CN114959477A - Production method of hot-rolled round steel with low yield ratio and high impact property - Google Patents

Production method of hot-rolled round steel with low yield ratio and high impact property Download PDF

Info

Publication number
CN114959477A
CN114959477A CN202210598437.4A CN202210598437A CN114959477A CN 114959477 A CN114959477 A CN 114959477A CN 202210598437 A CN202210598437 A CN 202210598437A CN 114959477 A CN114959477 A CN 114959477A
Authority
CN
China
Prior art keywords
less
equal
round steel
rolling
hot
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202210598437.4A
Other languages
Chinese (zh)
Inventor
沈锋
杨涛
杨瑞文
蒋凌枫
张成元
郑健
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hunan Valin Xiangtan Iron and Steel Co Ltd
Original Assignee
Hunan Valin Xiangtan Iron and Steel Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hunan Valin Xiangtan Iron and Steel Co Ltd filed Critical Hunan Valin Xiangtan Iron and Steel Co Ltd
Priority to CN202210598437.4A priority Critical patent/CN114959477A/en
Publication of CN114959477A publication Critical patent/CN114959477A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • 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
    • 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
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • 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
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • 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
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • 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

Abstract

The invention relates to a production method of hot-rolled round steel with low yield ratio and high impact property. The steel comprises, by mass, 0.09-0.14% of C, 0.17-0.35% of Si, 1.50-1.60% of Mn, less than or equal to 0.012% of P, less than or equal to 0.005% of S, 0.030% to 0.060% of Als, 0.04-0.06% of V, less than or equal to 0.05% of Cr, less than or equal to 0.05% of Cu, less than or equal to 0.05% of Ni, less than or equal to 0.05% of Nb, less than or equal to 0.05% of Mo, less than or equal to 0.0015% of O, 0.0060-0.0090% of N and 0.37-0.43% of carbon equivalent. The hot-rolled round steel with low yield ratio and high low-temperature impact performance is obtained through a production process of converter + LF + RH + continuous casting + hot rolling + slow cooling, the metallographic structure of the hot-rolled round steel is ferrite + pearlite, the surface grain size is grade 8, and the core grain size is grade 7-8. The yield ratio of the hot rolled round steel is less than or equal to 0.72, and the longitudinal impact absorption energy KV is below 40 DEG C 2 More than or equal to 100J, and the elongation after fracture is more than or equal to 25 percent. The hot-rolled round steel has good processing performance and is suitable for being used in industries such as automobiles, bridges, light industry, high-rise buildings and the like.

