CN113862578B - 80-grade cord steel, rolling method and application thereof - Google Patents
80-grade cord steel, rolling method and application thereof Download PDFInfo
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- CN113862578B CN113862578B CN202110992108.3A CN202110992108A CN113862578B CN 113862578 B CN113862578 B CN 113862578B CN 202110992108 A CN202110992108 A CN 202110992108A CN 113862578 B CN113862578 B CN 113862578B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
- B60C9/0007—Reinforcements made of metallic elements, e.g. cords, yarns, filaments or fibres made from metal
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- 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
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- 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
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
- B60C9/0007—Reinforcements made of metallic elements, e.g. cords, yarns, filaments or fibres made from metal
- B60C2009/0014—Surface treatments of steel cords
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Abstract
The application belongs to the field of metal materials, and particularly relates to 80-grade cord steel, a rolling method and application thereof; the chemical composition of the 80-grade cord steel comprises the following components in percentage by mass: c, Mn, Cr, Nb, V, Si, P, S, B, Als, Ti, and the balance of Fe and inevitable impurities; the metallographic structure of the 80-grade cord steel comprises lamellar pearlite, and the inter-lamellar spacing of the lamellar pearlite is 170-175 nm; the sorbitizing rate of the 80-grade cord steel is more than or equal to 95 percent; the method comprises the steps of obtaining a billet of the cord steel; heating the steel billet before rolling, hot rolling and cooling after rolling to obtain a cord steel wire rod; the application is to apply the cord steel in the tire framework material; the metallographic structure of the cord steel is controlled to be uniformly distributed through all components of the cord steel, so that the toughness of the cord steel can be improved while the cord steel reaches the standard.
Description
Technical Field
The application belongs to the field of metal materials, and particularly relates to 80-grade cord steel, a rolling method and application thereof.
Background
The cord steel is a base material for manufacturing a steel cord, known as "bright bead on an imperial crown in a wire product", and the cord steel generally satisfies a demand for strength improvement by increasing a carbon content, and is classified into 70C (normal strength), 80C (high strength), and 90C (ultrahigh strength) according to strength grades.
In the current processing process of the cord steel, the processing flow is long and complex, dozens of times of drawing and intermediate heat treatment are needed, the compression ratio of the steel wire is over 99 percent, the drawing length of ton steel is over 3000 kilometers, but the twisting and breaking rate of ton steel is required to be less than 4 times, if the structure of the cord steel is uneven, the fine defect of the cord steel is caused, the cord steel is exposed in the processing process, and the broken wire or the performance of the steel wire cannot reach the standard. Therefore, how to make the structure of the cord steel uniform and make the performance of the steel wire reach the standard is one of the technical problems to be solved at present.
Disclosure of Invention
The application provides 80-grade cord steel, a rolling method and application thereof, which aim to solve the technical problem that the steel wire performance is difficult to reach the standard due to the uneven structure of the cord steel in the prior art.
In a first aspect, the present application provides an 80-grade cord steel, wherein the chemical composition of the 80-grade cord steel comprises, by mass:
c: 0.80-0.85%, Mn: 0.15-0.25%, Cr: 0.31% -0.38%, Nb: 0.006% -0.012%, V: 0.006% -0.012%, Si: 0.15-0.25%, P is less than or equal to 0.01%, S is less than or equal to 0.01%, B: 0.0005-0.0009%, Als is less than or equal to 0.0008%, Ti is less than or equal to 0.0005%, and the balance of Fe and inevitable impurities;
the metallographic structure of the 80-grade cord steel comprises lamellar pearlite, and the inter-lamellar spacing of the lamellar pearlite is 170 nm-175 m; the sorbitizing rate of the 80-grade cord steel is more than or equal to 95 percent.
Optionally, the metallographic structure of the cord steel further comprises 90% -95% of sorbite and the balance pearlite in terms of volume fraction.
Optionally, the chemical composition of the 80-grade cord steel further comprises N, wherein,
(Nb + V)/N is 3-4.5, Nb represents the mass fraction of niobium element, V represents the mass fraction of vanadium element, and N represents the mass fraction of nitrogen element.
In a second aspect, the present application provides a rolling method of 80-grade cord steel, characterized in that the method comprises:
obtaining a steel billet of the cord steel;
heating the steel billet before rolling, hot rolling and cooling after rolling to obtain a cord steel wire rod;
the pre-rolling heating comprises a preheating section, a first heating section, a second heating section and a soaking section,
the hot rolling sequentially comprises rough rolling, intermediate rolling, pre-finish rolling, finish rolling and reducing and sizing.
