CN115430812A - Control method for medium-high carbon steel uniform structure for automobile constant-speed transmission shaft - Google Patents
Control method for medium-high carbon steel uniform structure for automobile constant-speed transmission shaft Download PDFInfo
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- CN115430812A CN115430812A CN202210973177.4A CN202210973177A CN115430812A CN 115430812 A CN115430812 A CN 115430812A CN 202210973177 A CN202210973177 A CN 202210973177A CN 115430812 A CN115430812 A CN 115430812A
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- 238000000034 method Methods 0.000 title claims abstract description 55
- 229910000677 High-carbon steel Inorganic materials 0.000 title claims abstract description 21
- 230000005540 biological transmission Effects 0.000 title claims abstract description 18
- 230000008569 process Effects 0.000 claims abstract description 40
- 238000009749 continuous casting Methods 0.000 claims abstract description 36
- 238000003756 stirring Methods 0.000 claims abstract description 32
- 238000005204 segregation Methods 0.000 claims abstract description 31
- 238000001816 cooling Methods 0.000 claims abstract description 28
- 230000009467 reduction Effects 0.000 claims abstract description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 23
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 21
- 239000010959 steel Substances 0.000 claims abstract description 21
- 238000005096 rolling process Methods 0.000 claims abstract description 20
- 239000000203 mixture Substances 0.000 claims abstract description 3
- 238000005266 casting Methods 0.000 claims description 12
- 229910001562 pearlite Inorganic materials 0.000 claims description 10
- 229910052799 carbon Inorganic materials 0.000 claims description 9
- 229910000859 α-Fe Inorganic materials 0.000 claims description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 7
- 238000007711 solidification Methods 0.000 claims description 4
- 230000008023 solidification Effects 0.000 claims description 4
- 238000009826 distribution Methods 0.000 claims description 3
- 239000007790 solid phase Substances 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- 238000004886 process control Methods 0.000 claims 1
- 239000013078 crystal Substances 0.000 abstract description 23
- 210000001787 dendrite Anatomy 0.000 abstract description 7
- 238000005272 metallurgy Methods 0.000 abstract description 2
- 238000004513 sizing Methods 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 8
- 238000011946 reduction process Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 3
- 238000003723 Smelting Methods 0.000 description 2
- 238000007689 inspection Methods 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
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- 239000007788 liquid Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
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- 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
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/1206—Accessories for subsequent treating or working cast stock in situ for plastic shaping of strands
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
- B21B1/463—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting in a continuous process, i.e. the cast not being cut before rolling
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- 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
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- 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
- B22D11/114—Treating the molten metal by using agitating or vibrating means
- B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
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- 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
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/122—Accessories for subsequent treating or working cast stock in situ using magnetic fields
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- 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
- B22D11/16—Controlling or regulating processes or operations
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- 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
- B22D11/16—Controlling or regulating processes or operations
- B22D11/18—Controlling or regulating processes or operations for pouring
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- 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
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
- B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/28—Normalising
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/002—Heat treatment of ferrous alloys containing Cr
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
Abstract
The invention belongs to the technical field of metallurgy, and particularly relates to a control method of a medium-high carbon steel uniform structure for an automobile constant-speed transmission shaft, which is characterized in that center segregation is relieved by combining double control of continuous casting dynamic soft reduction and tail end large electromagnetic stirring, wherein the total reduction is controlled to be 10 to 12mm, and the tail stirring current is 300A; the large electromagnetic stirring and secondary cooling and weak cooling control of the crystallizer are adopted, the equiaxial crystal area is enlarged, and the dendrite segregation is reduced, wherein the crystallizer electrically stirs the current 350A. The structure is uniform through an online normalizing controlled rolling controlled cooling process, and the normalizing process can replace the normalizing process, wherein the controlled rolling controlled cooling temperature is controlled by a water tank, and a KOCKS three-roller reducing sizing mill set is used for final rolling. The method improves the composition segregation of medium-high carbon steel, ensures that the steel structure has higher uniformity, and can replace normalizing, thereby obtaining high-quality and high-fatigue-life transmission shaft parts.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a control method for a uniform structure of medium-high carbon steel for an automobile constant-speed transmission shaft.
