Device and method for rapid heat treatment of cold-rolled low-carbon and ultra-low-carbon steel

Abstract

The invention provides a rapid heat treatment device and method for cold-rolled low-carbon and ultra-low-carbon steel, and belongs to the technical field of heat treatment. A series of research work is carried out on the rapid heat treatment device and technology suitable for the cold-rolled low-carbon steel and the ultra-low-carbon steel, and the heat treatment process of the cold-rolled low-carbon steel and the ultra-low-carbon steel is innovated. In addition, a new generation of continuous heat treatment unit has epoch-making significance for energy conservation, emission reduction and clean production. Therefore, the research on the influence of the rapid heat treatment device and technology on the performance and the structure of the carbon steel for the automobile so as to determine a proper rapid heat treatment process has very important significance. The production cycle of an existing cold rolling annealing unit is shortened, the production efficiency is improved, the product competitiveness is improved, and great significance is achieved for meeting the ever-increasing market requirements.

Description

Technical Field

[0001] The present invention relates to the field of heat treatment technology, and in particular to a device and method for rapid heat treatment of cold-rolled low-carbon and ultra-low-carbon steel. Background Art

[0002] In recent years, with the rise and rapid development of my country's automobile industry, my country's demand for automobile stamping steel has been increasing, and the requirements for its stamping forming performance have also been getting higher and higher. Due to the shortcomings of the traditional annealing method for producing automobile stamping steel, such as low production efficiency, complex and bulky equipment, and large required space, on the basis of ensuring that customer needs are met, reducing production costs, improving efficiency, and environmentally friendly production methods have always been the pursuit of the modern steel industry. Considering the streamlining of production processes and improving production efficiency, shortening the annealing time to the greatest extent has become the current focus of research.

[0003] In recent years, the emergence of rapid heating technology has provided an opportunity for the development of ultra-fast annealing. Rapid heat treatment technology, which is a heat treatment technology of rapid heating, short-term heat preservation, and then rapid cooling, will significantly refine the carbon steel structure and improve the mechanical properties of low-carbon steel. By researching and developing this technology, the length of the unit will be shortened, especially the high-temperature section can be greatly shortened, and the investment in the heat treatment production line will eventually be reduced. Shortening the length of the unit, especially the length of the high-temperature section of the furnace, is conducive to improving the flexibility of the unit production operation.

[0004] Once the rapid heat treatment technology is applied to industrial production, it will greatly reduce production costs and energy consumption for annealing per ton of steel. At the same time, it also provides a new means of controlling organization and texture for obtaining high-strength and excellent formability automotive steel, and expands the knowledge about annealing. Therefore, whether from the perspective of practical application or theoretical research, it is very necessary to carry out a series of research work on rapid heat treatment devices and technologies suitable for cold-rolled low-carbon steel and ultra-low-carbon steel. In addition, the new generation of continuous heat treatment units is also of epoch-making significance for energy conservation, emission reduction and clean production. Therefore, it is of great significance to study the influence of rapid heat treatment devices and technologies on the performance and organization of automotive carbon steel, so as to determine the appropriate rapid heat treatment process. It is of great significance to strive to shorten the production cycle of existing cold rolling annealing units, improve production efficiency, improve product competitiveness, and meet the growing market demand.

[0005] The existing published patent CN202010798219.6, "A vacuum rapid heat treatment equipment for metal materials", specifically discloses a vacuum rapid heat treatment equipment for metal materials, including a vacuum chamber connected to a vacuum system and a rapid heating system for heating metal materials, and the vacuum system and the rapid heating system are controlled and operated by a control system; wherein, the rapid heating system includes a positive electrode and a negative electrode, and a metal material to be rapidly heated fixed between the two electrodes; at the same time, the vacuum chamber is respectively connected to a gas cooling channel and an air release valve, and the gas cooling channel is used to rapidly cool the metal material after rapid heating; the present invention has the effect of rapidly and accurately heating and cooling metal materials, and improves the technical level of heat treatment of metal materials. The main design content of this patent is a metal heating system that uses two-stage electrodes for heating, and uses a vacuum method for heating. When using electrodes for rapid heating, the heating rate will be greatly limited, and the maximum heating rate is not clear. At the same time, when using a vacuum heating method to heat cold-rolled low-carbon steel and ultra-low-carbon steel products, since vacuuming requires process time, the heat treatment efficiency is reduced and is not sufficient to support the rapid heat treatment experimental process control of cold-rolled low-carbon steel and ultra-low-carbon steel.