Optionally, the temperature of the preheating section is less than or equal to 400 ℃, and the preheating time of the preheating section is more than or equal to 5 min;
the temperature of the first heating section is 400-800 ℃, and the heating time of the first heating section is more than or equal to 10 min;
the temperature of the second heating section is 800-1000 ℃, and the heating time of the second heating section is 60-100 min;
the temperature of the soaking section is 1000-1040 ℃, and the soaking time of the soaking section is 20-60 min.
Optionally, the rough rolling is performed by 5-8 passes;
the intermediate rolling is carried out by adopting 6-10 passes; the pre-finish rolling is carried out by adopting 5-7 passes;
the finish rolling is carried out for 8-12 times, and the inlet temperature of the finish rolling is 950-990 ℃;
the reducing and sizing are rolled by 3-5 times, the inlet temperature of the reducing and sizing is 940-980 ℃, and the spinning temperature of the reducing and sizing is 935-965 ℃.
Optionally, cooling after rolling is performed by adopting a stelmor air cooling line; the stelmor air cooling line comprises an inlet group roller way, N groups of roller ways and N +6 fans.
Optionally, the speed of the inlet group roller way is 15-20 m/min, when N is 1, the speed of the first group roller way is 30-40 m/min, and the speed of the nth group roller way is 5% -7% higher than that of the (N-1) th group roller way.
Optionally, the opening degree of the first fan and the second fan is 75% to 95%, when the temperature at the overlapping point of the third fan inlet wire rod is 655 ℃ to 705 ℃, the opening degree from the third fan to the sixth fan is 45% to 55%, and the rest N fans are all turned off.
In a third aspect, the present application provides a cord steel of the first aspect and a cord steel obtained by the method of the second aspect, which is applied to a tire frame material.
Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages:
according to the 80-grade cord steel provided by the embodiment of the application, by adding the chromium element, the niobium element and the vanadium element into the chemical components of the cord steel, the pearlite inter-sheet distance can be refined through chromium, the steel strength can be improved through refining grains, the hardenability can be improved, the austenite grains are prevented from growing greatly through niobium, the austenite grains are refined and heated, the decarburization sensitivity of medium-high carbon steel is reduced, the precipitation of eutectoid grain boundary cementite is reduced through vanadium, the austenite grains are inhibited from growing stably in the processing stage of the cord steel, the austenite grains grow stably through the added niobium and vanadium, and the inter-sheet distance of the lamellar pearlite is refined through chromium, so that the metallographic structure of the 80-grade cord steel is uniformly distributed, the cord steel can meet the standard, and the toughness of the cord steel is improved.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 is a schematic flow chart of a rolling method of 80-grade cord steel according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In one embodiment of the present application, there is provided a grade 80 cord steel, the chemical composition of which comprises, in mass fraction:
c: 0.80-0.85%, Mn: 0.15-0.25%, Cr: 0.31% -0.38%, Nb: 0.006% -0.012%, V: 0.006% -0.012%, Si: 0.15-0.25%, P is less than or equal to 0.01%, S is less than or equal to 0.01%, B: 0.0005 to 0.0009 percent of Fe, less than or equal to 0.0008 percent of Als, less than or equal to 0.0005 percent of Ti, and the balance of Fe and inevitable impurities;
the metallographic structure of the 80-grade cord steel comprises lamellar pearlite, and the inter-lamellar spacing of the lamellar pearlite is 170-175 nm; the sorbitizing rate of the 80-grade cord steel is more than or equal to 95 percent.
C is the most important constituent element in steel and has the most obvious influence on the strength and the plasticity of the wire rod; the reason for controlling the mass fraction of C to be 0.80-0.85% is to control the stability of the heat-conducting property and drawability of the final finished product and to control the strength and plasticity of the wire rod to be proper; when the value range of the mass fraction is too large, the carbon content is increased, so that the strength of the wire rod is continuously improved, the plasticity is rapidly reduced, the production control difficulty is higher, and the product quality stability is worse; when the value range of the mass fraction is too small, the carbon content is reduced, so that the strength of the wire rod is continuously reduced, the plasticity is rapidly improved, the production control difficulty is higher, and the product quality stability is poorer.
Si is an important strengthening element in steel, and can remarkably improve the elastic limit of the cord steel after drawing; the positive effect of controlling the mass fraction of Si to be 0.15-0.25% is to effectively reduce the strength reduction caused by heat treatment, and simultaneously, Si element can also slow down the breakage of cementite in the drawing process and improve the comprehensive mechanical property of the cord steel; when the value range of the mass fraction is too large, the content of Si is too high, and the brittleness of ferrite is increased; when the mass fraction value range is too small, the Si content is too low, and the adverse effect is that the elastic limit of the cord steel is insufficient and the cord steel is easy to break.
