WO2022207009A1 - 中碳含硼钢及在线正火处理的控轧控冷方法 - Google Patents

中碳含硼钢及在线正火处理的控轧控冷方法 Download PDF

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WO2022207009A1
WO2022207009A1 PCT/CN2022/092305 CN2022092305W WO2022207009A1 WO 2022207009 A1 WO2022207009 A1 WO 2022207009A1 CN 2022092305 W CN2022092305 W CN 2022092305W WO 2022207009 A1 WO2022207009 A1 WO 2022207009A1
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cooling
rolling
containing steel
boron
controlled
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English (en)
French (fr)
Inventor
张念
郑文超
凌鑫
陈平
黄国飘
何英武
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Daye Special Steel Co Ltd
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Daye Special Steel Co Ltd
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Priority to JP2023569673A priority Critical patent/JP7561289B2/ja
Priority to EP22779189.4A priority patent/EP4339317A4/en
Priority to KR1020237038960A priority patent/KR102708478B1/ko
Priority to US18/560,168 priority patent/US12234537B2/en
Publication of WO2022207009A1 publication Critical patent/WO2022207009A1/zh
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    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
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    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
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    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
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    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/573—Continuous furnaces for strip or wire with cooling
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    • 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
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
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    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working

Definitions

  • the invention relates to the field of steel rolling, in particular to a medium-carbon boron-containing steel and a method for controlled rolling and controlled cooling for on-line normalizing treatment.
  • Medium carbon boron-containing steel is a kind of alloy structural steel with good hardenability. It is mostly used to manufacture important parts such as automobile constant speed transmission shafts. Due to the requirements of processing and use conditions, there are strict requirements for material structure and hardness.
  • the existing technology generally requires off-line normalizing of the steel to meet the structural hardness requirements of the steel.
  • the finished material used in the production application is small in size (20-50mm)
  • professional normalizing is required.
  • Off-line normalizing in the furnace is not only low in production efficiency, but also prone to mixed crystal problems.
  • the production cycle of offline normalizing treatment of steel is increased by about one week, and the corresponding production cost is increased by about 400 yuan/ton, which seriously restricts the mass production and application of this product.
  • the purpose of the present invention is to provide a medium-carbon boron-containing steel and a method for controlled rolling and controlled cooling for on-line normalizing treatment.
  • the medium-carbon boron-containing steel prepared by the method can significantly refine the hot-rolled microstructure of the medium-carbon boron-containing steel. , to meet the requirements of Brinell hardness 190-220HBW, grain size ⁇ 7, and band structure ⁇ 2, thereby replacing the original off-line normalizing process. At the same time, it saves the production cycle and reduces the normalizing cost, thereby reducing the production cost of the enterprise and improving the competitiveness of the product.
  • the present invention provides the following technical solutions:
  • a medium carbon boron-containing steel according to mass percentage, the chemical composition of the medium carbon boron-containing steel comprises: C 0.37-0.45%, Si 0.17-0.37%; Mn 0.60-0.90%; Al 0.020-0.060%; B 0.0008- 0.0035%; Ti 0.030-0.060%; P ⁇ 0.025%; S ⁇ 0.025%; Cr ⁇ 0.25%; Ni ⁇ 0.20%; Mo ⁇ 0.10%; Cu ⁇ 0.20%; the rest are Fe and inevitable impurities.
  • the medium carbon boron-containing steel satisfies the Brinell hardness of 190-220 HBW, the grain size is ⁇ 7 grades, and the banded structure is ⁇ 2 grades.
  • the specification of the medium carbon boron-containing steel is ⁇ 20-50mm.
  • the present invention also provides a method for controlled rolling and controlled cooling suitable for the above-mentioned on-line normalizing treatment of medium carbon and boron-containing steel, which sequentially includes the following steps: heating, rough rolling, finishing rolling, cooling through water penetration, and slow cooling in a cooling bed.
  • the heating temperature of the billet in the heating furnace is 1100-1200°C, and the total heating time is 90-1200°C. 180min; preferably, the heating temperature in the billet heating furnace is 1130-1180°C, and the total heating time is 120-150min.
  • the inlet temperature of the billet into the rough rolling mill is 1000-1050°C.
  • the inlet temperature of the billet entering the finishing rolling unit is 780-830 °C; preferably, the inlet temperature of the billet entering the finishing rolling unit is 780-810°C; preferably, in the finishing rolling step, the reducing and sizing finishing rolling unit is used for finishing rolling.
  • water cooling refers to spray cooling through a water tank, and after water cooling, the water temperature of the finished steel is 700- 750°C; preferably, the water volume of the water tank is 40-60L/min, and the traveling speed of the finished steel is 3-8m/s; preferably, after cooling through water, the water outlet temperature of the finished steel is 710-730°C.
  • the cooling rate of the finished steel is 0.10-0.15°C/S;
  • the finished steel in the step of slow cooling on the cooling bed, the finished steel enters the thermal insulation cover to be cooled on the cooling bed, and is cooled to 500° C.
