CN114411045B - Production method of B-alloy-containing structural steel for automobile parts - Google Patents

Production method of B-alloy-containing structural steel for automobile parts Download PDF

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CN114411045B
CN114411045B CN202210085383.1A CN202210085383A CN114411045B CN 114411045 B CN114411045 B CN 114411045B CN 202210085383 A CN202210085383 A CN 202210085383A CN 114411045 B CN114411045 B CN 114411045B
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controlled
converter
rolling
steel
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CN114411045A (en
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邓向阳
叶玉奎
林俊
李仕超
谢有
沈艳
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Zenith Steel Group Co Ltd
Changzhou Zenith Special Steel Co Ltd
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Zenith Steel Group Co Ltd
Changzhou Zenith Special Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
    • 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
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating the molten metal
    • B22D11/111—Treating the molten metal by using protecting powders
    • 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
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating the molten metal
    • B22D11/116—Refining the metal
    • B22D11/117—Refining the metal by treating with gases
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006—Adding metallic additives
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/072—Treatment with gases
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • 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

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  • Metallurgy (AREA)
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  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
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  • Treatment Of Steel In Its Molten State (AREA)
  • Heat Treatment Of Sheet Steel (AREA)

Abstract

The invention belongs to the technical field of metallurgy, and discloses a production method of steel containing a B alloy structure for automobile parts, which comprises the following components: 0.36 to 0.40 percent of C, 0.18 to 0.35 percent of Si, 0.85 to 1.15 percent of Mn, 0.05 to 0.20 percent of Cr, less than or equal to 0.020 percent of P, 0.012 to 0.028 percent of S, 0.028 to 0.048 percent of Al, less than or equal to 0.15 percent of Cu, 0.025 to 0.050 percent of Ti, 0.0008 to 0.0030 percent of B, less than or equal to 0.0070 percent of N, and the balance of Fe and unavoidable impurities. The reasonable optimization of the smelting process (converter, LF refining and RH vacuum treatment process nitrogen removal), the continuous casting process (nitrogen absorption prevention) and the rolling process (controlled rolling and cooling control) are combined, so that the N content of the material is controlled, the tissue uniformity of the material is improved, and a normalizing process can be omitted for direct use.

