CN115945525A - Method for improving rolling stability of high-carbon steel for chain - Google Patents
Method for improving rolling stability of high-carbon steel for chain Download PDFInfo
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- CN115945525A CN115945525A CN202211740382.2A CN202211740382A CN115945525A CN 115945525 A CN115945525 A CN 115945525A CN 202211740382 A CN202211740382 A CN 202211740382A CN 115945525 A CN115945525 A CN 115945525A
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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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/20—Bonding
- B23K26/21—Bonding by welding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
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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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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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
- C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
- C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
- C21D8/1233—Cold rolling
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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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G3/00—Apparatus for cleaning or pickling metallic material
- C23G3/02—Apparatus for cleaning or pickling metallic material for cleaning wires, strips, filaments continuously
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Abstract
The invention discloses a method for improving rolling stability of high-carbon steel for a chain, belonging to the field of high-carbon steel rolling, and comprising the following process steps: hot rolled material → uncoiling → welding → descaling → acid washing, rinsing and drying → five-stand tandem rolling → coiling → coil stripping → annealing → leveling → shearing → cold rolling finished product. Compared with the prior art, the method has the characteristics of high rolling stability in the cold rolling stage, avoids frequent strip breakage of welding seams, and realizes stable production of high-carbon steel on an acid rolling line.
Description
Technical Field
The invention discloses a divisional application of a patent application of ' a method for increasing the rolling stability of 50Mn high-carbon steel for chains ' (2020108998261 '), and relates to a production process of high-carbon steel, in particular to a method for increasing the rolling stability of the high-carbon steel for chains.
Background
The high carbon steel sheet is a steel sheet containing 0.3wt% or more of carbon and having a pearlite crystal phase in its crystal structure. High carbon steel is a widely used high carbon steel product, and can be used in the industries of chains, sawteeth and the like due to high strength and high hardness. High carbon steel sheets are generally produced as intermediate products called hot-rolled steel sheets from slabs through a continuous hot rolling process, and the hot-rolled steel sheets are subjected to an acid pickling and spheroidizing annealing process and then to a cold rolling process to produce cold-rolled steel sheets. The cold-rolled steel sheet is then subjected to a cold-rolling process and an annealing process in sequence, and a cold-rolled steel sheet having a desired thickness is produced.
At present, domestic medium-high carbon strip steel is basically produced on a single-stand rolling mill, and the production efficiency is low. To solve this technical problem, many steel mills have attempted to produce high carbon steel in continuous pickling lines. But because the high-carbon steel has high content of C, si and Mn components and high strength, and is produced by a continuous rolling, continuous casting and hot rolling production line, the strength of the high-carbon steel is higher than that of the high-carbon steel of the traditional hot rolling process by more than 60MPa under the same specification. Therefore, as the strength is too high, for high-carbon steel with the carbon content of more than 0.5 percent and the thickness of less than or equal to 1.5mmmm, the thermal conductivity is poor, the high-carbon steel is produced on a continuous pickling line, the temperature difference between a welding part and a non-heated part is obvious, and when a molten pool is rapidly cooled, the crack is easily formed due to the internal stress caused in the welding line; the weld and the heat affected zone are more likely to generate hard and brittle high carbon martensite, so the quenching tendency and the crack sensitivity are larger, and the weldability is poor. Due to the influence of high welding temperature, crystal grains grow fast, carbides are easy to accumulate and grow on grain boundaries, welding seams are weak, the strength of welding joints is reduced, rolling is difficult in a cold rolling stage, and frequent strip breakage of the welding seams is caused. Therefore, in the current production mode of high-carbon steel, hot-rolled raw material coils are mostly subjected to acid pickling by an acid pickling unit, the iron scales of strip steel are washed off to form acid-pickled coils, then finished coils are transported backwards, and multi-pass rolling is carried out on a single-stand reversible rolling mill, so that the production of a five-pass rolling mill cannot be realized, and the production efficiency is low.
Therefore, in order to overcome the defect, the invention of China application (CN 201610571452.4) starts with product components, and adds various components of zinc, magnesium, copper, cadmium, scandium, strontium, cesium, barium sulfate, nano ceramic powder, diphenylsulfimide and a coating material consisting of zinc, aluminum, a fluorescent brightener, a surfactant, indium, an antioxidant and selenium and arranged on the surface of a base material besides carbon, manganese, silicon, phosphorus, sulfur, aluminum, chromium and nickel, thereby greatly increasing the production cost.
