CN111961965A - Steel strip of cold rolling finishing fine blanking material for automobile child seat locking device - Google Patents
Steel strip of cold rolling finishing fine blanking material for automobile child seat locking device Download PDFInfo
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- CN111961965A CN111961965A CN202010740936.3A CN202010740936A CN111961965A CN 111961965 A CN111961965 A CN 111961965A CN 202010740936 A CN202010740936 A CN 202010740936A CN 111961965 A CN111961965 A CN 111961965A
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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
- 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
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
- C21D1/20—Isothermal quenching, e.g. bainitic hardening
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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
- C21D1/32—Soft annealing, e.g. spheroidising
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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
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
- C21D1/773—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material under reduced pressure or vacuum
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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
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—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
- 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
- C21D8/0268—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment between cold rolling steps
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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
- C21D8/0273—Final recrystallisation annealing
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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
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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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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- Heat Treatment Of Sheet Steel (AREA)
Abstract
The invention discloses a steel strip of a cold-rolled finishing fine-punching material for a locking device of an automobile child seat, which comprises the following components in percentage by mass: carbon: 0.50-0.55%; 0.15 to 0.35 percent of silicon; 0.80 to 1.10 percent of manganese; phosphorus is less than or equal to 0.015 percent; sulfur is less than or equal to 0.01 percent; 0.90 to 1.20 percent of chromium; 0.10 to 0.20 percent of vanadium; less than or equal to 0.035 percent of aluminum; the performance parameters of the cold-rolled 51CrV4 steel strip are as follows: tensile strength is 510-560MPa, yield strength is 350-420MPa, and elongation is more than 12%; meanwhile, isothermal bainite quenching is adopted, the strength of the part can be improved from HRC42-46 to HRC47-55, and the hydrogen embrittlement resistance time is improved from 10min to 10 h; the force value attenuation after electroplating is less than 2 percent; the 51CrV4 structure obtained after the adjusted chemical components and the cold rolling annealing process is transformed into fine and dispersedly distributed granular pearlite from the original hot rolled flaky pearlite; the performance is stable and uniform; meanwhile, isothermal bainite quenching is adopted, the strength of the part can be improved from HRC42-46 to HRC47-55, and the hydrogen embrittlement resistance time is improved from 10min to 10 h; the force value decrement after electroplating is less than 2 percent.
Description
Technical Field
The invention relates to the field of new automobile material development, in particular to a cold-rolled finishing fine-punched material steel strip for an automobile child seat locking device.
Background
The safety seat is specially designed for children with different weights (or ages) and is installed in an automobile, so that the riding safety of the children can be effectively improved. In the event of a car crash or sudden deceleration, the impact force on the child can be reduced and the child's body movement can be restricted to mitigate injury to them. The chinese institute of industry predicts that the yield of child safety seats in china in 2017 will reach 1608 ten thousand. The children automobile safety seat spare and accessory part mainly comprises: seat body, locking device, buckle, meshbelt, ISOFIX interface. Wherein, the manufacturing level of the seat body is an important embodiment of the production and manufacturing level of products of children safety seat enterprises. Since the child seat is mainly required to protect a child when the automobile is stalled or crashes, the demand for the locking device is extremely high. The european union and north american association currently require seat instantaneous impact forces in excess of 2100 pounds (about 9341N). At present, related domestic part manufacturing enterprises select a material S50C in a cold rolling spheroidizing annealing state, the hardness after quenching can reach HRC42-46, and the material can resist certain impact toughness. However, the part needs to be subjected to heat treatment (850 ℃ quenching +390 ℃ tempering) after being stamped, and needs to be electroplated. The hydrogen embrittlement inevitably affects the parts, and the parts are cracked in the test process.
Disclosure of Invention
Technical problem to be solved
Aiming at the defects of the prior art, the invention provides a steel strip of a cold-rolled finishing fine stamping material for a locking device of an automobile child seat. On the basis of DIN10132-4, the chemical components of 51CrV4 are reasonably optimized according to the special processing technology (hydrogen embrittlement caused by electroplating) and the application requirements (light weight and impact resistance) of the child seat locking device, and the element components of C, S, PSi and the like of hydrogen embrittlement sensitive factors are reasonably controlled. And the microstructure and the mechanical property of the 51CrV4 are changed by repeated cold rolling and spheroidizing annealing, so that the 51CrV4 which is not suitable for fine blanking originally is improved to meet the requirements of the prior art. And simultaneously, the improved bainite quenching process is matched to obtain 100 percent lower bainite with more stable structure.