[0006] The existing published patent CN202010685311.1 "A 1100MPa-grade high-strength steel for engineering machinery and its production method" specifically discloses a 1100MPa-grade high-strength steel for engineering machinery, whose chemical composition weight percentage is: C: 0.20-0.24%, Si: 0.30-0.50%, Mn: 0.80-1.60%, Cr: 0.20-0.70%, Mo: 0.40-0.70%, W: 0-0.80%, Ni: 0.30-0.80%, Cu: 0-0.40%, Nb: 0.010-0.030%, Ti: 0.010-0.030%, V: 0.010-0.050%, B: 0.0005-0.003 0%, Al: 0.02-0.06%, Ca: 0.001-0.004%, N: 0.002-0.005%, P≤0.020%, S≤0.0050%, O≤0.0040%, and the rest are Fe and other inevitable impurities; and the above elements must also satisfy the following relationship: the metallographic structure of the high-strength steel is tempered troostite, wherein the tempered troostite grain size is 3-5μm, and the tempered troostite lamellar width is 30-90nm; the carbides in the high-strength steel are distributed in dispersed granular form, and more than 90% of the carbides are below 10nm in size; the yield strength of the high-strength steel is ≥1100MPa, the tensile strength is ≥1150MPa, the elongation is>16%, and the -60℃ impact energy is>100J. The main design content of this patent is the processing and manufacturing method for the hot rolling process of 1100MPa high-strength steel, and its heating rate is not high, only a relatively high cooling rate, and it does not involve the rapid heat treatment of cold-rolled low-carbon steel and ultra-low carbon steel. Therefore, it is not sufficient to support the production and experiments of rapid heat treatment of cold-rolled carbon steel and ultra-low carbon steel. Summary of the invention

[0007] According to the technical problems mentioned in the above-mentioned background technology, a device and method for rapid heat treatment of cold-rolled low-carbon and ultra-low-carbon steel are provided. The present invention innovates the heat treatment process of cold-rolled low-carbon steel and ultra-low-carbon steel by carrying out a series of research work on rapid heat treatment devices and technologies suitable for cold-rolled low-carbon steel and ultra-low-carbon steel. In addition, the new generation of continuous heat treatment units also has epoch-making significance for energy conservation, emission reduction and clean production. Therefore, it is of great significance to study the influence of rapid heat treatment devices and technologies on the performance and organization of carbon steel for automobiles, so as to determine a suitable rapid heat treatment process. Striving to shorten the production cycle of existing cold rolling annealing units, improve production efficiency, and improve product competitiveness is of great significance to meet the growing market demand.

[0008] The technical means adopted by the present invention are as follows:

[0009] A rapid heat treatment device for cold-rolled low-carbon and ultra-low-carbon steel, comprising: a heating part and a cooling part;

[0010] The heating part realizes the heating of the sample; the heating part includes: a computer control system, a temperature transmitter, a thermocouple, a vacuum box, a heating transformer, a thyristor, a conductive copper bar I and a conductive copper bar II; the thyristor is connected to the heating transformer through the live wire and the neutral wire of the power frequency power supply; the neutral wire of the heating transformer is connected to the conductive copper bar I, and then connected to the sample arranged in the vacuum box; the live wire of the heating transformer is connected to the conductive copper bar II, and then connected to the other end of the sample arranged in the vacuum box; the temperature transmitter obtains the temperature information of the sample in the vacuum box through the connected thermocouple, and feeds the temperature information back to the computer control system;

[0011] The cooling part includes: a cooling system and a quenching system; the cooling system uses high-pressure circulating water to cool the components of the heating part; the quenching system realizes forced cooling of the sample, and the quenching system controls the quenching water volume through a high-response CNC switch valve and a flow meter to realize the regulation of the quenching water volume.

[0012] Furthermore, the quenching system realizes forced cooling of the sample by spraying water, mist or air.

[0013] Furthermore, the heating unit heats the sample by short-circuiting the secondary side of the heating transformer and the sample.