In addition, in order to avoid the technical defects of weak welding seams and cold rolling cracks, the Chinese invention applies a high-carbon steel thin strip and a production method thereof (CN 201910777534.8) to directly replace a cold rolling annealing product by producing hot-rolled thin strip steel with the thickness of less than 2.5mm in one step. However, since the annealing and cold rolling processes are necessary for forming fine spheroidized cementite in the pearlite structure of the hot rolled high carbon steel sheet, this method has a small yield strength and a reduced fatigue life because of the pearlite contained therein, and thus the quality of the final product is not satisfactory, although it has a small thickness and stability.
Disclosure of Invention
The technical task of the invention is to provide a method for improving the rolling stability of high-carbon steel for chains aiming at the defects of the prior art.
The technical scheme for solving the technical problem is as follows: a method for improving the rolling stability of high-carbon steel for chains is characterized by comprising the following steps: the process comprises the following steps: hot rolled material → uncoiling → welding → descaling → acid washing, rinsing and drying → five-frame tandem rolling → coiling → coil stripping → annealing → flattening → shearing → cold rolled finished product; wherein, the welding step adopts 1 time of preheating and 2 times of annealing process, and the specific operation is as follows: after the welding seam is preheated for 1 time and annealed for 1 time, the laser welding function of the welding machine is closed by manual control, the annealing power is kept, a welding wheel of the welding machine moves away from the welding seam again, and the secondary annealing power plays a role in heating and insulating the welding seam; in the step of pickling, rinsing and drying, the thickness of the raw material is more than or equal to 2.5mm, and the speed of the pickling process section is less than or equal to 100m/min; the thickness of the raw material is less than 2.5mm, and the speed of the pickling process section is less than or equal to 120m/min; in the five-stand continuous rolling step, the thickness of the raw material is less than or equal to 2.5mm, and the compression ratio is 36-50%; the thickness of the raw material is more than 2.5mm, and the compression ratio is 31.5-43%; the annealing adopts a cover annealing process, the annealing temperature is heated from 400 ℃ to 720 ℃, and the heating time is 12-13 hours; the temperature is kept for 10 to 11 hours at the annealing temperature of 720 ℃.
The steel grade which is in lap joint welding with the steel grade in the welding step requires that the yield strength difference between the steel grade and the steel grade is less than or equal to 150MPa.
In the welding step, the thickness of the raw material is less than or equal to 50mm and less than 2mm, the welding speed is 7.2-7.8 m/min, the preheating power is 10-12KW, and the annealing power is 18-20KW; the thickness of the raw material is less than or equal to 2mm and less than or equal to 2.5mm, the welding speed is 7.8m/min, the preheating power is 14KW, and the annealing power is 22KW.
In the five-stand continuous rolling step, the load distribution of each stand is as follows: 18-22%, two frames: 20% -25%; three frames: 18 to 22 percent; four frames: 12 to 15 percent; five frames: 5 to 6 percent; 1. the tension between the second, third and fourth frames is 2-5%.
Compared with the prior art, the invention has the following outstanding beneficial effects:
1. the high-strength high-carbon steel is welded under the control of an acid rolling welding machine, so that the rolling stability in the cold rolling stage is ensured, frequent strip breakage of a welding line is avoided, and the stable production of the high-carbon steel on an acid rolling line is realized;
2. the compatibility of thin specification and stability is realized, the strength is ensured, the yield strength is high, the fatigue life is not influenced, the quality of the cold-rolled sheet product is ensured, and the use requirement of a user is met;
3. the existing equipment and facilities are utilized, the components are simple, the production cost is not increased, and the popularization is convenient.
Detailed Description
The present invention will be further described with reference to the following embodiments. Unless defined otherwise, technical or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The invention relates to a process method for producing cold-rolled plates by carrying out acid pickling cold rolling, cover annealing and flattening processes on high-strength high-carbon steel hot-rolled products developed and produced on the basis of a hot-rolling production line.
