简便易控的制造工艺，获得了成型性能优良、抗鳞爆性能优异和密着性能良好的搪瓷用钢，并且解决了电热水器搪瓷内胆用钢板强度低的问题， 满足了搪瓷内胆较高刚度的需求。
本公开的搪瓷用钢通过添加少量的稀土元素，控制RE/S的配比关系和Ca、Zr的含量，优化了有害夹杂物MnS的形态和分布，一方面大幅提高了搪瓷用钢的成形性能，另一方面改善了抗鳞爆性能，减少了对抗鳞爆性能起重要作用的微合金元素Ti的加入量。将Ti的质量百分比控制在0.02-0.05％，既可以减少Ti含量过高带来的钢水浇铸性差、钢板密着不良等问题，又可以降低合金成本。
本公开充分利用Ti的化合物在高温加热、高温卷取和连续高温快速退火工艺中的形成、溶解和析出特点，最终实现了细小、弥散的Ti(C，N)、TiC和Ti4C2S2在铁素体基体上均匀析出，不仅作为贮氢陷阱对抗鳞爆性能起到至关重要的作用，还起到了析出强化和抑制搪烧时晶粒长大的作用，提高了钢板的屈服强度和抗高温软化能力，使得钢板高温搪烧之后强度变化小，适用于制备大容积、对抗疲劳性能要求较高的搪瓷内胆。
基于此，本公开的搪瓷用钢实现了：屈服强度≥280MPa，抗拉强度≥340MPa，标距为50mm时的断裂延伸率为30-40％，各向异性指数Δr≤0.45，氢穿透值TH2≥7.0min/mm2。并且，本公开的搪瓷用钢在850℃的高温下搪烧10min后，屈服强度仍保持在270MPa以上。
附图说明
图1为实施例A1的搪瓷用钢的金相微观组织。
图2显示了实施例A1的搪瓷用钢在模拟高温搪烧后的金相微观组织。
具体实施方式
下面将结合具体的实施例和说明书附图对本公开的搪瓷用钢及其制造方法做进一步的解释和说明，然而该解释和说明并不对本公开的技术方案构成不当限定。实施例中所用试剂均可通过商业渠道获得。实施例中未注明具体条件的实验方法，系按照本领域已知的常规条件，或按照制造厂商所建议的条件进行操作。
实施例A1-A6和对比例B1-B2
表1列出了实施例A1-A6的搪瓷用钢和对比例B1-B2中各化学元素的质量百分比。
表1.(wt％，余量为Fe和除O、P以外的其他不可避免的杂质)