[0014] Furthermore, the rated capacity of the heating transformer is 27KVA~90KVA, the primary of the heating transformer is connected to a 380V voltage, and the secondary voltage is adjusted by the number of tap turns of the primary coil; the output voltage range of the heating transformer is 3V~10V, and the maximum secondary side current of the heating transformer is 9KA~10KA.

[0015] The present invention also includes a rapid heat treatment method for cold-rolled low-carbon steel and ultra-low-carbon steel, comprising the following steps:

[0016] Step 1: Process the test specimen into the shape of a pre-processed part;

[0017] Step 2: Estimating the heating rate and temperature of the sample to be tested;

[0018] Step 3: Measuring the actual temperature of the sample to be tested by a thermocouple welded on the surface of the sample as a feedback signal of the control system;

[0019] Step 4: By calculating the current system error and error change rate, using the adaptive fuzzy rule model for fuzzy reasoning, querying the fuzzy matrix table, and performing online self-tuning control on the PID parameters.

[0020] Furthermore, the calculation method of the current system error and the error change rate is:

[0021] The temperature value of the next cycle is predicted based on the temperature values ​​actually measured in the previous two cycles and the heating law of the test. The predicted value is compared with the actually measured temperature value. When the difference is greater than a certain deviation, the acquisition point falls outside the power-off area, and the acquisition time is reset.

[0022] Assume that the actual temperature during this period is t n , given temperature t′ n ; The actual temperature of the previous cycle is t n-1 , given temperature t′ n-1 ; The given temperature of the next cycle is t' n+1 ; Calculate the temperature deviation value of this cycle as:

[0023] Δt n =t′ n -t n ;

[0024] The temperature deviation of the last cycle is:

[0025] Δt n-1 =t′ n-1 -t n-1 ;

[0026] According to the heating system, the actual temperature of the next cycle is predicted to be:

[0027] ～ t n+1 =t′ n+1 +(Δt n +Δt n-1 ) / 2;

[0028] Among them, t n+1 Indicates the actual measured temperature of the next cycle;

[0029] When│ ～ t n+1 -t n+1 │≥5℃, the acquisition point of the temperature signal is judged to be a false signal; the acquisition signal trigger time is reset to:

[0030] T=T n +10 / 9ms;

[0031] Among them, T n Indicates the time value when the thyristor trigger angle is 0° in the current cycle.

[0032] Furthermore, the certain deviation is 3°C to 5°C.

[0033] Furthermore, in step 2, the method for estimating the heating rate and temperature of the sample to be tested is:

[0034] Assume the length of the sample is L, the cross-sectional area is A, the density is ρ, the resistivity is σ, the specific heat is c, and the heating rate is dT / dt; if the heat and electricity losses are not taken into account, the power W required per unit volume of the sample is:

[0035] W = ρcdT / dt;

[0036] The power P required to heat the entire sample is:

[0037] P = LAρcdT / dt;

[0038] The electric power P' consumed by the current in the sample is:

[0039] P′=I 2 R=I 2 σL / A;

[0040] From P=P′, we get:

[0041] dT / dt=I 2 σ / (A 2 ρc);

[0042] or

[0043] dT / dt=U 2 σ / (L 2 ρc);

[0044] Where U represents the voltage across the sample.

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] The rapid heat treatment device of the present invention is suitable for rapid heat treatment experiments of cold-rolled low-carbon steel and ultra-low-carbon steel, breaking the current situation of relying on production experience and preset database for annealing, and providing more reasonable experimental design support for various personalized demand products.

[0047] In the process of actual industrial application, the device and method of the present invention can be used to perform fine annealing process matching for different products according to the specifications and chemical composition of different cold-rolled products, using the device and heat treatment experimental method of the present invention, while accelerating the annealing process design process of new products and promoting the transformation of heat treatment technology towards industrial intelligence and digital twins. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0049] Figure 1 It is a schematic diagram of the rapid thermal processing device system of the present invention.

[0050] Figure 2 This is a schematic diagram of synchronous voltage acquisition according to the present invention.

[0051] Figure 3 This is the rapid heating temperature control curve of the present invention.

[0052] Figure 4 This is a schematic diagram of the sample to be tested of the present invention.