Description

Production method of B-alloy-containing structural steel for automobile parts
Technical Field
The invention belongs to the technical field of metallurgy, relates to B-alloy-containing structural steel for automobile parts and a production method thereof, and in particular relates to a steel-making and rolling process of B-alloy-containing structural steel for automobile parts.
Background
Boron, oxygen and nitrogen have strong affinity and can be combined with sulfur and carbon, and also can be combined with some metal compounds to form boride with higher hardness. The trace boron can obviously improve the hardenability and toughness of the steel, and since the beginning of the 20 th century, boron is added into the steel to improve the hardenability, and boron is taken as a microalloying element, a great deal of research and application are carried out in alloy high-strength steel, carbon structural steel, stainless steel, heat-resistant steel and high-temperature alloy. Many studies have also found that the addition of boron to steel in an amount that provides various improvements in yield strength, tensile strength, fatigue strength, wear resistance, etc.
In addition, with the development trend of light weight and energy saving of automobiles, boron-containing alloy structural steel is increasingly used for manufacturing automobile parts, such as core parts of gears, automobile transmission shafts, automobile half shafts, automobile engine connecting rods and the like. However, the uniformity of the structure of the medium carbon steel containing B is poor, mixed crystals are easy to occur, the fluctuation of hardenability is large, and how to ensure the uniformity of the structure of the medium carbon steel containing B, so that the hot rolling state is used for replacing the normalizing state, and a normalizing process is omitted, thus the method has become a great difficulty in the industry.
Disclosure of Invention
Aiming at the defects existing in the technology of the B-containing medium carbon steel, the invention aims to provide the B-containing medium carbon alloy structural steel (38 MnB) with uniform structure and fine grains and a production process thereof, which are used for producing parts such as automobile half shafts, transmission shafts and the like, and hot rolled materials are used for replacing normalizing materials, so that the same using effect is finally achieved.
The aim of the invention is mainly realized by the following technical scheme:
the invention relates to a B-alloy-containing structural steel for automobile parts and a production method thereof.
The aim of the invention is realized by the following technical scheme:
1. a B alloy containing structural steel for automobile parts is characterized in that: the alloy structural steel comprises the following components in percentage by weight: 0.35 to 0.40 percent of C, 0.16 to 0.38 percent of Si, 0.80 to 1.15 percent of Mn, less than or equal to 0.025 percent of P, 0.010 to 0.030 percent of S, 0.020 to 0.055 percent of Ti, 0.025 to 0.055 percent of Al, less than or equal to 0.0090 percent of N, 0.0005 to 0.0040 percent of B, less than or equal to 0.20 percent of Cu, and the balance of Fe and unavoidable impurities.
Preferably, the alloy structural steel comprises the following components in percentage by weight: 0.36 to 0.40 percent of C, 0.18 to 0.35 percent of Si, 0.85 to 1.15 percent of Mn, 0.05 to 0.20 percent of Cr, less than or equal to 0.020 percent of P, 0.012 to 0.028 percent of S, 0.028 to 0.048 percent of Al, less than or equal to 0.15 percent of Cu, 0.025 to 0.050 percent of Ti, 0.0008 to 0.0030 percent of B, less than or equal to 0.0070 percent of N, and the balance of Fe and unavoidable impurities.
The production process comprises the working procedures of 120t converter smelting, LF refining, RH vacuum treatment, continuous casting and rolling, and the process flow comprises the following steps:
(1) The molten iron ratio of the converter to the molten iron is controlled to be 87-90% (mass), the carbon content of the end point is controlled to be 0.05-0.10%, and a certain decarburization amount is ensured in the smelting process of the converter, so that the carbon-oxygen reaction in the converter is accelerated, the stirring strength of molten steel in the converter is enhanced, the degassing and impurity removing capacity of the converter smelting is finally improved, and meanwhile, the molten steel peroxidation caused by the excessively low carbon content of the end point can be prevented;
(2) The converter smelting process adopts molten steel bottom argon blowing, and increases the argon flow to 0.12Nm 3 T/min, thereby improving the degassing, in particular N-removing, capacity of the converter;
(3) The tapping temperature of the converter is controlled to be not higher than 1625 ℃, so that N is prevented from being absorbed in the tapping process due to high temperature; al-containing deoxidizing materials (calcium carbide can be adopted) are not added during tapping of the converter, and N absorption of molten steel during tapping can be prevented;