The raw materials of the invention are high-strength high-carbon steel hot-rolled products developed and produced based on a hot-rolling production line, and the production process of the raw materials comprises the following steps: heating a plate blank → rough rolling → finish rolling → cooling → coiling → hot rolled material.
Wherein, the high-carbon steel hot rolled material comprises the following components: 0.5 to 0.56 percent of C; 0.2 to 0.3 percent of Si; mn:0.6% -0.7%, P: less than or equal to 0.025 percent; s: less than or equal to 0.005 percent; and Als: less than or equal to 0.02 percent; cr: less than or equal to 0.02 percent; ni is less than or equal to 0.02 percent; cu is less than or equal to 0.02 percent, and the balance is Fe and inevitable impurities.
The hot rolled material obtained by the steps has the specification thickness of 1.5-3.8 mm, and the properties are shown in the following table:
| thickness of raw material (mm) | Yield strength MPa | Tensile strength MPa | Elongation percentage% |
| 1.5 | 597 | 870 | 17.6 |
| 1.8 | 578 | 865 | 18.5 |
| 2 | 540 | 846 | 19.3 |
| 2.25 | 530 | 843 | 19.4 |
| 2.5 | 527 | 840 | 20.2 |
| 2.75 | 523 | 837 | 20.2 |
| 3.25 | 514 | 820 | 20.5 |
| 3.8 | 489 | 785 | 20.9 |
The process steps of the invention comprise: hot rolled material → uncoiling → welding → descaling → acid washing, rinsing and drying → five-stand tandem rolling → coiling → coil stripping → annealing → flattening → shearing → cold rolling finished product.
(1) Uncoiling of hot rolled material
(2) Welding of
Because the high-carbon steel has high contents of C, si and Mn components and high strength, hard and brittle high-carbon martensite is more easily generated in a welding seam and a heat affected zone, and the welding performance is poor.
In order to ensure the welding stability and stable production, the yield strength difference between the high-carbon steel welding requirement and the steel grade required for lap welding with the steel grade is less than or equal to 150MPa, and the thickness difference between two steel coils is less than 10 percent or less than 0.1mm; the difference in width must not exceed 200mm.
The welding machine of the acid rolling combined unit is a Mibach wire filling welding machine. The basic parameters are: the maximum welding speed is 12m/min; the welding power is 12KW at maximum; the maximum pressure of the leveling wheel is 100Bar; the maximum preheating power is 40KW, the maximum annealing power is 40KW, and the maximum laser head pressure is 100Bar; the wire feeding speed of the wire filling is 15m/min.
The parameters of the lap welding of the high-carbon steel and the high-carbon steel are shown in the following table, and the process parameters in the table are percentages of the parameters of the welding machine.
Wherein, the first and the second end of the pipe are connected with each other,
the thickness of the raw material is less than or equal to 1.50mm and less than 2mm, and the welding speed is 60-65 percent of the maximum parameter of the welding machine
(7.2-7.8 m/min), the welding power is 75% (9 KW) of the maximum parameter of the welding machine, the pressure of the leveling wheel is 10% (10 Bar) of the maximum parameter of the welding machine, the preheating power is 25-30% (10-12 KW) of the maximum parameter of the welding machine, the annealing power is 45-50% (18-20 KW) of the maximum parameter of the welding machine, the pressure of the laser head is 25% (25 Bar) of the maximum parameter of the welding machine, and the wire feeding speed is 75% (11.25 m/min) of the maximum parameter of the welding machine.
The thickness of the raw material is less than or equal to 2mm and less than or equal to 2.5mm, the welding speed is 7.8m/min, the welding power is 9.6-10.2 KW, the pressure of a leveling wheel is 15-20 Bar, the preheating power is 14KW, the annealing power is 22KW, the pressure of a laser head is 30Bar, and the wire feeding speed is 12m/min.
When the thickness of the raw material is more than 2.5mm, the welding speed is 6-7.2 m/min, the welding power is 9.6-10.2 KW, the pressure of a leveling wheel is 20-30 Bar, the preheating power is 16-20 KW, the annealing power is 24-26 KW, the pressure of a laser head is 30-35 Bar, and the wire feeding speed is 12m/min.
The lap welding parameters of the high-carbon steel and the low-carbon steel are shown in the following table, wherein the process parameters are percentages of the parameters of the welding machine.