[0053] In the figure: 1. Water station; 2. Filter; 3. One-way shut-off valve; 4. Booster cylinder; 5. Solenoid switch valve; 6. CNC switch valve; 7. Flow meter; 8. Heating transformer; 9. Thyristor; 10. Vacuum box; 11. Test sample; 12. Thermocouple; 13. Axis II; 14. Axis I; 15. Circular quenching ejector; 16. Water-gas mixer; 17. Conductive copper busbar; 18. Temperature transmitter; 19. Computer control system; 20. Water flow indicator. DETAILED DESCRIPTION

[0054] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0055] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0056] like Figure 1 As shown, the present invention provides a rapid heat treatment device for cold-rolled low-carbon and ultra-low-carbon steel, comprising: a heating part and a cooling part.

[0057] In the present application, the heating part realizes the heating of the sample; the heating part includes: a computer control system, a temperature transmitter, a thermocouple, a vacuum box, a heating transformer, a thyristor, a conductive copper bar I and a conductive copper bar II; the thyristor is connected to the heating transformer through the live wire and the neutral wire of the power frequency power supply; the neutral wire of the heating transformer is connected to the conductive copper bar I, and then connected to the sample arranged in the vacuum box; the live wire of the heating transformer is connected to the conductive copper bar II, and then connected to the other end of the sample arranged in the vacuum box; the temperature transmitter obtains the temperature information of the sample in the vacuum box through the connected thermocouple, and feeds back the temperature information to the computer control system;

[0058] In this application, the cooling part includes: a cooling system and a quenching system; the cooling system uses high-pressure circulating water to cool the components of the heating part; the quenching system realizes forced cooling of the sample, and the quenching system controls the quenching water volume through a high-response CNC switch valve and a flow meter to achieve regulation of the quenching water volume. The quenching system can provide three forced cooling methods for the sample: water spray, mist and jet, and control the quenching water volume through a high-response CNC switch valve and a flow meter to achieve online regulation.

[0059] In this application, the heating part adopts direct resistance heating, that is, the secondary side of the heating transformer forms a short circuit state with the sample. Since the resistance of the sample itself is larger than other components in the circuit, the voltage drop is mainly concentrated on the sample, which causes the sample to be heated quickly. The transformer is selected with a rated capacity of 27KVA~90KVA, the primary can be connected to a 380V voltage, the secondary voltage is adjusted by the number of turns of the primary coil tap 7, the output voltage range is 3V~10V, and the current on the secondary side of the transformer can reach up to 9KA~10KA. According to Q=I 2 It can be seen from Rt that when this current passes through the sample, extremely high heat will be generated, thus achieving heating.

[0060] The present invention also includes a rapid heat treatment method for cold-rolled low-carbon steel and ultra-low-carbon steel, comprising the following steps:

[0061] Step 1: Process the sample to be tested into the shape of a pre-processed part; preferably, in the present embodiment, the shape of the pre-processed part is similar to an "H" shape. There are openings in the middle of the upper and lower parts, with a radius of 10 mm, a length of 120 mm, and a width of 50 mm. The test results of the mechanical properties of the sample in this application are compared with those of the standard size sample. There is basically no difference in yield strength and n value. In terms of tensile strength and elongation, the yield strength of the sample designed by this patent is 12MPa higher than that of the standard size sample, and the elongation after fracture is 4.2% higher than that of the standard size sample. Through the above comparative analysis, the rapid heat treatment experimental sample is prepared according to the above design scheme, which can not only meet the requirements of the rapid heat treatment device for the size of the sample, but also meet the requirements of the mechanical properties test of the finished product. The experimental sample for rapid heat treatment of low carbon steel and ultra-low carbon steel can be processed and prepared according to the design scheme.

[0062] Step 2: Estimate the heating speed and temperature of the test sample; after the material and size of the sample are determined, the transformer output power depends on the required heating speed and temperature. The heating speed can be estimated using the following method.

[0063] Assume the sample length is L, the cross-sectional area is A, the density is ρ, the resistivity is σ, the specific heat is c, and the heating rate is dT / dt. If the heat and electricity losses are not taken into account, the power required per unit volume of the sample is:

[0064] W = ρcdT / dt;

[0065] The power required to heat the entire sample is:

[0066] P = LAρcdT / dt;

[0067] The electric power consumed by the current in the sample is:

[0068] P′=I 2 R=I 2 σL / A;

[0069] From P = P', we can get

[0070] dT / dt=I 2 σ / (A 2 ρc);

[0071] or

[0072] dT / dt=U 2 σ / (L 2 ρc);

[0073] Where U is the voltage across the sample.