(II) technical scheme
In order to achieve the purpose, the invention provides the following technical scheme: a steel strip of cold-rolled finishing fine blanking material for a locking device of an automobile child seat comprises the following components in percentage by mass: carbon: 0.50-0.55%; 0.15 to 0.35 percent of silicon; 0.80 to 1.10 percent of manganese; phosphorus is less than or equal to 0.015 percent; sulfur is less than or equal to 0.01 percent; 0.90 to 1.20 percent of chromium; 0.10 to 0.20 percent of vanadium; less than or equal to 0.035 percent of aluminum;
the performance parameters of the cold-rolled 51CrV4 steel strip are as follows: tensile strength is 510-560MPa, yield strength is 350-420MPa, and elongation is more than 12%;
the specific requirements of the steel strip material are as follows: the tensile strength is 370-420MPa, the yield strength is 260-300MPa, the elongation is more than 30%, the hardness is less than 130HV10, the surface roughness is less than Ra0.2, the yield ratio is less than 0.6, and the spheroidization rate is 100%;
carbon is a major alloying element of ferrous materials, and therefore ferrous materials may also be referred to as iron carbon alloys. Carbon plays an important role in alloy processing, and the main roles of carbon in steel are as follows:
1. solid solution structures are formed, the strength of the steel is improved, such as ferrite and austenite structures, and carbon elements are dissolved;
2. forming carbide structure, and improving the hardness and wear resistance of the steel. E.g. cementite, i.e. Fe3C is the carbide structure.
Therefore, the higher the carbon content in the steel, the higher the strength and hardness of the steel, but the lower the plasticity and toughness; conversely, the lower the carbon content, the higher the plasticity and toughness of the steel, and the lower the strength and hardness.
Therefore, the level of carbon content determines the use of the steel: low carbon steel (carbon content < 0.25%), which is generally used as a profile and a stamping material; medium carbon steel (carbon content < 0.6%), which is generally used as a mechanical part; high carbon steels (carbon content > 0.7%) are commonly used as tools, cutters, molds, and the like.
In the steelmaking process, silicon exists as a reducing agent and a deoxidizing agent, so that the killed steel generally contains 0.15-0.30% of silicon. If the silicon content in the steel exceeds 0.5%, even if the steel contains silicon-containing alloy elements, the silicon can remarkably improve the elastic limit, yield point and tensile strength of the steel, so that the steel is commonly used as spring steel. The alloy content is high, the heat resistance and the corrosion resistance of the steel can be improved, low-carbon steel with silicon content of 1-4% is contained, the magnetic permeability is extremely high, and the alloy is commonly used for electrical industry and silicon steel sheets. But as the silicon content increases, the weldability of the steel decreases.
Manganese (Mn): in the steel-making process, manganese is a good deoxidant and desulfurizer, and the general steel contains 0.30-0.50% of manganese. When more than 0.70 percent of manganese steel is added into carbon steel, compared with the steel with the common steel amount, the manganese steel has enough toughness, higher strength and hardness, improves the quenching property of the steel and improves the hot working property of the steel, for example, the yield point of the 16Mn steel is higher than that of A3 by 40 percent. The steel containing 11-14% of manganese has extremely high wear resistance and is used for buckets of excavators, lining plates of ball mills and the like. The manganese content is increased, the corrosion resistance of the steel is weakened, and the welding performance is reduced.
Phosphorus (P): in general, phosphorus is a harmful element in steel, increases cold brittleness of steel, deteriorates welding properties, reduces plasticity, and deteriorates cold bending properties. Therefore, it is generally required that the phosphorus content in the steel is less than 0.045% (the smaller the value is, the better), and the higher the quality steel is required to be lower.