Mn is a precious alloy element, can be combined with sulfur to generate MnS, further reduces the harm of sulfur, can refine pearlite, and improves the structural uniformity of the cord steel, thereby improving the strength of the steel wire; the positive effect of controlling the mass fraction of Mn to be 0.15-0.25% is to prevent Mn from deviating in the cord steel, so that the structure of the cord steel is uniform and the performance of the cord steel is improved; when the mass fraction value range is too large, Mn is subjected to segregation, so that the structure and the performance are uneven, and the production cost is increased due to the excessively high Mn content; when the value range of the mass fraction is too small, it is said that the content of Mn is small, which causes an adverse effect that pearlite cannot be sufficiently refined, the degree of uniformity of the structure of the cord steel is insufficient, and the strength of the steel wire is insufficient.
P and S belong to harmful elements, wherein phosphorus is easy to generate cold brittleness, sulfur is easy to generate hot brittleness, and the positive effect of controlling the mass fraction of both P and S to be less than 0.01 percent is to prevent P and S from deteriorating the cord steel in the hot rolling stage.
Cr can refine the spacing of pearlite pieces, refine crystal grains, improve hardenability, improve the strength and work hardening rate of steel, and maintain the uniformity of a metallographic structure, so that the structure of the finally obtained cord steel is uniform; the positive effect of controlling the mass fraction of Cr to be 0.31-0.38% is to prevent martensite-type abnormal structure in the cord steel caused by excessively high Cr and to maintain the uniformity of the structure in the cord steel.
B can inhibit the enrichment of P in the grain boundary and improve the form of inclusions, thereby improving the cold processing performance of the wire rod; the positive effect of controlling the mass fraction of B to be 0.0005-0.0009% is to prevent excessive boron from weakening the grain boundary bonding force and influencing the uniformity of a metallographic structure, thereby deteriorating the mechanical properties of the cord wire steel wire rod.
Nb can prevent austenite grains from growing large, and the reheated austenite grains are refined to a certain extent, so that the metallographic structure of the cord steel is more uniform, the performance of the cord steel is improved, and niobium and carbon which are subjected to grain boundary segregation can form a relatively stable structure which can prevent the diffusion of carbon along the grain boundary, so that the decarburization sensitivity of medium-high carbon steel is reduced; the positive effect of controlling the mass fraction of Nb to be 0.006-0.012 percent is to prevent excessive Nb from degrading pearlite structures, accelerate spheroidization of cementite, influence the uniform distribution of metallographic structures and influence the strength performance of steel wires.
V can reduce the precipitation of eutectoid crystal boundary cementite, inhibit austenite grains from growing large, form precipitation strengthening and improve the strong plasticity of the wire rod and the steel wire; the positive effect of controlling the mass fraction of V to be 0.006-0.012 percent is that a proper amount of V can refine the interlayer spacing of the pearlite sheet, so that the structure is uniformly distributed, and the mechanical property of the cord steel is improved; when the mass fraction value range is too large, large V-N particles are formed, the space between the lamella is coarsened, the uniformity of the cord steel structure is influenced, and the steel wire is pulled or twisted and broken.
The active effect that the mass fraction of Als is less than or equal to 0.0008 percent is to control the content of acid-melted aluminum not to be too large and improve the content of acid-insoluble aluminum in the steel so as to improve the toughness of the steel.
The positive effect that the mass fraction of Ti is less than or equal to 0.0005 percent is that Ti can enhance the structure of the cord steel, and the Ti compound can enhance the hardness of the cord steel, so that the toughness of the cord steel is not facilitated, and the cord steel with better toughness can be obtained by controlling the content of Ti to be less than 0.0005 percent.
The positive effect that the sheet spacing of the lamellar pearlite is 170-175 m is that in the sheet spacing range, the lamellar pearlite can be uniformly distributed, so that the metallographic structure of the cord steel is uniformly distributed, the strength and the toughness of the cord steel are improved, and when the spacing value range is too large, the adverse effect is that the sheet spacing of the lamellar pearlite is too large, the strength of the longitudinal cord steel is influenced, and the toughness of the cord steel is influenced; when the range of the distance is too small, the adverse effect is that the lamellar spacing of lamellar pearlite is too small, affecting the strength of the cord steel in the transverse direction, and thus affecting the hardness of the cord steel.
The positive effect that the sorbite rate is more than or equal to 95 percent is that the sorbite has good mechanical property and is higher than pearlite in hardness, strength and impact toughness, so that the overall mechanical property of the cord steel can be improved; when the sorbite ratio is too small, the unfavorable effects of too low sorbite content and too low mechanical properties of the cord steel are caused.
As an optional embodiment, the metallographic structure of the cord steel further comprises 90-95% of sorbite by volume fraction, and the balance is pearlite.