[0074] For a C-Mn steel with a length of 10 mm, when the voltage across the two ends is 1 V, the heating rate can be estimated to be 4000℃ / s from the above formula; when the voltage across the two ends is 2 V, the heating rate can be estimated to be 8000℃ / s. Therefore, the direct resistance heating method can achieve the purpose of rapid heating and meet the requirements of rapid heat treatment experiments.

[0075] Step 3: The actual temperature of the sample to be tested is measured by the thermocouple welded on the surface of the sample as the feedback signal of the control system; the rapid heating system uses the thermocouple welded on the surface of the sample to measure the actual temperature of the sample as the feedback signal of the control system. The accuracy of the feedback signal is the basis of high-precision control. When the sample is directly heated by the resistor, an AC current of tens of thousands of amperes passes through the sample, which will form a very strong electromagnetic field in the sample and the space around it. This strong magnetic field generates very large interference signals in the thermocouple loop and the test instrument, and the correct temperature signal cannot be measured. In order to ensure the accuracy of temperature control, unconventional acquisition methods must be used.

[0076] The AC power frequency used in the heating process is 50Hz, and its cycle is 20ms. After the thyristor is rectified and triggered, the AC power is converted into pulsed DC (positive half cycle), which can make the cycle 10ms. The short period of about 20° phase angle before the thyristor is turned on in each cycle is used to cut off the power to collect the temperature value. The sampling period is 10ms. Before the thyristor is turned on, the voltage value at both ends of the sample is almost 0V, and no current flows, so the interference of the magnetic field is very small, which can achieve the purpose of accurate temperature measurement. Due to the slight fluctuation of industrial AC power, the fluctuation frequency range is generally 49.5~50.5Hz, and the fluctuation difference is about 1Hz. Therefore, under the condition that the sampling period remains unchanged, after several cycles, the collection point will run out of the collection area with a trigger angle of 20°. This phenomenon can be estimated theoretically. Assuming that the AC power always moves to the right, each time it fluctuates forward by 0.5Hz, the sampling period is 10ms, and the first temperature value is collected when the thyristor trigger angle is 10°. From this, the time occupied by the 20° trigger angle can be calculated as:

[0077] 20° / 180°×10ms=10 / 9ms;

[0078] The time taken when the firing angle is 10° is equal to:

[0079] 10 / 9÷2=5 / 9ms;

[0080] The forward fluctuation of 0.5Hz converted into time is

[0081] 0.5 / 50×10ms=0.1ms;

[0082] When the number of acquisitions is 5 / 9÷0.1≈6 times, the acquisition point may exceed the set 20° acquisition area. But in fact, the change of AC power is irregular. It may move forward in the previous cycle and move backward in the next cycle. This kind of movement property can offset each other. Therefore, in the actual acquisition process, it will take at least hundreds or thousands of acquisitions before the acquisition point falls outside the acquisition area. In order to ensure the accuracy of temperature control and obtain effective temperature acquisition values, it is necessary to know whether the acquisition point falls outside the power-off area. The judgment basis is: predict the temperature value of the next cycle based on the actual measured temperature values ​​of the previous two cycles and the heating law of the test, compare the predicted value with the actual measured temperature value, and when the difference is greater than a certain deviation (Δt=3~5℃), the acquisition point falls outside the power-off area, and the acquisition time needs to be reset.

[0083] Step 4: By calculating the current system error and error change rate, using the adaptive fuzzy rule model for fuzzy reasoning, querying the fuzzy matrix table, and performing online self-tuning control on the PID parameters. The calculation method for the current system error and error change rate is:

[0084] The temperature value of the next cycle is predicted based on the temperature values ​​actually measured in the previous two cycles and the heating law of the test. The predicted value is compared with the actually measured temperature value. When the difference is greater than a certain deviation, the collection point falls outside the power-off area and the collection time needs to be reset.