Background
The transmission shaft is an important part for transmitting power in an automobile transmission system, and a key part for ensuring the safe running of the automobile is provided. The constant-speed transmission shaft outer star wheel is generally made of medium-high carbon steel, the medium-high carbon steel has excellent processing and mechanical properties, but steel materials are heavier and heavier along with the increase of carbon content, and are more easy to generate structural non-uniformity such as banding, black core (center segregation), mixed crystal and the like, so that part heat treatment deformation and the like are caused, and the service fatigue life of the transmission shaft is seriously influenced.
Middle-high carbon steel due to liquid-solid line temperature (T) l ～T s ) The interval is large, in the process of casting blank solidification, the interaction of elements easy to segregate such as C, mn, S and P is easy to form serious center segregation, molten steel feeding along a liquid cavity, particularly the solidification tail end is hindered, the center of a casting blank is loosened, and shrinkage cavity is formed seriously. The severity of the central porosity, shrinkage cavity and segregation of the casting blank depends on the proportion of columnar crystals and equiaxed crystals, and the higher the temperature gradient of the liquid-solid line is, the more developed the growth of the columnar crystals and the heavier the central segregation and porosity are. Therefore, how to reduce the center segregation and center porosity of medium-high carbon steel has been a difficult problem in the industry.
The structural uniformity of steel is mainly influenced in several ways: firstly, dendritic segregation (microsegregation) of a casting blank can cause structural inhomogeneity of a ferrite-pearlite band (a band-shaped structure); secondly, the center segregation (macrosegregation) of the casting blank can cause the structural nonuniformity of the steel black core (center mixed crystal); thirdly, the rolling temperature and the process are not properly controlled, and the structure nonuniformity such as coarse grains, edge mixed crystals and the like is caused. At present, in general, in order to realize uniform organization, a user needs to normalize the steel before using the steel.
The invention aims to improve the component segregation (micro-segregation and macro-segregation) of medium-high carbon steel, realize the uniform structure substitution normalizing of ferrite and pearlite, improve the service performance of materials and obtain a transmission shaft with high quality and long fatigue life.
Disclosure of Invention
The purpose of the invention is: provides a control method of a medium-high carbon steel uniform structure for an automobile constant-speed transmission shaft, and provides a continuous casting and rolling process for improving component segregation and replacing normalizing by a uniform ferrite and pearlite structure.
In order to realize the purpose of the invention, the method is realized by the following technical scheme:
(1) The continuous casting adopts a large-section low-drawing-speed process, the section of a casting blank is 300mm multiplied by 325mm, the drawing speed is 0.75-0.80 m/min, the low superheat degree is controlled at 15-30 ℃, the temperature gradient is reduced, the developed growth of columnar crystals is prevented, the segregation of dendrites is reduced, and the generation of the structural non-uniformity of ferrite and pearlite bands is prevented.
(2) The continuous casting soft reduction process adopts large reduction and multi-roller (5 lower rollers) continuous small reduction, the total reduction is 10-12 mm, when the central solid phase rate is more than or equal to 0.50 and less than or equal to 1, the reduction is 8-10 mm, a No. 1-4 roller is used, and the single-roller reduction is less than or equal to 3.0mm; when the simulated core temperature of the cast slab is lower than the solidification (solid phase) temperature, the reduction amount is 2mm, and a No. 5 roll is used.
(3) The electromagnetic stirring process of the continuous casting tail end is matched with the process under the light pressure, the electric stirring current is 300A +/-10A, the frequency is 6.0 +/-0.2 HZ, and the electromagnetic stirring process and the process under the light pressure are combined for use, so that the center porosity and the center segregation are better improved, and the tissue nonuniformity caused by component segregation (particularly carbon elements) is reduced.
(4) The electromagnetic stirring process for continuous casting crystallizer adopts large current stirring with current 350A + -10A and frequency 2.0 + -0.2 HZ to break up columnar crystal, increase nucleation point, enlarge equiaxial crystal region and reduce dendrite segregation.