  • the following is air cooling from the insulation cover.
  • the cooling bed in the above-mentioned controlled rolling and controlled cooling method suitable for on-line normalizing treatment of medium carbon and boron-containing steel, in the slow cooling step of the cooling bed, the cooling bed is a step-by-step cooling bed.
  • the cross-sectional size of the steel billet is 240 mm ⁇ 240 mm.
  • the medium carbon and boron-containing steel manufactured by this method can meet the requirements of hardness 190-220HBW, actual grain size ⁇ 7, and banded structure ⁇ 2, and fully meet the user's technology after offline normalizing of the product indicator requirements.
  • Fig. 1 is the microstructure diagram at the radius 1/2 of the 40B steel with a specification of 32mm produced in Example 1;
  • Fig. 2 is the microstructure diagram at the radius 1/2 place of 40B steel with a specification of 28mm produced in Example 2;
  • Fig. 3 is the microstructure diagram of the radius 1/2 of the 40B steel with a specification of 30mm produced in Comparative Example 1;
  • Fig. 4 is the microstructure diagram at the radius of 1/2 of the 40B steel with the specification of 34mm produced in Comparative Example 2;
  • FIG. 5 is a microstructure diagram of the radius 1/2 of the 40B steel with a specification of 28 mm produced in Comparative Example 3.
  • a medium carbon boron-containing steel is provided.
  • the chemical composition of the medium carbon boron-containing steel includes:
  • medium carbon boron-containing steel mainly uses manganese Mn and boron B as alloying elements, if chromium Cr, nickel Ni, molybdenum If the content of alloying elements such as Mo or copper and Cu is too high, it is easy to form bainite and other structures after controlled rolling and controlled cooling, resulting in too high hardness.
  • the specification of the medium carbon boron-containing steel is ⁇ 20-50mm; the medium carbon boron-containing steel meets the Brinell hardness of 190-220HBW, the grain size is ⁇ 7 grades, and the band structure is ⁇ 2 grades.
  • the specification is ⁇ 20-50mm.
  • a method for controlled rolling and controlled cooling suitable for on-line normalizing treatment of medium carbon and boron-containing steel which sequentially includes the following steps: heating, rough rolling, finishing rolling, cooling by water penetration, and slow cooling by cooling bed , in which a billet with a section size of 240mm ⁇ 240mm is selected.
  • the heating temperature of the billet in the heating furnace is 1100-1200°C, (for example, 1100°C, 1110°C, 1120°C, 1130°C, 1140°C, 1150°C, 1160°C, 1170°C, 1180°C, 1190°C, 1200°C and the interval or interval point between any two temperatures), the total heating time is 90-180min; and the time point between any two time periods).
  • the heating temperature of the billet in the heating furnace is 1130-1180°C (for example, 1130°C, 1140°C, 1150°C, 1160°C, 1170°C, 1180°C and any two of them).
  • temperature interval or interval point the total heating time is 120-150min (such as 120min, 130min, 140min, 150min and the time point between any two time periods); select the corresponding heating temperature and heating time The purpose is to ensure that the billet is fully heated without overheating.
  • the inlet temperature into the rough rolling unit is 1000-1050°C (such as 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, 1050°C and any two temperatures between them). interval segment or interval point).
  • the rough rolling unit is 6 horizontal and vertical continuous rolling units, and the work roll diameter is 650mm.
  • the inlet temperature of the rough rolling mill is related to the temperature in the heating step. Between the heating step and the rough rolling step, the temperature of the steel billet will decrease due to phosphorus removal by high-pressure water.
  • the finishing rolling unit adopts a reducing and sizing finishing rolling unit, and the inlet temperature into the finishing rolling unit is 780-830°C (such as 780°C, 790°C, 800°C, 810°C, 820°C, 830°C) and the interval or interval point between any two temperatures), as a more preferred inlet temperature into the finishing mill is 780-810°C (such as 780°C, 790°C, 800°C, 810°C and interval or interval point between any two temperatures).
  • the finishing mill is 4 sets of three-roll reducing and sizing finishing mills. The use of three-roll reducing and sizing finishing mills has a large amount of deformation of the finished product, which is conducive to refining grains.
  • the water temperature of the finished steel after water penetration cooling is 700-750°C (for example, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, and any two of them). interval or interval point); as a more preferred finished steel, the outlet temperature of the finished steel after passing through water cooling is 710-730°C (such as 710°C, 720°C, 730°C and any two temperatures between them). interval segment or interval point).
  • the water volume of the water tank is 40-60L/min, and the traveling speed of the finished steel is preferably 3-8m/s (which can be selected according to the finished product specification). Water penetration cooling and the above parameter settings can prevent the steel from recovering and recrystallization during the rolling process, resulting in coarse grains.