As an alternative embodiment, the chemical composition of the 80-grade cord steel further comprises N, wherein,
(Nb + V)/N is 3-4.5, Nb represents the mass fraction of niobium element, V represents the mass fraction of vanadium element, and N represents the mass fraction of nitrogen element.
In the application, the positive effect that the sum of the mass fractions of Nb and V is 3-4.5 times of the mass fraction of N is that the effect of Nb and V microalloy elements in the cord steel cannot be separated from the combined N elements, the N element in the traditional cord steel needs to be strictly limited as a harmful element, and in the range that the sum of the mass fractions of Nb and V is 3-4.5 times of the mass fraction of N, the Nb and V composite microalloying effect can be fully exerted, the tissue uniformity degree in the cord steel is improved, and the deterioration of the steel performance by the N element can be avoided; when the value of the range is too large, the content of N is too large, which causes the deterioration of the performance of the cord steel; when the value of the range is too small, the content of N is low, and the action of Nb and V microalloy elements cannot be separated from the N element combined with the Nb and V microalloy elements, so that the action of the Nb and V microalloy elements cannot be started when the content of N is too small, austenite grains cannot be controlled, the metallographic structure is disordered, the uniformity of the cord steel structure is influenced, and the performance of the cord steel is influenced.
In a second aspect, as shown in fig. 1, the present application provides a rolling method of 80-grade cord steel, the method comprising:
s1, obtaining a steel billet of the cord steel;
s2, heating the steel billet before rolling, hot rolling and cooling after rolling to obtain a cord steel wire rod;
the pre-rolling heating comprises a preheating section, a first heating section, a second heating section and a soaking section,
the hot rolling sequentially comprises rough rolling, intermediate rolling, pre-finish rolling, finish rolling and reducing and sizing.
As an optional implementation mode, the temperature of the preheating section is less than or equal to 400 ℃, and the preheating time of the preheating section is more than or equal to 5 min;
the temperature of the first heating section is 400-800 ℃, and the heating time of the first heating section is more than or equal to 10 min;
the temperature of the second heating section is 800-1000 ℃, and the heating time of the second heating section is 60-100 min;
the temperature of the soaking section is 1000-1040 ℃, and the soaking time of the soaking section is 20-60 min.
In the application, the positive effect of limiting the temperature of the preheating section to be less than or equal to 400 ℃ is that steel before rolling can be fully heated in the temperature range, so that austenite in the steel starts to be gradually transformed; when the temperature value range is too large, the adverse effect is that the transformation speed of austenite can be improved by too high temperature, but the steel is overheated by too high temperature, and metallographic structure formation is easily influenced in the rolling process.
The positive effect that the preheating time is more than or equal to 5min is to provide sufficient preheating time to convert austenite to a target state; when the time value range is too small, the adverse effect is too short preheating time, so that the austenite conversion time is insufficient, the metallographic structure of rolled steel is uneven, and the strength and the toughness of the steel are influenced.
The positive effect that the temperature of the first heating section is 400-800 ℃ is that the steel heated by the preheating section can be further heated, so that the austenite of the steel in the first heating section starts to be rapidly converted; when the temperature value range is too large, the adverse effect is that the austenite transformation speed is too high due to too high temperature, and the uniformity of the metallographic structure forming in the first heating process is affected; when the temperature range is too small, an adverse effect is caused in that too low a temperature fails to convert austenite to a target state.
The positive effect that the heating time of the first heating section is more than or equal to 10min is that the heating time of the first heating section and the inner steel is enough, so that the austenite can be fully transformed in the first heating time; when the time value range is too small, the adverse effect is that the austenite transformation time is insufficient due to the too short first heating time, the metallographic structure of the rolled steel is not uniform, and the strength and the toughness of the steel are affected.
The positive effect that the temperature of the second heating section is 800-1000 ℃ is that the steel after the first heating can be further subjected to austenite transformation in the second heating section; when the temperature value range is too large, the adverse effect is that too high temperature leads to too high transformation speed of austenite, and the uniformity degree of the metallographic structure in the second heating process is influenced; when the temperature range is too small, an adverse effect will be caused in that too low a temperature will not transform the austenite to the target state.
The positive effect that the heating time of the second heating section is 60-100 min is that the heating time of the second heating section and the inner steel is enough, so that austenite can be fully transformed in the second heating time; when the time span is too small, the adverse effect is that the second heating time is too short, so that the austenite transformation time is insufficient, the metallographic structure of the rolled steel is not uniform, and the strength and toughness of the steel are affected.
