WO2021052315A1 - 30CrMo热轧钢板/带及其生产方法 - Google Patents

30CrMo热轧钢板/带及其生产方法 Download PDF

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WO2021052315A1
WO2021052315A1 PCT/CN2020/115286 CN2020115286W WO2021052315A1 WO 2021052315 A1 WO2021052315 A1 WO 2021052315A1 CN 2020115286 W CN2020115286 W CN 2020115286W WO 2021052315 A1 WO2021052315 A1 WO 2021052315A1
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strip
hot
steel
rolled steel
30crmo
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PCT/CN2020/115286
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English (en)
French (fr)
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吴建春
方园
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宝山钢铁股份有限公司
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Priority claimed from CN201910889384.XA external-priority patent/CN112522593B/zh
Priority claimed from CN201910888783.4A external-priority patent/CN112522579B/zh
Application filed by 宝山钢铁股份有限公司 filed Critical 宝山钢铁股份有限公司
Priority to DE112020004461.0T priority Critical patent/DE112020004461T5/de
Publication of WO2021052315A1 publication Critical patent/WO2021052315A1/zh

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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/1206—Accessories for subsequent treating or working cast stock in situ for plastic shaping of strands
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • 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
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • 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
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/613—Gases; Liquefied or solidified normally gaseous material
    • 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 by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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 by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
    • 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 by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
    • C21D8/0215—Rapid solidification; Thin strip casting
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • 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
    • C22C38/18—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
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the invention belongs to a continuous casting process, and specifically relates to a 30CrMo hot-rolled steel plate/strip and a production method thereof.
  • tin (Sn) and copper (Cu) are typical residual elements or harmful elements in steel. It is very difficult and very expensive to fully remove Sn and Cu during the steelmaking process. Once the steel contains Sn , Cu, basically can not be completely eliminated, only by diluting molten steel to reduce the content of Sn, Cu, these all cause the increase in the smelting cost of steel products.
  • Traditional thin strip steel is mostly produced by continuous rolling of cast billets with a thickness of 200-250mm through multiple passes.
  • the traditional hot rolling process is: continuous casting + billet reheating and heat preservation + rough rolling + finishing rolling + cooling + Coiling, that is, firstly obtain a cast slab with a thickness of about 200mm through continuous casting. After reheating and holding the cast slab, rough rolling and finishing rolling are performed to obtain a steel strip with a thickness generally greater than 2mm, and finally the steel strip is processed Laminar cooling and coiling complete the entire hot rolling production process. If the steel strip with a thickness of less than 2.0mm (inclusive) is to be produced, it is relatively difficult, and the hot-rolled steel strip is usually subjected to subsequent cold rolling and annealing to complete. In addition, the long process flow, high energy consumption, many units and equipment, and high capital construction costs result in high production costs.
  • the thin slab continuous casting and rolling process is: continuous casting + slab heat preservation and soaking + hot continuous rolling + cooling + coiling.
  • the main difference between this process and the traditional process is that the thickness of the cast slab in the thin slab process is greatly reduced to 50-120mm. Because the cast slab is thin, the cast slab only needs to undergo 1 to 2 passes of rough rolling (the thickness of the cast slab is 70-90mm When the thickness of the cast slab is 50mm, the thickness of the continuous casting slab in the traditional process must be repeatedly rolled to reduce the thickness to the required specifications before the finish rolling; and the thin slab casting process is not necessary to go through rough rolling (when the thickness of the cast slab is 50mm).
  • the billet directly enters the soaking furnace for soaking and heat preservation, or a small amount of temperature compensation, so the thin slab process greatly shortens the process flow, reduces energy consumption, reduces investment, and reduces production costs.
  • the faster cooling rate of thin slab continuous casting and rolling the strength of the steel will increase and the yield ratio will increase, thereby increasing the rolling load, so that the thickness specification of the hot-rolled product can be economically produced and the thickness specification is not too thin, generally ⁇ 1.5mm, see Chinese patent application numbers CN 2 00610123458.1, CN 2 00610035800.2 and CN 2 00710031548.2.
  • ESP all-headless thin slab continuous casting and rolling process
  • the flame cutting of slab and the heating furnace for heat preservation and soaking and slab transition are eliminated, and the length of the entire production line is greatly shortened to about 190 meters.
  • the thickness of the slab casted by the continuous casting machine is 90-110mm, and the width is 1100-1600mm.
  • the continuous casting slab passes through a section of induction heating roller table to keep the slab warm and soak, and then enters the rough rolling one by one. , Finish rolling, layer cooling, and coiling processes to obtain hot-rolled plates.
  • this process can obtain the thinnest hot-rolled sheet with a thickness of 0.8mm, which expands the specification range of the hot-rolled sheet.
  • its single production line output can reach 2.2 million tons/year.
  • the process has been rapidly developed and promoted.
  • the shorter process flow than thin slab continuous casting and rolling is the thin strip continuous casting and rolling process.
  • the thin strip continuous casting technology is a cutting-edge technology in the field of metallurgy and materials research. Its appearance has brought a revolution to the steel industry. It changes the production process of steel strip in the traditional metallurgical industry, integrating continuous casting, rolling, and even heat treatment into one, so that the produced thin strip can be formed into thin steel strip at one time after one online hot rolling.
  • the "one-fire material" of thin steel strip products greatly simplifies the production process and shortens the production cycle. The length of the process line is only about 50m; the equipment investment is also reduced, and the product cost is significantly reduced. It is a low-carbon and environmentally friendly hot rolling Thin strip production process.
  • the twin-roll thin strip continuous casting process is a main form of the thin strip continuous casting process, and it is also the world's only industrialized thin strip continuous casting process.
  • the typical process flow of twin-roll thin strip continuous casting is shown in Figure 1.
  • the molten steel in the ladle 1 is directly poured into one by two through the ladle nozzle 2, the tundish 3, the immersion nozzle 4 and the distributor 5
  • the molten steel solidifies on the rotating circumferential surfaces of the crystallizing rollers 8a, 8b to form a solidified shell and gradually grow, and then the two A 2-5mm thick cast strip 11 is formed at the smallest gap (nip point) of the crystallizing roller.
  • the cast strip is guided to the pinch roll 12 via the guide plate 9 and fed into the rolling mill 13 to be rolled into a thin strip of 0.7-2.5mm, and then passed through the cooling device 14 is cooled, after being cut by the flying shear device 16, it is finally sent to the coiler 19 to be wound into a roll.
  • 30CrMo alloy steel has high strength and toughness, good hardenability, and has excellent comprehensive mechanical properties after quenching low temperature tempering and quenching high temperature tempering. After quenching and tempering, this steel has high strength below 550°C, good low-temperature toughness, no temper brittleness, and good weldability, machinability and machinability.
  • 30CrMo is widely used in machinery manufacturing, petrochemical industry, boiler manufacturing and saw blade die industry, etc. According to market statistics, the market consumption of thin 30CrMo is 100,000 to 150,000 tons/year, and the market usage and future potential are huge.
  • the reasonable combination of Cr and Mo elements in 30CrMo steel enables the steel to have good room temperature and high temperature properties. It can obtain compact structure and high strength without significantly reducing plasticity. At the same time, it also improves the hardenability of steel and increases tempering. Time stability, eliminating temper brittleness and the tendency of grain growth at high temperature.
  • the mainstream production process of 30CrMo steel plate/strip is: converter / electric furnace-refining-conventional thick slab continuous casting-walking heating furnace-rough rolling-multi-stand finishing rolling-laminar cooling-coiling.
  • the 30CrMo steel plate/strip produced by this traditional production process mainly has the following problems: (1) Composition segregation and internal looseness: Due to the high alloy content in the steel, the drawing speed during continuous casting of thick slabs is low, and the molten steel is solidified. Slowly, it is easy to cause serious component segregation and internal looseness in the slab, which will eventually lead to uneven product quality and performance; (2) Surface decarburization: Because of the high carbon content in steel, a walking heating furnace is used to heat the slab.
  • the thin gauge 30CrMo hot-rolled steel sheet/strip has a characteristic thickness of 1.5-3.0mm. Due to the thin thickness of the product, it will be more difficult to use the above-mentioned traditional continuous casting + hot rolling production line for production. Even if thin slab continuous casting and rolling production is adopted, since the thickness of the slab must reach 70-120mm, there is no order of magnitude and essential difference in the size and thickness of the slab from the traditional thick slab continuous casting (slab thickness 200-250mm) Therefore, it is impossible to fundamentally solve the problem of element segregation.
  • the continuous casting slab still has to pass through a tunnel heating furnace or an electromagnetic induction heating section, and the problem of decarburization on the surface of the material cannot be completely eliminated; in addition, thinner specifications are rolled. Will cause the roll consumption of the roll to be larger. Therefore, the traditional thick slab continuous casting or thin slab continuous casting production process cannot completely solve the problems in the production of 30CrMo steel, and the production cost of the thin-gauge 30CrMo hot-rolled steel plate/strip will also be very high.
  • the products produced by thin strip continuous casting will generally have problems such as uneven structure, low elongation, and uneven performance. This is due to the austenite grains in the cast strip. Obvious inhomogeneity will result in uneven structure of the final product obtained after austenite transformation, resulting in unstable product performance, especially elongation and formability; at the same time, thin strip continuous casting is in the production of higher carbon
  • the molten steel is too late to feed, and it is easy to cause internal shrinkage/shrinkage cavities near the center area of the cast strip.
  • the purpose of the present invention is to provide a 30CrMo hot-rolled steel sheet/strip and its production method.
  • N element By adding an appropriate amount of N element, combined with a reasonable online hot rolling process and cooling measures after rolling, the uniformity of the structure is effectively improved, and the internal shrinkage and shrinkage are solved. Hole problem, improve product quality and performance, and realize the "single-fire material" of thin-gauge 30CrMo hot-rolled steel plate/strip.
  • the thin-gauge 30CrMo hot-rolled steel plate/strip produced by the invention is an ideal material for the thin-gauge steel in the field of machinery manufacturing, petrochemical industry, boiler manufacturing industry and saw blade and die industry.
  • the invention makes full use of the residual Sn, Cu and other elements in the scrap steel to smelt molten steel, and selectively adds Mo, Cr and other microalloy elements and B, N and other elements to the steel; during the smelting process, the alkalinity of the slag is controlled, The type and melting point of the inclusions in the steel, the free oxygen content in the molten steel, and the acid-soluble aluminum Als content; then double-roll thin strip continuous casting is carried out to cast a 2.0-5.0mm thick casting strip, and the casting strip directly enters a crystal roll after it exits the crystallizing roller.
  • the strip steel In the lower airtight chamber with non-oxidizing atmosphere, and enter the online rolling mill under airtight conditions to hot-roll the strip steel to 1.5-3.0mm thickness; after rolling, the strip steel is cooled by the gas atomization cooling method, and the gas mist
  • the cooling method can effectively reduce the thickness of the oxide scale on the surface of the strip, improve the uniformity of the strip temperature, and improve the uniformity and surface quality of the strip.
  • the thin-gauge 30CrMo hot-rolled steel plate/strip produced by the method of the present invention has uniform structure and performance, no internal shrinkage/shrinkage, few decarburization layers, good hardenability, good machinability and workability; the present invention
  • the manufacturing method realizes the "one-fire material" of the thin-gauge 30CrMo hot-rolled steel plate/strip, the production efficiency is greatly improved, and the production cost is greatly reduced. It is a low-carbon, green and environmentally friendly product.
  • the 30CrMo hot-rolled steel sheet/strip of the present invention has a composition weight percentage of: C: 0.24-0.34%, Si: 0.1-0.5%, Mn: 0.6-1.5%, P ⁇ 0.03%, S ⁇ 0.007 %, Cr: 0.80-1.50%, Mo: 0.10-0.30%, N: 0.004-0.010%, Als: ⁇ 0.001%, optional B: 0.001-0.006%, total oxygen [O] T : 0.007-0.020% ;
  • the balance is Fe and unavoidable impurities, and at the same time meet:
  • the microstructure of the 30CrMo hot-rolled steel sheet/strip of the present invention is acicular ferrite (AF) + massive ferrite (PF) + pearlite (P), wherein the proportion of AF: 60-80%, The proportion of PF: 10-25%, the proportion of P: 5-20%.
  • AF acicular ferrite
  • PF massive ferrite
  • P pearlite
  • the tensile strength of the hot-rolled steel sheet/strip of the present invention is less than or equal to 900 MPa, and the hardness is less than or equal to HRC 25.
  • the 30CrMo hot-rolled steel sheet/strip of the present invention has a tensile strength of 780-900 MPa, a yield strength of 590-750 MPa, an elongation of 11-23%, and a yield ratio of 0.75-0.83.
