Classifications

• • 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
  • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
  • C21D9/54—Furnaces for treating strips or wire
  • C21D9/56—Continuous furnaces for strip or wire
• • 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
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
  • C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
• • 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
  • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
  • C21D9/54—Furnaces for treating strips or wire
  • C21D9/56—Continuous furnaces for strip or wire
  • C21D9/573—Continuous furnaces for strip or wire with cooling
• • 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
  • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
  • C21D9/54—Furnaces for treating strips or wire
  • C21D9/56—Continuous furnaces for strip or wire
  • C21D9/62—Continuous furnaces for strip or wire with direct resistance heating
• • 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
  • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
  • C21D9/54—Furnaces for treating strips or wire
  • C21D9/56—Continuous furnaces for strip or wire
  • C21D9/561—Continuous furnaces for strip or wire with a controlled atmosphere or vacuum

Definitions

• the present invention relates to a continuous annealing method and equipment for a cold-rolled steel strip, and more particularly to a continuous method for producing a cold-rolled steel sheet capable of improving workability of a cold-rolled steel sheet, imparting high functionality with BH property, and improving productivity.
• a continuous annealing method and its equipment ⁇ > 0
• a high-temperature annealing technology using continuous annealing equipment is known as a basic technology for improving the workability of a cold-rolled steel sheet, such as the deep drawability and the overhang property.
• the main reason for this is that the cold rolled steel sheet has a fibrous structure and poor workability, so the workability is improved by growing the grains by recrystallization to recover the structure by annealing.
• continuous annealing enables uniform treatment of continuous strip-shaped cold-rolled steel sheets and obtains a homogeneous material as compared with coil annealing, so that the treatment time is short and the number of process days can be significantly reduced. It is excellent in such points.
• the continuous annealing equipment for cold-rolled steel sheets is provided with a heating zone, a soaking zone, a primary cooling zone, an overaging zone, and a secondary cooling zone from the entry side, and belt-shaped cold rolling through hearth rolls provided in each zone.
• the steel sheet is transported and continuously annealed.
• the basis of this technology is the thermal history of the steel sheet subjected to annealing.As a basic heat pattern, the cold-rolled steel sheet is heated above the recrystallization temperature, soaked for the required time, then cooled to the specified temperature, and After performing the overaging treatment for the required time within the predetermined temperature range, the secondary cooling is performed.
• Various heat exchangers are used depending on the quality conditions of the drawing steel sheet and high-strength steel sheet, etc.In order to realize these heat patterns, appropriate heating and cooling methods must be selected. is necessary.
• a method of annealing at a high temperature and re-dissolving a part of Ti C and NbC to leave solid solution C remains.
• the strip-shaped cold-rolled steel sheet is uncoiled, inserted into the continuous annealing equipment and recrystallized and annealed.
• the heat pattern is basically the same as the above-mentioned heat pattern, but the heatability is improved.
• the heating and soaking temperatures are set high to provide BH properties.
• Japanese Patent Publication No. Sho 60-26817 Japanese Patent Publication No. 56-116830
• Japanese Patent Publication No. Sho 60-26818 Japanese Patent Publication No. 56-116831
• Japanese Patent Application No. 4-60923 describes that an electric heating device is installed between hearth rolls in an atmosphere heating furnace.
• JP-A-11-142032 and JP-A-1-187789 disclose passages before and after a metal band passage penetrating an annular transformer.
• An electric roll is provided, and both energized rolls are connected by a conductive member to form a closed circuit by the metal band, the conductive roll and the conductive member, and the closed circuit is formed by applying an alternating current from an external power supply to the annular transformer.
• a method is described in which an induced current is generated as a secondary coil, and the metal band is heated by Joule heat generated by the induced current.
• the steel sheet temperature is divided into a low temperature range where the temperature reaches 600 to 700 and a high temperature range where it reaches 800 to 900.
• a continuous annealing method for a steel sheet is disclosed in which the temperature of a steel sheet exiting a low temperature range is measured, and the heating is controlled so as to reach a target heating temperature in a high temperature range.
• Japanese Patent Application Laid-Open No. 61-204319 discloses that in producing a Ti-added cold-rolled steel sheet by continuous annealing, the temperature in the soaking zone of the continuously annealed line is raised by 200 to 300 ° C higher than the soaking temperature.
• a continuous annealing method for cold-rolled steel sheets which is characterized by heating rapidly and then rapidly cooling, is disclosed.