[0085] Assume that the actual temperature during this period is t n , given temperature t′ n ; The actual temperature of the previous cycle is t n-1 , given temperature t′ n-1 ; The given temperature of the next cycle is t' n+1 ; Calculate the temperature deviation value of this cycle as:

[0086] Δt n =t′ n -t n ;

[0087] The temperature deviation of the last cycle is:

[0088] Δt n-1 =t′ n-1 -t n-1 ;

[0089] According to the heating system, the actual temperature of the next cycle is predicted to be:

[0090] ～ t n+1 =t′ n+1 +(Δt n +Δtn-1 ) / 2;

[0091] Among them, t n+1 Indicates the actual measured temperature of the next cycle;

[0092] When│ ～ t n+1 -t n+1 │≥5℃, the acquisition point of the temperature signal is judged to be a false signal; the acquisition signal trigger time is reset to:

[0093] T=T n +10 / 9ms;

[0094] Among them, T n Indicates the time value when the thyristor trigger angle is 0° in the current cycle.

[0095] Example 1

[0096] Fuzzy adaptive PID control is adopted. Based on the conventional PID algorithm, the current system error and error change rate are calculated, fuzzy rules are used for fuzzy reasoning, and the fuzzy matrix table is queried to perform online self-tuning control on the PID parameters. For different samples and heating speeds, the set value can be quickly tracked while suppressing disturbances. Figure 3 As shown, the tracking curve is almost the same as the set curve, with high control accuracy. The control cycle of the rapid heating system is 10ms, and the temperature accuracy is 1°C. From a practical point of view, it meets the requirements of the rapid heat treatment experiment. With the above-mentioned temperature acquisition strategy and fuzzy adaptive PID control method, the rapid heat treatment system has high control accuracy, which lays the foundation for the accuracy of the annealing process temperature during the rapid heat treatment process.

[0097] Example 2

[0098] As preferably, Figure 4 As shown, in order to meet the sample size for rapid heat treatment and mechanical stretching, the mechanical properties test results of the sample are compared with the standard size sample. There is basically no difference in yield strength and n value. In terms of tensile strength and elongation, the yield strength average of the sample designed by the present invention is 12MPa higher than that of the standard size sample, and the elongation after fracture is 4.2% higher than that of the standard size sample. Through the above comparative analysis, the rapid heat treatment experimental sample prepared according to the above design scheme can not only meet the limited requirements of the rapid heat treatment device on the sample size, but also meet the requirements of the mechanical properties test of the finished product. The experimental sample of rapid heat treatment of low carbon steel and ultra-low carbon steel can be processed and prepared according to the design scheme.

[0099] Example 3

[0100] The chemical composition of low carbon steel is calculated by mass percentage as follows: C≤0.10%, Si≤0.10%, Mn≤0.50%, P≤0.020%, S≤0.0050%, and the remainder is Fe and other inevitable impurities.

[0101] The corresponding rapid heat treatment process is: rapidly heating up to 820℃ / s to 830℃ at a heating rate of 300℃ / s to 400℃ / s, keeping warm for 5s, and cooling down to 30℃ to 40℃ at a cooling rate of 40℃ / s to 50℃ / s. This scheme is taken as the best process technology scheme for rapid heat treatment of low carbon steel.

[0102] Example 4

[0103] The chemical composition of ultra-low carbon steel is calculated by mass percentage as follows: C≤0.01%, Si≤0.05%, Mn≤0.20%, P≤0.010%, S≤0.0050%, and the remainder is Fe and other inevitable impurities.

[0104] The corresponding rapid heat treatment process is: rapidly heating up to 830℃ / s to 850℃ at a heating rate of 500℃ / s to 600℃ / s, keeping warm for 5s, and cooling down to 30℃ to 40℃ at a cooling rate of 30℃ / s to 40℃ / s. This scheme is used as the best process technology scheme for rapid heat treatment of ultra-low carbon steel.

[0105] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0106] In the above embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0107] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0108] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed over multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0109] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0110] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk and other media that can store program codes.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rapid heat treatment device for cold-rolled low-carbon and ultra-low-carbon steel, characterized in that: include: Heating section and cooling section; The heating part realizes the heating of the sample; the heating part includes: a computer control system, a temperature transmitter, a thermocouple, a vacuum box, a heating transformer, a thyristor, a conductive copper bar I and a conductive copper bar II; the thyristor is connected to the heating transformer through the live wire and the neutral wire of the power frequency power supply; the neutral wire of the heating transformer is connected to the conductive copper bar I, and then connected to the sample arranged in the vacuum box; the live wire of the heating transformer is connected to the conductive copper bar II, and then connected to the other end of the sample arranged in the vacuum box; the temperature transmitter obtains the temperature information of the sample in the vacuum box through the connected thermocouple, and feeds the temperature information back to the computer control system; The cooling part includes: a cooling system and a quenching system; the cooling system uses high-pressure circulating water to cool the components of the heating part; the quenching system realizes forced cooling of the sample, and the quenching system controls the quenching water volume through a high-response CNC switch valve and a flow meter to realize the regulation of the quenching water volume.