  • the finished steel after passing through the water cooling step enters the cooling bed for slow cooling, the cooling bed adopts a step-by-step cooling bed for slow cooling, and the cooling rate of the finished steel is 0.10-0.15°C/S;
  • the finished steel material enters into the heat preservation cover and is cooled on a cooling bed, and is cooled to below 500° C., and the finished steel material is removed from the heat preservation cover and then air-cooled.
  • the use of thermal insulation cover for air cooling has a slow cooling effect to prevent the finished steel from being deformed during subsequent turning or heat treatment due to high internal residual stress due to fast cooling. If the finished steel is directly air-cooled, the internal stress of the steel may be large, and the problem of deformation will occur in the subsequent processing.
  • the finished steel is cooled in a thermal hood on a cooling bed to avoid problems caused by direct air cooling.
  • the medium carbon and boron-containing steel produced by the method disclosed in this application can meet the requirements of Brinell hardness of 190-220 HBW, actual grain size ⁇ 7, and banded structure ⁇ 2 without the need for off-line normalizing. Meet the user's technical index requirements after offline normalization of the product.
  • the controlled rolling and controlled cooling method for preparing the medium carbon boron-containing steel saves the cost and time of the off-line normalizing step, reduces the investment in fixed equipment, shortens the production cycle, reduces the production cost, accelerates the production cycle and improves the competitiveness of the product.
  • the section size of the selected steel billet is 240mm ⁇ 240mm; according to the mass percentage, the chemical composition of the steel billet of the medium carbon boron-containing steel includes: C 0.38%; Si 0.25%; Mn 0.86%; Al 0.032%; B 0.0017%; Ti 0.047% ; P 0.013%; S 0.005%; Cr 0.14%; Ni 0.03%; Mo 0.02%; Cu 0.02%;
  • Heating step the heating temperature of the billet entering the heating furnace is 1140-1160°C, and the total heating time is 142min;
  • Rough rolling step the inlet temperature into the rough rolling mill is 1038°C;
  • Finishing rolling step a reducing and sizing finishing rolling unit is used, and the inlet temperature into the finishing rolling unit is 795°C;
  • Water penetration cooling step The finished steel rolled by the reducing and sizing finishing rolling unit is cut by flying shear and then sprayed in the water tank for cooling.
  • the water outlet temperature of the finished steel after water penetration cooling is 728°C;
  • Slow cooling step of cooling bed It is carried out in a stepping cooling bed, and the cooling rate of the finished steel is 0.10-0.15°C/S;
  • the cut-off finished steel is cooled by a step-by-step cooling bed with a thermal insulation cover, and the thermal insulation cover is closed to cool the finished steel slowly on the cooling bed, cooled to 475°C, and the thermal insulation cover is released for air cooling.
  • the hardness of the finished steel processed by the above steps is 204/208HBW at 1/2 of the section; the actual grain size is 8; as shown in Figure 1, the band structure is 1.5.
  • the chemical composition of the medium carbon boron-containing steel billet includes: C 0.38%; Si 0.25%; Mn 0.84%; Al 0.028%; B 0.0020%; Ti 0.045%; P 0.012%; S 0.008%; Cr 0.12 %; Ni 0.02%; Mo 0.03%; Cu 0.03%; the rest are Fe and inevitable impurities; the section size of the selected billet is 240mm ⁇ 240mm.
  • Example 1 The steps of the controlled rolling and controlled cooling method suitable for the on-line normalizing treatment of medium carbon and boron-containing steel are as in Example 1, and the parameters of each step of the controlled rolling and controlled cooling method suitable for the on-line normalizing treatment of medium carbon and boron-containing steel are shown in Table 1.
  • the hardness at 1/2 of the section of the finished steel processed in Example 2 is 212/215HBW; the actual grain size is grade 9; as shown in Figure 2, the banded structure is grade 1.5.
  • Table 1 shows the parameters of each step of Example 1 and Example 2 and the properties of the obtained steel
  • Example 1 Example 2 Billet size (mm) 240*240 240*240 Heating temperature (°C) 1140-1160 1145-1163 Total heating time (min) 142 135 Entering Roughing Mill Temperature (°C) 1038 1025 Into the finishing mill temperature (°C) 795 802 Outlet tank temperature (°C) 728 715 Cooling bed cooling rate (°C/S) 0.125 0.132 Temperature out of the insulation cover (°C) 475 462 Hardness at 1/2R (HBW) 204/208 212/215 Grain size (grade) 8 9 Band tissue (level) 1.5 1.5 1.5
  • Example 3-5 the parameters of each step of heating, rough rolling, finishing rolling, water cooling, and slow cooling in the cooling bed are shown in Table 2.
  • the properties of the finished steel include hardness at 1/2R, grain size and band shape
  • the organization level is also shown in Table 2.