Wherein the content of the first and second substances,
the thickness of the raw material is less than or equal to 1.50mm and less than 2mm, and the welding speed is 65-70 percent of the maximum parameter of the welding machine
(7.8-8.4 m/min), the welding power is 75-80% (9-9.6 KW) of the maximum parameter of the welding machine, the pressure of the leveling wheel is 10% (10 Bar) of the maximum parameter of the welding machine, and the preheating power is 25-30% of the maximum parameter of the welding machine
(10-12 KW), the annealing power is 30-45% (12-18 KW) of the maximum parameter of the welding machine, the pressure of the laser head is 25% (25 Bar) of the maximum parameter of the welding machine, and the wire feeding speed is 75% (11.25 m/min) of the maximum parameter of the welding machine.
The thickness of the raw material is not less than 2mm and not more than 2.5mm, the welding speed is 7.8m/min, the welding power is 9.6-10.2 KW, the pressure of a leveling wheel is 15Bar, the preheating power is 14KW, the annealing power is 22KW, the pressure of a laser head is 30Bar, and the wire feeding speed is 12m/min.
When the thickness of the raw material is more than 2.5mm, the welding speed is 6.6-7.2 m/min, the welding power is 9.6-10.2 KW, the pressure of a leveling wheel is 20-25 Bar, the preheating power is 18-20KW, the annealing power is 24-26 KW, the pressure of a laser head is 30-35 Bar, and the wire feeding speed is 12m/min.
The welding process of the wire filling welding machine comprises three steps of preheating, welding and annealing: the preheating temperature for welding the high-carbon steel is 250-350 ℃, the temperature for stress relief heat treatment is 600-650 ℃, and the selection of proper preheating power and annealing power in the welding process is crucial. The strength of the hot rolling raw material is higher than the yield strength and the tensile strength of the traditional hot rolling. Therefore, the preheating power and the annealing power are increased during welding, and the welding speed is slower. The welding speed is slow, the preheating function and the annealing power are high, and the welding of two welded steels can be better ensured.
In order to ensure that the structure of a heat affected zone of a high-carbon steel weld joint is sorbite and ferrite and ensure the stability of the weld joint, the invention has the most important welding process characteristic of adopting 1-time preheating and 2-time annealing process, and the specific operation is as follows: after the welding seam is preheated for 1 time and annealed for 1 time, the laser welding function of the welding machine is closed by manual control, the annealing power is kept, the welding wheel of the welding machine moves away from the welding seam again, and the secondary annealing power plays a role in heating and insulating the welding seam. The traditional high-carbon steel welding is generally 1 time of preheating and 1 time of annealing, because of high carbon content, the laser welding annealing belongs to air cooling, the cooling speed is high, when 1 time of annealing is adopted, the weld structure can not completely convert ferrite and pearlite, bainite and sorbite exist, and the toughness of the weld structure is poor. Meanwhile, the heat affected zone on one side is martensite and sorbite, the brittleness is high, the cup bulge experiment is directly cracked, and the welding line does not meet the production requirement. When 2 times of annealing is adopted, the effect of heat preservation on the weld joint structure is equivalent to that bainite and sorbite in the weld joint structure are completely replaced by ferrite and pearlite, martensite in the weld joint of the heat affected zone on one side is completely converted into ferrite and sorbite, the structure has good toughness and high strength, a vertical weld joint is cracked during a cup-convex test of the weld joint, and the weld joint meets the production requirement.
(3) Breaking scales
Because the high-carbon steel has high strength and relatively poor welding quality, the welding seam is easy to break in the repeated bending process of the phosphorus breaking machine. In order to ensure the stability of the high-carbon steel welding seam over-breaking phosphorus machine, the welding seam over-breaking phosphorus machine, a bending roller and a straightening roller of the phosphorus machine are opened.
(4) Acid washing, rinsing and drying
The welding line is broken when the strip steel is repeatedly bent by a tension roller or a phosphorus breaker roller, and the speed of the pickling section needs to be controlled in order to ensure the stable production of high-carbon steel.
The thickness of the raw material is more than or equal to 2.5mm, and the speed of the pickling process section is less than or equal to 100m/min.
The thickness of the raw material is less than 2.5mm, and the speed of the pickling process section is less than or equal to 120m/min.