Sulfur (S) is generally considered in steel as one of harmful elements remaining in steel. Sulfur (S) is mainly used to reduce ductility and toughness of steel, to deteriorate corrosion resistance of steel, and to adversely affect welding. Therefore, the content of the high-quality steel is controlled below 0.045%, namely, the content of the high-quality steel is not more than 0.055% in the ordinary steel (in the side-blown alkaline rotation)In furnace steel, relaxation is less than 0.065%). After the sulfur forms MnS in the steel, the MnS can be stretched and extended along the rolling direction during low-temperature rolling, so that the anisotropy of the steel is increased, the influence on the transverse impact is serious, the plasticity is greatly influenced, particularly the Z-directional performance of the steel plate is greatly influenced, and the steel plate is layered when the Z-directional performance is serious. High sulfur content, steel plate H resistance2The S intergranular corrosion capability is greatly reduced, and hydrogen-induced cracks are easy to appear. However, in certain conditions, the detriment may be converted into benefits, such as in sulfur-containing free cutting steels, i.e., increasing the sulfur and manganese content thereof, resulting in the formation of more manganese sulfide (MnS) particles to improve the machinability of the steel. Pounding and tellurium are in the same group as sulfur in the periodic table, have quite similar properties, and have similar effects in steel.
In order to overcome the harm of sulfur in steel, the content of sulfur in steel must be strictly controlled to realize ultra-low sulfur smelting, and the quality requirement of a high-quality medium plate can be met.
Aluminum (Al): aluminum is a commonly used deoxidizer in steel. A small amount of aluminum is added into the steel, so that the crystal grains can be refined, and the impact toughness can be improved, for example, the 08A steel used as a deep drawing thin plate. The aluminum also has oxidation resistance and corrosion resistance, and the combination of the aluminum, the chromium and the silicon can obviously improve the high-temperature non-peeling performance and the high-temperature corrosion resistance of the steel. The defect of aluminum is that the hot working performance, the welding performance and the cutting processing performance of steel are influenced, and the reasonable control of the content of aluminum (Al) is also an important research and plays an important role in optimizing the material performance and improving the overall performance of the material.
Chromium (Cr): chromium can significantly improve strength, hardness and wear resistance, but at the same time reduces plasticity and toughness in structural and tool steels. Chromium can improve the oxidation resistance and corrosion resistance of steel, so that the chromium is an important alloy element of stainless steel and heat-resistant steel. If the chromium (Cr) is on the surface of the part, the wear resistance can be effectively improved, meanwhile, the toughness of the center of the part can be improved by the chromium (Cr) in the core part, and the material with high content of the chromium (Cr) is suitable for twisting and rotating workpieces, so the measurement and control of the chromium (Cr) are also important factors for steel processing.
The V vanadium has the following functions in steel: the alloy cutter steel has the advantages of enhanced hardenability and carbide, high temperature resistance, strong secondary hardening effect, obvious effect on improving the hardness, grain refinement and stable structure, and can be widely used in alloy cutter steel.
The cold rolling and steel strip annealing process comprises the following specific processes:
step 1: taking a hot rolled steel coil with the thickness of 4.5 multiplied by 1250mm, splitting, then pickling and soaking, and cleaning by an ultrasonic cleaner to remove a surface oxide layer;
step 2: the specification of the strips is 4.5 multiplied by 234mm, and the strips are annealed;
the annealing process of the step 2 comprises the following steps:
1) heating to 300 ℃ for heat preservation, wherein the heat preservation time is 2 hours, removing water and oil stains on the surface of the steel strip, ensuring the cleanliness of the surface of the steel strip, ensuring the vacuum degree in the furnace (preventing impurity gas in the air from polluting the heat treatment environment), then flushing hydrogen, ensuring the concentration and purity of protective gas in the furnace, and preventing the surface of the steel strip from decarbonizing and oxidizing in the annealing heat treatment process;
2) heating to 720 ℃ for heat preservation, wherein the heat preservation time is 14 hours, and carrying out recrystallization treatment at a lower temperature; the spheroidizing annealing process is ensured to be completed, good texture and mechanical property are obtained, and carbide is changed into a sphere from a lamellar state;