The temperature of the soaking section is 1000-1040 ℃, and the positive effect is to keep the temperature required by austenite transformation; when the temperature range is too large, the adverse effect is that the overhigh temperature can completely transform austenite, but the energy consumption is too much, so that the process energy consumption is influenced; when the temperature value range is too small, the adverse effect is that austenite cannot start to transform, the metallographic structure of the steel is not uniform, and the strength and the toughness of the steel are affected;
the time of the soaking section is 20-60 min, so that the steel after the second heating can be subjected to complete austenite transformation in the soaking section; when the time value range is too large, the adverse effect is that too long time causes too long process time; when the time value range is too small, the adverse effect is that the austenite in the steel cannot be completely transformed within too short time, and the uniformity of the metallographic structure of the steel is affected.
As an optional embodiment, the rough rolling is performed by 5 to 8 passes;
the intermediate rolling is carried out by adopting 6-10 passes; the pre-finish rolling is carried out by adopting 5-7 passes;
the finish rolling is carried out for 8-12 times, and the inlet temperature of the finish rolling is 950-990 ℃;
the reducing and sizing are rolled by 3-5 times, the inlet temperature of the reducing and sizing is 940-980 ℃, and the spinning temperature of the reducing and sizing is 935-965 ℃.
In the application, the positive effect that the inlet temperature of finish rolling is 950-990 ℃ is that the finish rolling temperature is controlled, the metallographic structure of the steel is uniformly distributed, and the steel with target strength and toughness is obtained; when the value range of the temperature is too large, the adverse effect to be caused is that the energy consumption of the process is increased by the overhigh temperature, and when the value range of the temperature is too small, the adverse effect to be caused is that the distribution of the metallographic structure in the steel rolling process is not uniform by the overlow temperature, the uniformity degree of the metallographic structure is influenced, and further the strength and the toughness of the steel are influenced.
The positive effect that the inlet temperature of the reducing diameter is 940-980 ℃ is that the temperature of the reducing diameter is controlled, so that the metallographic structure of the steel subjected to reducing diameter is uniformly distributed, and the steel with target strength and toughness is obtained; when the value range of this temperature is too big, the adverse effect that will lead to is that too high temperature can increase the energy consumption of technology, and when the value range of this temperature is undersize, the adverse effect that will lead to is that too low temperature will lead to the inhomogeneous distribution of metallographic structure in the steel rolling process, influences the even degree of metallographic structure, and then influences the intensity and the toughness of steel.
The positive effect that the spinning temperature of the reducing diameter is 935-965 ℃ is to stabilize the metallographic structure of the formed cord steel, so that the strength and toughness of the cord steel are stabilized; when the value range of this temperature is too big, the adverse effect that will lead to is that too high temperature can increase the energy consumption of technology, and when the value range of this temperature is undersize, the adverse effect that will lead to is that too low temperature will lead to the inhomogeneous distribution of metallographic structure in the steel rolling process, influences the even degree of metallographic structure, and then influences the intensity and the toughness of steel.
As an optional embodiment, the post-rolling cooling is performed by using a stelmor air cooling line, where the stelmor air cooling line includes an inlet group of roller beds, N groups of roller beds, and N +6 fans.
In this application, the cooling adopts the positive effect of stelmor forced air cooling line to roll the back and strengthen the control of cooling stage to cooling rate, prevents that cooling rate is too fast or influence the homogeneous degree of the metallographic structure of steel too slowly.
As an optional embodiment, the speed of the inlet group roller way is 15-20 m/min, when N is 1, the speed of the first group roller way is 30-40 m/min, and the speed of the nth group roller way is 5% -7% higher than that of the N-1 group roller way.
In the application, the positive effect that the speed of the roller way of the inlet group is 15-20 m/min is to control the speed of the steel entering the air cooling process, so that the steel is completely cooled in the air cooling process; too big when the value range of this speed, the adverse effect that will lead to is that too fast entry speed will lead to steel to get into the speed of forced air cooling too fast, influences steel metallographic structure cooling shaping, and when the value range undersize of this speed, the adverse effect that will lead to is that too low speed will not in time make rolled steel get into the forced air cooling procedure, leads to steel to have passed through the cooling at the device kneck, influences the control to steel cooling degree.
The first group of roller ways has the positive effect that the speed is 30-40 m/min, and the motion speed of the steel when the steel starts to be cooled is controlled, so that the operation speed of the steel when the steel starts to be cooled is matched with the cooling speed; when the value range of the speed is too large, the adverse effect to be caused is that too fast running speed leads to insufficient time for cooling the steel, the cooling effect of the steel is influenced, and when the value range of the speed is too small, the adverse effect to be caused is that too slow running speed leads to uneven range for cooling the steel, the running speed of subsequent steel is influenced, and the cooling degree of the steel is influenced.