(5) The secondary cooling process for continuous casting adopts a weak cooling mode, is matched with a crystallizer to carry out large electromagnetic stirring, controls the specific water amount to be 0.12L/kg-0.15L/kg, lightens the temperature difference between the inside and the outside of a casting blank, prevents the developed growth of columnar crystals and enlarges an equiaxial crystal area. Wherein, each section is cooled: the full-water cooling is adopted for the foot roller section, the first area, the second area and the third area are cooled by gas fog, and the water distribution ratio is 45%:22%:20%:13 percent.
(6) The rolling on-line normalizing rolling-controlling cooling-controlling process is characterized in that the temperature before entering a KOCKS unit is controlled to be 800-850 ℃, the steel throwing temperature (upper cooling bed temperature) is 780-830 ℃, wherein a No. 1-4 water tank is used for a water tank before entering the KOCKS unit, a No. 5 water tank is not used, enough time is given for uniformly entering the temperature before the KOCKS, and a No. 6 water tank is used after rolling.
The invention has the beneficial effects that: the dynamic soft reduction of continuous casting and the large electromagnetic stirring at the tail end are combined to realize double control, so that the center segregation is reduced; the equiaxed crystal area is enlarged and the segregation of dendrite crystal is reduced by adopting large electromagnetic stirring of crystallizer and secondary cooling and weak cooling control. Through the rolling on-line normalizing rolling-controlled cooling process, the normalizing is replaced by the uniform structure. So as to improve the component segregation (micro-segregation and macro-segregation) of medium-high carbon steel, realize the purpose of uniform structure substitution of ferrite and pearlite for normalizing, improve the comprehensive use performance of materials and obtain the transmission shaft with high quality and long fatigue life.
Description of the drawings:
FIG. 1 is a photograph showing a low magnification test of the steel obtained in example 1.
FIG. 2 is a photograph showing a transverse structure of the steel obtained in example 1.
FIG. 3 is a photograph showing a low magnification examination of the steel obtained in comparative example 1.
FIG. 4 is a photograph showing a transverse structural inspection of the steel obtained in comparative example 1.
FIG. 5 is a photograph showing a transverse structure test of the steel obtained in comparative example 3.
FIG. 6 is a photograph showing the mixed crystal inspection of the steel obtained in comparative example 3.
Detailed Description
The present invention is further illustrated with reference to the following specific examples, but the scope of the present invention is not limited to the following examples.
Taking medium-high carbon steel 55 steel as an example, the chemical composition is as follows: 0.55% of C, 0.26% of Si, 0.78% of Mn, 0.27% of Cr, 0.010% of P, 0.016% of S, 0.025% of Al, and the balance of Fe and impurity elements. A5-machine 5-strand arc continuous casting machine with a cross section of 300mm multiplied by 325mm is adopted.
Example 1
(1) The continuous casting adopts a large-section low-drawing-speed process, the section of a casting blank is 300mm multiplied by 325mm, the drawing speed is 0.75/min, the low superheat degree is controlled at 28 ℃, the temperature gradient is reduced, the developed growth of columnar crystals is prevented, the segregation of dendrites is reduced, and the generation of the structural non-uniformity of ferrite and pearlite bands is prevented.
(2) The continuous casting soft reduction process adopts large reduction and multi-roller (5 lower rollers) continuous small reduction;
the continuous casting soft reduction process is shown in the following table:
| press roller | Number 1 | Number 2 | No. 3 | Number 4 | Number 5 | Total reduction mm |
| Reduction of | 1.5 | 2.2 | 2.3 | 2 | 2 | 10 |
(3) The electromagnetic stirring process of the continuous casting tail end is matched with the process under the light pressure, the electric stirring current 310A and the frequency 6.0HZ are combined with the process under the light pressure, and the center porosity and the center segregation are better improved, so that the structural nonuniformity caused by component segregation (particularly carbon elements) is reduced.
(4) The electromagnetic stirring process for continuous casting crystallizer adopts large current stirring, current is 350A, frequency is 2.0HZ, columnar crystal is broken, nucleation point is increased, equiaxial crystal area is enlarged, and dendrite segregation is reduced.