注：表1中的I＝6×Ti/(3.43×N+1.5×S-0.32×RE+4×C)≤1；式中各化学元素代入其质量百分比含量百分号前的数值。
实施例A1-A6的搪瓷用钢和对比例B1-B2的钢板采用以下步骤制得：
1)铁水预处理；
2)转炉冶炼：通过顶底复合吹炼，实现降碳、脱磷，去除有害气体和夹杂物，调整钢液的基本成分；
3)RH精炼：在真空条件下，进行深脱碳、脱氧、脱硫，进一步去除钢液中的夹杂物和氢气、氮气等有害气体，实现表1中的各化学元素质量百分比的精确控制；实现夹杂物的形态控制；
4)连铸：将钢水制成230mm厚的连铸坯；
5)将连铸坯采用辊道直接热装热送至保温坑；
6)铸坯加热：板坯加热温度为1120-1200℃，保温时间在240min以上；
7)热轧：终轧温度为780-920℃，然后钢板经层流冷却系统冷却至卷取温度进行卷取，卷取温度为620-700℃；
8)酸洗，去除钢板表面的氧化铁皮；
9)冷轧：冷轧压下率为60-80％；
10)连续退火：其中均热温度为750-860℃，均热时间为100-300s，过时效段温度为 300-420℃，过时效时间为200-400s；
11)平整：平整压下率为0.8-2.0％。
表2-1和表2-2列出了实施例A1-A6的搪瓷用钢和对比例B1-B2的钢板的具体工艺参数。
表2-1.
表2-2.
需要说明的是，实际操作过程中过时效温度是变化的，并非是稳定在一个固定值，而是在过时效时间段内，温度逐步降低，因此表2-2中的过时效温度在各实施例和对比例中呈现为一段范围值而不是点值。
对实施例A1-A6的搪瓷用钢和对比例B1-B2的钢板进行各项性能测试，结果列于表3 中。其中，实施例A1-A6和对比例B1-B2在室温下的横向力学性能包括屈服强度ReL、抗拉强度Rm、断裂延伸率A50mm和各向异性指数Δr。
此外，表3还列出了参照BS EN10209规定的电化学方法测得的钢板的氢穿透时间，然后换算成1mm厚钢板所对应的氢渗透值TH2。
将实施例A1-A6和对比例B1-B2放置在850℃的电阻加热炉中保温10min以进行模拟高温搪烧试验，然后取出并空冷至室温。对经过高温烧结的试样的屈服强度进行测试，结果也列于表3中。
表3.
结合表1和表3可以看出，实施例A1-A6在室温下的屈服强度在283-357MPa之间，抗拉强度在347-406MPa之间，断裂延伸率在31.3-38.9％之间，各项异性指数在0.42以下，氢穿透值TH2≥7min/mm2，并且在850℃下搪烧10min后，屈服强度保持在270MPa以上，屈服强度的下降幅度控制在15MPa以内。
可以看出，本公开的搪瓷用钢的各向异性小，有利于提升钢板的冲压均匀性，减少材料的切损率。此外，本公开的搪瓷用钢还具有优异的贮氢性能，可保证双面或单面涂搪后不发生鳞爆；并且高温模拟搪烧后仍可保持较高的屈服强度，这对于提高搪瓷内胆的抗疲劳能力和使用寿命非常有利。
相比之下，对比例B1-B2的横向拉伸强度低，各向异性较大，且搪烧之后屈服强度显著降低，且贮氢能力也不足。
图1示出了实施例A1的金相显微组织。可以看出，该钢板的显微组织为均匀的铁素体 晶粒+少量的珠光体，珠光体位于铁素体晶粒的三叉晶界处，铁素体基体上还分布有Ti和RE的复合硫化物、Ti的析出物。
在各实施例中，铁素体细小，铁素体的晶粒度均为9-10级。
在各实施例中，Ti和RE的复合硫化物为圆形或椭圆形的(Ti，Mn)S和(RE，Mn)S，其尺寸为2-20μm，横/纵尺寸比为0.8-2。Ti的析出物包括Ti(C，N)、TiC和Ti4C2S2，这些析出物的尺寸为1-300nm之间。
图2示出了实施例A1经模拟高温搪烧后的金相显微组织。可以看出，铁素体晶粒发生了均匀长大，平均晶粒尺寸由12.0μm增加至14.0μm，没有发生异常长大。
需要说明的是，本公开中各技术特征的组合方式并不限于权利要求中所记载的组合方式或实施例中的组合方式，本公开中记载的所有技术特征可以以任何方式进行自由组合或结合，除非相互之间产生矛盾。
需要注意的是，以上所列举的实施例仅为本公开的具体实例。显然本公开不局限于以上实施例，随之做出的类似变化或变形是本领域技术人员能从本公开公开的内容直接得出或者很容易便联想到的，均应属于本公开的保护范围。

Claims (15)