  • Table 2 is the parameters of each step of Examples 3-5 and the properties of the obtained steel
  • Example 3 Example 4 Example 5 Billet size (mm) 240*240 240*240 240*240 Heating temperature (°C) 1140-1150 1140-1155 1135-1150 Total heating time (min) 145 138 145 Entering Roughing Mill Temperature (°C) 1028 1033 1045 Into the finishing mill temperature (°C) 785 798 805 Outlet tank temperature (°C) 725 729 735 Cooling bed cooling rate (°C/S) 0.124 0.130 0.132 Temperature out of the insulation cover (°C) 473 465 468
  • the parameters of each step of heating, rough rolling, finishing rolling, water cooling, and slow cooling in the cooling bed in Examples 6-8 are shown in Table 3.
  • the properties of the finished steel include hardness at 1/2R, grain size and band shape
  • the organization level is also shown in Table 3.
  • Table 3 is the parameters and properties of each step of the steel obtained in Example 6-8
  • Example 6 Example 7 Example 8 Billet size (mm) 240*240 240*240 240*240 Heating temperature (°C) 1138-1150 1145-1160 1143-1162 Total heating time (min) 140 128 147 Entering Roughing Mill Temperature (°C) 1025 1042 1045 Into the finishing mill temperature (°C) 796 802 808 Outlet tank temperature (°C) 730 722 728 Cooling bed cooling rate (°C/S) 0.128 0.129 0.132 Temperature out of the insulation cover (°C) 470 460 462 Hardness at 1/2R (HBW) 204/207 205/209 215/218 Grain size (grade) 9 8 8 Band tissue (level) 1.5 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0
  • Table 4 shows the different step parameters and properties of the steel obtained in Comparative Examples 1-3
  • Comparative Example 1 Comparative Example 2 Comparative Example 3 Billet size (mm) 240*240 240*240 240*240 Heating temperature (°C) 1250-1300 1150-1165 1142-1158 Total heating time (min) 145 300 143 Entering Roughing Mill Temperature (°C) 1130 1035 1028 Into the finishing mill temperature (°C) 825 815 783 Outlet tank temperature (°C) 745 728 721 Cooling bed cooling rate (°C/S) 0.143 0.125 0.208 Temperature out of the insulation cover (°C) 455 478 none Hardness at 1/2R (HBW) 228/226 205/208 238/240 Grain size (grade) 8-5 8-5 8 Band tissue (level) 1.5 2.0 2.0 2.0 2.0