  • the 30CrMo hot-rolled steel sheet/strip of the present invention has a composition weight percentage of: C: 0.24-0.34%, Si: 0.1-0.5%, Mn: 0.6-1.5%, P ⁇ 0.03%, S ⁇ 0.007%, Cr: 0.80-1.50%, Mo: 0.10-0.30%, N: 0.004-0.010%, Als: ⁇ 0.001%, B: 0.001-0.006%, total oxygen [O] T : 0.007-0.020%
  • the balance is Fe and unavoidable impurities, and at the same time meets: Containing one or two elements of Cu: 0.10-0.60% and Sn: 0.005-0.04%, Mn/S ⁇ 250.
  • the microstructure of the 30CrMo hot-rolled steel sheet/strip is acicular ferrite (AF) + massive ferrite (PF) + pearlite (P), wherein the proportion of AF: 60-80%, PF The ratio of P: 10-25%, the ratio of P: 5-20%.
  • AF acicular ferrite
  • PF massive ferrite
  • P pearlite
  • the 30CrMo hot-rolled steel sheet/strip of the present invention has a composition weight percentage of: C: 0.24-0.34%, Si: 0.1-0.5%, Mn: 0.6-1.5%, P ⁇ 0.03%, S ⁇ 0.007%, Cr: 0.80-1.50%, Mo: 0.10-0.30%, N: 0.004-0.010%, Als: ⁇ 0.001%, total oxygen [O] T : 0.007-0.020%; the balance is Fe and non Avoid impurities, and meet at the same time: contain one or two elements of Cu: 0.10-0.60% and Sn: 0.005-0.04%, and Mn/S ⁇ 250.
  • Mn/S Preferably, in the 30CrMo hot-rolled steel sheet/strip of the present invention, Mn/S>250.
  • C is the most economical and basic strengthening element in steel.
  • the strength of the steel is improved by solid solution strengthening and precipitation strengthening to ensure quenching hardness and quenching.
  • C is an essential element for the precipitation of cementite during austenite transformation. Therefore, the level of C content determines the strength level of steel to a large extent, that is, a higher C content corresponds to a higher strength level.
  • the C content should not be too high, too high will result in high deformation resistance during rolling, lower toughness after quenching and tempering heat treatment, and also affect welding performance.
  • Si plays a solid solution strengthening effect in steel, and the addition of Si to steel can help deoxidize to form silicate, which helps to improve cutting performance and at the same time improve the purity of steel, but excessive Si content will affect weldability And increase the brittleness of steel. Therefore, the range of Si content used in the present invention is 0.1-0.5%.
  • Mn is one of the cheapest alloying elements. It can improve the hardenability and quenching hardness of steel. It has a considerable solid solubility in steel. It can improve the strength of steel through solid solution strengthening, and at the same time, it can improve the plasticity of steel. There is basically no damage to toughness. It is the most important strengthening element to increase the strength of steel. When combined with Si, it can also play a role in deoxidizing steel. However, if the Mn content is too high, the thermal stress and structural stress of the cast strip will increase, and the strip will be easily broken. Therefore, the range of Mn content used in the present invention is 0.6-1.5%.
  • P High content of P is easy to segregate in grain boundaries, increase the cold brittleness of steel, deteriorate welding performance, reduce plasticity, and deteriorate cold bending performance.
  • the solidification and cooling rate of the cast strip is extremely fast, which can effectively inhibit the segregation of P, thereby effectively avoiding the disadvantages of P and giving full play to the advantages of P. Therefore, in the present invention, a higher P content than the traditional production process is adopted, the P element content is appropriately relaxed, and the dephosphorization process is eliminated in the steelmaking process. In actual operation, there is no need to deliberately perform the dephosphorization process, and no additional process is required. Add phosphorus, the range of P content is ⁇ 0.03%.
  • S Under normal circumstances, S is a harmful element in steel, causing steel to produce hot brittleness, reducing the ductility and toughness of steel, and causing cracks during rolling. S also reduces welding performance and corrosion resistance. Therefore, in the present invention, S is controlled as an impurity element, and its content range is ⁇ 0.007%; in some embodiments, the S content is ⁇ 0.006%. And, Mn/S ⁇ 250. In some embodiments, Mn/S>250.
  • the N element can improve the strength of steel through interstitial solid solution.
  • the present invention uses the effect of N and B in the steel to generate the precipitated phase of BN, which requires a certain amount of N in the steel.
  • an appropriate amount of N can promote the precipitation of carbonitrides during the quenching and tempering heat treatment process, and improve the red hardness of the steel during cutting and machining; but too high N content will damage the toughness of the steel and increase the brittleness of the cast strip. Reduce manufacturability. Therefore, the range of N content used in the present invention is 0.004-0.010%.
  • Cr not only is an element that improves the hardenability of steel, it can also effectively improve the high-temperature oxidation resistance and creep resistance of steel. Adding Cr to thin-gauge 30CrMo hot-rolled steel is used to improve the hardenability of steel. , High temperature strength and creep strength, and secondly, it also has secondary hardening effect, which can improve the hardness and wear resistance of steel without making the steel brittle; the combination of Cr and Cu in scrap steel can also improve the corrosion resistance of steel. . However, if its content is too high, it will result in high deformation resistance during rolling, and reduced toughness after quenching and tempering heat treatment, which will affect the cutting process of users. In the present invention, the content of Cr is limited to 0.80-1.50%.
  • Mo can refine grains and improve strength and toughness. Part of Mo is solid-dissolved in ferrite to strengthen the ferrite matrix, and the other part is dispersed in the steel as carbides. Therefore, the Mo-containing steel has both solid solution strengthening and carbide dispersion strengthening. Because Mo diffuses slowly in ferrite at high temperatures, it can also significantly improve the high-temperature strength and tempering stability of steel. However, excessively high Mo will significantly increase the raw material smelting cost of steel. Therefore, in the present invention, the Mo content is limited to 0.10-0.30%.
  • Cu It mainly plays a solid solution and precipitation strengthening effect in steel.
  • the combined effect of Cu and Cr can also improve the corrosion resistance of 30CrMo steel, making the steel of the present invention suitable for some corrosive occasions, and weather resistance is not easy to rust.
  • the present invention uses scrap steel as a raw material, and there is no need to add Cu during smelting. Since Cu is an easily segregated element, the Cu content is generally strictly controlled in the traditional process. Using the rapid solidification effect of thin strip continuous casting, the present invention increases the upper limit of Cu to 0.60%. The increase of Cu content can make full use of scrap steel in a certain sense.
  • Sn It is also one of the main residual elements in scrap steel. It is recognized as a harmful element in steel. Because Sn is an element that is easy to segregate, a small amount of Sn will be enriched at the grain boundary, resulting in cracks and other defects. The content of Sn element in the process is strictly controlled. Due to the characteristics of rapid solidification of thin strip continuous casting, the segregation of elements in the dendrites is greatly reduced, which can greatly increase the amount of solid solution of the elements. Therefore, under the conditions of the thin strip continuous casting process, the range of Sn elements can be expanded, so it can greatly Reduce steelmaking costs.
  • Figure 2 is the relationship between the Sn element and the average heat flux. It can be seen from Fig.
  • FIG. 3 shows the relationship between Sn content and surface roughness. Because the cracks on the surface of the cast strip are usually produced at the uneven wrinkles on the surface of the cast strip, the surface roughness is used to characterize the occurrence of surface cracks. If the roughness is large, the probability of occurrence of cracks is high. It can be seen from Fig. 3 that the increase of Sn content does not adversely affect the surface quality of the cast strip under the conditions of rapid solidification. From the results of Fig. 2 and Fig. 3, it can be seen that Sn has no adverse effect on the solidification and surface quality of the cast strip. Therefore, in the present invention, the requirements for the content of Sn can be further relaxed. When Sn is contained, the content of Sn is designed to be in the range of 0.005-0.04%.
  • B The significant effect of B in steel is: a very small amount of boron can double the hardenability of steel, and B can preferentially precipitate coarse BN particles in high-temperature austenite, thereby inhibiting the precipitation of fine AlN and weakening the fineness
  • the pinning effect of AlN on grain boundaries improves the growth ability of grains, thereby coarsening and homogenizing austenite grains, which is beneficial to improve the machinability of steel coil products, and is beneficial to subsequent users for cutting or machining;
  • B The combination with N can effectively prevent the appearance of the low melting point phase B 2 O 3 of the grain boundary, thereby avoiding thermal embrittlement.
  • B is a lively and easily segregated element, which is easy to segregate in the grain boundary.
  • the B content is generally controlled very strictly, generally around 0.001-0.003%; while in the thin strip continuous casting process, solidification and cooling The speed is faster, which can effectively inhibit the segregation of B and solid-solve more B content, so the B content can be appropriately relaxed; it can also be controlled by a reasonable process to generate coarse BN particles, inhibit the precipitation of fine AlN, and achieve nitrogen fixation effect.
  • Studies have also shown that when B is added in combination with Mo, it will get better results, will reduce the segregation tendency of C atoms, and avoid the precipitation of grain boundary Fe23(C,B)6, so you can add more B. Therefore, in some embodiments of the present invention, a higher B content than the traditional process is used, and the range is 0.001-0.006%.
  • the production method of 30CrMo hot-rolled steel sheet/strip according to the present invention includes the following steps:
  • the MnO/SiO 2 (mass ratio) in the SiO 2 -Al 2 O 3 ternary inclusions is controlled at 0.5-2, preferably 1 to 1.8;
  • the free oxygen [O] Free content in the molten steel is: 0.0005 to 0.005%; Mn/S>250;
  • the continuous casting adopts double-roll thin strip continuous casting to form a 2.0-5.0mm thick cast strip (preferably, the thickness of the cast strip is formed at the smallest gap between the two crystallizing rolls; the diameter of the crystallizing roll is 500-1500mm, and the preferred roll diameter is 800mm, the inside of the crystallizing roll is cooled by water; the casting speed of the casting machine is 40-100m/min; the ladle opening temperature is controlled at 1580-1610°C; the continuous casting cloth flow adopts a two-stage molten steel distribution flow system, namely tundish + cloth flow Device.
  • the temperature of the casting belt is 1360-1430°C, and it enters the lower closed chamber directly.
  • the lower closed chamber is filled with non-oxidizing gas.
  • the oxygen concentration in the lower closed chamber is controlled at ⁇ 5%.
  • the casting belt at the exit of the lower closed chamber The temperature is between 1150-1280°C;
  • the cast strip is sent to the rolling mill via pinch rolls in the lower enclosed chamber and rolled into strip steel with a thickness of 1.5-3.0mm.
  • the rolling temperature is 1100-1250°C and the hot rolling reduction rate is 10-50%.
  • hot rolling The reduction rate is 30-50%;
  • Cooling the strip steel after online hot rolling the cooling adopts gas atomization cooling method, and the cooling rate of gas atomization cooling is 10-100°C/s;
  • the cooled hot-rolled steel strip is coiled into a coil, and the coiling temperature of the hot-rolled steel strip is controlled to be 700-760°C.
  • step 6 tempering heat treatment: oil quenching at 840-880°C, tempering at 400-440°C.
  • tempering heat treatment oil quenching at 840-880°C, tempering at 400-440°C.
  • the user performs cutting and machining according to the size of the final product, and finally performs the quenching and tempering heat treatment.
  • the quenching and tempering heat treatment can ensure that the material obtains a uniform sorbite structure and hardness distribution, and can reduce the deformation of the sheet.
  • the required material hardness can be obtained after quenching and tempering heat treatment: HRC35 ⁇ 2.
  • the smelting raw material can be made of 100% scrap steel without pre-screening, and the molten steel smelting adopts electric furnace steelmaking, which greatly reduces the raw material cost; or, the smelting adopts converter steelmaking, and the scrap steel accounts for more than 20% of the smelting raw material It is added to the converter without pre-screening, which maximizes the scrap ratio of the converter and greatly reduces the smelting cost and energy consumption; then enters the LF furnace, VD/VOD furnace or RH furnace for refining.
  • the non-oxidizing gas includes inert gas, N 2 , CO 2 gas obtained by sublimation of dry ice, and a mixed gas of N 2 and H 2.
  • the gas-water ratio of the gas atomization cooling is 15:1-10:1, the air pressure is 0.5-0.8 MPa, and the water pressure is 1.0-1.5 MPa.
  • air-water ratio refers to the flow ratio of compressed air and water, and the unit of flow is m 3 /h.
  • the coiling adopts the form of a double coiler, or adopts the form of a Carrousel coiling.