The positive effect that the speed of the Nth group of roller ways is improved by 5 to 7 percent compared with the speed of the Nth-1 group of roller ways is that the speed of the cooling roller is gradually increased, so that the running speed of the steel is gradually increased, the cooling time is gradually reduced, the gradient control of the cooling speed is realized, and the steel can be fully cooled.
As an optional embodiment, the first fan and the second fan have an opening ratio of 75% to 95%, when the temperature at the overlapping point of the third fan inlet wire rod is 655 ℃ to 705 ℃, the opening ratio of the third fan to the sixth fan is 45% to 55%, and all the remaining N fans are turned off.
In the application, the positive effect that the opening degrees of the first fan and the second fan are 75% -95% is to control the cooling degree of steel when the steel enters the device, so that the steel reaches the target cooling degree; when the value range of the opening degree is too large, the adverse effect to be caused is that the too high opening degree enables the cooling speed of the steel to be too high, the control on the cooling speed of the steel is influenced, and when the value range of the opening degree is too small, the adverse effect to be caused is that the too small opening degree reduces the cooling degree of the steel and influences the cooling effect of the steel.
The positive effect that the opening degrees of the third fan to the sixth fan are all 45% -55% is to control the subsequent cooling degree of the steel so that the cooling speed of the steel reaches the target cooling degree; when the value range of the opening degree is too large, the adverse effect to be caused is that the too high opening degree enables the cooling speed of the steel to be too high, the control on the cooling speed of the steel is influenced, and when the value range of the opening degree is too small, the adverse effect to be caused is that the too small opening degree reduces the cooling degree of the steel and influences the cooling effect of the steel.
As an optional embodiment, in the heating before rolling, the length and the width of the section of the billet are 160-200 mm and 160-200 mm respectively.
In the application, the positive effects that the length and the width of the steel billet are 160-200 mm and 160-200 mm respectively are that the obtained steel billets are uniformly distributed, and the subsequent rolling process is conveniently and smoothly carried out; when the length and width is too large, the maximum standard of machine rolling is not met, and when the length and width is too small, the stability of the billet in the rolling stage is influenced due to larger gap in the rolling process.
In a third aspect, the present application provides a cord steel of the first aspect and a cord steel obtained by the method of the second aspect, which is applied to a tire frame material.
The chemical composition of the comparative examples of each example is shown in table 1:
TABLE 1 chemical composition table of comparative examples (%)
| Item | C | Si | Mn | P | S | Cr | B | Nb | V | Multiple of | Als | Ti |
| Example 1 | 0.80 | 0.21 | 0.22 | 0.009 | 0.004 | 0.35 | 0.0006 | 0.008 | 0.011 | 4.5 | 0.0002 | 0.0004 |
| Example 2 | 0.80 | 0.15 | 0.25 | 0.005 | 0.008 | 0.35 | 0.0007 | 0.006 | 0.008 | 3.5 | 0.0003 | 0.0002 |
| Example 3 | 0.81 | 0.23 | 0.15 | 0.005 | 0.005 | 0.34 | 0.0008 | 0.009 | 0.009 | 3.5 | 0.0004 | 0.0003 |
| Example 4 | 0.82 | 0.23 | 0.25 | 0.003 | 0.005 | 0.38 | 0.0009 | 0.008 | 0.009 | 3.4 | 0.0005 | 0.0004 |
| Example 5 | 0.80 | 0.25 | 0.21 | 0.004 | 0.001 | 0.35 | 0.0008 | 0.007 | 0.010 | 3.1 | 0.0005 | 0.0005 |
| Example 6 | 0.83 | 0.19 | 0.15 | 0.001 | 0.005 | 0.34 | 0.0009 | 0.009 | 0.008 | 3.2 | 0.0004 | 0.0005 |
| Example 7 | 0.85 | 0.17 | 0.18 | 0.006 | 0.001 | 0.33 | 0.0009 | 0.009 | 0.006 | 4.1 | 0.0003 | 0.0004 |
| Example 8 | 0.84 | 0.16 | 0.15 | 0.004 | 0.004 | 0.31 | 0.0005 | 0.010 | 0.006 | 3.5 | 0.0005 | 0.0003 |
| Example 9 | 0.83 | 0.18 | 0.16 | 0.008 | 0.007 | 0.32 | 0.0006 | 0.011 | 0.008 | 3.5 | 0.0005 | 0.0004 |
| Example 10 | 0.82 | 0.18 | 0.17 | 0.005 | 0.006 | 0.33 | 0.0007 | 0.008 | 0.007 | 3.5 | 0.0004 | 0.0003 |
| Example 11 | 0.82 | 0.19 | 0.18 | 0.005 | 0.004 | 0.35 | 0.0005 | 0.009 | 0.009 | 3.4 | 0.0003 | 0.0005 |
| Example 12 | 0.81 | 0.20 | 0.19 | 0.001 | 0.008 | 0.34 | 0.0005 | 0.009 | 0.009 | 3.1 | 0.0005 | 0.0005 |
| Example 13 | 0.85 | 022 | 0.22 | 0.004 | 0.005 | 0.38 | 0.0006 | 0.010 | 0.009 | 4.2 | 0.0004 | 0.0004 |
| Example 14 | 0.81 | 0.23 | 0.23 | 0.007 | 0.005 | 0.35 | 0.0009 | 0.011 | 0.010 | 4.2 | 0.0005 | 0.0003 |