2. A rapid heat treatment device for cold-rolled low-carbon and ultra-low-carbon steel according to claim 1, characterized in that: The quenching system realizes forced cooling of the sample by spraying water, mist or air.

3. The rapid heat treatment device for cold-rolled low-carbon and ultra-low-carbon steel according to claim 1 is characterized in that: The heating unit heats the sample by short-circuiting the secondary side of the heating transformer and the sample.

4. The rapid heat treatment device for cold-rolled low-carbon and ultra-low-carbon steel according to claim 1 is characterized in that: The rated capacity of the heating transformer is 27KVA~90KVA, the primary of the heating transformer is connected to a 380V voltage, and the secondary voltage is adjusted by the number of tap turns of the primary coil; the output voltage range of the heating transformer is 3V~10V, and the maximum secondary side current of the heating transformer is 9KA~10KA.

5. A rapid heat treatment method for cold-rolled low-carbon steel and ultra-low-carbon steel, characterized in that: The following steps are involved: Step 1: Process the test specimen into the shape of a pre-processed part; Step 2: Estimating the heating rate and temperature of the sample to be tested; Step 3: Measuring the actual temperature of the sample to be tested by a thermocouple welded on the surface of the sample as a feedback signal of the control system; Step 4: By calculating the current system error and error change rate, using the adaptive fuzzy rule model for fuzzy reasoning, querying the fuzzy matrix table, and performing online self-tuning control on the PID parameters.

6. A rapid heat treatment method for cold-rolled low carbon steel and ultra-low carbon steel according to claim 5, characterized in that: The calculation method of the current system error and error change rate is: The temperature value of the next cycle is predicted based on the temperature values ​​actually measured in the previous two cycles and the heating law of the test. The predicted value is compared with the actually measured temperature value. When the difference is greater than a certain deviation, the acquisition point falls outside the power-off area, and the acquisition time is reset. Assume that the actual temperature during this period is t n , given temperature t′ n ; The actual temperature of the previous cycle is t n-1 , given temperature t′ n-1 ; The given temperature of the next cycle is t' n+1 ; Calculate the temperature deviation value of this cycle as: Δt n =t′ n -t n ; The temperature deviation of the last cycle is: Δt n-1 =t′ n-1 -t n-1 ; According to the heating system, the actual temperature of the next cycle is predicted to be: ～ t n+1 =t′ n+1 +(Δt n +Δt n-1 ) / 2; Among them, t n+1 Indicates the actual measured temperature of the next cycle; When│ ～ t n+1 -t n+1 │≥5℃, the acquisition point of the temperature signal is judged to be a false signal; the acquisition signal trigger time is reset to: T=T n +10 / 9ms; Among them, T n Indicates the time value when the thyristor trigger angle is 0° in the current cycle.

7. A rapid heat treatment method for cold-rolled low carbon steel and ultra-low carbon steel according to claim 6, characterized in that: The certain deviation is 3℃~5℃.

8. A rapid heat treatment method for cold-rolled low carbon steel and ultra-low carbon steel according to claim 5, characterized in that: In step 2, the method for estimating the heating rate and temperature of the sample to be tested is: Assume the length of the sample is L, the cross-sectional area is A, the density is ρ, the resistivity is σ, the specific heat is c, and the heating rate is dT / dt; if the heat and electricity losses are not taken into account, the power W required per unit volume of the sample is: W = ρcdT / dt; The power P required to heat the entire sample is: P = LAρcdT / dt; The electric power P' consumed by the current in the sample is: P′=I 2 R=I 2 σL / A; From P=P′, we get: dT / dt=I 2 σ / (A 2 ρc); or dT / dt=U 2 σ / (L 2 ρc); Where U represents the voltage across the sample.

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