(4) In the LF refining process, medium and high alkalinity foam slag is produced, and the slag alkalinity is controlled to be 3.8-5.0, so that submerged arc operation of an electrode is facilitated, ionization nitrogen absorption in the LF power transmission process is prevented, argon stirring flow is controlled to be not more than 200L/min in the LF whole process, the phenomenon that molten steel is exposed to absorb nitrogen due to overlarge argon flow is prevented, and Cr, si, mn, al, ti, S elements are adjusted in place in the refining process;
(5) The RH process strengthens the degassing and inclusion removal treatment of molten steel, ensures the time of the extreme vacuum treatment to be not less than 22 minutes, and adjusts B to be in place (to 0.018-0.025 percent) after the vacuum treatment so as to improve the yield of B, and finally carries out calcium treatment on the molten steel, and feeds 60-80 m calcium silicate wires after adding boron for 5 minutes;
(6) The continuous casting process adopts protection pouring, argon blowing and asbestos sealing ring double protection are carried out on a large ladle long nozzle, residual air is swept out by a tundish after argon blowing for more than half an hour before pouring, and the tundish molten steel adopts pellet covering agent and carbonized rice husk double protection;
(7) In order to prevent decarburization in the steel rolling process, the air-fuel ratio in a heating furnace in the whole heating process is controlled to be not more than 0.6, and the atmosphere of the heating furnace is controlled to be slightly positive pressure by 5-20pa; preventing the heating furnace from sucking in and removing air to cause surface decarburization.
(8) The rolling process adopts a controlled rolling and cooling process, and is mainly realized by adjusting the rolling speed and starting the water tank to penetrate water: the final rolling temperature of KOCKS is controlled to be 830-880 ℃, the upper cooling bed temperature is 840-870 ℃, if the final rolling temperature is too low, surface fine crystals are brought, the grain size difference between the surface and the inside of the material is caused, mixed crystal abnormal tissue rolling occurs, water does not penetrate after rolling, if martensite abnormal tissue is easily generated on the surface after water penetrating and controlled cooling is performed, uniform and fine material tissue can be obtained through a controlled rolling and controlled cooling process, and mixed crystals and banded tissue exceeding is prevented.
The beneficial effects of the invention are as follows: considering the defects of poor 38MnB structure uniformity, easy mixed crystal, poor hardenability stability and the like, the alloy can be used after normalizing. The invention works as follows:
(1) the chemical components are optimized and regulated, and particularly the hardenability influencing elements such as Mn, al, ti, B and the like. Wherein Mn is further preferably 1.05 to 1.10%; cr is preferably controlled to be 0.08-0.10%; si 0.16-0.38% is designed according to the comprehensive requirements of the strip structure, toughness requirement, hardenability, cutting performance and the like of the steel.
(2) The N removal of the molten steel is enhanced in the converter, LF refining and RH vacuum treatment processes, and the excessive high content of N in the molten steel is prevented, so that the effective B content is reduced, and the fluctuation of hardenability is brought.
(3) And the casting work is well protected in the continuous casting process, so that nitrogen absorption of molten steel is prevented.
(4) And the air-fuel ratio is controlled in the heating process of the steel rolling to lighten the decarburization of the material surface, and meanwhile, the rolling and cooling control process is adopted to uniformly structure the material so as to prevent the mixed crystal structure.
Through the efforts, the material core and the surface structure are uniform and consistent, mixed crystals are avoided, the hardenability of the material is stabilized, a normalizing process is omitted, and the user performance of the material is improved.
The present invention will be described in detail with reference to specific examples. The conditions not limited thereto are 38MnB conventional conditions.
Example 1:
the B-alloy-containing structural steel for the automobile parts comprises the following chemical components in percentage by weight: 0.38% of C, 0.23% of Si, 1.09% of Mn, 0.10% of Cr, 0.035% of Al, 0.015% of P, 0.020% of S, 0.034% of Ti, 0.03% of Cu, 0.0037% of N, 0.0020% of B and the balance of Fe.
The process comprises the working procedures of 120t converter smelting, LF refining, RH vacuum treatment, continuous casting pouring and rolling
(1) Smelting in a converter: controlling the molten iron ratio of the converter to 88%, adopting molten steel bottom argon blowing in the converter smelting process with the carbon content of 0.07% in the tapping of the converter, and increasing the argon flow to 0.12Nm 3 Controlling the tapping temperature of the converter to 1615 ℃ per t/min, and adding no Al-containing deoxidizing material during tapping of the converter;