Description

Production method of hot-rolled round steel with low yield ratio and high impact property
Technical Field
The invention belongs to the technical field of metallurgy, and relates to a production method of hot-rolled round steel with low yield ratio and high impact property.
Background
With the trend of light weight development of automobiles and the acceleration of the construction process of railways and highways, the application of the hot-rolled round steel with low yield ratio and high impact performance is increasing day by day, and the hot-rolled round steel with low yield ratio and high impact performance also becomes a hotspot of research and development. Compared with the round steel with a common structure, the round steel has lower yield ratio and good low-temperature impact toughness in a hot rolling state. The material has high deformation and damage resistance when being subjected to external force, does not deform or brittle damage, and has high safety. The alloy has low content of alloy elements, simple processing technology and relatively low cost, so the alloy is widely applied to industries such as automobiles, bridges, light industry, high-rise buildings and the like.
Disclosure of Invention
The invention aims to provide a production method of hot-rolled round steel with low yield ratio and high impact performance, which reduces the yield ratio while ensuring the low-temperature impact toughness and strength and produces the hot-rolled round steel with good obdurability, low yield ratio and high-low temperature impact performance.
A production method of hot-rolled round steel with low yield ratio and high impact performance comprises the following steps of converter smelting, LF furnace refining, RH furnace vacuum degassing, rectangular billet continuous casting, billet heating, controlled rolling, slow cooling and warehousing, wherein the steel comprises the following chemical components, by mass, 0.09-0.14% of C, 0.17-0.35% of Si, 1.50-1.60% of Mn, 0.012% or less of P, 0.005% or less of S, 0.030% or less of Als, 0.060% or less of V, 0.04-0.06% of V, 0.05% or less of Cr, 0.05% or less of Cu, 0.05% or less of Ni, 0.05% or less of Nb, 0.05% or less of Mo, 0.0015% or less of O, 0-0.0060.0090% of N and 0.37-0.43% of carbon equivalent. The key process steps comprise:
(1) smelting: the end point P of the converter is less than or equal to 0.010 percent; an LF + RH furnace refining process is adopted, and the alkalinity range of LF refining slag is controlled to be 6.0-8.0; RH vacuum pumping and degassing, starting circulation flow and increasing nitrogen in the vacuum pumping process, keeping the vacuum time below 0.5tor for not less than 8min, soft blowing for 15-20 min after breaking the vacuum, and enabling the outbound molten steel N = 60-90 ppm;
(2) continuous casting: the size of the rectangular blank is 350mm multiplied by 430mm, and the whole process is protected and cast; the water quantity of the crystallizer and the secondary cooling water quantity adopt weak cooling, and the superheat degree of molten steel is controlled to be 15-25 ℃; adopting dynamic soft reduction, wherein the total reduction is 21 mm; standing for 15min before pouring the molten steel;
(3) heating: heating the billet at 1160-1190 ℃ for 300-350 min, at 1160-1180 ℃ in a soaking section and at 1130-1150 ℃ in a discharging temperature;
(4) rolling: carrying out high reduction rolling by adopting a phi 1100 two-roller reversible rolling mill, wherein the reduction of the first pass and the reduction of the second pass are 65mm and 70mm respectively; the continuous rolling temperature is 950-970 ℃, and the final rolling temperature is 890-920 ℃;
(5) slow cooling: after rolling, slowly cooling the round steel by adding a heat preservation cover on a round steel cooling bed, wherein the temperature of the rolled round steel enters the heat preservation cover is 770-820 ℃, the temperature of the rolled round steel is 450-550 ℃, and the round steel is rolled into a pit for slow cooling after being taken off line.
The round steel produced by the method has the metallographic structure of ferrite and pearlite in a hot rolling state, the surface grain size of 8 grades, the core grain size of 7-8 grades, the yield ratio of less than or equal to 0.72 and the longitudinal impact absorption energy KV at minus 40 DEG C 2 Not less than 100J and not less than 25% elongation after fracture.
The invention relates to a production method of hot-rolled round steel with low yield ratio and high impact performance, which reduces impurities in steel by adopting converter low P smelting control, LF refining high-alkalinity reducing slag, RH vacuum degassing and long-time soft blowing and standing technologies. The continuous casting adopts a large-section casting blank to increase the compression ratio of a rolled material, and adopts weak cooling and dynamic soft reduction to improve the quality of the internal casting blank. The rolling adopts high-pressure initial rolling and controlled rolling, a cooling bed heat-insulating cover and a pit are adopted for slow cooling after rolling, the structure design adopts a plastic structure taking fine-grained ferrite and pearlite as matrixes, and the phenomena of pearlite structures and mixed crystals which are harmful to the impact performance and are distributed along a grain boundary in a continuous band shape can not occur, so that the yield ratio and the impact performance are controlled.