  1. 一种搪瓷用钢，其中，所述搪瓷用钢除含有Fe和不可避免的杂质之外，还含有质量百分比如下的下述化学元素：
    C：0.03-0.08％，Si：0.01-0.04％，Mn：0.15-0.35％，S：0.002-0.012％，Al：0.015-0.055％，
    N≤0.006％，Ti：0.02-0.05％，RE：0.005-0.015％，0＜Ca≤0.008％，0＜Zr≤0.008％，以及
    选自Cu：0.01-0.06％、Cr：0.01-0.05％和Ni：0.005-0.05％中的至少一种；
    其中，所述搪瓷用钢不含Nb和B元素。
  2. 如权利要求1所述的搪瓷用钢，其中，所述搪瓷用钢的各化学元素的质量百分比含量如下：
    C：0.03-0.08％，Si：0.01-0.04％，Mn：0.15-0.35％，S：0.002-0.012％，Al：0.015-0.055％，
    N≤0.006％，Ti：0.02-0.05％，RE：0.005-0.015％，0＜Ca≤0.008％，0＜Zr≤0.008％，以及
    选自Cu：0.01-0.06％、Cr：0.01-0.05％和Ni：0.005-0.05％中的至少一种；余量为Fe和不可避免的杂质。
  3. 如权利要求1或2所述的搪瓷用钢，其中，RE和S元素的质量百分比含量满足：RE/S＝1-3。
  4. 如权利要求1或2所述的搪瓷用钢，其中，各化学元素的质量百分比含量还满足：
    6×Ti/(3.43×N+1.5×S-0.32×RE+4×C)≤1；
    式中各化学元素代入其质量百分比含量百分号前的数值。
  5. 如权利要求1或2所述的搪瓷用钢，其中，所述不可避免的杂质包括P和/或O，并且P≤0.03％和/或O≤0.005％。
  6. 如权利要求1或2所述的搪瓷用钢，其中，所述搪瓷用钢的微观组织为铁素体+珠光体，珠光体分布在铁素体的三叉晶界处，珠光体的体积相比例低于6％。
  7. 如权利要求1或2所述的搪瓷用钢，其中，铁素体基体上还分布有Ti和RE的复合硫化物、Ti的析出物。
  8. 如权利要求7所述的搪瓷用钢，其中，Ti和RE的复合硫化物为圆形或椭圆形的(Ti，Mn)S和(RE，Mn)S，所述复合硫化物的尺寸为2-20μm，横/纵尺寸比为0.8-2。
  9. 如权利要求7所述的搪瓷用钢，其中，Ti的析出物包括Ti(C，N)、TiC和Ti4C2S2，所述析出物的尺寸为1-300nm。
  10. 如权利要求6所述的搪瓷用钢，其中，铁素体的晶粒度为9-10级。
  11. 如权利要求1或2所述的搪瓷用钢，其中，所述搪瓷用钢的屈服强度≥280MPa，抗拉强度≥340MPa，标距为50mm时的断裂延伸率为30-40％，各向异性指数Δr≤0.45，氢穿透值TH2≥7.0min/mm2。
  12. 一种制造权利要求1-11中任一项所述的搪瓷用钢的方法，其中，包括如下步骤：
    (1)冶炼、精炼和连铸，得到铸坯；
    (2)将铸坯热装热送至保温坑；
    (3)铸坯加热；
    (4)热轧和卷取；
    (5)酸洗；
    (6)冷轧，其中冷轧压下率为60-80％；
    (7)连续退火，其中均热温度为750-860℃，均热时间为100-300s，过时效温度为300-420℃，过时效时间为200-400s；
    (8)平整。
  13. 如权利要求12所述的方法，其中，在步骤(3)中，加热温度为1120-1200℃，保温时间≥240min。
  14. 如权利要求12所述的方法，其中，在步骤(4)中，热轧的终轧温度为780-920℃，卷取温度为620-700℃。
  15. 如权利要求12所述的方法，其中，在步骤(8)中，平整压下率为0.8-2.0％。
PCT/CN2024/071439 2023-01-10 2024-01-09 一种搪瓷用冷轧高强钢及其制造方法 Ceased WO2024149263A1 (zh)

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JPH02156040A (ja) * 1988-12-08 1990-06-15 Kobe Steel Ltd 高強度グラスライニング用鋼
JPH02235551A (ja) * 1989-03-09 1990-09-18 Nippon Steel Corp 耐爪とび性の優れた連続鋳造製ほうろう用鋼板の製造方法
CN101812630A (zh) * 2009-02-25 2010-08-25 宝山钢铁股份有限公司 深冲用热轧高强度搪瓷钢板及其制造方法
CN102747309A (zh) * 2012-07-27 2012-10-24 宝山钢铁股份有限公司 一种搪瓷用钢及其制造方法
CN110777301A (zh) * 2018-07-30 2020-02-11 宝山钢铁股份有限公司 一种冷轧搪瓷钢及其制造方法
CN112119174A (zh) * 2018-05-17 2020-12-22 日本制铁株式会社 钢板以及搪瓷制品
CN113684413A (zh) * 2020-05-18 2021-11-23 宝山钢铁股份有限公司 一种深冲内胆用冷轧搪瓷钢及其制造方法

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02156040A (ja) * 1988-12-08 1990-06-15 Kobe Steel Ltd 高強度グラスライニング用鋼
JPH02235551A (ja) * 1989-03-09 1990-09-18 Nippon Steel Corp 耐爪とび性の優れた連続鋳造製ほうろう用鋼板の製造方法
CN101812630A (zh) * 2009-02-25 2010-08-25 宝山钢铁股份有限公司 深冲用热轧高强度搪瓷钢板及其制造方法
CN102747309A (zh) * 2012-07-27 2012-10-24 宝山钢铁股份有限公司 一种搪瓷用钢及其制造方法
CN112119174A (zh) * 2018-05-17 2020-12-22 日本制铁株式会社 钢板以及搪瓷制品
CN110777301A (zh) * 2018-07-30 2020-02-11 宝山钢铁股份有限公司 一种冷轧搪瓷钢及其制造方法
CN113684413A (zh) * 2020-05-18 2021-11-23 宝山钢铁股份有限公司 一种深冲内胆用冷轧搪瓷钢及其制造方法

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