  • step 5 after the cooled hot-rolled steel strip is cut by a cutting head to remove the poor quality head, it is directly coiled into a coil, and the coiling temperature of the hot-rolled steel strip is controlled to be 700-760°C.
  • MnO-SiO 2 -Al 2 O 3 ternary inclusions In order to improve the castability of thin strip continuous casting molten steel, it is necessary to obtain low melting point MnO-SiO 2 -Al 2 O 3 ternary inclusions, as shown in the shaded area in Figure 4, MnO-SiO 2 -Al 2 O 3 ternary inclusions
  • the MnO/SiO 2 in the composition is controlled to be 0.5-2, preferably 1 to 1.8.
  • oxygen (O) in the steel is an essential element for the formation of oxidized inclusions.
  • the present invention requires the formation of low melting point ternary inclusions of MnO-SiO 2 -Al 2 O 3 ,
  • the required free oxygen [O] Free range in molten steel is: 0.0005-0.005%.
  • the diameter of the crystallization roller of the present invention is between 500-1500mm, preferably 800mm; the inside of the crystallization roller is cooled by water.
  • the casting speed of the casting machine ranges from 40-100m/min.
  • the liquidus temperature of the 30CrMo steel grade designed by the invention is about 1500°C, and the ladle opening temperature range is 1580-1610°C.
  • the temperature of the casting belt is 1360-1430°C, and it enters the lower closed chamber directly.
  • the lower closed chamber is protected by non-oxidizing gas to protect the casting belt from oxidation. It can be N 2 , Ar can also be other non-oxidizing gases, such as CO 2 gas obtained by sublimation of dry ice, a mixed gas of N 2 and H 2 , etc.
  • the oxygen concentration in the lower enclosed chamber is controlled to ⁇ 5%.
  • the lower airtight chamber protects the cast strip from oxidation to the entrance of the rolling mill 13.
  • the temperature of the casting strip at the outlet of the lower closed chamber is 1150-1280°C.
  • thermodynamic equations of boron and nitrogen, aluminum and nitrogen in ⁇ -Fe in steel are as follows:
  • the initial precipitation temperature of BN in steel is about 1280°C, and the precipitation of BN tends to be balanced at 980°C, while the precipitation of AlN has just begun (the precipitation temperature of AlN is about 980°C).
  • the precipitation of BN has priority over AlN.
  • the invention completes the combination of B and N in the lower closed chamber to generate coarse BN particles, thereby inhibiting the precipitation of fine AlN, weakening the pinning effect of fine AlN on grain boundaries, improving the growth ability of grains, and thereby coarsening austenite
  • the grains make the austenite grains more uniform, which is beneficial to improve the cutting performance and machinability of the material; in addition, the combination of B and N can effectively prevent the appearance of the low melting point phase B 2 O 3 at the grain boundary.
  • the cast strip is sent to the rolling mill via pinch rolls in the lower enclosed chamber and rolled into a thin strip with a thickness of 1.5-3.0mm.
  • the rolling temperature is 1100-1250°C, and a higher rolling temperature can effectively solve the problem of edge cracks that are easy to occur in traditional processes.
  • the hot rolling reduction rate is 10-50%.
  • the hot rolling reduction rate is in the range of 30-50%.
  • the larger reduction rate of a single stand can completely solve the problem near the center area of the cast strip caused by the higher C content. Internal shrinkage/shrinkage problem.
  • the cooling method adopts gas atomization cooling method.
  • the gas atomization cooling method can effectively reduce the thickness of the oxide scale on the surface of the strip, improve the temperature uniformity of the strip, and improve the performance and surface of the strip. quality.
  • the gas-water ratio of gas atomization cooling is 15:1 ⁇ 10:1, the air pressure is 0.5 ⁇ 0.8MPa, and the water pressure is 1.0 ⁇ 1.5MPa.
  • high-pressure water mist is sprayed on the surface of the steel strip. On the one hand, it can reduce the temperature of the steel strip. On the other hand, the water mist will form a dense gas film covering the surface of the steel strip, which can prevent the strip from being oxidized.
  • This cooling method can avoid the problems caused by traditional spraying or laminar cooling, make the surface temperature of the strip drop uniformly, improve the uniformity of the strip temperature, and achieve the effect of homogenizing the internal microstructure; at the same time, the uniform cooling can improve the strip The shape quality and performance stability of the steel; effectively reduce the thickness of the oxide scale on the surface of the strip.
  • the cooling rate of gas atomization cooling is in the range of 10-100°C/s.
  • the cooled hot-rolled steel strip is cut by the cutting head to remove the poor quality head, and then directly coiled into a coil.
  • Control the coiling temperature of the hot-rolled strip from 700 to 760°C.
  • the high coiling temperature can ensure that the steel of the present invention obtains the lowest possible tensile strength (less than 900MPa) and hardness (under HRC25), so that it can be coiled smoothly; for downstream manufacturing users, it is also easier to perform various cutting and Machining.
  • the coiling adopts the form of double coiling machine, and can also adopt the form of Carrosel coiling to ensure the continuous production of strip steel.
  • the coiling adopts the Carrousel coiling form, which can make the length of the production line shorter and more compact.
  • the most obvious feature of the present invention which is different from the existing thin strip continuous casting technology is the roll diameter of the crystallizing roll and the corresponding flow distribution method.
  • the technical feature of EUROSTRIP is ⁇ 1500mm large diameter crystallizing roller, large crystallizing roller, large molten steel capacity in molten pool, easy flow distribution, high cost of crystallizing roller manufacturing and operation and maintenance.
  • the technical feature of CASTRIP is the ⁇ 500mm small diameter crystallizing roller, the crystallizing roller is small, the molten steel volume is small, and the flow distribution is very difficult, but the cost of manufacturing and operation and maintenance of the casting machine is low.
  • CASTRIP adopts a three-stage molten steel distribution flow system (tundish + transition bag + flow distributor).
  • the use of a three-stage flow distribution system directly leads to an increase in the cost of refractory materials; more importantly, the three-stage flow distribution system makes the path of molten steel flow longer and the temperature drop of molten steel is also greater.
  • the tapping temperature needs to be greatly increased. The increase in the tapping temperature will cause problems such as increased steelmaking costs, increased energy consumption, and shortened life of refractory materials.
  • the crystal roll with a diameter of 500-1500mm, preferably 800mm adopts a two-stage molten steel distribution system (tundish + flow distributor).
  • the molten steel flowing out of the distributor forms different distribution patterns along the roller surface and the two end surfaces, and flows in two paths without interfering with each other. Due to the use of a two-stage flow distribution system, compared with a three-stage flow system, the cost of refractory materials is greatly reduced; the shortening of the molten steel flow path reduces the temperature drop of the molten steel, which can lower the tapping temperature, compared with the three-stage flow system , The tapping temperature can be reduced by 30-50°C.
  • the lowering of the tapping temperature can effectively reduce the cost of steelmaking, save energy and extend the life of refractory materials.
  • the invention is matched with a crystallizing roller with a roller diameter of ⁇ 800mm and adopts a two-stage molten steel distribution system, which not only realizes the requirement of stable molten steel distribution, but also realizes the goals of simple structure, convenient operation and low processing cost.
  • Cia Patent Publication No. CN101773929B discloses a method for producing 30CrMo hot-rolled steel plate.
  • the method is based on the thin slab continuous casting and rolling process, which mainly includes: smelting, refining, thin slab continuous casting, soaking, high-pressure water descaling, hot continuous Rolling, cooling, coiling and other steps.
  • Its composition is C: 0.26-0.34%, Si: 0.17-0.37%, Mn: 0.40-0.70%, P: ⁇ 0.035%, S ⁇ 0.035%, Cr: 0.80-1.10, Mo: 0.15-0.25%, the rest is Fe and unavoidable impurities.
  • the 30CrMo hot-rolled steel plate produced by this patent has the characteristics of uniform structure and performance, high thermal stability and high strength, and its quality has been significantly improved.
  • the essential difference between this patent and the 30CrMo steel and production method proposed by the present invention is that the production process used is different.
  • the present invention adopts the twin-roll thin strip continuous casting process, and the designed composition is also different, so that no segregation and no surface can be obtained. Decarburized layer, products with better quality and performance.
  • Chinese Patent Publication No. CN107419192A discloses a 30CrMo steel strip and its production method.
  • the invention is also based on the thin slab continuous casting and rolling process, which mainly includes: converter smelting, LF refining, thin slab continuous casting, heating, hot rolling and coiling. Take the process. Its composition is C: 0.26-0.34%, Si: 0.17-0.30%, Mn: 0.40-0.70%, P: ⁇ 0.025%, S ⁇ 0.025%, Als ⁇ 0.010%, Cr: 0.80-1.10%, Mo: 0.15 -0.25%, Ni ⁇ 0.30%, Cu ⁇ 0.30%, the balance is Fe and unavoidable impurities.
  • the invention eliminates the central segregation and central shrinkage of the continuous casting billet, reduces surface decarburization, and can produce 2.5-4.0mm thick hot-rolled thin gauge steel strip, realizing the low cost of 30CrMo steel produce.
  • the patent and the 30CrMo steel and production method proposed by the present invention are also essentially different in the production process.
  • the present invention adopts the twin-roll thin strip continuous casting process, which simplifies the production process, and the design composition is different, which can be obtained A product with no segregation, no surface decarburization layer, and better quality performance.
  • Chinese Patent Publication No. CN100366779C discloses a stone cutting saw blade steel and its manufacturing method. Its chemical composition weight percentage is C 0.45-0.60%, Si 0.1-0.6%, Mn 1.3-1.8%, P ⁇ 0.02%, S ⁇ 0.01%, V 0.05-0.20%, Cr 0.15-0.30%, N 0.005-0.020%, Ca 0-0.0050%, Al 0.005-0.040%, the rest are Fe and unavoidable impurities.
  • the method includes: smelting, casting, and continuous casting billets adopt hot charging and hot delivery processes to ensure that the temperature of the slab before heating is above 300°C, the slab heating temperature is above 1150°C, and the final rolling temperature is controlled to be above 900°C during hot rolling.
  • Air-cooled coiling after rolling, the coiling temperature is above 700°C.
  • the inventive steel has high hardenability, and is particularly suitable for manufacturing saw blades for stone cutting with a diameter of more than 1000 mm.
  • This patent is different from the steel type involved in the present invention.
  • the carbon content of the patent is 0.45-0.60%, and the carbon content of the present invention is 0.24-0.34%. There are essential differences in the production process. The casting process further simplifies the production process.
  • Chinese Patent Publication No. CN102345071B discloses a structural steel 30CrMo plus B steel plate for alloys and its production method.
  • the plate contains the following mass percentages of chemical composition: C: 0.28-0.33%, Si: 0.20-0.35%, Mn: 0.60- 0.80%, P: ⁇ 0.018%, S: ⁇ 0.005%, Cr: 0.90-1.10%, Mo: 0.15-0.25%, Als: 0.20-0.40%, B: 0.0008-0.0015%, the rest is Fe and residual elements.
  • the production methods adopted include: converter steelmaking, LF refining, vacuum refining, pouring, billet/steel heating, rolling, slow cooling, heat treatment, and successfully developed high-strength 30CrMo plus B steel ⁇ 100mm.
  • this invention also adds a trace amount of B, because it uses the most traditional and backward mold casting process, the solidification rate is very slow, B is easy to segregate, and the low melting point B 2 O 3 phase is easy to appear in the grain boundary to cause hot cracks. Therefore, the addition amount of B is very low, only 0.0008-0.0015%, and the effect is very small.
  • the thickness specifications of the produced products are also relatively thick, with thicknesses of 50 mm and 100 mm.
  • the invention adopts an advanced twin-roll thin strip continuous casting process to directly produce a 1.5-3.0mm steel plate/belt.
  • the addition amount of B can reach 0.006%, and the quality performance is more excellent. It has the same composition and production method as the patent. The difference.
  • the present invention uses thin strip continuous casting technology to produce thin gauge 30CrMo hot-rolled steel containing tin (Sn), copper (Cu)/tin (Sn), copper (Cu), nitrogen (N) and optionally boron (B) There is no report so far.
  • Sn tin
  • Cu copper
  • Cu copper
  • N nitrogen
  • B optionally boron
  • the present invention eliminates the need for complex processes such as slab heating and multi-pass repeated hot rolling. Through double-roll thin strip continuous casting + one online hot rolling process, the production process is shorter, the efficiency is higher, and the investment cost of the production line is reduced. The production cost is greatly reduced.
  • the present invention omits many complicated intermediate steps in the traditional production process. Compared with the traditional production process, the energy consumption and CO 2 emission of production are greatly reduced, and it is a green and environmentally friendly product.