(2) In the LF refining process, the alkalinity of slag is controlled to be 4.2, the argon stirring flow is controlled in the LF whole process, and the argon flow in the whole process is not more than 190L/min (100-190L/min); while refining adjusts the Cr, si, mn, al, ti, S element into place.
(3) RH vacuum treatment, wherein the treatment time is 23min under high vacuum (less than or equal to 67 pa); and (3) adjusting the B to be in place after vacuum treatment, and finally, carrying out calcium treatment on the molten steel.
(4) And (3) continuous casting and pouring: the continuous casting process adopts protection pouring, argon blowing and asbestos sealing ring double protection are carried out on a large ladle long nozzle, residual air is swept out by a tundish after argon blowing for more than half an hour before pouring, and the tundish molten steel adopts pellet covering agent and carbonized rice husk double protection; continuous casting section 200mm x 260mm;
(5) And (3) rolling: the air-fuel ratio in the heating furnace is controlled to be 0.55 in the whole heating process, the atmosphere of the heating furnace is controlled to be slightly positive pressure of 5-20pa, the temperature of the KOCKS is controlled to be 845 ℃, the temperature of the upper cooling bed is controlled to be 850 ℃, and the heating furnace is rolled and then is slowly cooled in a pit.
Example 2:
the B-alloy-containing structural steel for the automobile parts comprises the following chemical components in percentage by weight: 0.39% of C, 0.24% of Si, 1.10% of Mn, 0.08% of Cr, 0.032% of Al, 0.014% of P, 0.022% of S, 0.035% of Ti, 0.04% of Cu, 0.0038% of N, 0.0021% of B and the balance of Fe.
(1) Smelting in a converter: controlling the molten iron ratio of the converter to 88.5%, adopting molten steel bottom argon blowing in the converter smelting process with the carbon content of 0.06% in the tapping of the converter, and increasing the argon flow to 0.12Nm 3 Controlling the tapping temperature 1620 ℃ of the converter at t/min, and adding no Al-containing deoxidizing material during tapping of the converter;
(2) In the LF refining process, the alkalinity of slag is controlled to be 4.4, the stirring flow of argon is controlled in the LF whole process, and the argon flow in the whole process is not more than 195L/min; while refining adjusts the Cr, si, mn, al, ti, S element into place.
(3) RH vacuum treatment, wherein the treatment time is 23min under high vacuum (less than or equal to 67 pa); and (3) adjusting the B to be in place after vacuum treatment, and finally, carrying out calcium treatment on the molten steel.
(4) And (3) continuous casting and pouring: the continuous casting process adopts protection pouring, argon blowing and asbestos sealing ring double protection are carried out on a large ladle long nozzle, residual air is swept out by a tundish after argon blowing for more than half an hour before pouring, and the tundish molten steel adopts pellet covering agent and carbonized rice husk double protection; continuous casting section 200mm x 260mm;
(5) And (3) rolling: the air-fuel ratio in the heating furnace is controlled to be 0.56 in the whole heating process, the atmosphere of the heating furnace is controlled to be slightly positive pressure of 5-20pa, the temperature of the KOCKS is controlled to be 848 ℃, the temperature of the upper cooling bed is controlled to be 850 ℃, and the heating furnace is rolled and then is slowly cooled in a pit.
Example 3:
the B-alloy-containing structural steel for the automobile parts comprises the following chemical components in percentage by weight: 0.38% of C, 0.22% of Si, 1.07% of Mn, 0.12% of Cr, 0.032% of Al, 0.013% of P, 0.021% of S, 0.030% of Ti, 0.04% of Cu, 0.0040% of N, 0.0019% of B and the balance of Fe.
(1) Smelting in a converter: controlling the molten iron ratio of the converter to 88%, adopting molten steel bottom argon blowing in the converter smelting process with the carbon content of 0.08% in the tapping of the converter, and increasing the argon flow to 0.12Nm 3 Controlling the tapping temperature of the converter to 1618 ℃ per t/min, and adding no Al-containing deoxidizing material during tapping of the converter;
(2) In the LF refining process, the alkalinity of slag is controlled to be 4.5, the stirring flow of argon is controlled in the LF whole process, and the argon flow in the whole process is not more than 200L/min; while refining adjusts the Cr, si, mn, al, ti, S element into place.
(3) RH vacuum treatment, wherein the treatment time is 23min under high vacuum (less than or equal to 67 pa); and (3) adjusting the B to be in place after vacuum treatment, and finally, carrying out calcium treatment on the molten steel.
(4) And (3) continuous casting and pouring: the continuous casting process adopts protection pouring, argon blowing and asbestos sealing ring double protection are carried out on a large ladle long nozzle, residual air is swept out by a tundish after argon blowing for more than half an hour before pouring, and the tundish molten steel adopts pellet covering agent and carbonized rice husk double protection; continuous casting section 200mm x 260mm;