The invention principle is as follows:
1. design of chemical composition
The low-C low-P, S high-Mn component system is adopted in component design, Al with a certain content reduces the O content in steel and refines crystal grains, trace V elements are added, the refined crystal grains are strengthened through precipitation, the strength and toughness of the material are enhanced, and the low-temperature impact property of the material is improved. And a certain content of N in the steel is ensured, and the N is used as an alloy element of low alloy steel under the coordination of Al, V and other elements, so that the performance of the steel is further improved.
2. Control of molten steel purity
The tapping end point P of the converter is less than or equal to 0.010 percent, the aluminum-iron alloy is added after tapping the converter for precipitation pre-deoxidation, the Al content is controlled to be 0.020-0.040 percent, and the later-stage Al regulation is reduced. And adding 400kg of lime and 200kg of synthetic slag in the tapping process, and blowing argon for 5min after tapping to promote the adsorption of inclusions.
After the LF furnace is subjected to first power transmission and temperature rise, Al is deoxidized and adjusted in place once, the Al content is controlled according to 0.045-0.065%, and coral-shaped Al with a high melting point is mainly formed 2 0 3 And (4) clustering. The inclusion has large particle size and large collision bonding force, and is beneficial to Al 2 0 3 Impurities float upwards and are captured and adsorbed by the top slag, and only a small amount of compact cluster Al is left 2 0 3 Inclusion and individual Al 2 0 3 The particles remained in the steel bath and were less than 30um in size. If Al deoxidation is carried out in two or more steps, some plate-shaped Al may appear 2 0 3 And impurities with the particle size of 5-20 um are difficult to float and remove.
The molten steel temperature is low in the early stage of LF refining, the refining slag is in a high melting point region, the melting point is higher than 1500 ℃, in order to reduce the melting point of the slag and ensure the arc burying property, the CaO content of the refining initial slag is properly reduced (controlled to be about 50%), the Al2O3 content is properly increased (controlled to be about 25%), SiO2 is maintained at 10%, the CaO content is increased (controlled to be about 55-60%) in the middle stage of refining, and the alkalinity of the refining slag is controlled to be 6.0-8.0.
When the temperature of molten steel in the LF furnace exceeds 1580 ℃, nitrogen is increased in a nitrogen feeding line mode, the nitrogen content is controlled to be 60-90 ppm, the nitrogen content is not changed greatly in the later refining process, and ferrovanadium is added.
And (3) starting circulation flow nitrogen increasing in the vacuumizing process of the RH furnace, controlling the loss of nitrogen in the vacuum process, keeping the vacuum time below 0.5tor for not less than 8min, blowing soft argon for 15-20 min after the vacuum is broken, keeping the soft argon blowing time not too long, reducing secondary pollution of molten steel, standing the molten steel for 15min after the soft argon blowing, casting, and promoting the floating of inclusions.
3. Control of slab quality
The method is characterized in that a large-section rectangular billet is adopted for casting, the size of the casting blank is 350mm multiplied by 430mm, the whole process is protected for casting, the superheat degree of molten steel is controlled at 15-25 ℃, crystallizer electromagnetic stirring and tail end electromagnetic stirring are adopted, the water quantity of a crystallizer and secondary cooling water quantity are weakly cooled, dendritic crystal segregation can be reduced, a continuous casting blank with uniform components is obtained, the temperature difference between the center of a narrow surface and the center of a wide surface at the outlet of the crystallizer can be reduced, the thickness distribution of a solidified blank shell is promoted to be more uniform, and the surface crack incidence rate of the casting blank is reduced. The straightening process of the continuous casting billet adopts dynamic soft reduction, the reduction amount is 21mm in total, and the low-power quality of the continuous casting billet is further improved.
4. Control of round steel quality