3) after the temperature is raised to about 600 ℃, the temperature in the furnace is quickly reduced to 380 ℃ so that the tissue is slightly changed;
4) slowly cooling to 300 ℃, spraying water on the surface of the outer wall of the inner cover, accelerating cooling to about 100 ℃, discharging at 70 ℃, wherein the structure has no phase change, the production cost is saved, and the heat treatment rhythm is accelerated;
and step 3: carrying out small variable cold rolling on the annealed material, wherein the first pass is from 4.5 multiplied by 234 cold rolling to 4.1 multiplied by 234 cold rolling; the second cold rolling is carried out to 3.8 multiplied by 234, the third cold rolling is carried out to 3.5 multiplied by 234, and the fourth cold rolling is carried out to 3.2 multiplied by 234; cold rolling to 3.0 × 234 in the fifth pass;
and 4, step 4: and (3) carrying out secondary heat treatment (intermediate annealing) on the steel strip subjected to the fifth cold rolling in the third step, wherein the secondary heat treatment comprises the following steps:
a) heating to 300 ℃ for heat preservation, wherein the heat preservation time is 2 hours, removing water and oil stains on the surface of the steel strip, ensuring the cleanliness of the surface of the steel strip, ensuring the vacuum degree in the furnace (preventing impurity gas in the air from polluting the heat treatment environment), then flushing hydrogen, ensuring the concentration and purity of protective gas in the furnace, and preventing the surface of the steel strip from decarbonizing and oxidizing in the annealing heat treatment process;
b) heating to 700 deg.C, maintaining for 14 hr, and recrystallizing at lower temperature. The spheroidizing annealing process is ensured to be completed, good texture and mechanical property are obtained, and carbide is changed into a sphere from a lamellar state;
c) after the temperature is raised to about 600 ℃, the temperature in the furnace is quickly reduced to 380 ℃ so that the tissue is slightly changed;
d) slowly cooling to 300 ℃, spraying water on the surface of the outer wall of the inner cover, accelerating cooling to about 100 ℃, discharging at 70 ℃, wherein the structure has no phase change, the production cost is saved, and the heat treatment rhythm is accelerated;
and 5: rolling the material subjected to intermediate billet annealing to obtain a finished product, wherein the rolling process is a sixth cold rolling process from 3.0 multiplied by 234 to 2.7 multiplied by 234; the seventh cold rolling is carried out to 2.5 multiplied by 234, the eighth cold rolling is carried out to 2.3 multiplied by 234, and the ninth cold rolling is carried out to 2.1 multiplied by 234;
step 6: and (4) carrying out third heat treatment (finished product annealing) on the steel strip subjected to the ninth-pass cold rolling in the fifth step, wherein the third heat treatment step is as follows:
6.1) heating to 300 ℃ for heat preservation, wherein the heat preservation time is 2 hours, removing water and oil stains on the surface of the steel strip, and ensuring the cleanliness of the surface of the steel strip. Ensuring the vacuum degree in the furnace (preventing impurity gas in the air from polluting the heat treatment environment), then flushing hydrogen, ensuring the concentration and purity of protective gas in the furnace, and preventing the surface of the steel strip from decarbonizing and oxidizing in the annealing heat treatment process;
6.2) heating to 680 ℃ for heat preservation, wherein the heat preservation time is 14 hours, and the recrystallization treatment is carried out at a lower temperature. The spheroidizing annealing process is ensured to be completed, good texture and mechanical property are obtained, and carbide is changed into a sphere from a lamellar state;
6.3) rapidly reducing the temperature in the furnace to 380 ℃ after the temperature is raised to about 600 ℃ so as to enable the tissue to generate slight change;
6.4) slowly cooling to 300 ℃, spraying water on the surface of the outer wall of the inner cover, accelerating cooling to about 100 ℃, discharging at 70 ℃, wherein the structure has no phase change, the production cost is saved, and the heat treatment rhythm is accelerated;
and 7: and (5) leveling and slitting the finished product. The flatness of the strips is adjusted according to the thickness tolerance +/-0.01 mm, the width tolerance: -0.2 execution, final finished product specification of 2.0 × 100.
Preferably, the structure state of the 51CrV4-M steel strip is as follows: the grain size is 8-10 grade, the depth of the decarburized layer is less than or equal to 0.01mm, the size of the carbide is 1.5-2 grade (SEP1520), and the spheroidization rate of the carbide is 100 percent.
Preferably, the hardness of the finished seat angle adjuster made of the cold-rolled fine stamping material 20CrMo and 15CrMo is more than 150HV10, the finished seat angle adjuster can bear 20G overload and 17KN impact force, and the fatigue life is more than 10 ten thousand times.