• the target steel type is limited to Ti-added steel, and the temperature rise and rapid heating in the solitary tropics are also limited to induction heating.
• the heating temperature is 200 to 300, and does not describe at all the detailed conditions related to the input energy such as heating rate, holding time, cooling rate and the purpose of imparting BH property.
• gas jet cooling is non-oxidizing and can be uniformly cooled, and has a sufficiently large cooling capacity for thin materials with a thickness of 0.4 or less, but for thick materials with a thickness exceeding 0.4 band. Will be lacking in ability.
• Roll contact cooling can provide higher cooling capacity than gas jet cooling, but it has problems with uniform cooling and has limitations when higher cooling capacity is required.
• gas-liquid cooling has the problem that the surface of the steel sheet is lightly oxidized, but the cooling capacity, uniform cooling property, and cooling controllability This is a good way to reject.
• Japanese Patent Publication No. 59-577 describes a short-time continuous annealing method for cold-rolled steel sheets that combines gas-liquid cooling and direct-fired heating, which activates the characteristics of gas-liquid cooling and directly injects high-temperature gas onto the steel sheet. ing.
• direct flame heating the heating rate of the high temperature part is only 50 ° CZ second at most, and there is a problem in the ability to follow the heating temperature and speed when changing the annealing conditions, and the characteristics of gas-liquid cooling are fully utilized. I can't say that.
• each of the above-mentioned patent publications has a very short heating method by combining a heating means for applying an electric current to the steel sheet itself and utilizing the Joule heat of the steel sheet itself and a cooling means by gas-liquid.
• a heating means for applying an electric current to the steel sheet itself and utilizing the Joule heat of the steel sheet itself and a cooling means by gas-liquid.
• a continuous annealing method for cold-rolled steel sheets that rapidly heats and cools over time. Disclosure of the invention
• a first object of the present invention is to provide a continuous annealing method and equipment having good controllability and capable of promptly responding to a wider range of annealing conditions, while avoiding lengthening of the continuous annealing equipment.
• a second object of the present invention is to provide a continuous annealing equipment with an optional heating step.
• An object of the present invention is to provide a continuous annealing equipment capable of shortening an annealing time and a line as much as possible.
• the heating step refers to a step including both the heating and soaking steps.
• the continuous annealing method of the present invention is as follows:
• the heating step includes a heating step by Joule heat
• the cooling step includes a cooling step by gas-liquid.
• a continuous annealing method for steel sheets characterized in that the heating by Joule heat in the heating process is a heating means by electric heating.
• the steel sheet After heating to 400 ° C in a heating step by energization, the steel sheet is heated to 700 to 900 ° C by another heating means in a non-oxidizing or reducing atmosphere. Continuous annealing method.
• the temperature is rapidly and quickly increased at any part of the subsequent soaking, and the heating control is performed so that the value of the annealing parameter (AP) becomes -33 or more.
• AP annealing parameter
• the entire heating zone including the soaking zone should include heating means by Joule heat
• the cooling zone should include a cooling means by gas-liquid.
• heating means by Joule heat in the entire heating zone is heating means by electric heating.
• a heating device that heats the steel sheet to a specified temperature, raises the temperature quickly and in a short time in any part of the soaking zone, and controls the heating so that the value of the annealing parameter (AP) becomes -33 or more This is a continuous annealing facility for steel sheets.
• the heating means by energization is means for causing the steel sheet to penetrate through the annular transformer and generating an induced current in the steel sheet by passing an alternating current through the annular transformer to heat the steel sheet. Annealing equipment.
• the structure of the continuous annealing equipment of 7 to ⁇ ⁇ shall consist of heating zone, soaking zone, primary cooling zone, overage treatment zone and secondary cooling zone.
• the means for raising the temperature quickly and in a short time in any part of the solitary tropics shall be an electric heating device or an induction heating device.
• a heating method a method and an apparatus are used in which an electric current is passed through the steel sheet itself and the steel sheet itself is heated using the Joule heat.
• Two types of heating using Joule heat are mainly used, that is, energization heating and induction heating. In the present invention, however, description will be made mainly on energization heating. Heating by energization makes the steel sheet itself a heating element, so there is no need to raise the ambient temperature and efficiency is high.