  • the present invention provides a controlled rolling and controlled cooling method suitable for on-line normalizing treatment of medium carbon and boron-containing steel.
  • On-line normalizing treatment makes the hardness and structure of the hot-rolled steel meet the requirements of the original normalizing state.

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Abstract

本发明提供一种中碳含硼钢，按照质量百分比，该中碳含硼钢的化学成分包含：C 0.37-0.45％，Si 0.17-0.37％；Mn 0.60-0.90％；Al 0.020-0.060％；B 0.0008-0.0035％；Ti 0.030-0.060％；P≤0.025％；S≤0.025％；Cr≤0.25％；Ni≤0.20％；Mo≤0.10％；Cu≤0.20％；其余为Fe和不可避免的杂质。适用于中碳含硼钢在线正火处理的控轧控冷方法，依次包括以下步骤：加热，粗轧，精轧，穿水冷却，冷床缓冷。中碳含硼钢可满足硬度190-220HBW，实际晶粒度≥7级，带状组织≤2级的要求。

Description

中碳含硼钢及在线正火处理的控轧控冷方法 技术领域
本发明涉及轧钢领域，具体涉及一种中碳含硼钢及在线正火处理的控轧控冷方法。
背景技术
中碳含硼钢是一类具有良好淬透性的合金结构钢，多用来制造汽车等速传动轴等重要零部件，因加工和使用条件要求，对材料组织和硬度有严格的要求。
在制造过程中，现有技术一般都需要对钢材进行离线正火处理才能满足钢材的组织硬度要求，但因为生产应用中所使用的成品材料规格较小(20-50mm)，需要使用专业的正火炉进行离线正火处理，不仅生产效率低还容易出现混晶问题。同时对钢材进行离线正火处理生产周期增加约一周，相应的生产成本增加约400元/吨，严重制约了该产品批量生产和应用。
发明内容
本发明的目的在于提供一种中碳含硼钢及在线正火处理的控轧控冷方法，采用该方法制备的中碳含硼钢，可明显细化中碳含硼钢的热轧态组织，满足布氏硬度190-220HBW，晶粒度≥7级，带状组织≤2级的要求，从而替代原离线正火处理的工艺。同时节约生产周期，降低正火成本从而降低企业生产成本，提高产品竞争力。
为了实现上述目的，本发明提供如下技术方案：
一种中碳含硼钢，按照质量百分比，该中碳含硼钢的化学成分包含：C 0.37-0.45％，Si 0.17-0.37％；Mn 0.60-0.90％；Al 0.020-0.060％；B 0.0008-0.0035％；Ti 0.030-0.060％；P≤0.025％；S≤0.025％；Cr≤0.25％；Ni≤0.20％；Mo≤0.10％；Cu≤0.20％；其余为Fe和不可避免的杂质。
进一步地，所述中碳含硼钢满足布氏硬度190-220HBW，晶粒度≥7级， 带状组织≤2级。
进一步地，所述中碳含硼钢的规格为Φ20-50mm。
本发明还提供一种适用于上述中碳含硼钢在线正火处理的控轧控冷方法，依次包括以下步骤：加热，粗轧，精轧，穿水冷却，冷床缓冷。
进一步地，在上述适用于中碳含硼钢在线正火处理的控轧控冷方法中，在所述加热步骤中，钢坯在加热炉内的加热温度为1100-1200℃，总加热时间90-180min；优选地，钢坯加热炉内的加热温度为1130-1180℃，总加热时间为120-150min。
进一步地，在上述适用于中碳含硼钢在线正火处理的控轧控冷方法中，所述粗轧步骤中，钢坯进入粗轧机组的入口温度为1000-1050℃。
进一步地，在上述适用于中碳含硼钢在线正火处理的控轧控冷方法中，所述精轧步骤中，钢坯进入精轧机组的入口温度为780-830℃；优选地，所述精轧步骤中，钢坯进入精轧机组的入口温度为780-810℃；优选地，所述精轧步骤中，采用减定径精轧机组进行精轧。
进一步地，在上述适用于中碳含硼钢在线正火处理的控轧控冷方法中，穿水冷却是指经过水箱进行喷水冷却，经过穿水冷却后，成品钢材的出水温度为700-750℃；优选地，所述水箱水量为40-60L/min，成品钢材的行进速度为3-8m/s；优选地，经过穿水冷却后，成品钢材的出水温度为710-730℃。
进一步地，在上述适用于中碳含硼钢在线正火处理的控轧控冷方法中，在冷床缓冷步骤中，成品钢材的冷却速度为0.10-0.15℃/S；
进一步地，在上述适用于中碳含硼钢在线正火处理的控轧控冷方法中，在冷床缓冷步骤中，所述成品钢材进入保温罩中在冷床上进行冷却，冷却至500℃以下出保温罩空冷。
进一步地，在上述适用于中碳含硼钢在线正火处理的控轧控冷方法中，在冷床缓冷步骤中，所述冷床为步进式冷床。
进一步地，在上述适用于中碳含硼钢在线正火处理的控轧控冷方法中，所述钢坯的截面尺寸为240mm×240mm。
与现有技术相比，本发明的有益效果是：
(1)在生产过程中不需要对钢材成分再次进行调整，不需要添加额外的 离线正火的生产设备，仅通过对轧制成型和冷却工艺进行调整可实现该类产品在线正火处理，同时能满足钢材的组织硬度要求；
(2)在生产过程各阶段温度控制范围较宽，工业化生产容易控制实现；
