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CN-121992277-A - Preparation process of medium-carbon high-toughness steel rail

CN121992277ACN 121992277 ACN121992277 ACN 121992277ACN-121992277-A

Abstract

The invention discloses a preparation process of a medium-carbon high-toughness steel rail, which comprises the steps of desulfurizing pre-treated molten iron, smelting by a 150t top-bottom combined blown converter, LF refining, VD vacuum degassing refining, billet continuous casting, heating, high-pressure water descaling, BD1 rough rolling, BD2 rough rolling, rolling by a universal rolling mill and on-line heat treatment; the bead rail steel comprises the following element components in percentage by mass: c: 0.55-0.65%, si 0.45-0.55%, mn 0.75-0.95%, cr 0.20-0.25%, P less than or equal to 0.020%, S less than or equal to 0.025%, V0.06-0.12%; 0.015-0.025% of Cu+Ni+Nb+RE, 0.006-0.008% of N and the balance of iron and impurities. The invention aims to prepare a steel rail with good strength and toughness proportion and excellent wear resistance, so that the steel rail can be applied to severe regional environments.

Inventors

  • WEN HAORAN
  • XUE HUDONG
  • LIANG ZHENGWEI
  • BIAN YING
  • WANG JIAWEI

Assignees

  • 包头钢铁（集团）有限责任公司

Dates

Publication Date
20260508
Application Date
20251202

Claims (7)

  1. 1. The process flow comprises the steps of desulfurizing pre-treated molten iron, smelting by a 150t top-bottom combined blown converter, LF refining, VD vacuum degassing refining, billet continuous casting, heating, high-pressure water descaling, BD1 rough rolling, BD2 rough rolling, universal rolling mill rolling, online heat treatment, straightening, flaw detection, processing, checking and warehousing, and is characterized in that: The steelmaking comprises the steps of preprocessing molten iron by adopting magnesium-based powder injection desulfurization, charging molten iron S less than or equal to 0.030%, controlling a converter smelting end point to be more than 0.08%, controlling tapping temperature T to be more than 1620 ℃ and controlling P to be less than or equal to 0.120%, and adding ferrosilicon, ferromanganese and ferrosilicon alloy into tapping to perform in-tank deoxidization alloying; LF refining adopts Si-Ca-Ba deoxidation, ferrosilicon and ferrochrome are added, and chemical components are desulfurized and finely adjusted; Adding 1-2 kg/t of 15% FeV alloy in an LF furnace in place, performing fine adjustment and heating operation on components, sampling after 10min, wherein when the V content is 0.06%, the nitrogen content in molten steel is obviously improved to be 0.004%, adding 1-2kg of 10% VN alloy, controlling the V content to be 0.09% and controlling the N content to be 0.008% when refining is out of place, heating for 25min at 1565 ℃ and 1580 ℃ when the LF furnace is out of place, ensuring that the VD vacuum degree is not more than 0.10KPa, performing deep vacuum treatment for not less than 15min, ensuring that the soft blowing time is more than 15min after the vacuum treatment is finished, and ensuring that the surface of the molten steel is not exposed in the whole soft blowing process; The covering agent of the tundish of the bloom continuous casting machine adopts calcium magnesium particles, the crystallizer adopts low-aluminum covering slag, the whole process is protected for casting, the electromagnetic stirring and solidification end soft pressing mode of the crystallizer is synchronously started, and the whole process is operated at a constant pulling speed of 0.85m/min; The rolling comprises the steps of heating a continuous casting blank for 3.5 hours by a three-stage step heating furnace, and then rolling 13 passes in a No. 2 line, wherein the compression ratio is 13.1, and rolling passes are distributed, namely, 3 passes of BD1 cogging, 7 passes of BD2 rough rolling and 3 passes of a universal rolling mill, the BD1 rolling start temperature is 1100-1160 ℃, and the final rolling temperature is 920-960 ℃; The online heat treatment process comprises the steps of carrying out online waste heat quenching on a cooling medium which is a pure air or air mist mixed medium, carrying out online heat treatment on the steel rail at a start waste heat treatment temperature of 750-830 ℃, discharging a heat treatment production line after online heat treatment, carrying out online first-stage strong cooling on the top surface, two sides and the lower jaw and the bottom of a rail head of the steel rail, carrying out actual cooling at a cooling speed of 2.2-5.7 ℃ per second, carrying out rail head surface temperature of 620-660 ℃ after cooling the steel rail, carrying out second-stage weak cooling on the top surface, two sides and the lower jaw and the bottom of the rail head of the steel rail, carrying out cold speed of 1.5-2.0 ℃ per second, carrying out third-stage weak cooling, wherein the cold speed is less than or equal to 1.0 ℃ per second, and the rear outlet rail head temperature is 450-520 ℃, and carrying out natural air cooling to room temperature; The bead rail steel comprises the following element components ：C：0.55-0.65％,Si:0.45-0.55％,Mn:0.75-0.95％,Cr:0.20-0.25％,P≤0.020％,S≤0.025％,V:0.06～0.12％;Cu+Ni+Nb+RE:0.015-0.025％,N:0.006～0.008％, by mass percent and the balance of Fe and impurities.
  2. 2. The process for preparing a medium carbon high toughness steel rail according to claim 1, wherein the size of the casting blank is 280mm x 380mm.
  3. 3. The process for preparing a medium carbon high toughness steel rail according to claim 1, wherein the liquidus temperature of the steel rail is 1464 ℃, and the superheat degree delta T is controlled at 29 ℃.
  4. 4. The process for preparing the medium-carbon high-toughness steel rail according to claim 1, wherein the bead rail steel comprises, by mass, 0.58% of C, 0.48% of Si, 0.79% of Mn, 0.22% of Cr, 0.013% of P, 0.007% of S, 0.08% of V, 0.019% of Cu+Ni+Nb+RE, 0.0072% of N, and the balance of Fe and impurities.
  5. 5. The process for preparing the medium-carbon high-toughness steel rail according to claim 1, wherein the bead rail steel comprises, by mass, 0.60% of C, 0.55% of Si, 0.82% of Mn, 0.25% of Cr, 0.011% of P, 0.003% of S, 0.11% of V, 0.016% of Cu+Ni+Nb+RE, 0.0069% of N, and the balance of Fe and impurities.
  6. 6. The process for preparing the medium-carbon high-toughness steel rail according to claim 1, wherein the bead rail steel comprises, by mass, 0.62% of C, 0.52% of Si, 0.75% of Mn, 0.28% of Cr, 0.019% of P, 0.003% of S, 0.1% of V, 0.022% of Cu+Ni+Nb+RE, 0.0065% of N, and the balance of Fe and impurities.
  7. 7. The process for preparing the medium-carbon high-toughness steel rail according to claim 1, wherein the prepared steel rail has the tensile strength of more than 1000MPa, the yield strength of more than 300MPa, the impact energy of more than 15J at-40 ℃ and the fracture toughness of more than 35 MPa-m 0.5 at-20 ℃.