• the heating capacity can be easily controlled by adjusting the current value, and it is possible to easily control the heating capacity to more than 1000 ° C / sec to a high temperature of 500 to 900 ° C through a current of 40 AZ mm or more. Rapid heating is also possible.
• the dimension of the annealing parameter (AP) is a dimensionless parameter related to the distance over which the iron atoms are diffused by the applied thermal energy, in other words, the distance over which the grain boundary has moved. Therefore, the larger the AP, the greater the effect of annealing. Therefore, soft annealing has the significance of releasing the strain introduced by cold rolling by annealing to impart formability to the steel sheet. It has been found that such formability can be uniquely expressed by AP. This AP can be expressed by the following equation.
• cooling is performed by spraying two fluids consisting of water and an in-furnace gas mainly composed of nitrogen gas onto the heated steel sheet surface.
• This cooling method has the advantage that a uniform and extremely high cooling rate can be obtained, and that the cooling capacity and the cooling end point temperature can be controlled by adjusting the ratio of gas to water and the absolute amount of water. 7 It is possible to cool a steel plate at a cooling speed range of 50 to 200 in a nosec range, and it is possible to control the end point temperature with an accuracy of 10 ° C for soil at a plate temperature range of 250 to 550 ° C.
• gas-liquid cooling a thin oxide film is formed on the surface of the steel sheet by the reaction between the steel sheet and water vapor, but the thickness of the film is on the order of a few micron and can be easily removed by simple pickling.
• Heating by energization and cooling by gas-liquid have the above-mentioned advantages.Each of them can exert sufficient effects alone, but the present invention combines heating by energization and cooling by gas-liquid. However, the following specific effects can be obtained. 1 The continuous annealing equipment will be made more compact.
• the steel plate length in the furnace is 1/8 in the heating zone and 1Z4 in the primary cooling zone, and considerable equipment is used. Is compacted. Furthermore, when the heating rate is slow, usually 10 to 20 ° CZ seconds, the soaking time is set to 20 because the dissolved carbon eluted from the cementite slows the growth of recrystallized grains during the heating process from the heating. You need to take more than a second.
• Heating by energization is originally a heating method with extremely excellent thermal controllability.It is set in advance when heating from room temperature to the recrystallization temperature or higher, or when using it for partial heating from around 600 ° C to soaking temperature.
• the heating rate and heating temperature can be freely and precisely controlled simply by controlling the current value.
• a flexible heat pattern can be realized with high precision by using cooling with good thermal control.
• gas-liquid cooling makes it easy to control the cooling rate and the end point temperature, so that it is possible to realize a flexible annealing heat pattern by using both heating by energizing and cooling by gas-liquid. It will be possible to meet the demand for mass production.
• Both the heating by energization and the cooling by gas-liquid are extremely excellent in thermal responsiveness as well as thermal controllability. Therefore, it is possible to respond quickly to changes in conditions such as threading size and annealing temperature.
• the continuous annealing equipment of the radiant tube heating and gas jet cooling type when changing the thickness or the annealing temperature, the adjusting coil is passed or the speed is reduced until the specified annealing conditions are reached. Production capacity had to be sacrificed.
• the combined use of heating by energization and cooling by gas-liquid eliminates the sacrifice of productivity as described above, and can improve production capacity.
• the equipment can be made compact, it is possible to reduce defects in sheet passing caused by heart rolls, and to achieve high-speed sheet passing.
• Rapid heating and rapid cooling and high-temperature aging rapid cooling can be achieved by the combined use of heating by energization and cooling by gas-liquid.
• seizure hardening The BH property is improved, and the crystal of the high-strength steel sheet is refined, and the hole expandability and the like are improved.
• it is an index of deep drawability by controlling the annealing parameter (AP) value to -33 or more.
• Elongation (EI%) as an index of average r value and overhanging property; Yield strength and tensile strength TS can be higher than the target, which is the performance as a steel sheet for deep drawing.
• the combined use of heating by energization and cooling by gas-liquid produces an effect that is greater than the sum of the two. Furthermore, since the equipment is compact, it is easy to control the atmosphere in the furnace. For example, in gas-liquid cooling, the water vapor generated in the cooling zone is prevented from entering the heating zone and the solitary tropics. Is easy. This is because the volume of the heating zone and the soaking zone can be made compact, so that the atmospheric pressure in each zone can be easily controlled, and the pressure difference between the soaking zone and the cooling zone can be stably secured. It is effective in controlling and heating the oxide film on the steel sheet and preventing deterioration of the refractory material.