And (3) drying: ensuring that the strip steel comes out from the rinsing section and does not carry water after being dried by the dryer.
(5) Five stand rolling
The five-stand continuous rolling process is adopted, and the following parameters are controlled:
(1) compression ratio:
because the alloy composition is high, the raw material strength is high, the rolling force in the production process is large, in order to avoid the abnormal conditions of uneven thick plates, poor plate shape or broken welding seams in the production process of a rolling mill, the rolling is usually carried out by adopting a proper compression ratio, so that the rolling force of each frame of the rolling mill can be reduced, and therefore, the design of the compression ratio adopts the design idea of a small compression ratio.
The thickness of the raw material is less than or equal to 2.5mm, and the compression ratio is 36-50%.
The thickness of the raw material is more than 2.5mm, and the compression ratio is 31.5-43%.
(2) Load distribution for racks
The high-carbon steel is produced in a five-stand acid rolling combined unit, has higher strength, and is used for stabilizing strip steel entering a rolling mill and preventing the conditions of slipping and weld breakage.
The loads of each rack are distributed as follows:
a frame: 18 to 22 percent of the total weight of the mixture,
II, two frames: 20 to 25 percent.
Three frames: 18-22 percent
Four frames: 12-15%, mainly adopting tension adjustment and inclination adjustment to ensure the plate shape, and simultaneously rolling the plate to the target thickness.
And five frames: 5-6%, and has the effects of leveling and further improving the plate shape.
1. The tension between the second, third and fourth frames is 2-5%, so that the strip steel is prevented from slipping.
(3) The speed of the outlet of the rolling mill is controlled to be less than or equal to 600M/min; when the welding seam passes through each frame of the rolling mill, the positive bending roll is manually reduced. And recovering the roller after the welding seam.
(4) Control of roll profile
After the working roll and the supporting roll are rolled for a long time, the roll shape is greatly changed due to thermal expansion, the roll curve is abraded into an irregular shape at the last stage of the roll, the effect of the positive bending roll is reduced, and the condition that the thickness of the strip steel is not consistent or the strip shape is poor is easy to occur. Therefore, high carbon steel is arranged to be rolled at the early stage of the work rolls in order to ensure smooth rolling. The working roll period is within 2500 tons of rolling quantity, and one working roll adopts a 0.05mm roll curve; 2. and the curves of the three and four frames adopt 0.06mm rollers. Five rolls used 0mm roll curves. 1. And the cycle of the second and third support rolls is in the capacity of 60000 tons for production. Four and five support rollers can be used for production ranging within 35000 tons. And meanwhile, the coil stock 5 in front of the working roll is not allowed to discharge high-carbon steel.
(5) Emulsion parameters of rolling mill
Controlling the temperature of the rolling liquid to be 50 ℃, and enhancing the cooling effect; the concentration is controlled according to the upper limit, the target concentration of the emulsion A system of the rolling mill is 3.0 percent, the control concentration range of the emulsion L system is 0.3 to 1.0 percent, the optimization target is 0.7 percent, the lubricating effect of the rolling liquid is enhanced, and the rolling force is reduced. 1. The flow rate of the second and third emulsions is controlled to be more than 5600L/min.
(6) Coiling
(7) Coil stripping
(8) Annealing of
The high-carbon steel treated by the process is not suitable for production in a continuous annealing unit and is suitable for production in a traditional bell-type furnace. Therefore, the invention adopts the cover annealing process, the annealing temperature is heated from 400 ℃ to 720 ℃, and the heating time is 12-13 hours; the temperature is kept for 10 to 11 hours at the annealing temperature of 720 ℃.
(9) Leveling
The thickness is less than or equal to 1.5mm, and the leveling elongation is 1.0%; the thickness is more than 1.5mm, and the flat elongation is 1.2%.
(10) And shearing to obtain a cold-rolled finished product.
To better compare the process of the present application with the prior art, comparative tests were performed.
The acid rolling process adopted by the control group comprises the following steps: hot rolled material → uncoiling → welding → descaling → acid washing and rinsing → five-stand rolling → coiling → coil unloading → annealing → leveling → shearing → cold rolled finished product.