  • the present invention adopts thin strip continuous casting process to produce thin gauge 30CrMo hot-rolled steel. Due to the advanced nature of the process, it can completely solve the problems of surface decarburization, element segregation and edge cracking in the traditional process.
  • the speed of continuous casting of thin strip reaches 80-150m/min, the solidification speed of molten steel reaches 10 2 -10 4 °C/s, and the thickness of continuous casting is only 2-5mm.
  • the alloying elements in 30CrMo steel are in a short time ( 0.1-0.2s) It is completely solidified before the segregation occurs. This rapid solidification effect effectively eliminates the problem of element segregation;
  • the continuously cast steel strip quickly enters the lower closed room with a protective atmosphere, and then directly enters the online hot rolling mill for hot rolling.
  • the whole process of protection casting and rolling makes the surface of the strip steel hardly decarburized. ;
  • the thin strip continuous casting and rolling process organically integrates the traditional continuous casting, heating, hot continuous rolling and other independent processes.
  • the production cycle is greatly shortened, the production efficiency is greatly improved, the energy consumption is greatly reduced, and the product quality and performance are greatly improved. .
  • the invention adopts the addition of a trace amount of N element, which can promote the precipitation of carbonitrides during the quenching and tempering heat treatment of the invention steel, effectively improve the red hardness of 30CrMo steel in the cutting and machining process, and is beneficial to prolong the service life of the final product .
  • the present invention makes full use of scrap steel in raw materials without screening, and uses scrap steel containing Cu and Sn, combined with the sub-rapid solidification effect of thin strip continuous casting, to play the role of alloying residual elements , Greatly reduce the cost of smelting, "turn harm into profit" for Cu and Sn in steel, realize full utilization of existing scrap steel or low-quality inferior mineral resources (high tin ore, high copper ore), and promote the recycling of scrap steel Utilize, reduce production costs, and realize the sustainable development of the steel industry.
  • the smelting of the invention adopts electric furnace steelmaking, and the raw materials for smelting can realize 100% scrap steel smelting in a true sense without pre-screening, which greatly reduces the cost of raw materials; if the smelting adopts converter steelmaking, the scrap steel accounts for more than 20% of the smelting raw materials.
  • the converter is added without pre-screening, which maximizes the scrap ratio of the converter and greatly reduces the smelting cost and energy consumption.
  • the present invention adopts the strip steel gas atomization cooling method after rolling, which can avoid the problems caused by traditional spraying or laminar cooling, so that the surface temperature of the strip can be uniformly reduced, and the uniformity of the strip temperature can be improved, thereby achieving uniform internal microcosmic
  • uniform cooling can improve the shape quality and performance stability of the strip; effectively reduce the thickness of the oxide scale on the surface of the strip.
  • the precipitation of alloying elements occurs during the cooling process of the traditional slab, and the utilization rate of the alloying elements is often reduced due to insufficient re-dissolution of the alloying elements when the slab is reheated.
  • the high-temperature cast strip is directly hot-rolled, and the added alloy elements mainly exist in a solid solution state, which can improve the alloy utilization rate.
  • the present invention uses a hot-rolled steel strip Carrousel coiler, which effectively shortens the length of the production line; at the same time, the co-coiling can greatly improve the control accuracy of the coiling temperature and improve the stability of the product performance.
  • Figure 1 is a schematic diagram of the process layout of the twin-roll thin strip continuous casting process
  • Figure 2 is a schematic diagram of the relationship between Sn content and average heat flux
  • Figure 3 is a schematic diagram of the relationship between the Sn content and the surface roughness of the cast strip
  • Figure 4 is a ternary phase diagram of MnO-SiO 2 -Al 2 O 3 (shaded area: low melting point area);
  • Figure 5 is a schematic diagram of the thermodynamic curves of the precipitation of BN and AlN.
  • the molten steel in accordance with the chemical composition design of the present invention is directly poured in a large ladle 1, through a ladle nozzle 2, a tundish 3, an immersion nozzle 4, and a distributor 5, which is rotated by two relative rotations and can be quickly
  • the molten steel solidifies on the rotating circumferential surfaces of the crystallizing rollers 8a, 8b, and then forms a solidified shell and gradually grows on the two crystallizing rollers.
  • a 2.0-5.0mm thick cast strip 11 is formed; after the cast strip 11 exits the crystallizing rollers 8a, 8b, the temperature of the cast strip is 1360-1430°C, directly enters the lower airtight chamber 10, and is airtight.
  • the chamber 10 is protected by an inert gas to protect the strip steel from oxidation.
  • the atmosphere for the anti-oxidation protection can be N 2 , Ar or other non-oxidizing gases, such as a mixture of N 2 and H 2
  • the oxygen concentration in the lower airtight chamber 10 is controlled to be less than 5%, such as CO 2 gas obtained by sublimation of dry ice and dry ice.
  • the lower airtight chamber 10 protects the cast strip 11 from oxidation to the entrance of the rolling mill 13.
  • the temperature of the cast strip at the outlet of the lower closed chamber 10 is 1150-1280°C; then the cast strip is sent to the hot rolling mill 13 through the swinging guide plate 9, the pinch roll 12, and the roller table 15.
  • the gas atomization rapid cooling device 14 is used to cool the hot rolled strip steel in a gas atomization cooling manner to improve the temperature uniformity of the strip steel.
  • the cutting head falls into the flying shear pit 18 along the flying shear guide plate 17, and the hot-rolled strip after the cutting head enters the Carrousel coiler 19 for coiling. After the steel coil is removed from the coiler, it is naturally cooled to room temperature.
  • the user performs cutting and mechanical processing according to the size of the final product, and finally applies a quenching and tempering heat treatment: 840-880°C oil quenching, 400-440°C tempering, adjustment
  • the hardness of the material obtained after the quality heat treatment is within the range of HRC35 ⁇ 2, which ensures the required hardness distribution of the material, and can reduce the deformation of the sheet, and meets and exceeds the performance requirements of the thin-gauge 30CrMo traditional hot-rolled steel.
  • the chemical composition of the embodiment of the present invention is shown in Table 1, and its composition balance is Fe and other unavoidable impurities.
  • the process parameters are shown in Table 2, and the mechanical properties of the finally obtained hot-rolled strip are shown in Table 3.
  • the present invention utilizes thin strip continuous casting technology and makes full use of scrap steel.
  • the 30CrMo hot-rolled steel plate/strip manufactured according to the steel grade composition design range provided by the present invention has a tensile strength of less than 900MPa and a hardness of less than HRC25. , It can be coiled smoothly, and for downstream manufacturing users, it is easy to carry out various cutting and machining.
  • the thin-gauge 30CrMo hot-rolled steel plate/strip produced by the method of the present invention has uniform structure and performance, no internal shrinkage/shrinkage, less decarburization layer, good hardenability, good machinability and machinability, and is a mechanical It is an ideal material for thin-gauge steel in manufacturing, petrochemical, boiler manufacturing, and saw blade die industry.
  • Table 1 The chemical composition of the example steel (wt.%)
  • Example 1 0.24 0.34 1.45 0.018 0.005 0.0087 0.0093 0.0009 1.25 0.23 0.36
  • Example 2 0.26 0.15 0.95 0.023 0.003 0.0073 0.0110 0.0006 1.13 0.21
  • Example 3 0.28 0.10 1.38 0.005 0.004 0.0066 0.0150 0.0004 1.05 0.19 0.10 0.013
  • Example 4 0.30 0.27 1.20 0.016 0.004 0.0055 0.0130 0.0008 1.14 0.28 0.26 0.040
  • Example 5 0.32 0.48 0.66 0.008 0.002 0.0054 0.0120 0.0007 0.93 0.18 0.48
  • Example 6 0.28 0.46 0.69 0.015 0.002 0.0048 0.0070 0.0008 0.86 0.15 0.55
  • Example 7 0.27 0.19 0.86 0.016 0.003 0.0040 0.0100 0.0005 1.02 0.10 0.12 0.025
  • Example 8 0.26 0.36 1.10 0.027 0.004 0.0100 0.0085 0.0006
  • the chemical composition of the B-containing steel examples of the present invention is shown in Table 3, and the composition balance is Fe and unavoidable impurities.
  • the process parameters are shown in Table 4, and the mechanical properties of the finally obtained hot-rolled strip are shown in Table 5.
  • the 30CrMo hot-rolled steel plate/strip manufactured by the thin strip continuous casting process technology according to the steel grade composition design range provided by the present invention has a tensile strength of less than 900 MPa and a hardness of less than HRC 25, which can be successfully coiled and has a downstream effect. For manufacturing users, it is easy to perform various cutting and machining processes.
  • the user performs cutting and mechanical processing according to the size of the final product, and finally applies a quenching and tempering heat treatment: 840-880°C oil quenching, 400-440°C tempering, adjustment
  • the hardness of the material obtained after the quality heat treatment is within the range of HRC35 ⁇ 2, which ensures the required hardness distribution of the material, and can reduce the deformation of the sheet, and meets and exceeds the performance requirements of the thin-gauge 30CrMo traditional hot-rolled steel.
  • the thin-gauge 30CrMo hot-rolled steel plate/strip produced by the method of the present invention has uniform structure and performance, no internal shrinkage/shrinkage, less decarburization layer, good hardenability, good machinability and machinability, and is a mechanical It is an ideal material for thin-gauge steel in manufacturing, petrochemical, boiler manufacturing, and saw blade die industry.
  • the invention can also realize the "one-fire material" of the thin-gauge 30CrMo hot-rolled steel plate/strip, the production cost is greatly reduced, and it is a low-carbon, green and environment-friendly product.