Description

Preparation process of medium-carbon high-toughness steel rail Technical Field The invention belongs to the field of steel materials, and particularly relates to a preparation process of a medium-carbon high-toughness steel rail. Background With the extension of railway construction lines, rail outlet trade is increased, and on the basis of meeting the requirements of strength and wear resistance, the rails are required to have the capability of resisting low-temperature brittle failure in some areas with high altitude and low-temperature severe cold environments, and the rails are required to have excellent low-temperature toughness below-40 ℃. The high-carbon pearlite steel rail has high C content meeting the requirement of wear resistance, and the carbon content of the steel rail material is over 0.70 percent generally, so that the strength and hardness of the material are achieved. However, the pearlitic steel rail has low impact energy, and the impact energy of-40 DEG is less than 10J. At present, steel rails at home and abroad are basically high-carbon pearlite steel rails, different contents of V and N are added into C-Si-Mn-Cu-Cr-Ni pearlite steel to improve the toughness of materials and reduce the influence of C on toughness, and rolling and heat treatment are carried out to obtain nano V (C, N) precipitated particles in the pearlite steel so as to improve the strength and hardness of the steel rails. VN alloy has been used in structural steel for strengthening and toughening, and V refining and N strengthening are both achieved by adding VN to the steel, and C content in the steel can be reduced to improve toughness of the steel. Along with the development of railway construction, rail export trade increases, and russia proposes russian standard low-temperature resistant rail purchasing requirements. Therefore, the low temperature (-60 ℃) steel rail material is developed, the market precedent can be preempted, and positive social benefits are brought to enterprises. Disclosure of Invention The invention aims to provide a preparation process of a medium-carbon high-toughness steel rail, which is used for preparing the steel rail with good strength, toughness ratio and excellent wear resistance, so that the steel rail can be applied to severe regional environments. In order to solve the technical problems, the invention adopts the following technical scheme: The invention discloses a preparation process of a medium-carbon high-toughness steel rail, which comprises the steps of desulfurizing pre-treated molten iron, smelting by a 150t top-bottom combined blown converter, LF refining, VD vacuum degassing refining, billet continuous casting, heating, high-pressure water descaling, BD1 rough rolling, BD2 rough rolling, universal rolling mill rolling, online heat treatment, straightening, flaw detection, processing, checking and warehousing, and is characterized in that the preparation process comprises the following steps: The steelmaking comprises the steps of preprocessing molten iron by adopting magnesium-based powder injection desulfurization, charging molten iron S less than or equal to 0.030%, controlling a converter smelting end point to be more than 0.08%, controlling tapping temperature T to be more than 1620 ℃ and controlling P to be less than or equal to 0.120%, and adding ferrosilicon, ferromanganese and ferrosilicon alloy into tapping to perform in-tank deoxidization alloying; LF refining adopts Si-Ca-Ba deoxidation, ferrosilicon and ferrochrome are added, and chemical components are desulfurized and finely adjusted; Adding 1-2 kg/t of 15% FeV alloy in an LF furnace in place, performing fine adjustment and heating operation on components, sampling after 10min, when the V content is 0.06%, obviously improving the nitrogen content in molten steel by about 0.004%, adding 1-2kg of 10% VN alloy, controlling the V content to be 0.09% and controlling the N content to be 0.008% when refining is out of place, heating for 25min at 1565 ℃ at 1580 ℃ in place, ensuring that the VD vacuum degree is not more than 0.10KPa, performing deep vacuum treatment for not less than 15min, ensuring that the soft blowing time is more than 15min after vacuum treatment is finished, and ensuring that the surface of molten steel is not exposed in the whole soft blowing process; The covering agent of the tundish of the bloom continuous casting machine adopts calcium magnesium particles, the crystallizer adopts low-aluminum covering slag, the whole process is protected for casting, the electromagnetic stirring and solidification end soft pressing mode of the crystallizer is synchronously started, and the whole process is operated at a constant pulling speed of 0.85m/min; The rolling comprises the steps of heating a continuous casting blank for 3.5 hours by a three-stage step heating furnace, and then rolling 13 passes in a No. 2 line, wherein the compression ratio is 13.1, and rolling passes are distributed, namely, 3 pas