In the welding procedure, the traditional technological parameters are adopted, and 1 preheating and 1 annealing process are adopted. In the same thickness specification, the preheating power and the annealing power are respectively adjusted down by 5 percent in a maximum parameter table of a welding machine, and the welding speed is 7.2m/min. 1 preheating and 1 annealing process is adopted. The speed of the pickling process section is 120m/min. Other process parameters are the same as those of the raw material thickness in the same specification embodiment.
The comparison result shows that the thickness specification of the raw material of 1.5-3.8 mm in the example has no broken welding line in the process production, the specification of 1.5mm in the comparison group cannot be produced due to frequent broken welding line, and the broken welding line frequency in the specifications of 1.8mm, 2mm, 2.25mm, 2.5mm, 2.75mm, 3.25mm and 3.8mm is 5%, 3%, 4%, 6%, 7%, 8% and 11% respectively. The results show that the high-strength and high-carbon steel produced by the process of the invention realizes good rolling stability in the cold rolling stage and avoids frequent strip breakage of welding seams by controlling welding and pickling in an acid rolling welding machine.
And the yield strength of the thickness specification of the raw material with the thickness of 1.5-3.8 mm in the embodiment is 480-597 Mpa, the compatibility of thin specification and stability is realized, the fatigue life is not influenced, the quality of the final product of the cold-rolled sheet is guaranteed, and the use requirement of a user is met.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes in the invention can be made therein without departing from the spirit and scope thereof.
Claims (5)
1. A method for improving the rolling stability of high-carbon steel for chains is characterized by comprising the following steps: in the high-carbon steel: 0.5 to 0.56 percent of C; mn:0.6% -0.7%; the process comprises the following steps: hot rolled material → uncoiling → welding → descaling → acid washing, rinsing and drying → five racks for tandem rolling → coiling → coil stripping → annealing → leveling → shearing → cold rolling finished product; wherein the thickness of the hot rolled material is more than or equal to 1.5mm, the welding step adopts 1 preheating and 2 annealing processes, the preheating temperature is 250-350 ℃, the stress relief heat treatment temperature is 600-650 ℃, and the concrete operations are as follows: after the welding seam is preheated for 1 time and annealed for 1 time, the laser welding function of the welding machine is closed by manual control, the annealing power is kept, and a welding wheel of the welding machine moves away from the welding seam again; in the step of pickling, rinsing and drying, the thickness of the raw material is more than or equal to 2.5mm, and the speed of the pickling process section is less than or equal to 100m/min; the thickness of the raw material is less than 2.5mm, and the speed of the pickling process section is less than or equal to 120m/min; in the step of rolling by the five-stand continuous rolling, the thickness of the raw material is less than or equal to 2.5mm, and the compression ratio is 36-50%; the thickness of the raw material is more than 2.5mm, and the compression ratio is 31.5-43%; the annealing adopts a cover annealing process, the annealing temperature is heated from 400 ℃ to 720 ℃, and the heating time is 12-13 hours; the temperature is kept for 10 to 11 hours at the annealing temperature of 720 ℃.
2. The method for increasing rolling stability of high carbon steel for chains according to claim 1, characterized in that: the steel grade which is in lap joint welding with the steel grade in the welding step requires that the yield strength difference between the steel grade and the steel grade is less than or equal to 150MPa.
3. The method for increasing rolling stability of high carbon steel for chains according to claim 1, characterized in that: in the welding step, the thickness of the raw material is less than or equal to 1.50mm and less than 2mm, the welding speed is 7.2-7.8 m/min, the preheating power is 10-12KW, and the annealing power is 18-20KW; the thickness of the raw material is less than or equal to 2mm and less than or equal to 2.5mm, the welding speed is 7.8m/min, the preheating power is 14KW, and the annealing power is 22KW.
4. The method for increasing rolling stability of high carbon steel for chains according to claim 1, characterized in that: in the five-stand continuous rolling step, the load distribution of each stand is as follows: 18-22%, two frames: 20% -25%; three frames: 18 to 22 percent; four frames: 12 to 15 percent; five frames: 5 to 6 percent; 1. the tension among the second, third and fourth frames is 2-5%.
5. The method for increasing rolling stability of high carbon steel for chains according to claim 1, wherein: the thickness is less than or equal to 1.5mm, and the leveling elongation is 1.0%; the thickness is more than 1.5mm, and the flat elongation is 1.2%.
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