The heating temperature of the billet is 1160-1190 ℃, the heating time is 300-350 min, the tapping temperature is 1130-1150 ℃, and the coarseness and the serious decarburization of crystal grains are controlled. The primary rolling technology of large reduction of a phi 1100 two-roller reversible rolling mill is adopted, the reduction of the first two passes is 65mm and 70mm, and crystal grains are crushed. The initial rolling is carried out in the recrystallization temperature range, and the deformed austenite is recrystallized to refine austenite grains. And controlling the continuous rolling temperature to be 950-970 ℃, namely, the continuous rolling is in the austenite non-recrystallization region for deformation. The finishing rolling temperature is controlled to be 890-920 ℃, the whole finishing rolling process is completed in an austenite region, the size of austenite grains is controlled, more nucleation positions are provided for phase change in the cooling process after rolling, the structure is uniform, and the grains are uniform and fine. And (3) after rolling, slowly cooling the round steel on a cooling bed by adding a heat preservation cover, controlling the temperature of the round steel entering the heat preservation cover to be 770-820 ℃, controlling the cooling rate to be 0.15 ℃/s, controlling the temperature of the round steel exiting the heat preservation cover to be 450-550 ℃, bundling the round steel, inserting the round steel into a pit for slow cooling, and further releasing hydrogen.
The invention has the following remarkable effects: the invention creates a low-C, low-P, S, high-Mn component system and an LF and RH composite refining technology, strictly controls the purity and dendritic crystal segregation of molten steel, adopts a new technology of controlled rolling and slow cooling of round steel, and successfully develops the hot-rolled round steel with low yield ratio and high impact property. The hot-rolled round steel product is suitable for being used in industries such as automobiles, bridges, light industry, high-rise buildings and the like. The invention breaks through the production process of the conventional round steel with the hot rolling structure, utilizes the existing equipment and process conditions of a steel mill, does not increase the investment and the production cost, meets the requirements of special users and saves the production cost.
Drawings
FIG. 1 is a metallographic picture of hot-rolled round steel of example 1 of the present invention, 100X, and a grain size of 7-8 grades; .
FIG. 2 is a metallographic structure of the bar in the delivered state.
Detailed Description
The invention will be further illustrated with reference to the following examples:
example 1
The production of the hot-rolled round steel with low yield ratio and high impact property is carried out according to the process flows of converter-LF-RH-continuous casting-rolling and the like. The chemical components of the steel are shown in the table 1 in percentage by weight, CEQ = 0.40, and the balance is Fe and inevitable impurities; the process comprises the following steps:
(1) converter end point P: 0.008 percent, 6.8 percent of alkalinity of LF refining final slag, 8min of RH vacuumizing, degassing, circulating flow nitrogen increasing, soft blowing for 18min after vacuum breaking, and 70ppm of nitrogen content of the outbound molten steel;
(2) the continuous casting speed is 0.58m/min, and the superheat degree of a tundish is 16-25 ℃; the water quantity of the crystallizer is 3400L/min, the specific water quantity of secondary cooling water is 0.16L/kg, the electric stirring parameter of the crystallizer is 150A/2.5Hz, and the electric stirring parameter of the tail end is 350A/8 Hz; starting the 5 th to the 9 th frames for dynamic soft pressing, wherein the pressing amounts are respectively 2mm, 3mm, 4mm, 6mm and 6mm, and the accumulated pressing amount is 21 mm.
(3) The heating temperature of the steel billet is 1165-1188 ℃, the total heating time is 320min, the soaking forging is 1162-1175 ℃, the heating time of the soaking section is 85min, and the tapping temperature is 1132-1145 ℃.
(4) Rolling: the reduction of the first pass and the second pass of the primary rolling are respectively 65mm and 70 mm; the continuous rolling temperature is 952-970 ℃, and the final rolling temperature is 894-921 ℃.
(5) Slow cooling: and (3) feeding rolled round steel to a cooling bed 772-815 ℃, slowly cooling the rolled round steel, discharging the rolled round steel out of the heat preservation cover at the temperature of 460-520 ℃, and bundling the round steel into a slow cooling pit.
Example 2
The production of the hot-rolled round steel with low yield ratio and high impact performance is carried out according to the process flows of converter-LF-RH-continuous casting-rolling and the like. The chemical components of the steel are shown in the weight percentage in table 1, CEQ = 0.41, and the balance of Fe and inevitable impurities; the process comprises the following steps:
(1) converter end point P: 0.007 percent, the alkalinity of LF refining final slag is 7.3, RH vacuum-pumping, degassing, circulating flow nitrogen increasing is carried out, the vacuum-maintaining time is 9min, soft blowing is carried out for 19min after the vacuum breaking, and the nitrogen content of the outbound molten steel is detected to be 75 ppm;
(2) the continuous casting speed is 0.58m/min, and the superheat degree of a tundish is 19-24 ℃; the water quantity of the crystallizer is 3400L/min, the specific water quantity of secondary cooling water is 0.16L/kg, the electric stirring parameter of the crystallizer is 150A/2.5Hz, and the electric stirring parameter of the tail end is 350A/8 Hz; starting the racks from the 5 th to the 9 th to perform dynamic soft pressing, wherein the pressing amounts are respectively 2mm, 3mm, 4mm, 6mm and 6mm, and the accumulated pressing amount is 21 mm;
(3) heating the steel billet at 1161-1189 ℃, heating for 331min in total, soaking at 1162-1171 ℃, heating for 81min in a soaking section, and discharging at 1129-1146 ℃;