  • Example C Si Mn P S N O Als Cr Mo Cu Sn B 15 0.28 0.25 1.35 0.008 0.005 0.0077 0.0093 0.0009 1.15 0.20 0.37

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Abstract

一种30CrMo热轧钢板/带及其生产方法，其成分重量百分比为：C 0.24-0.34％，Si 0.1-0.5％，Mn 0.6-1.5％，P≤0.03％，S≤0.007％，Cr 0.80-1.50％，Mo 0.10-0.30％，N 0.004-0.010％，任选的B：0.001-0.006％，Als<0.001％，总氧[O] T：0.007-0.020％，含有Cu 0.10-0.60％和Sn 0.005-0.04％中一种或两种元素；Mn/S≥250；余Fe和不可避免杂质。本发明充分利用废钢中残余的Sn、Cu等元素进行冶炼，并选择地添加Mo、Cr、N等元素；控制渣的碱度、钢中夹杂物类型及熔点、钢水中的游离氧含量、酸溶铝Als含量；采用双辊薄带连铸工艺获得铸带，再在线热轧至带钢。本发明实现了薄规格30CrMo热轧钢板/带的"一火成材"，生产效率大大提高，生产成本大为降低。

Description

30CrMo热轧钢板/带及其生产方法 技术领域
本发明属于连铸工艺，具体涉及30CrMo热轧钢板/带及其生产方法。
背景技术
在传统钢铁生产流程中，锡(Sn)、铜(Cu)是钢中典型的残余元素或有害元素，炼钢过程中要充分地去除Sn、Cu非常困难而且也是非常昂贵，一旦钢中含有Sn、Cu，基本是无法彻底消除的，只能通过稀释钢水来降低Sn、Cu的含量，这些都造成钢铁产品冶炼成本的升高。
近年来，由于废钢的连续循环利用，废钢资源越来越多，电价也持续降低，国内基于废钢的短流程电炉炼钢日益兴起，导致钢中的Sn、Cu等残余元素的含量逐渐升高，钢中的Sn、Cu是易偏析元素，容易富集在晶界导致裂纹等缺陷发生，因此在传统的工艺中Sn、Cu元素的含量是被严格控制的，在普通结构用钢中，对Sn、Cu的含量均有明确的要求：Sn(wt％)≤0.005％；Cu(wt％)≤0.2％。
因此，如果能对钢(特别是废钢)中Sn、Cu等残余元素做到合理利用，“化害为利”，将对整个冶金界产生积极的影响；可以实现对现有废钢或低品质劣质矿资源(高锡矿、高铜矿)的有效利用，促进钢的循环利用，降低生产成本，实现钢铁业可持续发展。
传统的薄带钢大都是由厚达200-250mm的铸坯经过多道次连续轧制生产出来的，传统热轧工艺流程是：连铸+铸坯再加热保温+粗轧+精轧+冷却+卷取，即首先通过连铸得到厚度为200mm左右的铸坯，对铸坯进行再加热并保温后，再进行粗轧和精轧，得到厚度一般大于2mm的钢带，最后对钢带进行层流冷却和卷取，完成整个热轧生产过程。如果要生产厚度小于2.0mm(含)的钢带，则难度相对较大，通常要对热轧钢带进行后续冷轧以及退火来完成。且工艺流程长、能耗高、机组设备多、基建成本高，导致生产成本较高。
薄板坯连铸连轧工艺流程是：连铸+铸坯保温均热+热连轧+冷却+卷取。该 工艺与传统工艺的主要区别是：薄板坯工艺的铸坯厚度大大减薄，为50-120mm，由于铸坯薄，铸坯只要经过1～2道次粗轧(铸坯厚度为70-90mm时)或者不需要经过粗轧(铸坯厚度为50mm时)，而传统工艺的连铸坯要经过反复多道次轧制，才能减薄到精轧前所需规格；而且薄板坯工艺的铸坯不经冷却，直接进入均热炉进行均热保温，或者少量补温，因此薄板坯工艺大大缩短了工艺流程，降低了能耗，减少了投资，从而降低了生产成本。但薄板坯连铸连轧由于较快的冷速会导致钢材强度提高，屈强比提高，从而增加轧制载荷，使得可经济地生产热轧产品的厚度规格也不可能太薄，一般为≥1.5mm，参见中国专利申请号CN 200610123458.1，CN 200610035800.2以及CN 200710031548.2。
近年来兴起的一种全无头薄板坯连铸连轧工艺(简称：ESP)，是在上述半无头薄板坯连铸连轧工艺的基础上发展起来的一种改进工艺，ESP实现了板坯连铸的无头轧制，取消了板坯火焰切割和起保温均热、板坯过渡作用的加热炉，整条产线长度大大缩短到190米左右。连铸机连铸出来的板坯厚度在90-110mm，宽度在1100-1600mm，连铸出来的板坯通过一段感应加热辊道对板坯起到保温均热的作用，然后再依次进入粗轧、精轧、层冷、卷取工序得到热轧板。这种工艺由于实现了无头轧制，可以得到最薄0.8mm厚度的热轧板，拓展了热轧板的规格范围，再加上其单条产线产量可达220万t/年规模。目前该工艺得到了快速发展和推广，目前世界上已有多条ESP产线在运营生产。
比薄板坯连铸连轧更短的工艺流程是薄带连铸连轧工艺，薄带连铸技术是冶金及材料研究领域内的一项前沿技术，它的出现为钢铁工业带来一场革命，它改变了传统治金工业中钢带的生产过程，将连续铸造、轧制、甚至热处理等整合为一体，使生产的薄带坯经过一道次在线热轧就一次性形成薄钢带，实现薄钢带产品的“一火成材”，大大简化了生产工序，缩短了生产周期，其工艺线长度仅50m左右；设备投资也相应减少，产品成本显著降低，是一种低碳环保的热轧薄带生产工艺。双辊薄带连铸工艺是薄带连铸工艺的一种主要形式，也是世界上唯一实现产业化的一种薄带连铸工艺。
双辊薄带连铸典型的工艺流程如图1所示，大包1中的熔融钢水通过大包长水口2、中间包3、浸入式水口4以及布流器5直接浇注在一个由两个相对转动并能够快速冷却的结晶辊8a、8b和侧封装置6a、6b围成的熔池7中，钢水在结晶辊8a、 8b旋转的周向表面凝固形成凝固壳并逐渐生长，进而在两结晶辊辊缝隙最小处(nip点)形成2-5mm厚的铸带11，铸带经由导板9导向夹送辊12送入轧机13中轧制成0.7-2.5mm的薄带，随后经过冷却装置14冷却，经飞剪装置16切头后，最后送入卷取机19卷取成卷。
30CrMo合金钢具有较高的强度和韧性，淬透性好，在淬火低温回火后、淬火高温回火后都具有优异的综合力学性能等优点。该钢种经调质后，在低于550℃以下具有较高的强度，而且低温韧性好，并且无回火脆性，焊接性能和可切削性可加工性良好。30CrMo广泛应用于机械制造、石油化工、锅炉制造业以及锯片刀模行业等，据市场统计，薄规格的30CrMo市场用量在10-15万t/年，市场用量和未来潜力巨大。30CrMo钢中Cr、Mo元素的合理配合，使钢具有良好的常温和高温性能，在获得致密组织、高强度的同时而不显著降低塑性，同时，还提高了钢的淬透性，增加回火时的稳定性，消除回火脆性与高温时晶粒长大的倾向。
目前，30CrMo钢板/带的主流生产工艺流程为：转炉/电炉—精炼—常规厚板坯连铸—步进式加热炉—粗轧—多机架精轧—层流冷却—卷取。这种传统的生产流程生产出来的30CrMo钢板/带，主要存在以下问题：(1)成分偏析和内部疏松：由于钢中合金含量较高，厚板坯连铸时的拉速较低，钢水凝固缓慢，容易造成板坯内部严重的成分偏析和内部疏松，最终导致产品质量性能不均匀；(2)表面脱碳：因钢中含碳量较高，采用步进式加热炉加热板坯，加热时间长，温度高，会导致铸坯表面脱碳严重，直接影响产品的表面硬度、耐磨性和热稳定性；(3)铸坯表面和边部裂纹严重：30CrMo的液相线温度较低，厚板坯连铸速度慢，导致铸坯温度低，进入高温脆性区后容易在铸坯表面和边部产生裂纹，直接影响产品质量。
薄规格30CrMo热轧钢板/带产品规格特征厚度1.5-3.0mm，由于产品厚度较薄，假如采用上述传统的连铸+热连轧产线进行生产将更加困难。即使采用薄板坯连铸连轧生产，由于板坯厚度也要达到70-120mm，在铸坯尺寸厚度上与传统厚板坯连铸(铸坯厚度200-250mm)没有出现数量级、本质上的差异，因此无法从根本上解决元素偏析问题；同时，连铸出来的板坯仍然要经过隧道式加热炉或电磁感应加热段，材料表面脱碳问题也无法完全消除；此外轧制较薄的规格，会导致轧辊的辊耗也较大。因此，采用传统的厚板坯连铸还是薄板坯连铸生产工艺流程，都无法完全解决30CrMo钢生产出现的问题，而且生产出来的薄规格30CrMo热轧钢板/带的生 产成本也会非常高。
另外，还需说明的是，热轧带钢作为薄规格热轧板产品使用时，对带钢表面质量要求很高。一般要求带钢表面氧化皮的厚度越薄越好，这就需要在铸带后续的各个阶段控制氧化铁皮的生成，如在薄带连铸工艺中，在结晶辊直至轧机入口均采用密闭室装置防止铸带氧化，在密闭室装置内如美国专利US6920912添加氢气以及在美国专利US20060182989中控制氧气含量小于5％，均可以控制铸带表面的氧化皮厚度。但是在轧机至卷取这段输送过程如何控制氧化皮的厚度很少有关专利涉及，尤其是在采用层流冷却或喷淋冷却对带钢进行冷却的过程中，高温的带钢与冷却水接触，铸带表面的氧化皮厚度增长很快。同时，高温的带钢与冷却水接触还会带来很多问题：其一，会在带钢表面形成水斑(锈斑)，影响表面质量；其二，层流冷却或喷淋冷却用的冷却水容易造成带钢表面局部冷却不均匀，造成带钢内部微观组织的不均匀，从而造成带钢性能的不均匀，影响产品质量；其三，带钢表面局部冷却不均匀，会造成板形的恶化，影响板形质量。
诚然，薄带连铸由于其本身的快速凝固工艺特性，生产出来的产品会普遍存在组织不均匀、延伸率偏低、性能不均匀等问题，这是由于铸带内部的奥氏体晶粒具有明显的不均匀性，会导致奥氏体相变后所获得的最终产品组织也不均匀，从而导致产品的性能特别是延伸率和成形性能不稳定；同时，薄带连铸在生产较高碳含量的钢种时，由于凝固收缩，钢液来不及补缩，容易在铸带中心区域附近出现内部缩松/缩孔问题。
因此，采用薄带连铸工艺来生产薄规格30CrMo热轧钢板/带产品，同样具有一定难度和挑战，需要在成分和工艺上有突破。
发明内容
本发明的目的在于提供一种30CrMo热轧钢板/带及其生产方法，通过添加适量的N元素，配合合理的在线热轧工艺以及轧后冷却措施，有效改善组织均匀性，解决内部缩松缩孔问题，提高产品质量和性能，实现薄规格30CrMo热轧钢板/带的“一火成材”。本发明生产的薄规格30CrMo热轧钢板/带是机械制造、石油化工、锅炉制造业以及锯片刀模行业薄规格用钢领域的理想用材。
为达到上述目的，本发明的技术方案是：
本发明充分利用废钢中残余的Sn、Cu等元素进行钢水的冶炼，并在钢中有选择地添加Mo、Cr等微合金元素和B、N等元素；冶炼过程中通过控制渣的碱度、钢中夹杂物类型及熔点、钢水中的游离氧含量、酸溶铝Als含量；然后进行双辊薄带连铸浇铸出2.0-5.0mm厚的铸带，铸带出结晶辊后直接进入到一个有非氧化性气氛的下密闭室中，并在密闭情况下进入到在线轧机进行热轧至1.5-3.0mm厚的带钢；轧制后采用气雾化冷却方式对带钢进行冷却，气雾化冷却方式可以有效减小带钢表面氧化皮厚度，改善带钢温度均匀性，提高带钢性能均匀性和表面质量。采用本发明所述方法生产的薄规格30CrMo热轧钢板/带，组织性能均匀、内部无缩松/缩孔、脱碳层少、淬透性好、可切削性及可加工性好；本发明制造方法实现了薄规格30CrMo热轧钢板/带的“一火成材”，生产效率大大提高，生产成本大大降低，是一种低碳、绿色环保产品。
具体的，本发明所述的30CrMo热轧钢板/带，其成分重量百分比为：C：0.24-0.34％，Si：0.1-0.5％，Mn：0.6-1.5％，P≤0.03％，S≤0.007％，Cr：0.80-1.50％，Mo：0.10-0.30％，N：0.004-0.010％，Als：<0.001％，任选的B：0.001-0.006％，总氧[O] T：0.007-0.020％；余量为Fe和不可避免杂质，且同时满足：
含有Cu：0.10-0.60％和Sn：0.005-0.04％中的一种或两种元素；
Mn/S≥250。
本发明所述30CrMo热轧钢板/带的显微组织为针状铁素体(AF)+块状铁素体(PF)+珠光体(P)，其中，AF的比例：60-80％，PF的比例：10-25％，P的比例：5-20％，存在适当比例的P，有利于30CrMo产品后续的可加工性能，同时由于薄带连铸工艺特征，组织中存在较大比例的AF，有利于提高30CrMo产品的综合性能。
本发明所述热轧钢板/带的抗拉强度≤900MPa，硬度≤HRC25。在一些实施方案中，本发明所述30CrMo热轧钢板/带的抗拉强度为780-900MPa，屈服强度为590-750MPa，延伸率为11-23％，屈强比为0.75-0.83。