(5) The secondary cooling process for continuous casting adopts a weak cooling mode, is matched with a crystallizer to stir in a large electromagnetic way, controls the specific water amount to be 0.14L/kg, lightens the temperature difference between the inside and the outside of a casting blank, prevents columnar crystals from growing well and enlarges an equiaxed crystal area. Wherein, each section is cooled: full water cooling is adopted in sufficient roller section, and first district, second district, three district adopt aerial fog cooling, and the water distribution ratio is 45%:22%:20%:13 percent.
(6) The rolling on-line normalizing rolling-controlling cooling-controlling process is characterized in that the temperature before entering a KOCKS unit is controlled to be 800 ℃, and the steel throwing temperature (the temperature of an upper cooling bed) is 780 ℃, wherein a water tank 1-4 is used before entering the KOCKS unit, a water tank 5 is not used, enough time is given for uniformly entering the temperature before entering the KOCKS, and a water tank 6 is used after rolling.
Example 2
(1) The continuous casting speed is 0.78m/min, and the superheat degree is 25 ℃.
(2) The electromagnetic stirring current at the tail end is 300A, the frequency is 6HZ, and the continuous casting soft reduction process is shown in the following table:
| press roller | Number 1 | Number 2 | No. 3 | Number 4 | Number 5 | Total reduction mm |
| Reduction of | 2.1 | 2.5 | 2.5 | 2.1 | 2 | 11.2 |
(3) The rolling on-line normalizing process has the temperature of 820 ℃ before entering KOCKS and the steel throwing temperature of 806 ℃.
(4) The other processes were the same as in example 1.
Example 3
(1) The continuous casting speed is 0.80m/min, and the superheat degree is 26 ℃.
(2) The electromagnetic stirring current at the tail end 295A, the frequency of 6HZ and the continuous casting soft reduction process are shown in the following table:
| press roller | Number 1 | Number 2 | No. 3 | Number 4 | Number 5 | Total reduction mm |
| Reduction of | 2.3 | 2.6 | 2.6 | 2.5 | 2 | 12 |
(3) The rolling on-line normalizing process has the temperature of 850 ℃ before entering KOCKS and the steel throwing temperature of 812 ℃.
(4) The other processes were the same as in example 1.
Comparative example 1
(1) The continuous casting adopts a large-section low-drawing-speed process, the section of a casting blank is 300mm multiplied by 325mm, the drawing speed is 0.75/min, the low superheat degree is controlled at 28 ℃, the temperature gradient is reduced, the developed growth of columnar crystals is prevented, the segregation of dendrites is reduced, and the generation of the structural non-uniformity of ferrite and pearlite bands is prevented.
(2) And in the continuous casting tail end electromagnetic stirring process, the electric stirring current is 100A, and the frequency is 6HZ.
The electromagnetic stirring process, the secondary cooling process and the on-line normalizing rolling cooling control process of the continuous casting crystallizer are the same as those in the embodiment 1.
Comparative example 2
(1) The continuous casting adopts a large-section low-drawing-speed process, a continuous casting soft-pressing process and a continuous casting tail end electromagnetic stirring process which are the same as those in the embodiment 1.
The electromagnetic stirring process current at the tail end of the continuous casting is 250A, and the frequency is 2.0HZ; the secondary cooling process of continuous casting adopts a medium-intensity cooling mode, and the specific water amount is 0.20L/kg.
The rolling on-line normalizing rolling-controlling cooling-controlling process is the same as that in the embodiment 1.
Comparative example 3
Steps (1) to (5) were the same as in example 1.
And (6) a rolling online normalizing process is not adopted, the temperature is 880 ℃ before entering KOCKS, the steel throwing temperature is 872 ℃, and the temperature is not controlled by a water tank.
The central carbon segregation (difference between the central carbon content of steel and the carbon content of smelting components/smelting components) of the inventive examples 1-3 and the comparative examples 1-3, the ferrite and pearlite structure uniformity rating (GB/T13320), the mixed crystal phenomenon, and the grain size grade are as follows:
the results show that: the method improves the center segregation by combining continuous casting dynamic soft reduction and tail end large electromagnetic stirring with double control, enlarges an equiaxial crystal area by large electromagnetic stirring and secondary cooling and weak cooling control of a crystallizer, and obtains a uniform structure of ferrite and pearlite by an online normalizing rolling control and cooling control process, thereby completely replacing the normalizing.