(5) And (3) rolling: the air-fuel ratio in the heating furnace is controlled to be 0.58 in the whole heating process, the atmosphere of the heating furnace is controlled to be slightly positive pressure of 5-20pa, the temperature of the KOCKS is controlled to be 840 ℃, the temperature of the upper cooling bed is controlled to be 842 ℃, and the heating furnace is rolled and then is put into a pit for slow cooling.
Example 4:
the B-alloy-containing structural steel for the automobile parts comprises the following chemical components in percentage by weight: 0.38% of C, 0.26% of Si, 1.07% of Mn, 0.09% of Cr, 0.036% of Al, 0.017% of P, 0.025% of S, 0.033% of Ti, 0.03% of Cu, 0.0036% of N, 0.0024% of B and the balance of Fe.
(1) Smelting in a converter: controlling the molten iron ratio of the converter to 89%, and controlling the converter toIn the converter smelting process with the tapping carbon content of 0.10 percent, molten steel bottom argon blowing is adopted, and the argon flow is increased to 0.12Nm 3 Controlling the tapping temperature of the converter at 1610 ℃ at t/min, wherein an Al-containing deoxidizing material is not added during tapping of the converter;
(2) In the LF refining process, the alkalinity of slag is controlled to be 4.0, the stirring flow of argon is controlled in the LF whole process, and the argon flow in the whole process is not more than 197L/min; while refining adjusts the Cr, si, mn, al, ti, S element into place.
(3) RH vacuum treatment, wherein the treatment time is 23min under high vacuum (less than or equal to 67 pa); and (3) adjusting the B to be in place after vacuum treatment, and finally, carrying out calcium treatment on the molten steel.
(4) And (3) continuous casting and pouring: the continuous casting process adopts protection pouring, argon blowing and asbestos sealing ring double protection are carried out on a large ladle long nozzle, residual air is swept out by a tundish after argon blowing for more than half an hour before pouring, and the tundish molten steel adopts pellet covering agent and carbonized rice husk double protection; continuous casting section 200mm x 260mm;
(5) And (3) rolling: the air-fuel ratio in the heating furnace is controlled to be 0.50 in the whole heating process, the atmosphere of the heating furnace is controlled to be slightly positive pressure of 5-20pa, the KOCKS temperature is controlled to be 855 ℃, the upper cooling bed temperature is controlled to be 860 ℃, and the heating furnace is rolled and then is put into a pit for slow cooling.
Comparative example 1
Comparative example 1 is different from example 1 in that: the procedure of example 1 was repeated except that Cr element was not added.
Comparative example 2
Comparative example 2 is different from example 1 in that: the procedure of example 1 was repeated except that the content of B element was reduced and the content of B in the steel composition was controlled to 0.0015%.
Comparative example 3
Comparative example 3 is different from example 1 in that: the refining argon flow was not controlled and was up to 300L/min, otherwise the procedure was as in example 1.
Comparative example 4
Comparative example 4 is different from example 1 in that: the rolling process was not performed by the controlled rolling and cooling process (no water passing through the rolling process), the final rolling temperature of KOCKS was controlled to 905℃and the upper cooling bed temperature was controlled to 900℃and the other operations were the same as in example 1.
Comparative example 5
Comparative example 5 example 1 differs in that: KOCKS temperature 845 ℃, water passing after rolling, upper cooling bed temperature 795 ℃ and other operations as in example 1.
Inventive examples 1 to 5, comparative examples 1 to 5 were compared with the overall performance index (measured directly after rolling without heat treatment), as shown in table 1 below:
table 1 overall performance comparison
Figure BDA0003487588280000081
Surface martensite abnormal structures also appear in comparative examples 1 to 5, and the surface structures of examples 1 to 4 are: ferrite + pearlite normal structure.
The results show that: through reasonable optimization design of components, particularly optimization design of elements Cr and B with strong hardenability, N reduction, protection casting and other measures are adopted in the smelting process and the continuous casting process, a controlled rolling and cooling process is adopted in the rolling process, uniformity of material organization is improved, comprehensive performance and final use performance of a product reach the international advanced level, a normalizing process can be omitted, and effects of energy conservation, environmental protection, enterprise benefit improvement and the like are achieved.
The raw materials and equipment used in the invention are common raw materials and equipment in the field unless specified otherwise; the methods used in the present invention are conventional in the art unless otherwise specified. The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the invention, but all modifications of the foregoing embodiments according to the technical principles of the present invention are included in the scope of the present invention.