在一些实施方案中，本发明所述的30CrMo热轧钢板/带，其成分重量百分比为：C：0.24-0.34％，Si：0.1-0.5％，Mn：0.6-1.5％，P≤0.03％，S≤0.007％，Cr：0.80-1.50％，Mo：0.10-0.30％，N：0.004-0.010％，Als：<0.001％，B：0.001-0.006％，总氧[O] T：0.007-0.020％；余量为Fe和不可避免杂质，且同时满足：含有Cu：0.10-0.60％和 Sn：0.005-0.04％中的一种或两种元素，Mn/S≥250。优选地，该30CrMo热轧钢板/带的显微组织为针状铁素体(AF)+块状铁素体(PF)+珠光体(P)，其中AF的比例：60-80％，PF的比例：10-25％，P的比例：5-20％。
在一些实施方案中，本发明所述的30CrMo热轧钢板/带，其成分重量百分比为：C：0.24-0.34％，Si：0.1-0.5％，Mn：0.6-1.5％，P≤0.03％，S≤0.007％，Cr：0.80-1.50％，Mo：0.10-0.30％，N：0.004-0.010％，Als：<0.001％，总氧[O] T：0.007-0.020％；余量为Fe和不可避免杂质，且同时满足：含有Cu：0.10-0.60％和Sn：0.005-0.04％中的一种或两种元素，和Mn/S≥250。
优选地，本发明所述的30CrMo热轧钢板/带中，Mn/S＞250。
在本发明所述30CrMo热轧钢板/带的成分设计中：C：C是钢中最经济、最基本的强化元素，通过固溶强化和析出强化来提高钢的强度，是保证淬火硬度和淬透性的重要元素。C是奥氏体转变过程中析出渗碳体必不可少的元素，因此C含量的高低在很大程度上决定钢的强度级别，即较高的C含量对应较高的强度级别。但是，C含量不能过高，太高会导致轧制时变形抗力高，调质热处理后韧性降低，还会影响焊接性能。同时，对常规板坯连铸来说，在包晶反应区浇铸易产生铸坯表面裂纹，严重时会发生漏钢事故。对薄带连铸来说也同样如此，在包晶反应区浇铸铸带坯易发生表面裂纹，严重时会发生断带。因此，Fe-C合金的薄带连铸同样需要避开包晶反应区。故本发明采用的C含量范围是0.24-0.34％。
Si：Si在钢中起固溶强化作用，且钢中加Si能协助脱氧形成硅酸盐，有助于改善切削加工性能，同时能提高钢质纯净度，但Si含量过高会影响可焊性和增加钢的脆性。故本发明采用的Si含量范围是0.1-0.5％。
Mn：Mn是价格最便宜的合金元素之一，它能提高钢的淬透性和淬火硬度，在钢中具有相当大的固溶度，通过固溶强化提高钢的强度，同时对钢的塑性和韧性基本无损害，是提高钢的强度最主要的强化元素，跟Si配合，还可以在钢中起到脱氧的作用。但Mn含量过高会导致铸带热应力和组织应力加大，容易断带。故本发明采用的Mn含量范围是0.6-1.5％。
P：高含量的P容易在晶界偏析，增加钢的冷脆性，使焊接性能变坏，降低塑性，使冷弯性能变坏。在薄带连铸工艺中，铸带的凝固和冷却速率极快，可有效抑制P的偏析，从而可有效避免P的劣势，充分发挥P的优势。故在本发明中，采用 较传统工艺生产时高的P含量，适当放宽P元素的含量，炼钢工序中取消脱磷工序，在实际操作中，不需要刻意进行脱磷工序，也不需要额外添加磷，P含量的范围≤0.03％。
S：在通常情况下S是钢中有害元素，使钢产生热脆性，降低钢的延展性和韧性，在轧制时造成裂纹。S还会降低焊接性能和耐腐蚀性。故在本发明中，S作为杂质元素来控制，其含量范围是≤0.007％；在一些实施方案中，S含量≤0.006％。且，Mn/S≥250。在一些实施方案中，Mn/S＞250。
Als：为控制钢中的夹杂物，本发明要求不能用Al脱氧，耐材的使用中，也应尽量避免Al的额外引入，严格控制酸溶铝Als的含量：<0.001％。
N：与C元素类似，N元素可通过间隙固溶提高钢的强度。在一些实施方案中，本发明要利用钢中的N跟B作用生成BN的析出相，需要钢中有一定的N含量。同时适量的N可以促进调质热处理过程中碳氮化物的析出，提高钢在切削、机械加工过程中的红硬性；但过高的N含量会损坏钢的韧性，也会增加铸带的脆性，降低可制造性。因此，本发明采用的N含量范围是0.004-0.010％。
Cr：不仅是提高钢的淬透性的元素，还可以有效提高钢的高温抗氧化性和抗蠕变性能，在薄规格30CrMo热轧钢中添加Cr，一是用于提高钢的淬透性、高温强度和蠕变强度，二是还有二次硬化作用，可提高钢的硬度和耐磨性能，不使钢变脆；Cr与废钢中的Cu配合还有提高钢的耐腐蚀性能的作用。但是其含量太高会导致轧制时变形抗力高，调质热处理后韧性降低，影响用户的切削加工，本发明中将Cr含量限定在0.80-1.50％。
Mo：Mo可以细化晶粒，提高强度和韧性。Mo一部分固溶于铁素体中，强化了铁素体基体，另一部分以碳化物弥散存在于钢中，因此含Mo钢同时具有固溶强化和碳化物弥散强化的作用。Mo由于高温下在铁素体中扩散速度较慢，因而还可显著提高钢的高温强度和回火稳定性。但过高的Mo会显著增加钢的原料冶炼成本。因此本发明中将Mo含量限定在0.10-0.30％。
Cu：在钢中主要起固溶和沉淀强化作用，Cu与Cr的共同作用，还可以提高30CrMo钢耐腐蚀性，使本发明钢适用于一些腐蚀性场合，而且耐候不容易生锈。值得说明的是，本发明利用废钢作为原料，冶炼时无需额外添加Cu。由于Cu是易偏析元素，传统工艺流程中一般对Cu含量有较严格的控制。运用薄带连铸的快速 凝固效应，本发明将Cu的上限提高到0.60％。Cu含量的提高，在一定意义上可以充分利用废钢，可以在废钢原料准备时不加筛选，提高冶炼作业率和降低成本，促进钢的循环利用，实现可持续发展的目的；还可实现劣质矿资源(如高铜矿)中铜的有效利用。在一些实施方案中，含有Cu时，其添加量可在0.1-0.6％的范围内。
Sn：也是废钢中的主要残余元素之一，它被公认为钢中的有害元素，因为Sn是易偏析元素，少量的Sn就会在晶界富集，导致是裂纹等缺陷发生，因此在传统的工艺中Sn元素的含量是被严格控制的。薄带连铸由于快速凝固的特点，元素在枝晶间的偏析大大减小，可以大大提高元素的固溶量，因此在薄带连铸工艺条件下，Sn元素的范围可以扩大，因此可以大大降低炼钢成本。图2是Sn元素与平均热流密度的关系。由图2可见，当Sn加入量小于0.04％时，对热流密度的影响不大，即对薄带凝固过程没有影响。图3是Sn含量与表面粗糙度的关系。因为铸带表面的裂纹通常都是在铸带表面凹凸不平的皱褶处产生，用表面粗糙度来表征表面裂纹发生情况。如果粗糙度大，则裂纹发生的概率高。由图3可知，Sn含量的增加，在快速凝固条件下并没有对铸带的表面质量产生不良的影响。由图2和图3的结果可知，Sn没有对铸带的凝固和表面质量产生不良影响。故在本发明中，对Sn含量的要求可进一步放宽，含有Sn时，设计Sn的含量范围在0.005-0.04％。
B：B在钢中的显著作用是：极微量的硼就可以使钢的淬透性成倍增加，B可以在高温奥氏体中优先析出粗大的BN颗粒从而抑制细小AlN的析出，减弱细小AlN对晶界的钉扎作用，提高晶粒的生长能力，从而粗化和均匀化奥氏体晶粒，有利于改善钢卷产品的可加工性能，利于后续用户进行切削或机械加工；另外B与N的结合可以有效防止晶界低熔点相B 2O 3的出现，从而避免热脆。
B是活泼易偏析元素，容易在晶界偏聚，传统工艺生产含B钢时，B含量一般控制的非常严格，一般在0.001-0.003％左右；而在薄带连铸工艺中，凝固和冷却速率较快，可有效抑制B的偏析，固溶更多的B含量，因此B的含量可以适当放宽；还可以通过合理的工艺控制生成粗大的BN颗粒，抑制细小的AlN析出，起到固氮的作用。还有研究表明，B在和Mo复合添加时，会得到更好的效果，会减小C原子的偏聚倾向，避免了晶界Fe23(C,B)6的析出，因此可以添加更多的B。故在本发明一些实施方案中，采用较传统工艺更高的B含量，范围是0.001-0.006％。
本发明所述的30CrMo热轧钢板/带的生产方法，其包括如下步骤：
1)冶炼、连铸
按所述成分进行冶炼，炼钢过程造渣的碱度a＝CaO/SiO 2(质量比)控制在a<1.5，优选a<1.2，或a＝0.7-1.0；钢水中低熔点的MnO-SiO 2-Al 2O 3三元夹杂物中的MnO/SiO 2(质量比)控制在0.5～2，优选为1～1.8；钢水中的自由氧[O] Free含量为：0.0005-0.005％；Mn/S＞250；
连铸采用双辊薄带连铸，形成2.0-5.0mm厚的铸带(优选地，在两结晶辊辊缝隙最小处形成该厚度的铸带；结晶辊直径为500-1500mm，优选辊径为800mm，结晶辊内部通水冷却；铸机的浇铸速度40-100m/min；控制大包开浇温度为1580-1610℃；连铸布流采用两级钢水分配布流***即中间包+布流器。
2)下密闭室保护
铸带出结晶辊后，铸带温度在1360-1430℃，直接进入到下密闭室内，下密闭室通非氧化性气体，下密闭室内的氧浓度控制在<5％，下密闭室出口铸带温度在1150-1280℃；
3)在线热轧
铸带在下密闭室内经夹送辊送至轧机，轧制成1.5-3.0mm厚度的带钢，轧制温度为1100-1250℃，热轧压下率为10-50％，优选地，热轧压下率为30-50％；
4)轧后冷却
对在线热轧后的带钢进行冷却，冷却采用气雾化冷却方式，气雾化冷却的冷却速率为10-100℃/s；
5)卷取
冷却后的热轧带钢进行卷取成卷，控制热轧带钢的卷取温度700～760℃。
进一步，还包括步骤6)调质热处理：840-880℃油淬，400-440℃回火。优选地，调质热处理前，钢板/带经过开平和剪切后，用户根据最终产品的尺寸进行切削加工和机械加工，最后再施以调质热处理。调质热处理可确保材料获得均匀的索氏体组织和硬度分布，并可减少片体的变形。调质热处理后可获得所需的材料硬度：HRC35±2。
优选的，步骤1)中，冶炼原料可选用100％全废钢，无需预筛选，钢水冶炼采用电炉炼钢，从而大大降低原料成本；或者，冶炼采用转炉炼钢，废钢按占冶炼原料20％以上的比例加入转炉，且无需预筛选，最大限度提高转炉废钢比，大大降 低冶炼成本和能耗；然后再进入LF炉、VD/VOD炉或RH炉精炼。
优选的，步骤2)中，所述非氧化性气体包括惰性气体、N 2、干冰升华得到的CO 2气体、以及N 2和H 2的混合气体。
优选的，步骤4)中，气雾化冷却的气水比为15：1～10：1，气压0.5～0.8MPa，水压1.0～1.5MPa。本文中，气水比指压缩空气和水的流量比，流量的单位为m 3/h。
优选的，步骤5)中，卷取采用双卷取机形式，或采用卡罗塞尔卷取形式。
优选的，步骤5)中，冷却后的热轧带钢经切头剪切除质量较差的头部后，直接进行卷取成卷，控制热轧带钢的卷取温度700～760℃。
在本发明所述钢的生产方法中：
为提高薄带连铸钢水的可浇铸性，炼钢过程造渣的碱度a＝CaO/SiO 2控制在a<1.5，优选a<1.2，或a＝0.7-1.0。
为提高薄带连铸钢水的可浇铸性，需要获得低熔点MnO-SiO 2-Al 2O 3三元夹杂物，如图4的阴影区域，MnO-SiO 2-Al 2O 3三元夹杂物中的MnO/SiO 2控制在0.5～2，优选为1～1.8。
为提高薄带连铸钢水的可浇铸性，钢中的氧(O)是形成氧化夹杂物的必要元素，本发明需要形成低熔点的MnO-SiO 2-Al 2O 3的三元夹杂物，要求钢水中的自由氧[O] Free范围为：0.0005-0.005％。
为提高薄带连铸钢水的可浇铸性，上述成分中，Mn和S的控制须满足如下关系式：Mn/S≥250。
本发明结晶辊直径在500-1500mm之间，优选800mm；结晶辊内部通水冷却。根据铸带厚度不同，铸机的浇铸速度范围介于40-100m/min。
本发明设计的30CrMo钢种液相线温度在1500℃左右，控制大包开浇温度范围1580-1610℃。
铸带出结晶辊后，铸带温度在1360-1430℃，直接进入到下密闭室内，下密闭室通非氧化性气体保护铸带，实现对铸带的防氧化保护，防氧化保护的气氛可以是N 2，也可以是Ar，也可以是其他非氧化性气体，比如干冰升华得到的CO 2气体、N 2和H 2的混合气体等，下密闭室内的氧浓度控制在<5％。下密闭室对铸带的防氧化保护到轧机13入口。下密闭室出口铸带的温度在1150-1280℃。
铸带在下密闭过程中涉及到的BN析出相的理论基础：
钢中硼与氮、铝和氮在γ-Fe中的热力学方程如下：
BN＝B+N；Log[B][N]＝-13970/T+5.24  (1)
AlN＝Al+N；Log[Al][N]＝-6770/T+1.03  (2)