(III) advantageous effects
The invention designs a cold-rolled steel strip with low yield ratio, high elongation and good bending property, and the 51CrV4 structure obtained by the chemical components and the cold rolling annealing process after the adjustment of the invention is changed into granular pearlite with fine dispersion from the original hot-rolled flaky pearlite; the performance is stable and uniform, metal flow in the stamping process is facilitated, and the quality of the section after stamping is improved; meanwhile, isothermal bainite quenching is adopted, the strength of the part can be improved from HRC42-46 to HRC47-55, and the hydrogen embrittlement resistance time is improved from 10min to 10 h; the force value attenuation after electroplating is less than 2 percent; part impact strength increased from the current 2100 lbs (9341N) to 2800 lbs.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and 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 invention.
The specific implementation mode is as follows: a steel strip of cold-rolled finishing fine blanking material for a locking device of an automobile child seat comprises the following components in percentage by mass: carbon: 0.50-0.55%; 0.15 to 0.35 percent of silicon; 0.80 to 1.10 percent of manganese; phosphorus is less than or equal to 0.015 percent; sulfur is less than or equal to 0.01 percent; 0.90 to 1.20 percent of chromium; 0.10 to 0.20 percent of vanadium; less than or equal to 0.035 percent of aluminum;
the performance parameters of the cold-rolled 51CrV4 steel strip are as follows: tensile strength is 510-560MPa, yield strength is 350-420MPa, and elongation is more than 12%;
the cold rolling and steel strip annealing process comprises the following specific processes:
step 1: taking a hot rolled steel coil with the thickness of 4.5 multiplied by 1250mm, splitting, then pickling and soaking, and cleaning by an ultrasonic cleaner to remove a surface oxide layer;
step 2: the specification of the strips is 4.5 multiplied by 234mm, and the strips are annealed;
the annealing process of the step 2 comprises the following steps:
1) heating to 300 ℃ for heat preservation for 2 hours, removing water and oil stains on the surface of the steel strip, and ensuring the cleanliness of the surface of the steel strip. Ensuring the vacuum degree in the furnace (preventing impurity gas in the air from polluting the heat treatment environment), then flushing hydrogen, ensuring the concentration and purity of protective gas in the furnace, and preventing the surface of the steel strip from decarbonizing and oxidizing in the annealing heat treatment process;
2) heating to 720 ℃ for heat preservation, wherein the heat preservation time is 14 hours, and carrying out recrystallization treatment at a lower temperature; the spheroidizing annealing process is ensured to be completed, good texture and mechanical property are obtained, and carbide is changed into a sphere from a lamellar state;
3) after the temperature is raised to about 600 ℃, the temperature in the furnace is quickly reduced to 380 ℃ so that the tissue is slightly changed;
4) slowly cooling to 300 ℃, spraying water on the surface of the outer wall of the inner cover, accelerating cooling to about 100 ℃, discharging at 70 ℃, wherein the structure has no phase change, the production cost is saved, and the heat treatment rhythm is accelerated;
and step 3: carrying out small variable cold rolling on the annealed material, wherein the first pass is from 4.5 multiplied by 234 cold rolling to 4.1 multiplied by 234 cold rolling; the second cold rolling is carried out to 3.8 multiplied by 234, the third cold rolling is carried out to 3.5 multiplied by 234, and the fourth cold rolling is carried out to 3.2 multiplied by 234; cold rolling to 3.0 × 234 in the fifth pass;
and 4, step 4: and (3) carrying out secondary heat treatment (intermediate annealing) on the steel strip subjected to the fifth cold rolling in the third step, wherein the secondary heat treatment comprises the following steps:
a) heating to 300 ℃ for heat preservation for 2 hours, removing water and oil stains on the surface of the steel strip, and ensuring the cleanliness of the surface of the steel strip. Ensuring the vacuum degree in the furnace (preventing impurity gas in the air from polluting the heat treatment environment), then flushing hydrogen, ensuring the concentration and purity of protective gas in the furnace, and preventing the surface of the steel strip from decarbonizing and oxidizing in the annealing heat treatment process;
b) heating to 700 deg.C, maintaining for 14 hr, and recrystallizing at lower temperature. The spheroidizing annealing process is ensured to be completed, good texture and mechanical property are obtained, and carbide is changed into a sphere from a lamellar state;