| Example 15 | 0.84 | 0.25 | 0.25 | 0.003 | 0.001 | 0.34 | 0.0009 | 0.012 | 0.011 | 4.3 | 0.0004 | 0.0005 |
| Comparative example 1 | 0.87 | 0.22 | 0.50 | 0.006 | 0.005 | 0.001 | 0.0003 | 0.0005 | 0.0004 | / | 0.0010 | 0.0008 |
| Comparative example 2 | 0.88 | 0.23 | 0.51 | 0.004 | 0.005 | 0.005 | 0.0002 | 0.0004 | 0.0006 | / | 0.0010 | 0.0009 |
| Comparative example 3 | 0.88 | 0.22 | 0.48 | 0.008 | 0.001 | 0.006 | 0.0003 | 0.0007 | 0.0005 | / | 0.0009 | 0.0008 |
Wherein the multiple means that the sum of the mass fractions of Nb and V is a multiple of the mass fraction of N.
The process parameters for the pre-roll heating of each example and comparative example are shown in table 2:
TABLE 2 Process parameters for pre-roll heating of examples and comparative examples
The process parameters of the hot rolling process of each example and comparative example are shown in table 3:
TABLE 3 Process parameter Table of hot rolling process of examples and comparative examples
The process parameters for the post-rolling cooling of the examples and comparative examples are shown in table 4:
TABLE 4 Process parameters for post-roll Cooling of examples and comparative examples
Related experiments:
the cord steel prepared in examples 1 to 15 and comparative examples 1 to 3 were subjected to the performance test, and the test results are shown in table 5.
TABLE 5 Performance test results
In the context of Table 5, the following examples are given,
the tensile strength of the hot-rolled wire rod means the tensile strength of the wire rod obtained after the hot rolling is finished, and when the tensile strength is higher, the higher the toughness of the cord steel wire rod after the hot rolling is.
The tensile strength of the final cord steel monofilament means the tensile strength of the finally obtained cord steel monofilament, and when the tensile strength is higher, the toughness of the cord steel product is better.
The final strand-twisting and filament-breaking rate of the cord steel monofilament refers to the toughness of the finally obtained cord steel monofilament, and when the strand-twisting and filament-breaking rate is lower, the toughness of the cord steel product is better.
From the data of examples 1-15, it can be seen that:
(1) by controlling the technological parameters of heating before rolling, hot rolling and cooling after rolling, the uniformity of the metallographic structure of the cord steel can be influenced under the condition that the contents of the chemical components of the cord steel are close to each other, so that the strength, toughness and tensile property of the cord steel are controlled, and the strand twisting and thread breakage rate can be adjusted to a certain degree.
(2) Metallographic analysis of the metallographic structure of the obtained cord steel shows that the lamellar pearlite has the lamellar spacing of 170-175 nm and the sorbite rate is more than or equal to 95 percent.
From the data of comparative examples 1 to 3:
(1) if the proportional relation between the sum of the mass fractions of Nb and V and the mass fraction of N is not controlled, if N is not added, the tensile strength of the hot rolled wire rod and the tensile strength of the final cord steel monofilament are reduced, and the strand twisting and filament breakage rate is obviously increased.
One or more technical solutions in the embodiments of the present application at least have the following technical effects or advantages:
(1) the 80-grade cord steel product provided by the embodiment of the application can influence the uniformity of the metallographic structure of cord steel through the interaction among all the components in the cord steel raw material under the condition of not increasing the carbon content, thereby improving the toughness and the tensile strength of the cord steel, and all the performances of the obtained cord steel are superior to those of the traditional 86-grade cord steel, so that the production cost of steel enterprises is reduced, the requirement of downstream users on improving the steel wire plasticity is met, the product has good market application prospect, and the product is expected to comprehensively replace the traditional cord steel.
(2) By controlling the content of chromium, the degree of uniformity of a metallographic structure in the cord steel can be finely adjusted, so that the tensile strength and the strand twisting and breaking rate of the finally obtained cord steel monofilament change along with the change of the metallographic structure, and the cord steel monofilament is suitable for different market product requirements.