如图5所示，钢中BN的开始析出温度在1280℃左右，980℃时BN的析出趋于平衡，而此时AlN的析出才刚刚开始(AlN的析出温度在980℃左右)，从热力学上讲，BN的析出要优先于AlN。本发明在下密闭室内完成B与N的结合，生成粗大的BN颗粒，从而抑制了细小的AlN析出，减弱细小AlN对晶界的钉扎作用，提高晶粒的生长能力，从而粗化奥氏体晶粒，使奥氏体晶粒更加均匀，有利于提高材料的切削性能和可加工性能；另外B与N的结合可以有效防止晶界低熔点相B 2O 3的出现。
铸带在下密闭室内经夹送辊送至轧机，轧制成1.5-3.0mm厚度的薄带材。轧制温度为1100-1250℃，较高的轧制温度可以有效解决传统工艺易出现的边裂问题。热轧压下率为10-50％，优选地，热轧压下率范围是30-50％，单机架较大的压下率可以完全解决因C含量较高引起的铸带中心区域附近的内部缩松/缩孔问题。
对在线热轧后的带钢进行轧后冷却，冷却采用气雾化冷却方式，气雾化冷却方式可以有效减小带钢表面氧化皮厚度，改善带钢温度均匀性，提高带钢性能和表面质量。气雾化冷却的气水比为15：1～10：1，气压0.5～0.8MPa，水压1.0～1.5MPa。气雾化后形成高压水雾喷射在钢带表面，一方面起到了降低钢带温度的作用，另一方面水雾会形成致密的气膜包覆在带钢表面，起到带钢防氧化的作用，从而有效控制了热轧带钢表面氧化皮的生长。该种冷却方式可以避免传统喷淋或者层流冷却带来的问题，使带钢表面温度均匀下降，提高带钢温度均匀性，从而达到均匀化内部微观组织的效果；同时冷却均匀，可以提高带钢的板形质量和性能稳定性；有效减少带钢表面的氧化皮厚度。气雾化冷却的冷却速率范围为10-100℃/s。
冷却后的热轧带钢经切头剪切除质量较差的头部后，直接进行卷取成卷。控制热轧带的卷取温度700～760℃。高的卷取温度可保证本发明钢获得尽可能低的抗拉强度(小于900MPa)和硬度(HRC25以下)，从而能够顺利卷取；对下游制造用户而言，也更容易进行各种切削和机械加工。
卷取采用双卷取机形式，也可以采用卡罗塞尔卷取形式，保证带钢的连续生产。优选地，卷取采用卡罗塞尔卷取形式，可以使产线长度更短，更紧凑。
本发明与现有技术对比：
本发明区别于现有薄带连铸技术最明显的一个特征就是结晶辊的辊径及其相对应的布流方式。EUROSTRIP技术特征就是Φ1500mm大辊径结晶辊，结晶辊大、熔池钢水容量大，布流容易，结晶辊制造及运维成本高。CASTRIP技术特征就是Φ500mm小辊径结晶辊，结晶辊小、熔池钢水容量小，布流非常困难，但铸机设备制造与运维成本低。CASTRIP为解决小熔池的均匀布流问题，采用三级钢水分配布流***(中间包+过渡包+布流器)。由于采用了三级布流***，会直接导致耐材成本增加；更为主要的是，三级布流***使钢水流动的路径变长，钢水的温降也较大，为了满足熔池钢液的温度，出钢温度需要大大提高。出钢温度的提高，会导致炼钢成本增加、能耗增加以及耐材寿命缩短等问题。
本发明结晶辊直径在500-1500mm优选800mm辊径的结晶辊，采用两级钢水分配布流***(中间包+布流器)。从布流器流出的钢水，沿辊面和两个端面形成不同的布流模式，且分两路流动，互不干扰。由于采用了两级布流***，相比三级布流***，耐材成本大幅度降低；钢水流动路径的缩短，使钢水温降减小，可以降低出钢温度，相比三级布流***，出钢温度可降低30-50℃。出钢温度的降低，可有效降低炼钢成本、节约能耗以及延长耐材寿命。本发明配合优选Φ800mm辊径的结晶辊，采用两级钢水分配布流***，既实现了钢水稳定布流的要求，又实现了结构简单、操作方便、加工成本低的目标。
中国专利公开号CN101773929B公开了一种生产30CrMo热轧钢板的方法，该方法基于薄板坯连铸连轧流程，主要包括：冶炼、精炼、薄板坯连铸、均热、高压水除鳞、热连轧、冷却、卷取等步骤。其成分为C：0.26-0.34％，Si：0.17-0.37％，Mn：0.40-0.70％，P：≤0.035％，S≤0.035％，Cr：0.80-1.10，Mo：0.15-0.25％，其余为Fe和不可避免杂质。该专利生产的30CrMo热轧钢板，具有组织性能均匀、热稳定性高、强度高的特点，质量也得到显著改善。该专利与本发明提出的30CrMo钢及生产方法，其本质区别是采用的生产工艺不一样，本发明采用双辊薄带连铸工艺，而且设计的成分也不一样，可以得到无偏析、无表面脱碳层、质量性能更优的产品。
中国专利公开号CN107419192A公开了一种30CrMo钢带及其生产方法，该发明也是基于薄板坯连铸连轧流程，主要包括：转炉冶炼、LF精炼、薄板坯连铸、 加热、热连轧和卷取工序。其成分为C：0.26-0.34％，Si：0.17-0.30％，Mn：0.40-0.70％，P：≤0.025％，S≤0.025％，Als≥0.010％，Cr：0.80-1.10％，Mo：0.15-0.25％，Ni≤0.30％，Cu≤0.30％，余量为Fe和不可避免杂质。该发明从全流程工艺角度出发，消除连铸坯的中心偏析、中心缩孔、降低表面脱碳，并可生产出2.5-4.0mm厚的热轧薄规格钢带，实现了30CrMo钢的低成本生产。该专利与本发明提出的30CrMo钢及生产方法，同样是在生产工艺上存在本质区别，本发明采用双辊薄带连铸工艺，更加简化了生产流程，而且设计的成分也不一样，可以得到无偏析、无表面脱碳层、质量性能更优的产品。
中国专利公开号CN100366779C公开了一种石材切割锯片钢及其制造方法，其化学成分重量百分比为C 0.45-0.60％、Si 0.1-0.6％、Mn 1.3-1.8％、P≤0.02％、S≤0.01％、V 0.05-0.20％、Cr 0.15-0.30％、N 0.005-0.020％、Ca 0-0.0050％、Al 0.005-0.040％，其余为Fe和不可避免杂质。该方法包括：冶炼、浇铸、连铸坯采用热装热送工艺，保证板坯进入加热前的温度在300℃以上，板坯加热温度1150℃以上，热轧时控制终轧温度在900℃以上，轧后空冷卷取，卷取温度在700℃以上。该发明钢淬透性高，特别适用于制造直径1000mm以上的石材切割用锯片。该专利与本发明涉及的钢种不同，该专利的含碳量在0.45-0.60％，本发明含碳量在0.24-0.34％，而且生产工艺上存在本质区别，本发明采用双辊薄带连铸工艺，更加简化了生产流程。
中国专利公开号CN102345071B公开了一种合金用结构钢30CrMo加B钢板及其生产方法，该板包含如下质量百分比的化学成分：C：0.28-0.33％、Si：0.20-0.35％、Mn：0.60-0.80％、P：≤0.018％、S：≤0.005％、Cr：0.90-1.10％、Mo：0.15-0.25％、Als：0.20-0.40％、B：0.0008-0.0015％，其余为Fe和残留元素。采取的生产方法包括：转炉炼钢、LF精炼、真空精炼、浇注、铸坯/钢锭加热、轧制、缓冷、热处理，成功开发出≤100mm高强30CrMo加B钢，实物机械性能：屈服强度、抗拉强度、高温回火布氏硬度均高于普通30CrMo钢。该发明虽然也添加了微量B，但由于采用的是最传统最落后的模铸工艺，凝固速度非常慢，B很容易偏析，而且容易在晶界出现低熔点的B 2O 3相导致热裂纹，因此B的加入量非常低，仅0.0008-0.0015％，效果甚微。此外，在实施例中看出生产的产品厚度规格也较厚，在50mm、100mm的厚度。本发明采用先进的双辊薄带连铸工艺，直接生产出1.5-3.0mm的钢板/带，B的加入量可达到0.006％，质量性能更加优异，与该专利在成分和生产方法上均 有所差别。
本发明的主要优点：
本发明利用薄带连铸技术生产含锡(Sn)、铜(Cu)/含锡(Sn)、铜(Cu)、氮(N)和任选的硼(B)的薄规格30CrMo热轧钢，迄今为止尚未见报导，归纳优点如下：
1.本发明省去了板坯加热、多道次反复热轧等复杂过程，通过双辊薄带连铸+一道次在线热轧工序，生产流程更短、效率更高，产线投资成本和生产成本大幅降低。
2.本发明省去了传统工艺生产中诸多复杂的中间步骤，与传统生产工艺相比，生产的能耗和CO 2排放大幅度降低，是一种绿色环保的产品。
3.本发明采用薄带连铸工艺生产薄规格30CrMo热轧钢，由于工艺本身的先进性，可完全解决传统工艺中存在的表面脱碳、元素偏析以及边裂等问题。
薄带连铸的速度达到80-150m/min，钢水的凝固速度达到10 2-10 4℃/s，连铸出来的厚度仅有2-5mm，30CrMo钢中的合金元素在很短的时间(0.1-0.2s)内来不及偏析就完全凝固了，这种快速凝固效应有效消除了元素的偏析问题；
由于拉速较快，连铸出来的带钢很快进入带有保护气氛的下密闭室，然后直接进入在线热轧机进行热轧，全程保护浇铸和轧制使带钢表面几乎没有脱碳层；
由于高拉速，即使30CrMo钢液相线温度较低，连铸出来的带钢温度也较高，进入轧机的轧制温度也相应较高，有效避开了带钢进入高温脆性区进行轧制，有效避免了带钢表面和边部裂纹的发生；
薄带连铸连轧工艺将传统的连铸、加热、热连轧等独立的工序有机地集合在一起，生产周期大大缩短、生产效率大大提高、能耗大大降低、产品质量和性能大幅度提升。
4.本发明采用添加微量的N元素，可促进发明钢在调质热处理过程中碳氮化物的析出，有效提高30CrMo钢在切削、机械加工过程中的红硬性，有益于延长最终产品的使用寿命。
5.本发明在采用电炉炼钢时，原料上100％充分利用废钢，不加筛选，利用含Cu、Sn的废钢，结合薄带连铸的亚快速凝固效应，起到残余元素合金化的作用，大大降低冶炼成本，对钢中的Cu、Sn做到“化害为利”，实现对现有废钢或低品质 劣质矿资源(高锡矿、高铜矿)的充分利用，促进废钢的循环利用，降低生产成本，实现钢铁业可持续发展。
本发明冶炼采用电炉炼钢，冶炼的原料可以从真正意义上实现100％全废钢冶炼，无需进行预筛选，大大降低原料成本；如果冶炼采用转炉炼钢，废钢按占冶炼原料20％以上的比例加入转炉，且无需预筛选，最大限度提高转炉废钢比，大大降低冶炼成本和能耗。
6.本发明采用轧后带钢气雾化冷却方式，可以避免传统喷淋或者层流冷却带来的问题，使带钢表面温度均匀下降，提高带钢温度均匀性，从而达到均匀化内部微观组织的效果；同时冷却均匀，可以提高带钢的板形质量和性能稳定性；有效减少带钢表面的氧化皮厚度。
7.传统工艺板坯冷却过程中发生合金元素析出，板坯再加热时往往会由于合金元素回溶不充分而降低合金元素利用率。本发明薄带连铸工艺中，高温铸带直接热轧，所添加的合金元素主要以固溶态存在，可提高合金利用率。
8.本发明选用热轧钢带卡罗塞尔卷取机，有效缩短产线长度；同时同位卷取可以大大提高卷取温度的控制精度，提高产品性能的稳定性。
附图说明
图1为双辊薄带连铸工艺的工艺布置示意图；
图2为Sn含量与平均热流密度的关系示意图；
图3为Sn含量与铸带表面粗糙度的关系示意图；
图4为MnO-SiO 2-Al 2O 3三元相图(阴影区域：低熔点区)；
图5为BN，AlN析出的热力学曲线示意图。
具体实施方式
下面用实施例对本发明作进一步阐述，但这些实施例绝非对本发明有任何限制。本领域技术人员在本说明书的启示下对本发明实施中所作的任何变动都将落在本发明权利要求保护范围内。
参见图1，将符合本发明化学成分设计的钢水经大包1，通过大包长水口2、中间包3、浸入式水口4以及布流器5直接浇注在一个由两个相对转动并能够快速 冷却的结晶辊8a、8b和侧封板装置6a、6b围成的熔池7中，钢水在结晶辊8a、8b旋转的周向表面凝固，进而形成凝固壳并逐渐生长随后在两结晶辊辊缝隙最小处(nip点)形成2.0-5.0mm厚的铸带11；在铸带11出结晶辊8a、8b后，铸带温度在1360-1430℃，直接进入到下密闭室10内，下密闭室10通惰性气体保护带钢，实现对带钢的防氧化保护，防氧化保护的气氛可以是N 2，也可以是Ar，也可以是其他非氧化性气体，比如N 2和H 2的混合气、干冰升华得到的CO 2气体等，下密闭室10内的氧浓度控制在<5％。下密闭室10对铸带11的防氧化保护到轧机13入口。下密闭室10出口铸带的温度在1150-1280℃；然后通过摆动导板9、夹送辊12、辊道15将铸带送至热轧机13，热轧后形成1.5-3.0mm的热轧带钢，使用气雾化快速冷却装置14以气雾化冷却方式对热轧带钢进行冷却，改善带钢温度均匀性。经飞剪装置16切头之后，切头沿着飞剪导板17掉入飞剪坑18中，切头后的热轧带进入卡罗塞尔卷取机19进行卷取。将钢卷从卷取机上取下后，自然冷却至室温。