The above embodiments are only preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and all modifications of the above embodiments according to the technical spirit of the present invention are included in the scope of the present invention.
Claims (6)
1. A control method for a medium-high carbon steel uniform structure for an automobile constant-speed transmission shaft is characterized by comprising the following steps: the method comprises the following steps of continuous casting under light press, continuous casting electromagnetic stirring, continuous casting secondary cooling and rolling on-line normalizing, and specifically comprises the following steps:
(1) Continuous casting adopts a large-section low-pulling-speed and low-superheat-degree process, and the section of a casting blank is 300mm multiplied by 325mm;
(2) The continuous casting soft reduction adopts large reduction and multi-roller continuous small reduction, and the total reduction under the soft reduction is 10-12 mm;
(3) Electromagnetic stirring is carried out at the tail end of the continuous casting, and the electric stirring current is 300A +/-10A and the frequency is 6.0 +/-0.2 HZ by matching with a light pressure process;
(4) Electromagnetic stirring is carried out on the continuous casting crystallizer, and high-current stirring is adopted, wherein the current is 350A +/-10A, and the frequency is 2.0 +/-0.2 HZ;
(5) Secondary cooling of continuous casting, adopting a weak cooling mode, matching with large electromagnetic stirring of a crystallizer, and controlling the specific water amount to be 0.12L/kg-0.15L/kg;
(6) The rolling on-line normalizing rolling-controlling cooling-controlling process controls the temperature before entering the KOCKS unit to be 800-850 ℃ and the steel throwing temperature to be 780-830 ℃, wherein a No. 1-4 water tank is used for a water tank before entering the KOCKS unit, a No. 5 water tank is not used, and a No. 6 water tank is used after rolling.
2. The method for controlling the uniform structure of the medium-high carbon steel for the constant-speed transmission shaft of the automobile according to claim 1, wherein the drawing speed in the step (1) is 0.75-0.80 m/min, and the superheat degree is controlled to be 15-30 ℃.
3. The method for controlling the uniform structure of the medium-high carbon steel for the constant speed transmission shaft of the automobile according to claim 1, wherein in the step (2), when the solid phase ratio of the casting blank center is 0.50 ≤ fs ≤ 1, the reduction is 8-10 mm, and a number 1-4 roller is used, and the reduction of a single roller is ≤ 3.0mm; when the core temperature of the cast slab is lower than the solidification temperature, the reduction amount is 2mm, and a No. 5 roller is used.
4. The method for controlling the uniform structure of medium-high carbon steel for an automobile constant velocity transmission shaft according to claim 1, wherein the cooling of each stage in the step (5): the full-water cooling is adopted for the foot roller section, the first area, the second area and the third area are cooled by gas fog, and the water distribution ratio is 45%:22%:20%:13 percent.
5. The method for controlling the uniform structure of the medium-high carbon steel for the constant speed transmission shaft of the automobile according to claim 1, wherein the medium-high carbon steel has a chemical composition in percentage by weight; 0.50 to 0.56 percent of C, 0.15 to 0.30 percent of Si, 0.65 to 0.80 percent of Mn, 0.020 to 0.030 percent of Cr, less than or equal to 0.020 percent of P, 0.010 to 0.025 percent of S, 0.015 to 0.040 percent of Al, and the balance of Fe and impurity elements.
6. The medium-high carbon steel for the constant velocity transmission shaft obtained by the method according to any one of claims 1 to 5, wherein the medium-high carbon steel has a central carbon segregation of 8% or less, a uniform ferrite and pearlite structure, and a grain size of 7 or more.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210973177.4A CN115430812B (en) | 2022-08-15 | 2022-08-15 | Control method for uniform structure of medium-high carbon steel for automobile constant-speed transmission shaft |
Applications Claiming Priority (1)
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