(3)利用加热步骤在线正火替代离线正火，减少了固定设备投资，缩短生产周期(约1周时间)，降低生产成本(约400元/吨)，加快生产周期，降低生产成本，提高产品竞争力。
(4)使用本方法制造的中碳含硼钢，可满足硬度190-220HBW，实际晶粒度≥7级，带状组织≤2级的要求，完全满足用户对该产品离线正火后的技术指标要求。
附图说明
下面结合附图，对本实用新型的具体实施方式作进一步阐明，需要说明的是，构成本申请的一部分的说明书附图用来提供对本发明的进一步理解，本发明的示意性实施例及其说明用于解释本发明，并不构成对本发明的不当限定。其中：
图1为实施例1生产的规格为32mm的40B钢半径1/2处显微组织图；
图2为实施例2生产的规格为28mm的40B钢半径1/2处显微组织图；
图3为对比例1生产的规格为30mm的40B钢半径1/2处显微组织图；
图4为对比例2生产的规格为34mm的40B钢半径1/2处显微组织图；
图5为对比例3生产的规格为28mm的40B钢半径1/2处显微组织图。
具体实施方式
下面将参考附图并结合实施例来详细说明本发明。各个示例通过本发明的解释的方式提供而非限制本发明。实际上，本领域的技术人员将清楚，在不脱离本发明的范围或精神的情况下，可在本发明中进行修改和变型。例如，示为或描述为一个实施例的一部分的特征可用于另一个实施例，以产生又一个实施例。因此，所期望的是，本发明包含归入所附权利要求及其等同物的范围内的此类修改和变型。
所附附图中示出了本发明的一个或多个示例。详细描述使用了数字和字母标记来指代附图中的特征。附图和描述中的相似或类似标记的已经用于指 代本发明的相似或类似的部分。
如图1至图2所示，根据本发明的实施例，提供了一种适用于中碳含硼钢，按照质量百分比，该中碳含硼钢的化学成分包含：
C 0.37-0.45％；Si 0.17-0.37％；Mn 0.60-0.90％；Al 0.020-0.060％；B 0.0008-0.0035％；Ti 0.030-0.060％；P≤0.025％；S≤0.025％；Cr≤0.25％；Ni≤0.20％；Mo≤0.10％；Cu≤0.20％；其余为Fe和不可避免的杂质；中碳含硼钢主要是以锰Mn和硼B作为合金元素，若铬Cr、镍Ni、钼Mo或者铜Cu等合金元素含量过高，经控轧控冷后容易形成贝氏体等组织，导致硬度过高。
所述中碳含硼钢的规格为Φ20-50mm；所述中碳含硼钢满足布氏硬度190-220HBW，晶粒度≥7级，带状组织≤2级，所述中碳含硼钢的规格为Φ20-50mm。
根据本发明的实施例，提供了一种适用于中碳含硼钢在线正火处理的控轧控冷方法，依次包括以下步骤：加热，粗轧，精轧，穿水冷却，冷床缓冷，其中选择截面尺寸为240mm×240mm的钢坯。
在所述加热步骤中，钢坯在加热炉内的加热温度为1100-1200℃，(比如1100℃、1110℃、1120℃、1130℃、1140℃、1150℃、1160℃、1170℃、1180℃、1190℃、1200℃及之中任意二个温度之间的区间段或区间点)，总加热时间90-180min；(比如90min、100min、110min、120min、130min、140min、150min、160min、170min、180min及之中任意二个时间段之间的时间点)。
作为优选实施方式，在所述加热步骤中，钢坯在加热炉内的加热温度为1130-1180℃(比如1130℃、1140℃、1150℃、1160℃、1170℃、1180℃及之中任意二个温度之间的区间段或区间点)，总加热时间为120-150min(比如120min、130min、140min、150min及之中任意二个时间段之间的时间点)；选择相应的加热温度和加热时间的目的在于，既要保证钢坯充分加热，又不能出现过热。
在所述粗轧步骤中，其中进入粗轧机组的入口温度为1000-1050℃(比如1000℃、1010℃、1020℃、1030℃、1040℃、1050℃及之中任意二个温度之间的区间段或区间点)。粗轧机组为6架平立式连轧机组，工作辊径为650mm。粗轧机组入口温度与加热步骤中的温度有关，在加热步骤和粗轧步骤之间因经过高压水除磷，钢坯的温度会降低。
在所述精轧步骤中，精轧机组采用减定径精轧机组，进入精轧机组的入口温度为780-830℃(比如780℃、790℃、800℃、810℃、820℃、830℃及之中任意二个温度之间的区间段或区间点)，作为更为优选的进入精轧机组的入口温度为780-810℃(比如780℃、790℃、800℃、810℃及之中任意二个温度之间的区间段或区间点)。精轧机组为4架三辊减定径精轧机，使用三辊减定径精轧机成材变形量大，有利于细化晶粒。
在所述穿水冷却步骤中，成品钢材经过穿水冷却后的出水温度为700-750℃(比如700℃、710℃、720℃、730℃、740℃、750℃及之中任意二个温度之间的区间段或区间点)；作为更为优选的成品钢材经过穿水冷却后的出水温度为710-730℃(比如710℃、720℃、730℃及之中任意二个温度之间的区间段或区间点)。水箱的水量为40-60L/min，成品钢材的行进速度优选为3-8m/s(可根据成材规格的选择)。穿水冷却及上述参数设置能够防止钢材在轧制过程中温度升高发生回复再结晶导致晶粒粗大。