(3) In the chemical components of the cord steel provided by the embodiment of the application, the components can cooperate with each other, and a cord steel monofilament product with low stranding and breaking rate can be obtained by controlling the proportional relation between the sum of the mass fractions of Nb and V and the mass fraction of N.
(4) According to the rolling process provided by the embodiment of the application, the process parameters in the processes of heating before rolling, hot rolling and cooling after rolling can be adjusted, so that the tensile strength of the hot-rolled wire rod and the tensile strength of the final cord steel monofilament can be adjusted, and the strand twisting and filament breakage rate can be finely adjusted, so that the processes of heating before rolling, hot rolling and cooling after rolling can be controlled according to the use requirements of different products, and the cord steel product meeting the requirements can be obtained.
It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in the process, method, article, or apparatus that comprises the element.
The foregoing are merely exemplary embodiments of the present invention, which enable those skilled in the art to understand or practice the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (9)
1. An 80-grade cord steel, characterized in that the chemical composition of the 80-grade cord steel comprises the following components in mass fraction:
c: 0.80-0.85%, Mn: 0.15-0.25%, Cr: 0.31% -0.38%, Nb: 0.006% -0.012%, V: 0.006% -0.012%, Si: 0.15-0.25%, P is less than or equal to 0.01%, S is less than or equal to 0.01%, B: 0.0005 to 0.0009 percent of Fe, less than or equal to 0.0008 percent of Als, less than or equal to 0.0005 percent of Ti, and the balance of Fe and inevitable impurities;
the metallographic structure of the 80-grade cord steel comprises lamellar pearlite, and the inter-lamellar spacing of the lamellar pearlite is 170-175 nm; the sorbitizing rate of the 80-grade cord steel is more than or equal to 95 percent, the chemical components of the 80-grade cord steel also comprise N, wherein,
([ Nb ] + [ V ])/[ N ] is 3 to 4.5, [ Nb ] represents the mass fraction of the niobium element, [ V ] represents the mass fraction of the vanadium element, and [ N ] represents the mass fraction of the nitrogen element.
2. The 80-grade cord steel according to claim 1, further comprising 90 to 95% sorbite, and the balance pearlite, in terms of volume fraction, in the metallographic structure of the cord steel.
3. A rolling method of 80 grade cord steel according to claim 1 or 2, characterized in that the method comprises:
obtaining a steel billet of the cord steel;
heating the steel billet before rolling, hot rolling and cooling after rolling to obtain a cord steel wire rod;
the pre-rolling heating comprises a preheating section, a first heating section, a second heating section and a soaking section,
the hot rolling sequentially comprises rough rolling, intermediate rolling, pre-finish rolling, finish rolling and reducing and sizing.
4. The method according to claim 3, wherein the temperature of the preheating section is less than or equal to 400 ℃, and the preheating time of the preheating section is more than or equal to 5 min;
the temperature of the first heating section is 400-800 ℃, and the heating time of the first heating section is more than or equal to 10 min;
the temperature of the second heating section is 800-1000 ℃, and the heating time of the second heating section is 60-100 min;
the temperature of the soaking section is 1000-1040 ℃, and the soaking time of the soaking section is 20-60 min.
5. The method according to claim 3, wherein the rough rolling is performed in 5-8 passes;
the intermediate rolling is carried out by adopting 6-10 passes; the pre-finish rolling is carried out by adopting 5-7 passes;
the finish rolling is carried out for 8-12 times, and the inlet temperature of the finish rolling is 950-990 ℃;
the reducing and sizing are rolled by 3-5 times, the inlet temperature of the reducing and sizing is 940-980 ℃, and the spinning temperature of the reducing and sizing is 935-965 ℃.
6. The method of claim 3, wherein the post-rolling cooling is performed using a stelmor air cooling line; the stelmor air cooling line comprises an inlet group roller way, N groups of roller ways and N +6 fans.
7. The method according to claim 6, wherein the speed of the roller way of the inlet group is 15-20 m/min, when N is 1, the speed of the roller way of the first group is 30-40 m/min, and the speed of the roller way of the Nth group is 5-7% higher than that of the roller way of the Nth-1 group.
8. The method of claim 6, wherein the first fan and the second fan have an opening ratio of 75% to 95%, and when the temperature at the third fan inlet wire rod lap joint point is 655 ℃ to 705 ℃, the opening ratio of the third fan to the sixth fan is 45% to 55%, and all of the remaining N fans are off.
9. Use of a cord steel according to claim 1 or 2 or obtained by a method according to any one of claims 3 to 8 in a tyre carcass material.
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