• a typical heat pattern in the continuous annealing method that includes heating by energization and cooling by gas-liquid is as follows: after heating to 700 to 900 ° C in the heating process with energization, soaking for 5 seconds or more, and cooling in the gas-liquid cooling process. It cools at a cooling rate of 0 to 300 t / s.
• a soaking temperature of 700 to 900 ° C. is a temperature necessary for recrystallization and grain growth of a rolled structure.
• the heating rate can be higher than the rate of solid solution from the steel, the delay in recrystallization speed due to solid solution carbon can be prevented, and excellent workability can be imparted to the steel sheet even with a short soaking time of about 5 seconds.
• the upper limit of the gas-liquid cooling rate was set to 300 ° CZ seconds because the amount of alloying elements added for non-aging and improvement of strength can usually be reduced with increasing cooling rate. This is because the effect saturates at 300 ° CZ seconds, and the steel sheet is likely to be inferior in shape due to cooling.
• the lower limit was set to 10 ° C / sec because the cooling time was too long, resulting in longer equipment and an increase in the oxide film thickness on the steel sheet surface.
• the heating means by energization should be placed after the heating zone including the existing solitary zone. After heating up to 600 ° C with the existing heating means, it can be heated to 700 to 900 ° C rapidly by energizing.
• an energization heating facility may be provided before the entire heating zone. In this case, there is no effect on the material, but the thermal responsiveness is used.
• the advantage of heating by energization can be taken advantage of, and it is possible to respond promptly to changes in the threading size and annealing conditions, so that an improvement in productivity can be expected. .
• the same effect can be expected when a heating means by energization is provided after the entire heating zone.However, adoption of heating means by energization in a region where the temperature of the steel sheet is low makes inexpensive equipment that does not require high-temperature durability. Not only can this be done, but it is also possible to cut off the existing furnace equipment and install it in front of the heating zone, eliminating the need to modify the existing furnace, thus making it possible to make the equipment even cheaper.
• Fig. 1 shows the entire continuous annealing equipment, which includes a winding machine 1, an inlet shearing machine 2, a welding machine 3, a washing machine 4, an inlet looper 5, and a heating zone 6 including an electric heating device.
• An electric heater, a current-carrying heating device or an induction heating device is provided in the solitary zone 7, and a cooling device such as a gas jet is provided in the slow cooling zone 8.
• the slow cooling zone 8 may not be provided in some cases.
• the primary cooling zone 9 is an example equipped with a gas-liquid cooling device.Therefore, a drying zone 10 is provided, and an overaging zone 11, a secondary cooling zone 12, a cooling tank 13 and a post-treatment tank are provided. 14 are provided.
• the post-treatment tank 14 usually includes four pickling tanks, a primary washing tank, an electrolytic treatment tank, and a secondary washing tank. It has a dryer 15, an exit looper 16, a temper rolling mill 17, an inspection and refinement section 18, an exit shearing machine 19, and a winder 20.
• FIG. 2 is a diagram showing an example of a heating zone, a solitary tropical zone, and a primary cooling zone of the continuous annealing equipment of the present invention.
• the steel sheet 21 wound in a coil shape through the cold rolling step is continuously sent out and charged into the heating zone 6.
• An electric current heating device for generating an induced current in the steel sheet 21 using the annular transformer 24 is provided, and an electric current is supplied to the steel sheet 21 through the current supply rolls 22 and 23 connected by a conductive member, and the steel sheet is heated by Joule heat. Heat 21.
• the rapidly heated steel plate 21 is then soaked in the soaking zone 7.
• current-carrying rolls 25 and 26 are also arranged in the soaking zone 7, and soaking treatment is performed by heating by energization.
• the heating zone 6 is a horizontal furnace and the tropical zone 7 is a vertical furnace, but the horizontal and vertical furnaces may be selected according to the equipment capacity. In other words, in the case of a high production facility, a vertical facility is indispensable because the line length becomes long, but in the case of a low production facility, the horizontal type is easier to operate.
• the steel sheet 21 is guided to the primary cooling zone 9 and rapidly cooled by the gas-liquid cooling device 27. Thereafter, the steel sheet 21 is reheated and overaged if necessary, to remove an oxide film generated on the steel sheet surface.
• FIG. 3 is a schematic explanatory view of a horizontal electric heating device.