在冷床缓冷步骤中，经过穿水冷却步骤后的成品钢材进入冷床进行缓冷，冷床采用步进式冷床进行缓冷，成品钢材的冷却速度为0.10-0.15℃/S；所述成品钢材进入进保温罩中在冷床上进行冷却，冷却至500℃以下，将成品钢材移出保温罩再进行空冷。利用保温罩进行空冷，有缓冷作用，防止成品钢材因冷却速度快内部残余应力大，在后续车削或热处理过程中出现变形的问题。如果将成品钢材直接空冷可能会导致钢材内应力大，在后续加工过程中出现变形的问题。成品钢材进保温罩在冷床上进行冷却可避免直接空冷导致的问题。
通过本申请公开的方法生产制造的中碳含硼钢，不需要离线正火的工艺就可满足布氏硬度190-220HBW，实际晶粒度≥7级，带状组织≤2级的要求，完全满足用户对该产品离线正火后的技术指标要求。制备该中碳含硼钢的控轧控冷方法，节约离线正火步骤的成本和时间，减少了固定设备投资，缩短生产周期，降低生产成本，加快生产周期，提高产品竞争力。
实施例1
选择钢坯的截面尺寸为240mm×240mm；按照质量百分比，该中碳含硼钢的钢坯的化学成分包含：C 0.38％；Si 0.25％；Mn 0.86％；Al 0.032％；B  0.0017％；Ti 0.047％；P 0.013％；S 0.005％；Cr 0.14％；Ni 0.03％；Mo 0.02％；Cu 0.02％；其余为Fe和不可避免的杂质；钢坯的截面尺寸为240mm×240mm。
加热步骤：钢坯在进入加热炉的加热温度为1140-1160℃，总加热时间为142min；
粗轧步骤：进入粗轧机组的入口温度为1038℃；
精轧步骤：采用减定径精轧机组，进入精轧机组的入口温度为795℃；
穿水冷却步骤：经减定径精轧机组轧制出的成品钢材经飞剪切断后经过水箱进行喷水冷却，成品钢材经过穿水冷却后的出水箱温度为728℃；
冷床缓冷步骤：在步进式冷床中进行，成品钢材的冷却速度为0.10-0.15℃/S；
切断后的成品钢材上带保温罩的步进式冷床进行冷却，关闭保温罩使成品钢材在冷床上缓慢冷却，冷却至475℃出保温罩再进行空冷。
经过上述步骤所处理后的成品钢材，截面1/2处硬度为204/208HBW；实际晶粒度为8级；如图1所示，带状组织为1.5级。
实施例2
按照质量百分比，该中碳含硼钢钢坯的化学成分包含：C 0.38％；Si 0.25％；Mn 0.84％；Al 0.028％；B 0.0020％；Ti 0.045％；P 0.012％；S 0.008％；Cr 0.12％；Ni 0.02％；Mo 0.03％；Cu 0.03％；其余为Fe和不可避免的杂质；选择钢坯的截面尺寸为240mm×240mm。
适用于中碳含硼钢在线正火处理的控轧控冷方法的步骤如实施例1，其中适用于中碳含硼钢在线正火处理的控轧控冷方法各步骤参数对比参见表1，经过实施例2步骤所处理后的成品钢材截面1/2处硬度为212/215HBW；实际晶粒度为9级；如图2所示，带状组织为1.5级。
表1为实施例1和实施例2的各步骤参数及所得钢材的性能
  实施例1 实施例2
钢坯尺寸(mm) 240*240 240*240
加热温度(℃) 1140-1160 1145-1163
总加热时间(min) 142 135
进粗轧机温度(℃) 1038 1025
进精轧机温度(℃) 795 802
出水箱温度(℃) 728 715
冷床冷却速度(℃/S) 0.125 0.132
出保温罩温度(℃) 475 462
1/2R处硬度(HBW) 204/208 212/215
晶粒度(级) 8 9
带状组织(级) 1.5 1.5
实施例3-5
实施例3-5的中碳含硼钢钢坯的化学成分与实施例1相同。
实施例3-5中加热，粗轧，精轧，穿水冷却，冷床缓冷各步骤的参数如表2所示，成品钢材的性能包括1/2R处硬度，晶粒级度和带状组织级度也如表2所示。
表2为实施例3-5的各步骤参数及所得钢材的性能
  实施例3 实施例4 实施例5
钢坯尺寸(mm) 240*240 240*240 240*240
加热温度(℃) 1140-1150 1140-1155 1135-1150
总加热时间(min) 145 138 145
进粗轧机温度(℃) 1028 1033 1045
进精轧机温度(℃) 785 798 805
出水箱温度(℃) 725 729 735
冷床冷却速度(℃/S) 0.124 0.130 0.132
出保温罩温度(℃) 473 465 468
1/2R处硬度(HBW) 202/203 210/208 212/214
晶粒度(级) 8 8.5 8
带状组织(级) 2.0 1.5 1.5
由表2可知，实施例3-5中得到的钢材的1/2R处硬度为202-214HBW，晶粒级度为8-8.5级和带状组织级度为1.5-2.0级。
实施例6-8
实施例3-5的中碳含硼钢钢坯的化学成分与实施例1相同。
实施例6-8中加热，粗轧，精轧，穿水冷却，冷床缓冷各步骤的参数如表3所示，成品钢材的性能包括1/2R处硬度，晶粒级度和带状组织级度也如表3所示。
表3为实施例6-8所得钢材的各步骤参数及性能
  实施例6 实施例7 实施例8
钢坯尺寸(mm) 240*240 240*240 240*240
加热温度(℃) 1138-1150 1145-1160 1143-1162
总加热时间(min) 140 128 147
进粗轧机温度(℃) 1025 1042 1045
进精轧机温度(℃) 796 802 808
出水箱温度(℃) 730 722 728
冷床冷却速度(℃/S) 0.128 0.129 0.132
出保温罩温度(℃) 470 460 462