(4) rolling: the reduction of the first pass and the second pass of the primary rolling are respectively 65mm and 70 mm; carrying out continuous rolling at 951-968 ℃ and finishing at 891-918 ℃;
(5) slow cooling: and (3) feeding rolled round steel to a cooling bed 775-821 ℃, discharging the rolled round steel out of the heat preservation cover after slow cooling at a temperature of 458-524 ℃, and bundling the round steel into a slow cooling pit.
Example 3
The production of the hot-rolled round steel with low yield ratio and high impact performance is carried out according to the process flows of converter-LF-RH-continuous casting-rolling and the like. The chemical components of the steel are shown in the weight percentage in table 1, CEQ = 0.40, and the balance of Fe and inevitable impurities; the process comprises the following steps:
(1) converter end point P: 0.006 percent, the alkalinity of LF refining final slag is 7.8, RH vacuum-pumping degassing circulation nitrogen increasing is carried out, the vacuum-maintaining time is 8min, soft blowing is carried out for 16min after the vacuum breaking, and the nitrogen content of the outbound molten steel is detected to be 79 ppm;
(2) the continuous casting speed is 0.58m/min, and the superheat degree of a tundish is 13-23 ℃; the water quantity of the crystallizer is 3400L/min, the specific water quantity of secondary cooling water is 0.16L/kg, the electric stirring parameter of the crystallizer is 150A/2.5Hz, and the electric stirring parameter of the tail end is 350A/8 Hz; starting the 5 th to the 9 th racks for dynamic soft pressing, wherein the pressing amounts are respectively 2mm, 3mm, 4mm, 6mm and 6mm, and the accumulated pressing amount is 21 mm;
(3) heating the billet at 1160-1185 ℃, the total heating time is 326min, soaking forging is 1158-1173 ℃, the soaking section heating time is 90min, and the tapping temperature is 1131-1147 ℃;
(4) rolling: the reduction of the first pass and the second pass of the primary rolling are respectively 65mm and 70 mm; the continuous rolling temperature is 954-968 ℃, and the final rolling temperature is 891-919 ℃;
(5) slow cooling: and (3) feeding rolled round steel to a cooling bed 772-811 ℃, slowly cooling the rolled round steel, discharging the rolled round steel out of a heat preservation cover at a temperature of 457-525 ℃, and bundling the round steel into a slow cooling pit.
Example 4
The production of the hot-rolled round steel with low yield ratio and high impact performance is carried out according to the process flows of converter-LF-RH-continuous casting-rolling and the like.
The chemical components of the steel are shown in the weight percentage in table 1, CEQ = 0.41, and the balance of Fe and inevitable impurities; the process comprises the following steps:
(1) converter end point P: 0.009%, the alkalinity of LF refining final slag is 7.2, RH vacuum-pumping, degassing, circulating flow nitrogen increasing, vacuum-maintaining time is 8min, soft blowing is carried out for 22min after vacuum breaking, and the nitrogen content of the outbound molten steel is detected to be 67 ppm;
(2) the continuous casting speed is 0.58m/min, and the superheat degree of a tundish is 17-22 ℃; the water quantity of the crystallizer is 3400L/min, the specific water quantity of secondary cooling water is 0.16L/kg, the electric stirring parameter of the crystallizer is 150A/2.5Hz, and the electric stirring parameter of the tail end is 350A/8 Hz; starting the 5 th to the 9 th racks for dynamic soft pressing, wherein the pressing amounts are respectively 2mm, 3mm, 4mm, 6mm and 6mm, and the accumulated pressing amount is 21 mm;
(3) the heating temperature of the steel billet is 1161-1182 ℃, the total heating time is 330min, the soaking forging is 1165-1179 ℃, the soaking section heating time is 81min, and the tapping temperature is 1131-1148 ℃;
(4) rolling: the reduction of the first pass and the second pass of the primary rolling are respectively 65mm and 70 mm; the continuous rolling temperature is 953-968 ℃, and the final rolling temperature is 891-916 ℃;
(5) slow cooling: and (3) feeding rolled round steel to a cooling bed 771-817 ℃, slowly cooling the rolled round steel, discharging the rolled round steel out of the heat preservation cover at a temperature of 457-516 ℃, and bundling the round steel into a slow cooling pit.
TABLE 1 chemical composition (%)
Figure 88264DEST_PATH_IMAGE001
Table 2 example hot-rolled round steel performance test results
Figure 336843DEST_PATH_IMAGE002
The mechanical properties of the hot-rolled round steel of each example are measured and shown in Table 2.
The embodiment shows that the method can obtain the steel bar with a metallographic structure of ferrite and pearlite, the surface grain size of 8 grades, the core grain size of 7-8 grades, the yield ratio of the steel bar less than or equal to 0.72, and the low-temperature longitudinal impact energy KV-40 DEG C 2 More than or equal to 100J, and the elongation after fracture is more than or equal to 25 percent. The alloy content of the steel is low, the production process is simple, the production cost is low, and the produced round steel has the characteristics of low yield ratio, high toughness and good low-temperature impact property, and can realize batch production.