• Current-carrying rolls 22 and 23 are provided on the lower surface of the steel plate 21 to be heated, and presser rolls 28 and 29 are provided on the upper surface thereof in opposition to the current-carrying rolls 22 and 23.
• the holding rolls 28 and 29 hold the steel plate 21 between the opposing energizing rolls 22 and 23 by pressing means made of, for example, cylinders 30 and 31, respectively.
• An annular transformer 24 is disposed between the low-temperature side energizing roll 22 and the high-temperature side energizing roll 23 around the steel plate 21.
• These energized rolls 22 and 23 are connected by a conductive member 32 such as copper, whose electric resistance value is much smaller than that of the steel plate 21, and a closed circuit is formed by the steel plate 21, the energized rolls 22 and 23 and the conductive member 32.
• An AC current is supplied from an external power supply 33 to the annular transformer 24 to generate an induced current using the closed circuit as a secondary coil, and the steel sheet 21 is heated by Joule heat caused by the induced current.
• the heating rate and the heating temperature can be controlled by the specific resistance value of the material to be heated and a predetermined amount of alternating current calculated based on conditions such as sheet thickness, sheet width, and sheet speed.
• the current-carrying heating device uses this transformer-type current-carrying heating method and a method for directly supplying electricity There is a formula, but the former is more desirable because a large current can be efficiently passed through the steel plate.
• FIG. 4 is a schematic explanatory diagram of the cooling zone.
• a plurality of gas-liquid cooling chambers 34 are arranged in a down path 36, and a liquid draining device 35 is provided immediately below each chamber 34.
• a vertical downpass is the most effective in order to maintain the cooling symmetry of the front and back surfaces and to prevent uneven cooling due to dripping water in the high temperature part of the steel plate 21.
• a plurality of gas-liquid mixing nozzles 37 including a gas-liquid injection nozzle header 39 and a liquid injection nozzle header 38 are provided in the gas-liquid cooling chamber 34. It is arranged vertically along the passing direction with the steel plate 21 interposed therebetween.
• the gas-liquid mixing unit 37 performs gas-liquid mixing immediately before spraying to keep the atomization state stable. Cooling rate in cooling by the gas-liquid is 1 minute question by adjusting the liquid flow rate control valve 41 which kicked set in the liquid pipe 40 which conducts the liquid injection nozzle to Dda 38, in the amount of water or 1 m 2 Ah The liquid density expressed and the end point temperature are controlled by the number of nozzle units by turning on and off the liquid flow control valve 41.o
• Figure 6 (A) and Figure 6 (B) show examples of continuous annealing equipment and an annealing heat cycle, respectively, in which an electric heating device 6 'is provided in front of the heating zone 6 using a radiant tube.
• an electric heating device 6 ′ By providing the electric heating device 6 ′, when the annealing temperature and the plate size are changed, current control of only the electric heating device can be used immediately, so schedule-free one annealing becomes possible and the production capacity is improved.
• Figures 7 (A) and 7 (B) show examples of continuous annealing equipment and an annealing heat cycle in which a current-carrying heating device 6 'is installed between the soaking zone 7 and the primary cooling zone 9, respectively. Show.
• a current-carrying heating device 6 ' is installed between the soaking zone 7 and the primary cooling zone 9, respectively.
• the electric heating device 6 ′ between the soaking zone 7 and the gas-liquid cooling device, it is possible to change the annealing temperature and the strip size.
• the heating device 6 ′ be installed at the front of the heating zone 6, but also it can be heated more quickly than the heating capacity of the existing radiant tube.
• New quality improvement such as improvement and BH property is also possible.
• Figure 1 is a diagram showing the entire continuous annealing equipment.
• FIG. 2 is a diagram showing an example of the continuous annealing equipment of the present invention.
• FIG. 3 is a diagram showing details of the electric heating device.
• FIG. 4 is a diagram showing an outline of the gas-liquid cooling device.
• FIG. 5 is a diagram showing details of the gas-liquid cooling device.
• FIG. 6A is a diagram showing an example of the continuous annealing equipment of the present invention
• FIG. 6B is a diagram showing an example of an annealing heat cycle.
• FIG. 7A is a diagram illustrating an example of a continuous annealing facility in which the fourth embodiment of the present invention is performed
• FIG. 7B is a diagram illustrating an example of a heat pattern performed in the fourth embodiment.
• FIG. 7 is a diagram showing a relationship between a seven value, an E1 value, and YP and TS.