c) after the temperature is raised to about 600 ℃, the temperature in the furnace is quickly reduced to 380 ℃ so that the tissue is slightly changed;
d) slowly cooling to 300 ℃, spraying water on the surface of the outer wall of the inner cover, accelerating cooling to about 100 ℃, discharging at 70 ℃, wherein the structure has no phase change, the production cost is saved, and the heat treatment rhythm is accelerated;
and 5: rolling the material subjected to intermediate billet annealing to obtain a finished product, wherein the rolling process is a sixth cold rolling process from 3.0 multiplied by 234 to 2.7 multiplied by 234; the seventh cold rolling is carried out to 2.5 multiplied by 234, the eighth cold rolling is carried out to 2.3 multiplied by 234, and the ninth cold rolling is carried out to 2.1 multiplied by 234;
step 6: and (4) carrying out third heat treatment (finished product annealing) on the steel strip subjected to the ninth-pass cold rolling in the fifth step, wherein the third heat treatment step is as follows:
6.1) heating to 300 ℃ for heat preservation, wherein the heat preservation time is 2 hours, removing water and oil stains on the surface of the steel strip, and ensuring the cleanliness of the surface of the steel strip. Ensuring the vacuum degree in the furnace (preventing impurity gas in the air from polluting the heat treatment environment), then flushing hydrogen, ensuring the concentration and purity of protective gas in the furnace, and preventing the surface of the steel strip from decarbonizing and oxidizing in the annealing heat treatment process;
6.2) heating to 680 ℃ for heat preservation, wherein the heat preservation time is 14 hours, and the recrystallization treatment is carried out at a lower temperature. The spheroidizing annealing process is ensured to be completed, good texture and mechanical property are obtained, and carbide is changed into a sphere from a lamellar state;
6.3) rapidly reducing the temperature in the furnace to 380 ℃ after the temperature is raised to about 600 ℃ so as to enable the tissue to generate slight change;
6.4) slowly cooling to 300 ℃, spraying water on the surface of the outer wall of the inner cover, accelerating cooling to about 100 ℃, discharging at 70 ℃, wherein the structure has no phase change, the production cost is saved, and the heat treatment rhythm is accelerated;
and 7: and (5) leveling and slitting the finished product. The flatness of the strips is adjusted according to the thickness tolerance +/-0.01 mm, the width tolerance: -0.2 execution, final finished product specification of 2.0 × 100.
Further, the structure state of the 51CrV4-M steel strip is as follows: the grain size is 8-10 grade, the depth of the decarburized layer is less than or equal to 0.01mm, the size of the carbide is 1.5-2 grade (SEP1520), and the spheroidization rate of the carbide is 100 percent.
Further, the hardness of the finished seat angle adjuster made of the cold-rolled fine stamping material 20CrMo and 15CrMo is more than 150HV10, the seat angle adjuster bears 20G overload and 17KN impact force, the fatigue life is more than 10 ten thousand times, when a fatigue test is carried out, a fatigue life machine is used for testing, and a batch 2-by-one mode is used for testing; the test is carried out by adopting 24 hours, and continuous impact can not be carried out discontinuously, and the test can not be stopped.
The 51CrV4 structure obtained after the chemical components and the cold rolling annealing process are adjusted by the method is changed into fine and dispersedly distributed granular pearlite from the original hot rolling flaky pearlite; the performance is stable and uniform, metal flow in the stamping process is facilitated, and the quality of the section after stamping is improved; meanwhile, isothermal bainite quenching is adopted, the strength of the part can be improved from HRC42-46 to HRC47-55, and the hydrogen embrittlement resistance time is improved from 10min to 10 h; the force value attenuation after electroplating is less than 2 percent; part impact strength increased from the current 2100 lbs (9341N) to 2800 lbs.
On the basis of DIN10132-4, the chemical components of 51CrV4 are reasonably optimized according to the special processing technology (hydrogen embrittlement caused by electroplating) and the application requirements (light weight and impact resistance) of the child seat locking device, and the element components of C, S, PSi and the like of hydrogen embrittlement sensitive factors are reasonably controlled. And the microstructure and the mechanical property of the 51CrV4 are changed by repeated cold rolling and spheroidizing annealing, so that the 51CrV4 which is not suitable for fine blanking originally is improved to meet the requirements of the prior art. And simultaneously, the improved bainite quenching process is matched to obtain 100 percent lower bainite with more stable structure.