1/2R处硬度(HBW) 204/207 205/209 215/218
晶粒度(级) 9 8 8
带状组织(级) 1.5 2.0 2.0
由表3可知，实施例6-8中得到的钢材的1/2R处硬度为204-218HBW，晶粒级度为8-9级，带状组织级度为1.5-2.0级。
对比例1-3
对比例1-3的中碳含硼钢钢坯的化学成分与实施例1相同。
对比例1-3中加热，粗轧，精轧，穿水冷却，冷床缓冷各步骤的参数如表4所示。
表4为对比例1-3所得钢材的不同步骤参数及性能
  对比例1 对比例2 对比例3
钢坯尺寸(mm) 240*240 240*240 240*240
加热温度(℃) 1250-1300 1150-1165 1142-1158
总加热时间(min) 145 300 143
进粗轧机温度(℃) 1130 1035 1028
进精轧机温度(℃) 825 815 783
出水箱温度(℃) 745 728 721
冷床冷却速度(℃/S) 0.143 0.125 0.208
出保温罩温度(℃) 455 478 无
1/2R处硬度(HBW) 228/226 205/208 238/240
晶粒度(级) 8-5 8-5 8
带状组织(级) 1.5 2.0 2.0
由表4可知，其中，
对比例1，除加热步骤中的加热温度不同外，导致进粗轧机的温度偏高，其它步骤的工艺参数均在本申请的保护范围内。由于加热步骤中加热温度的过高，如图3所示，导致原材料原始奥氏体晶粒粗大、轧制过程冷却水量增加，成材后局部晶粒度粗大、硬度偏高。
对比例2，除加热步骤中的总加热时间不同外，其它步骤的工艺参数均在本申请的保护范围内。由于加热时间过长，如图4所示，导致原材料原始奥氏体晶粒粗大，成材后局部晶粒度粗大。
对比例3，除在冷床缓冷步骤中未使用保温罩直接进入冷床冷却外，其 它步骤的工艺参数均在本申请的保护范围内。由于未使用保温罩导致冷却速度过快，如图5所示，导致原材料硬度偏高，残余内应力大，存在后续加工变形的风险。
结合实施例1-8和对比例1-3分析，本发明提供了一种适用于中碳含硼钢在线正火处理的控轧控冷方法，通过调整钢材轧制时的温度和冷却速度达到在线正火处理，使热轧状态钢材硬度和组织达到原正火状态的要求。
以上所述仅为本发明的优选实施例，并不用于限制本发明，对于本领域的技术人员来说，本发明可以有各种更改和变化。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (7)

  1. 一种中碳含硼钢，其特征在于，按照质量百分比，该中碳含硼钢的化学成分包含：
    C 0.37-0.45％，Si 0.17-0.37％；Mn 0.60-0.90％；Al 0.020-0.060％；B 0.0008-0.0035％；Ti 0.030-0.060％；P≤0.025％；S≤0.025％；Cr≤0.25％；Ni≤0.20％；Mo≤0.10％；Cu≤0.20％；其余为Fe和不可避免的杂质；
    所述中碳含硼钢由在线正火处理的控轧控冷方法制备，
    所述在线正火处理的控轧控冷方依次包括以下步骤：加热，粗轧，精轧，穿水冷却，冷床缓冷；
    钢坯在加热炉内的加热温度为1100-1200℃，总加热时间为90-180min；
    所述粗轧步骤中，钢坯进入粗轧机组的入口温度为1000-1050℃；
    所述精轧步骤中，钢坯进入精轧机组的入口温度为780-830℃；
    穿水冷却是指经过水箱进行喷水冷却，经过穿水冷却后，成品钢材的出水温度为700-750℃；
    所述水箱的水量为40-60L/min，成品钢材的行进速度为3-8m/s；
    在冷床缓冷步骤中，成品钢材的冷却速度为0.10-0.15℃/S；
    在冷床缓冷步骤中，所述成品钢材进入保温罩中在冷床上进行冷却，冷却至500℃以下出保温罩空冷。
  2. 根据权利要求1所述的中碳含硼钢，其特征在于，所述中碳含硼钢满足布氏硬度190-220HBW，晶粒度≥7级，带状组织≤2级，
    所述中碳含硼钢的规格为Φ20-50mm。
  3. 一种适用于中碳含硼钢在线正火处理的控轧控冷方法，其特征在于，
    所述中碳含硼钢为权利要求1-2中任一项所述的中碳含硼钢，
    所述方法依次包括以下步骤：加热，粗轧，精轧，穿水冷却，冷床缓冷；
    在所述加热步骤中，钢坯在加热炉内的加热温度为1100-1200℃，总加热时间90-180min。
  4. 根据权利要求3所述的适用于中碳含硼钢在线正火处理的控轧控冷方法，其特征在于，
    所述精轧步骤中，钢坯进入精轧机组的入口温度为780-810℃；
    所述精轧步骤中，采用减定径精轧机组进行精轧。
  5. 根据权利要求3所述的适用于中碳含硼钢在线正火处理的控轧控冷方法，其特征在于，
    经过穿水冷却后，成品钢材的出水温度为710-730℃。
  6. 根据权利要求3所述的适用于中碳含硼钢在线正火处理的控轧控冷方法，其特征在于，
    在冷床缓冷步骤中，所述冷床为步进式冷床。
  7. 根据权利要求3所述的适用于中碳含硼钢在线正火处理的控轧控冷方法，其特征在于，
    所述钢坯的截面尺寸为240mm×240mm。
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