• Example 1 the best mode for carrying out the present invention will be described based on examples.
• the instantaneous temperature reached 860 ° C by a current-carrying heating device, and then the rapid cooling annealing cycle was used.
• BH property was able to be given while maintaining 7 values. This utilizes the phenomenon that C is eluted by a high-temperature treatment even for a moment.
• the same strength can be achieved even if the Mn of the alloy component is reduced from 1.5% to 1.0% by rapid heating and rapid cooling annealing. Expandability also improved. This is because the solid solution of C is suppressed by rapid heating, and the crystal is refined by quenching from the austenitic two-phase region with a high C concentration.
• FIG. 7 (B) is a diagram showing an example of a heat pattern implemented in the present invention.
• a is a stage in which a cold-rolled steel strip is unwound and heated in a continuous annealing furnace.
• the heating pattern is a heating rate of 1 to 200 ° C / sec, and an ultimate temperature of 500 to 900. It is.
• b is the stage of soaking the steel strip, the soaking temperature is 500-900 ° C, and the holding time is 0-300 sec.
• c is abrupt due to current heating, which is a feature of the present invention. Raise the temperature quickly and for a short time.
• the heating rate is 40 ⁇ 1000 ° CZsec, and heating up to 750 ⁇ 900 ° C.
• d is the stage of cooling immediately after rapid heating for a short time. In the case of equipment with an overaging zone, e is cooled immediately after quenching and heated, and is maintained at an overaging temperature of 250 to 450 and then cooled to room temperature.
• FIG. 8 is a diagram showing the relationship between the annealing parameter (AP) according to the present invention and "F value, E1 value, YP, TS, and FIG. 8 (A), FIG. 8 (B), FIG. ).
• the average r value as an index of deep drawability and the elongation E1 (%)
• the average r value is 1.5 or more when ⁇ is -33 or more
• E1 (%) is 42% or more
• YP is 180N bandage 2 or more
• TS is 320NZNZmm 2 or more.
• the partial heating can be performed in the range of 0.5 to 15 seconds by arranging the electric heating or the induction heating between the equal-tropical passes.
• the reason why the electric heating device or the induction heating device is used is that, for example, as a heating method in a continuous annealing furnace for cold steel sheets, a direct-fired non-oxidizing heating method or a radiation tube heating method is used.
• a heating method using heat transfer since each of these methods is a heating method using heat transfer, the heating capacity per unit time is not very high, and the required total amount of heat can be ascertained. In order to maintain the temperature, the heating time must be long, which necessarily increases the length of the heating zone.
• induction heating In induction heating, a heating coil is arranged around the steel strip and power is supplied from a high-frequency power source. An induction current is applied to the steel strip by the magnetic field generated by the heating coil, parallel to the longitudinal direction of the steel strip or the length of the steel strip. This is because the steel strip is heated by Joule heat by flowing in a direction perpendicular to the direction, and rapid heating is possible. Auxiliary heating is performed using these electric heating or induction heating devices, whereby the annealing parameter (AP) can be easily controlled, and at the same time, the above-mentioned steel strip longitudinal direction or steel strip is used. Direct heating or thermal compensation in the vertical direction with respect to the longitudinal direction of the band makes it possible to obtain uniform characteristics. Industrial applicability
• the continuous annealing method and equipment including Joule heat, preferably heating by energization and cooling by gas-liquid, according to the present invention can be made into extremely compact equipment. It has the effects of improving production capacity and improving quality. In addition, it is possible to obtain a high surface quality without heat backlash or breakage of the sheet, and no surface flaws, etc., and to improve productivity and cost by using a free time through the sheet. By controlling the value of AP to -33 or more, it is possible to manufacture cold-rolled steel sheets with excellent workability and BH properties. Things.

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• Physics & Mathematics (AREA)
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• Crystallography & Structural Chemistry (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)

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• 1995
  • 1995-10-13 BR BR9508762A patent/BR9508762A/pt not_active Application Discontinuation
  • 1995-10-13 WO PCT/JP1995/002111 patent/WO1997000975A1/ja not_active Application Discontinuation
  • 1995-10-13 EP EP95934304A patent/EP0779370A1/en not_active Ceased
  • 1995-10-13 CN CN95195187A patent/CN1158641A/zh active Pending
  • 1995-10-13 KR KR1019970701147A patent/KR100221789B1/ko not_active IP Right Cessation

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