It is noted that, herein, 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.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. The steel strip for the cold-rolled finishing fine stamping material for the locking device of the child seat of the automobile is characterized in that the cold-rolled 51CrV4 steel strip comprises the following components in percentage by mass: carbon: 0.50-0.55%; 0.15 to 0.35 percent of silicon; 0.80 to 1.10 percent of manganese; phosphorus is less than or equal to 0.015 percent; sulfur is less than or equal to 0.01 percent; 0.90 to 1.20 percent of chromium; 0.10 to 0.20 percent of vanadium; less than or equal to 0.035 percent of aluminum;
the performance parameters of the cold-rolled 51CrV4 steel strip are as follows: tensile strength is 510-560MPa, yield strength is 350-420MPa, and elongation is more than 12%;
the cold rolling and steel strip annealing process comprises the following specific processes:
step 1: taking a hot rolled steel coil with the thickness of 4.5 multiplied by 1250mm, splitting, then pickling and soaking, and cleaning by an ultrasonic cleaner to remove a surface oxide layer;
step 2: the specification of the strips is 4.5 multiplied by 234mm, and the strips are annealed;
the annealing process of the step 2 comprises the following steps:
1) heating to 300 ℃ for heat preservation, pumping out air in the annealing furnace, and then filling hydrogen to ensure the concentration and purity of protective gas in the furnace and prevent decarburization and oxidation of the surface of the steel strip in the annealing heat treatment process;
2) heating to 100 ℃ for heat preservation and recrystallization; the spheroidizing annealing process is ensured to be completed, good texture and mechanical property are obtained, and carbide is changed into a sphere from a lamellar state;
3) after the temperature is raised to about 600 ℃, the temperature in the furnace is quickly reduced to 380 ℃ so that the tissue is slightly changed;
4) slowly cooling to 300 ℃, spraying water on the surface of the outer wall of the inner cover, accelerating cooling to about 100 ℃, discharging at 70 ℃, wherein the structure has no phase change, the production cost is saved, and the heat treatment rhythm is accelerated;
and step 3: carrying out small variable cold rolling on the annealed material, wherein the first pass is from 4.5 multiplied by 234 cold rolling to 4.1 multiplied by 234 cold rolling; the second cold rolling is carried out to 3.8 multiplied by 234, the third cold rolling is carried out to 3.5 multiplied by 234, and the fourth cold rolling is carried out to 3.2 multiplied by 234; cold rolling to 3.0 × 234 in the fifth pass;
and 4, step 4: and (3) carrying out secondary heat treatment on the steel strip subjected to the fifth cold rolling in the third step, wherein the secondary heat treatment comprises the following steps:
a) heating to 300 ℃ for heat preservation, removing water and oil stains on the surface of the steel strip, ensuring the cleanliness of the surface of the steel strip and the vacuum degree in the furnace, then flushing hydrogen, ensuring the concentration and purity of protective gas in the furnace, and preventing decarburization and oxidation of the surface of the steel strip in the annealing heat treatment process;
b) heating to 700 deg.C, keeping the temperature, and recrystallizing at lower temperature. The spheroidizing annealing process is ensured to be completed, good texture and mechanical property are obtained, and carbide is changed into a sphere from a lamellar state;
c) after the temperature is raised to about 600 ℃, the temperature in the furnace is quickly reduced to 380 ℃ so that the tissue is slightly changed;
d) slowly cooling to 300 ℃, spraying water on the surface of the outer wall of the inner cover, accelerating cooling to about 100 ℃, discharging at 70 ℃, wherein the structure has no phase change, the production cost is saved, and the heat treatment rhythm is accelerated;
and 5: rolling the material subjected to intermediate billet annealing to obtain a finished product, wherein the rolling process is a sixth cold rolling process from 3.0 multiplied by 234 to 2.7 multiplied by 234; the seventh cold rolling is carried out to 2.5 multiplied by 234, the eighth cold rolling is carried out to 2.3 multiplied by 234, and the ninth cold rolling is carried out to 2.1 multiplied by 234;
step 6: and (4) carrying out third heat treatment on the steel strip subjected to the ninth-pass cold rolling in the fifth step, wherein the third heat treatment step is as follows:
6.1) heating to 300 ℃ for heat preservation, pumping out air in the annealing furnace, and then filling hydrogen to ensure the concentration and purity of protective gas in the furnace and prevent decarburization and oxidation of the surface of the steel strip in the annealing heat treatment process;
6.2) heating to 680 ℃ for heat preservation, and carrying out recrystallization treatment at a lower temperature; the spheroidizing annealing process is ensured to be completed, good texture and mechanical property are obtained, and carbide is changed into a sphere from a lamellar state;
6.3) rapidly reducing the temperature in the furnace to 380 ℃ after the temperature is raised to about 600 ℃ so as to enable the tissue to generate slight change;
6.4) slowly cooling to 300 ℃, spraying water on the surface of the outer wall of the inner cover, accelerating cooling to about 100 ℃, discharging at 70 ℃, wherein the structure has no phase change, the production cost is saved, and the heat treatment rhythm is accelerated;
and 7: and (5) leveling and slitting the finished product.