Claims (1)

1. A production process of a B-alloy-containing structural steel for automobile parts is characterized by comprising the following steps of:
the alloy structural steel comprises the following components in percentage by weight: 0.36 to 0.40 percent of C, 0.18 to 0.35 percent of Si, 0.85 to 1.05 percent of Mn, 0.08 to 0.09 percent of Cr, less than or equal to 0.020 percent of P, 0.012 to 0.028 percent of S, 0.028 to 0.048 percent of Al, and Cu:0.03 to 0.15 percent, 0.025 to 0.050 percent of Ti, 0.0008 to 0.0030 percent of B, less than or equal to 0.0070 percent of N, and the balance of Fe and unavoidable impurities; the core of the steel material containing the B alloy structure is uniform and consistent with the surface structure;
the process comprises the following steps: the process flow of the process comprises the following steps of 120t converter smelting, LF refining, RH vacuum treatment, continuous casting pouring and rolling:
(1) Controlling the molten iron ratio of the molten iron fed into the converter to 87-90%, controlling the carbon content of the end point to 0.05-0.10%, adopting molten steel bottom argon blowing in the converter smelting process, and controlling the argon flow to 0.12Nm 3 Controlling the tapping temperature of the converter to 1615-1625 ℃ per t/min, wherein an Al-containing deoxidizing material is not added during tapping of the converter;
(2) In the LF refining process, the alkalinity of slag is controlled to be 3.8-5.0, the stirring flow of argon is controlled to be 190-200L/min in the LF whole process, and Cr, si, mn, al, ti, S elements are adjusted to be in place in the refining process;
(3) The RH process ensures that the time of the extreme vacuum treatment is not less than 22 minutes, B is adjusted to be in place after the vacuum treatment, and finally, the molten steel is subjected to calcium treatment, boron is added for 5 minutes, and then 60-80 m of calcium silicate wires are fed;
(4) The continuous casting process adopts protection pouring, argon blowing and asbestos sealing ring double protection are carried out on a large ladle long nozzle, argon blowing is carried out for more than half an hour before pouring, residual air is swept out on a tundish, and the tundish molten steel adopts pellet-shaped covering agent and carbonized rice husk double protection;
(5) The air-fuel ratio in the furnace is controlled to be 0.55-0.6 in the whole heating process in the steel rolling process; controlling the micro positive pressure of the atmosphere of the heating furnace to be 5-20pa; and adopting a controlled rolling and cooling process, controlling the final rolling temperature of KOCKS to be 830-880 ℃, and the upper cooling bed temperature to be 840-870 ℃, and slowly cooling after rolling in a pit.
CN202210085383.1A 2022-01-25 2022-01-25 Production method of B-alloy-containing structural steel for automobile parts Active CN114411045B (en)

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JPS61174327A (en) * 1985-01-29 1986-08-06 Sumitomo Metal Ind Ltd Manufacture of machine structural steel having superior delayed fracture resistance
CN100500916C (en) * 2007-10-17 2009-06-17 莱芜钢铁集团有限公司 Boron-containing steel and preparation method thereof
CN106834960B (en) * 2017-01-24 2018-06-01 中天钢铁集团有限公司 A kind of automobile using boracic top grade gear steel and its production technology
CN113957340B (en) * 2021-10-14 2022-04-08 中天钢铁集团有限公司 Control method for medium-carbon high-manganese vanadium-containing alloy structure round steel material structure

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