进一步，生产的钢板/带经过开平和剪切后，用户根据最终产品的尺寸进行切削加工和机械加工，最后再施以调质热处理：840-880℃油淬，400-440℃回火，调质热处理后获得的材料硬度均在HRC35±2范围内，确保了材料所需的硬度分布，并可减少片体的变形，达到并且超过了薄规格30CrMo传统热轧钢的性能要求。
本发明实施例化学成分如表1所示，其成分余量Fe和其他不可避免杂质。经本发明的制造方法，工艺参数见表2，最终获得热轧带的力学性能见表3。
综上所述，本发明利用薄带连铸工艺技术，充分使用了废钢，按本发明提供的钢种成分设计范围制造的30CrMo热轧钢板/带，抗拉强度均小于900MPa，硬度在HRC25以下，能够顺利卷取，对下游制造用户而言，容易进行各种切削和机械加工。
采用本发明所述方法生产的薄规格30CrMo热轧钢板/带，组织性能均匀、内部无缩松/缩孔、脱碳层少、淬透性好、可切削性及可加工性好，是机械制造、石油化工、锅炉制造业以及锯片刀模行业薄规格用钢领域的理想用材。
表1：实施例钢的化学成分(wt.％)
  C Si Mn P S N O Als Cr Mo Cu Sn
实施例1 0.24 0.34 1.45 0.018 0.005 0.0087 0.0093 0.0009 1.25 0.23 0.36  
实施例2 0.26 0.15 0.95 0.023 0.003 0.0073 0.0110 0.0006 1.13 0.21   0.005
实施例3 0.28 0.10 1.38 0.005 0.004 0.0066 0.0150 0.0004 1.05 0.19 0.10 0.013
实施例4 0.30 0.27 1.20 0.016 0.004 0.0055 0.0130 0.0008 1.14 0.28 0.26 0.040
实施例5 0.32 0.48 0.66 0.008 0.002 0.0054 0.0120 0.0007 0.93 0.18 0.48  
实施例6 0.28 0.46 0.69 0.015 0.002 0.0048 0.0070 0.0008 0.86 0.15 0.55  
实施例7 0.27 0.19 0.86 0.016 0.003 0.0040 0.0100 0.0005 1.02 0.10 0.12 0.025
实施例8 0.26 0.36 1.10 0.027 0.004 0.0100 0.0085 0.0006 1.13 0.26 0.60  
实施例9 0.25 0.38 0.88 0.028 0.0035 0.0048 0.0200 0.0003 1.26 0.30 0.35 0.038
实施例10 0.29 0.48 0.60 0.030 0.001 0.0095 0.0125 0.0004 1.50 0.27   0.016
实施例11 0.30 0.50 0.75 0.010 0.002 0.0083 0.0090 0.0005 1.47 0.28 0.53  
实施例12 0.32 0.28 1.50 0.022 0.006 0.0078 0.0118 0.0003 0.80 0.21 0.38 0.018
实施例13 0.29 0.47 1.39 0.018 0.004 0.0057 0.0132 0.0006 1.42 0.26   0.027
实施例14 0.28 0.29 1.46 0.016 0.003 0.0068 0.0075 0.0005 0.98 0.19 0.27  
表2：实施例的工艺参数
Figure PCTCN2020115286-appb-000001
Figure PCTCN2020115286-appb-000002
表3：实施例钢的产品力学性能
Figure PCTCN2020115286-appb-000003
本发明含B的钢实施例化学成分如表3所示，其成分余量为Fe和不可避免杂 质。经本发明的制造方法，工艺参数见表4，最终获得热轧带的力学性能见表5。
由表5可知，利用薄带连铸工艺技术按本发明提供的钢种成分设计范围制造的30CrMo热轧钢板/带，抗拉强度均小于900MPa，硬度在HRC25以下，能够顺利卷取，对下游制造用户而言，容易进行各种切削和机械加工。进一步，生产的钢板/带经过开平和剪切后，用户根据最终产品的尺寸进行切削加工和机械加工，最后再施以调质热处理：840-880℃油淬，400-440℃回火，调质热处理后获得的材料硬度均在HRC35±2范围内，确保了材料所需的硬度分布，并可减少片体的变形，达到并且超过了薄规格30CrMo传统热轧钢的性能要求。
采用本发明所述方法生产的薄规格30CrMo热轧钢板/带，组织性能均匀、内部无缩松/缩孔、脱碳层少、淬透性好、可切削性及可加工性好，是机械制造、石油化工、锅炉制造业以及锯片刀模行业薄规格用钢领域的理想用材。本发明还可实现薄规格30CrMo热轧钢板/带的“一火成材”，生产成本大大降低，是一种低碳、绿色环保产品。
表3：实施例钢的化学成分(wt.％)
实施例 C Si Mn P S N O Als Cr Mo Cu Sn B
15 0.28 0.25 1.35 0.008 0.005 0.0077 0.0093 0.0009 1.15 0.20 0.37   0.003
16 0.24 0.10 0.90 0.013 0.003 0.0063 0.0110 0.0006 1.11 0.25   0.005 0.001
17 0.25 0.37 1.28 0.015 0.004 0.0056 0.0150 0.0004 1.02 0.18 0.10 0.023 0.004
18 0.32 0.28 1.10 0.013 0.004 0.0085 0.0130 0.0008 1.13 0.27 0.22 0.040 0.006
19 0.30 0.47 0.65 0.009 0.002 0.0054 0.0120 0.0007 0.90 0.17 0.45   0.003
20 0.26 0.45 0.67 0.012 0.002 0.0048 0.0070 0.0008 0.85 0.14 0.57   0.005
21 0.25 0.18 0.85 0.015 0.003 0.0040 0.0100 0.0005 1.00 0.10 0.16 0.035 0.003
22 0.27 0.37 1.00 0.024 0.004 0.0100 0.0085 0.0006 1.15 0.24 0.60   0.002
23 0.28 0.36 0.84 0.018 0.0035 0.0058 0.0200 0.0003 1.24 0.30 0.33 0.028 0.004
24 0.26 0.47 0.60 0.030 0.001 0.0075 0.0125 0.0004 1.50 0.24   0.015 0.006
25 0.30 0.50 0.65 0.010 0.002 0.0093 0.0090 0.0005 1.44 0.25 0.43   0.003
26 0.34 0.26 1.50 0.012 0.006 0.0088 0.0118 0.0003 0.80 0.22 0.33 0.013 0.002
27 0.28 0.44 1.37 0.008 0.004 0.0047 0.0132 0.0006 1.48 0.25   0.037 0.005
28 0.27 0.26 1.40 0.017 0.003 0.0066 0.0075 0.0005 0.94 0.18 0.25   0.004
表4：实施例的工艺参数
Figure PCTCN2020115286-appb-000004
表5：实施例钢的产品力学性能
Figure PCTCN2020115286-appb-000005
Figure PCTCN2020115286-appb-000006

Claims (13)

  1. 一种30CrMo热轧钢板/带，其成分重量百分比为：C：0.24-0.34％，Si：0.1-0.5％，Mn：0.6-1.5％，P≤0.03％，S≤0.007％，Cr：0.80-1.50％，Mo：0.10-0.30％，N：0.004-0.010％，任选的B：0.001-0.006％，Als：<0.001％，总氧[O] T：0.007-0.020％；余量为Fe和其他不可避免杂质，且须同时满足：
    含有Cu：0.10-0.60％和Sn：0.005-0.04％中的一种或两种元素；
    Mn/S≥250。
  2. 如权利要求1所述的30CrMo热轧钢板/带，其特征在于，所述热轧钢板/带的抗拉强度≤900MPa，硬度≤HRC25。
  3. 如权利要求1所述的30CrMo热轧钢板/带，其特征在于，所述热轧钢板/带的显微组织为针状铁素体+块状铁素体+珠光体。
  4. 如权利要求3所述的30CrMo热轧钢板/带，其特征在于，所述30CrMo热轧钢板/带的显微组织中针状铁素体的体积比为60-80％，块状铁素体的体积比为10-25％，珠光体的体积比为5-20％。
  5. 如权利要求1所述的30CrMo热轧钢板/带，其特征在于，所述30CrMo热轧钢板/带的厚度为1.5-3.0mm。
  6. 如权利要求1所述的30CrMo热轧钢板/带，其特征在于，所述30CrMo热轧钢板/带的抗拉强度为780-900MPa，屈服强度为590-750MPa，延伸率为11-23％，屈强比为0.75-0.83。
  7. 如权利要求1-6中任一项所述的30CrMo热轧钢板/带的生产方法，其特征是，包括如下步骤：
    1)冶炼、连铸
    按权利要求1所述成分进行冶炼，炼钢过程造渣的碱度a＝CaO/SiO 2控制在a<1.5，优选a<1.2，或a＝0.7-1.0；钢水中MnO-SiO 2-Al 2O 3三元夹杂物中的MnO/SiO 2控制在0.5～2，优选为1～1.8；钢水中的自由氧[O] Free范围为：0.0005-0.005％；
    连铸采用双辊薄带连铸，形成2.0-5.0mm厚的铸带；结晶辊直径为500-1500mm，优选为800mm，结晶辊内部通水冷却；浇铸速度40-100m/min；控制大包开浇温度范围1580-1610℃；连铸布流采用两级钢水分配布流***，即中间包+布流器；
    2)下密闭室保护
    铸带出结晶辊后，铸带温度在1360-1430℃，直接进入到下密闭室内，下密闭室内通非氧化性气体，下密闭室内的氧浓度控制在<5％，下密闭室出口铸带温度在1150-1280℃；
    3)在线热轧
    铸带在下密闭室内经夹送辊送至轧机，轧制成1.5-3.0mm厚度的钢带，轧制温度为1100-1250℃，热轧压下率为10-50％，优选地，热轧压下率为30-50％；
    4)轧后冷却
    对在线热轧后的钢带进行冷却，冷却采用气雾化冷却方式，气雾化冷却的冷却速率为10-100℃/s；
    5)卷取
    冷却后的热轧带钢进行卷取成卷，控制热轧带钢的卷取温度700～760℃。
  8. 如权利要求7所述的30CrMo热轧钢板/带的生产方法，其特征是，还包括步骤6)调质热处理：840-880℃油淬，400-440℃回火。
  9. 如权利要求7所述的利用废钢的30CrMo热轧钢板/带的生产方法，其特征是，步骤1)中，冶炼原料为100％全废钢，无需预筛选，钢水冶炼采用电炉炼钢；或者，冶炼采用转炉炼钢，废钢按占冶炼原料20％以上的比例加入转炉，且无需预筛选；然后再进入LF炉、VD/VOD炉或RH炉精炼。
  10. 如权利要求7所述的30CrMo热轧钢板/带的生产方法，其特征是，步骤2)中，所述非氧化性气体包括惰性气体、N 2、干冰升华得到的CO 2气体、和N 2和H 2的混合气体。
  11. 如权利要求7所述的30CrMo热轧钢板/带的生产方法，其特征是，步骤4)中，气雾化冷却的气水比为15：1～10：1，气压0.5～0.8MPa，水压1.0～1.5MPa。
  12. 如权利要求7所述的30CrMo热轧钢板/带的生产方法，其特征是，步骤5)中，卷取采用双卷取机形式，或采用卡罗塞尔卷取形式。
  13. 如权利要求7所述的30CrMo热轧钢板/带的生产方法，其特征是，步骤5)中，冷却后的热轧带钢经切头剪切除质量较差的头部后直接进行卷取成卷。
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