2. The steel strip of cold rolled finished fine blanking material for child car seat locking device according to claim 1, wherein the structure state of 51CrV4-M steel strip is: the grain size is 8-10 grade, the depth of the decarburized layer is less than or equal to 0.01mm, the size of the carbide is 1.5-2 grade, and the spheroidization rate of the carbide is 100 percent.
3. The steel strip of cold rolled finishing fine blanking material for locking device of child seat for car according to claim 1, wherein said cold rolled fine blanking material 20CrMo, 15CrMo finished seat angle adjuster hardness > 150HV10 endures 20G overload and 17KN impact force, fatigue life is more than 10 ten thousand times.
4. The steel strip of cold rolled finished fine blanking material for locking device of child seat for car according to claim 1, wherein said strip of step 7 is flattened to a thickness tolerance of ± 0.01mm, a width tolerance of: -0.2 execution, final finished product specification of 2.0 × 100.
5. The steel strip of cold rolled finished fine blanking material for locking device of child seat for car according to claim 1, wherein the holding time of heating to 250 ℃ in step 6 is 2 hours.
6. The steel strip of cold rolled finished fine blanking material for locking device of child seat for car according to claim 1, wherein the holding time of heating to 680 ℃ in step 6 is 14 hours.
7. The steel strip of cold rolled finished fine blanking material for locking device of child seat for car according to claim 1, wherein said heating of step 2 to 250 ℃ for holding time is 2 hours.
8. The steel strip of cold rolled finished fine blanking material for locking device of child seat for car according to claim 1, wherein said step 2 heating to 720 ℃ for holding time is 14 hours.
9. The steel strip of cold rolled finished fine blanking material for locking device of child seat for car according to claim 1, wherein the heating to 250 ℃ in step 4 is performed for 2 hours.
10. The steel strip of cold rolled finished fine blanking material for locking device of child seat for car according to claim 1, wherein the heating to 700 ℃ in step 4 is carried out for 14 hours.
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| CN202010740936.3A CN111961965A (en) | 2020-07-29 | 2020-07-29 | Steel strip of cold rolling finishing fine blanking material for automobile child seat locking device |
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| CN105401073A (en) * | 2015-12-30 | 2016-03-16 | 苏州翔楼金属制品有限公司 | Heat treatment technology of alloy spring cold-rolled steel strip 51CrV4 of automobile clutch diaphragm |
| CN108385019A (en) * | 2018-01-18 | 2018-08-10 | 苏州翔楼新材料股份有限公司 | A kind of automobile child seat locking device cold rolling fine steel band and preparation method |
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2020
- 2020-07-29 CN CN202010740936.3A patent/CN111961965A/en active Pending
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105401073A (en) * | 2015-12-30 | 2016-03-16 | 苏州翔楼金属制品有限公司 | Heat treatment technology of alloy spring cold-rolled steel strip 51CrV4 of automobile clutch diaphragm |
| CN108385019A (en) * | 2018-01-18 | 2018-08-10 | 苏州翔楼新材料股份有限公司 | A kind of automobile child seat locking device cold rolling fine steel band and preparation method |
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| 王顺兴: "《金属热处理原理与工艺》", 31 January 2019, 哈尔滨工业大学出版社 * |
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Application publication date: 20201120 |