Claims (1)

1. A production method of hot-rolled round steel with low yield ratio and high impact performance adopts a process route of converter smelting, LF furnace refining, RH furnace vacuum degassing, rectangular billet continuous casting, billet heating, controlled rolling, slow cooling and warehousing, and is characterized in that: the steel comprises, by mass, 0.09-0.14% of C, 0.17-0.35% of Si, 1.50-1.60% of Mn, less than or equal to 0.012% of P, less than or equal to 0.005% of S, 0.030% to 0.060% of Als, 0.04-0.06% of V, less than or equal to 0.05% of Cr, less than or equal to 0.05% of Cu, less than or equal to 0.05% of Ni, less than or equal to 0.05% of Nb, less than or equal to 0.05% of Mo, less than or equal to 0.0015% of O, 0.0060-0.0090% of N and 0.37-0.43% of carbon equivalent; the key process steps comprise:
(1) smelting: the end point P of the converter is less than or equal to 0.010 percent; an LF + RH furnace refining process is adopted, and the alkalinity range of LF refining slag is controlled to be 6.0-8.0; RH vacuum-pumping and degassing, starting circulation and increasing nitrogen in the vacuum-pumping process, keeping the vacuum for not less than 8min below the vacuum degree of 0.5tor, soft-blowing for 15-20 min after vacuum breaking, and enabling the outbound molten steel N = 60-90 ppm;
(2) continuous casting: the size of the rectangular blank is 350mm multiplied by 430mm, and the whole process is protected and cast; the water quantity of the crystallizer and the secondary cooling water quantity adopt weak cooling, and the superheat degree of molten steel is controlled to be 15-25 ℃; adopting dynamic soft reduction, wherein the total reduction is 21 mm; standing for 15min before pouring the molten steel;
(3) heating: heating the billet at 1160-1190 ℃ for 300-350 min, at 1160-1180 ℃ in a soaking section and at 1130-1150 ℃ in a discharging temperature;
(4) rolling: carrying out high reduction rolling by adopting a phi 1100 two-roller reversible rolling mill, wherein the reduction of the first pass and the reduction of the second pass are 65mm and 70mm respectively; the continuous rolling temperature is 950-970 ℃, and the final rolling temperature is 890-920 ℃;
(5) slow cooling: after rolling, slowly cooling the round steel by adding a heat preservation cover on a round steel cooling bed, wherein the temperature of the rolled round steel enters the heat preservation cover is 770-820 ℃, the temperature of the rolled round steel is 450-550 ℃, and the round steel is rolled into a pit for slow cooling after being taken off line.
CN202210598437.4A 2022-05-30 2022-05-30 Production method of hot-rolled round steel with low yield ratio and high impact property Pending CN114959477A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210598437.4A CN114959477A (en) 2022-05-30 2022-05-30 Production method of hot-rolled round steel with low yield ratio and high impact property

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210598437.4A CN114959477A (en) 2022-05-30 2022-05-30 Production method of hot-rolled round steel with low yield ratio and high impact property

Publications (1)

Publication Number Publication Date
CN114959477A true CN114959477A (en) 2022-08-30

Family

ID=82957261

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202210598437.4A Pending CN114959477A (en) 2022-05-30 2022-05-30 Production method of hot-rolled round steel with low yield ratio and high impact property

Country Status (1)

Country Link
CN (1) CN114959477A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117089757A (en) * 2023-09-23 2023-11-21 湖南华菱湘潭钢铁有限公司 Production method of non-quenched and tempered steel for 700 Mpa-level hydraulic piston rod

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109988973A (en) * 2019-05-22 2019-07-09 湖南华菱湘潭钢铁有限公司 A kind of production method of axle head hot rolled circular steel
CN113186452A (en) * 2021-03-30 2021-07-30 湖南华菱湘潭钢铁有限公司 Production method of steel for thermal forming end socket

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109988973A (en) * 2019-05-22 2019-07-09 湖南华菱湘潭钢铁有限公司 A kind of production method of axle head hot rolled circular steel
CN113186452A (en) * 2021-03-30 2021-07-30 湖南华菱湘潭钢铁有限公司 Production method of steel for thermal forming end socket

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117089757A (en) * 2023-09-23 2023-11-21 湖南华菱湘潭钢铁有限公司 Production method of non-quenched and tempered steel for 700 Mpa-level hydraulic piston rod

Similar Documents

Publication Publication Date Title
CN105755375B (en) A kind of continuous casting billet production low compression ratio high performance ultra-thick steel plate and its manufacture method
CN101160183B (en) Process and installation for producing a lightweight structural steel with a high manganese content
EP3859042A1 (en) High-strength high-toughness non-quenched and tempered round steel and preparation method
CN110592478B (en) Weather-resistant steel for railway bogie and manufacturing method thereof
CN101921953A (en) Production method of anti-corrosion and high strength ultra-thick steel plates
CN112662933A (en) Preparation method of low-temperature impact toughness-resistant wind power steel
CN111455278A (en) Thick hot-rolled high-strength steel plate coil with excellent low-temperature toughness and for 800MPa cold forming and manufacturing method thereof
CN102912221A (en) Large-thickness structural steel plate for high-rise building and production method thereof
CN109161671B (en) High-strength EH36 steel plate for high heat input welding and manufacturing method thereof
CN104988390A (en) E-level extra-thick high-intensity steel plate produced by using continuous casting billet and production method thereof
CN111979483A (en) Method for producing Q345R steel plate by using conventional hot rolling production line
CN113265502B (en) Preparation method of high-strength 550L automobile girder steel
CN102268615B (en) Engineering steel material with excellent core low-temperature impact toughness and lamellar tearing resisting performance and production method thereof
CN110592480A (en) Thick Q345R steel plate with excellent low-temperature impact toughness at core and manufacturing method thereof
CN110878405A (en) 700 Mpa-grade high-strength weather-resistant steel strip and CSP (cast Steel plate) process production method thereof
CN110029268B (en) 09MnNiDR steel plate for low-temperature pressure vessel with core low-temperature toughness protection and manufacturing method thereof
CN114959477A (en) Production method of hot-rolled round steel with low yield ratio and high impact property
CN113528976B (en) Non-quenched and tempered bar without surface cracks and preparation method thereof
CN110184534B (en) 100-150 mm thick super-thick steel plate with excellent performance after die welding treatment and production method thereof
CN111101070A (en) Steel for low-temperature liquid container tank car and preparation method thereof
CN110565024A (en) Niobium-titanium-containing 550 MPa-grade thick weathering resistant steel and production method thereof
CN110592475A (en) Large-size high-carbon silicon-manganese steel and manufacturing method thereof
CN114395736B (en) Vanadium microalloying production method for Q355B section steel
CN105543646A (en) Production process for medium-high carbon steel through thin slabs
CN114657467A (en) Production method of weather-resistant steel plate with yield strength of 415MPa

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination