KR101395047B1 - Flexible strip steel processing line suitable for producing various kinds of high-strength steel - Google Patents

Abstract

An elastic strip steel manufacturing line for manufacturing various high strength steels includes an uncoiling and washing station; A heating station; A soaking station; A delay cooling station in turn; A high hydrogen jet cooling station and a water quenching station arranged side by side; Wherein the high hydrogen jet cooling station includes a reheat station; An overflow station; A final cooling station; A planarization station; A finishing station; A greasing station; A winding station is arranged successively; Wherein the water quenching station is arranged in succession with a pickling station and an electroplating station; A hot dip zinc plating station is arranged to be connected to the rear of the reheating station; A galvanizing annealing station is disposed behind the hot dipping hot dipping hot dipping and is connected to the final cooling station through a connecting passage; Wherein the pickling station and the electroplating station are connected to the reheating station via connection channels, respectively; The electroplating station is also connected directly to the uncoiling and cleaning station via one connection channel; The water quenching station is connected to the delay cooling station via a fixed bypass passage; And the reheat station is also connected downstream of the overflow station via a movable bypass passage. The process line can incorporate the production of various high strength steels in a single unit for flexible (flexible) production.

Description

TECHNICAL FIELD [0001] The present invention relates to a production line of an elastic strip steel suitable for manufacturing various high-strength steels,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for heat treatment and surface treatment of strip steel, and more specifically, to an elastic strip steel manufacturing line suitable for manufacturing various high strength steel.

The need for environmental protection and the need for sustainable development have been recognized in the 21st century as one of human universal perspectives. The general trend in the development of the Hyundai automotive industry is to reduce weight and save energy. Studies on light vehicles have shown that high-strength steels must be used on a large scale in the automotive industry in order to achieve the goals of making the steel thinner and reducing weight, saving energy and reducing emissions . The requirements for high strength cold rolled and hot dip galvanized iron sheets have increased significantly accordingly.

The high-strength cold-rolled steel sheet is produced using a continuous annealing unit having a high-speed cooling device. In order to give the product strength of 980 MPa or more and to provide good process performance, continuous annealing units require fast cooling equipment such as quenching, spray cooling or high hydrogen jet cooling. The main processes for continuous annealing are as follows.

Uncoiling (unwinding) - Washing - Heating - Soaking - Delay cooling - Rapid cooling - (pickling) - Reheating - Overaging (tempering) - Cooling - Planing - Finishing - High Strength Cold Rolled Steel Sheet

In a continuous annealing process, the cold rolled steel that is uncoiled and washed is heated to a predetermined temperature and maintained for a predetermined time, and then slowly cooled to a predetermined temperature and cooled at a high cooling rate in a high- Cool to overaging temperature.

As the cooling method which has the fastest cooling rate at present, the water quenching method is an inexpensive method used for producing high strength steel. By adding a small amount of alloy elements, high level strength biphase, multiphase, and martensitic high strength steels can be produced. However, an oxide film layer may be formed on the strip steel surface during water quenching and additional pickling is required. And, when water quenching is used, it is difficult to stop the cooling operation at overshoot temperature. Accordingly, the strip steel should be cooled to 100 DEG C or lower, and it is necessary to reheat the strip steel to a predetermined tempering temperature for tempering to ensure anti-aging stability.

When high hydrogen jet cooling is used in the continuous annealing process, the terminal cooling temperature has strong controllability and can avoid supercooling to room temperature and oxidation of the strip steel. Therefore, the strip steel can proceed immediately after aggressive treatment or after reheating without pickling. However, the cooling rate of high hydrogen jet cooling methods is slower than that of water quenching. Thus, when the same alloy element is added, the strength level of the cold rolled steel sheet produced by high hydrogen jet cooling is much lower than that produced by water quenching.

High-strength hot dip galvanizing steel sheets are produced by a continuous high-temperature immersion galvanizing unit having a high-speed cooker. In order to maximize substrate strength and maximize hot galvanizing capacity, the continuous hot dip galvanizing unit should be equipped with a high-speed cooling device with high hydrogen jet cooling, a water quenching or spray cooling device and a pickling device. The main processes for continuous hot dip galvanizing include:

Uncoiling - Cleaning - Heating - Immersion - Delay cooling - Fast cooling - (pickling) - (reheating) - Hot dip Zinc plating (or galvanized annealing included) - Cooling - Planarization - Finishing - High strength, high temperature immersion galvanized steel.

In a continuous hot dip galvanizing process, the uncoiled and washed cold rolled steel is heated to a soaking temperature, held for a predetermined period of time, and slowly cooled to a predetermined temperature, To a zinc plating pot temperature or room temperature at a high cooling rate.

The water quenched strip is washed with an acid to remove the oxide film on its surface and then heated prior to entering the galvanizing port for hot dip galvanizing or zinc plating annealing. Finally, the strips are cooled and then carry out subsequent processing procedures such as planarization.

Hot dip galvanizing of the strip steel is performed at about 460 DEG C and galvanization annealing after hot dip galvanizing is performed at about 500 DEG C and hot dip galvanized steel sheets of high level strength are produced by conventional continuous hot dip galvanizing production If produced in a line, a large amount of alloy components must be added into the substrate (substrate). However, such an operation results in an increase in the alloy composition of the steel sheet, such as Mn and Si, on the surface of the steel sheet prior to galvanizing, and thus, the hot dip galvanized sheet containing galvanized annealed sheet having excellent surface quality is produced Can not be. Thus, when a process involving water quenching + pickling + reheating + hot dip galvanizing (or including galvanized annealing) is used, the strength level of the steel sheet increases significantly in one aspect, but on the other hand, Can be removed by pickling, thereby making it possible to produce galvanized annealed plates having high strength and high-temperature-immersed zinc-plated sheets and excellent surface quality.

If a high hydrogen rapid cooling process is used, the strip may be introduced into the galvanizing port directly or without re-heating after galvanizing (including galvanizing annealing) without pickling, after which subsequent processing such as planarization Processes are carried out. However, when such processes are used, too much of the alloying constituents should be added to improve the zinc plating ability. Given the same chemical composition, the final product according to such a process has a significantly lower intensity level. Thus, compared to water quenching, the high hydrogen cooling process can produce galvanized annealed plates with a low level of strength in hot dip galvanized sheets and in a range of alloy compositions.

As described above, in the manufacturing processes for producing the high-strength cold-rolled steel sheet and the high-temperature-immersed galvanized steel sheet, the cleaning apparatus provided at the inlet of the initial steel sheet, the immersion apparatus for annealing, As well as the configuration of the planarization, greasing and winding devices installed at the outlet side are all the same as those of the apparatus (e.g., water quenching, pickling and reheating devices, etc.). Therefore, the production of high-strength cold-rolled steel sheets and the production of high-strength hot-dip galvanized steel sheets occur together in a single unit. More importantly, if the production lines of the high-strength cold-rolled steel sheet and the high-strength hot-dip galvanized steel sheet are made separately, respectively, since there are many requirements for the products which are not both of the high-strength cold-rolled steel sheet and the high- The cost will increase significantly, and none of the units will be available for their production lines. On the other hand, units for producing high-strength steels, and more particularly ultra-high-strength steels, are not suitable for producing soft steel products having high surface quality, but they are not suitable for producing general, low-grade soft steel products with relatively poor surface quality And thus consumes a large amount of resources. Therefore, a great deal of interest in the steel industry is that there is a rational construction of devices in various unit sections, research and development of shift devices for passing steel plates, and many specifications and varieties, as well as high strength and ultra high strength cold- High-temperature immersion zinc-plated steel sheet which does not have the required requirements, and the like.

Japanese Patent Application Laid-Open (Kokai) H2003-253413 discloses a dual purpose apparatus and a dual purpose method for producing a high strength cold-rolled galvanized steel sheet and a hot-dip galvanized steel sheet. In the above method, a steel sheet produced from an annealing furnace having a heating section, an immersion section and a gas jet cooling section is supplied to a galvanizing apparatus in a galvanizing passage to produce a hot-dip galvanized steel sheet. Alternatively, the steel sheet produced from the annealing furnace is supplied to a water quenching bath rather than a galvanizing device in a bare steel cold rolling passageway to produce a high strength cold rolled steel sheet.

The above patent relates to a dual purpose method for producing a hot dip galvanized steel sheet and a high strength cold rolled steel sheet, and is characterized by having a shift device for switching between the two process passages. For dual purpose manufacture of hot dip galvanized steel sheets and high strength cold rolled steel sheets, three methods of influencing the process have been applied. That is, (1) the shift device is installed between the zinc plating port and the water quenching tank immediately after the gas jet cooling section. (2) The shift is performed by lifting or lowering the rolls between the galvanizing port and the water quenching bath. (3) Conversion (shift) is carried out by infusing a zinc solution or water into a common water bath for zinc plating and water quenching.

However, the main drawbacks of the patent are as follows.

First, in the dual purpose production method of the patent, since the high hydrogen jet cooling and water quenching processes capable of high-speed cooling and pickling processes are not used, a phase-change hardened High temperature immersion galvanized steel sheets and galvanized steel sheets can not be manufactured. Only high strength high temperature immersion galvanized steel sheets and galvanized steel sheets are realized.

Secondly, since the dual purpose production method of the above patent does not use the washing process after the water quenching and tempering process by reheating, the high strength cold-rolled steel sheet has bad surface quality, firing and anti-aging stability.

Finally, the second and third process steps for implementing the dual purpose production method of the above patent are difficult in practice. Specifically, when a shift occurs between the galvanized steel sheet and the cold-rolled steel sheet, the residual zinc on the roll surface seriously affects the surface quality of the cold-rolled steel sheet and the operation of the unit. And, the general use of galvanizing ports and water quenching tanks is accompanied by difficult-to-solve problems such as cracking of the zinc plated ports, and there is a problem of increased sheet costs.

An object of the present invention is to provide an elastic thin-strip steel manufacturing line for producing various high-strength steels, in which not only high-strength cold-rolled steel sheet, hot-dip galvanized steel sheet but also galvanized steel sheet and nickel- Cold rolled and cured rolled cured materials and hot rolled pickled plates. General cold-rolled steel sheets, hot-dip galvanized steel sheets and galvanized steel sheets are solidified into a single unit, resources can be effectively used, and investment costs are reduced. The electro-galvanized steel sheet and the nickel-plated steel sheet can be produced in the above-mentioned process line by using the connecting passage, and the hot-dip galvanized steel sheet and the galvanized steel sheet can also be produced. Using a pickling process prior to hot dip galvanizing or Fe, Ni electroplating processes, the drawbacks of the coarse zinc plating stability of high strength steels, especially ultra high strength steels, are completely eliminated in the production process and apparatus of the present invention, A high-strength high-temperature-immersed galvanized steel sheet and a galvanized annealed steel sheet can be produced.

In order to achieve the above object, the present invention provides the following technical solutions.

An elastic strip steel manufacturing line for manufacturing various high strength steels includes an uncoiling and washing station; A heating station; A soaking station; A delay cooling station; Followed by a high hydrogen jet cooling station and a water quenching station arranged side by side. Wherein the high hydrogen jet cooling station is followed by a reheat station, an overfiring station, a final cooling station, a planarization station, a finishing station, a drawing station and a cooling station arranged in succession; The water quenching station is followed by a pickling station and electroplating station arranged in succession. In addition, a hot dip galvanizing station is arranged behind and connected to a reheating station, and an electroplating annealing station is arranged behind and connected to the hot dip galvanizing station, Wherein said pickling station and said electroplating station are respectively connected to said reheating station via a connecting channel; The electroplating station is also connected directly to the uncoiling and cleaning station via a connection channel; The water quenching station is connected to the delay cooling station via a fixed bypass passage; And wherein the reheating station is also connected to a downstream overflow station via a movable bypass passage wherein the movable bypass passage is connected when a subsequently annealed cold rolled steel plate product is manufactured, The passageway is separate from the sealed nozzle when the hot dip galvanized product or the galvanized annealed product is produced. In this case, the finishing station is a process for performing a normal operation such as surface grinding, removal of surface contaminants, or removal of edge deformation by mechanical machining.

 In addition, the manufacturing line further includes passivating and other post-processing stations arranged rearward (e.g., downstream) and connected to the electroplating station and the planarization station, , And is connected to the finishing station.

In addition, the bypass passage is different from the connecting passage. That is, the electrons are substantially the same sealing passages as in the furnace for the atmospheric annealing, for example, the furnace requires a protective gas of a mixture of nitrogen and hydrogen, which comprises 2 to 7% by volume of hydrogen.

In addition, the high hydrogen jet cooling section is equipped with a high-power injection heater, preferably an induction heater with a frequency of 1000 Hz or higher. Compared to the process lines of other prior art patents, the process line according to the present invention is capable of adjusting the temperature and reheating rate and temperature of the high-speed cooled strip steel, without pickling, The conditions of the manufacturing process of the steel sheet are sufficiently satisfied.

The gas for cooling a high hydrogen jet according to the present invention is a mixture of nitrogen and hydrogen in which hydrogen accounts for 20% or more of the volume.

The present invention also provides a manufacturing process using an elastic strip steel manufacturing line suitable for producing various high strength steels according to the present invention wherein the strip steel is uncoiled, washed, heated and dipped, slowly cooled, Some of the cold strip steel may become overblown by further cooling by high-hydrogen jets, for example post-treatment such as cooling and planarization to produce high strength cold rolled steel. And other parts can be reheated and transferred into a device for subsequent processes such as galvanizing ports and galvanized annealing furnaces to produce high strength hot dip galvanized or galvanized annealed sheets.

In addition, in an elastic strip steel manufacturing line suitable for producing various high strength steels according to the present invention, the strip steel is uncoiled, washed, heated and dipped, slowly cooled, water quenched and further washed with acid , And then the washed strip is reheated to produce high strength hot dip galvanized steel and can be transported into the galvanizing port; Or directly into an overfitting section to produce an ultra high strength cold rolled steel sheet; Or may be electroplated with Zn or Ni and proceed directly to a post-treatment such as passivation to produce an ultra-high strength zinc electroplated sheet; Or may be electroplated to have a very thin layer of Ni or Fe, and then re-heated to produce ultra-high strength hot dip galvanized sheets and zinc annealed sheets, such as reheating devices, zinc plated ports and galvanized annealing furnaces And proceeds to improve its zinc plating properties before entering the devices of the processes.

Generally, both high strength plates and high surface quality plates (e.g., automotive outer panels) are produced in prior art cold rolling / continuous heat treatment units.

However, high strength steels, especially ultra high strength steels, have a demand for high surface quality sheets and overall surface quality. Due to their use in automotive structures, the demands on the surface quality of high strength steels are not high. Conversely, automotive exterior panels are extremely sensitive to its surface quality. When small amounts of high strength steel, especially ultra high strength steel, are produced in large scale continuous heat treatment units, nodule formation or local scratches and scratches can occur on the rolls of the furnace due to high strength and bad shape of the steel sheet. As such, the unit can no longer be used to produce high surface quality plates after high strength steel is completed. And the unit must be shut down for replacement of rolls in the damaged furnace. The loss resulting from the interruption of the large continuous heat treatment furnace to replace the rolls is surprising. Therefore, manufacturing high strength steel, especially ultra high strength steel, and high surface quality plates in the same unit is a completely different matter.

In specifications, high-strength steels, especially ultra-high strength steels, are typically thick and narrow, while high surface quality plates, typically represented by automotive exterior panels, are wide and thin.

When a continuous heat treatment unit is designed to accommodate both products, there is a high technical difficulty as well as the complexity and huge size of the unit, as well as large investments.

There is also a difference in furnace cooling technology. Units for producing high surface quality plates do not have a high demand for the cooling rate of the furnace, but their demands have high demands on high speed stable pass technology to prevent buckling and band rupture at high temperatures , A low tension is required and stability is required for each part of the furnace. In contrast, the unit for making high strength steels has a high demand for cooling rate in the rapid cooling zone of the furnace. In addition, originally thick, narrow, high strength steels tend to have deviations, and this tendency becomes worse after such steels undergo phase change under rapid cooling, and the shape of the plates becomes worse this way. Therefore, it is required that the tension in each furnace portion of the unit be large, and that the correcting capability is required to be larger.

The demand for planarization machines is also different. The requirement for a high surface quality for production is extremely important in enhancing the surface quality by planarization in addition to improving the shape of the plate and controlling the material properties by planarization. On the other hand, if a high strength steel product has a high yield strength and if the diameter of the planarizing roll is too large, the rolling pressure of the planarizing machine will be greatly increased , And the energy consumption and investment costs of the planarization machine will increase significantly. The small diameter of the planarizing roll, the large rolling pressure and the large tension during planarization are generally required to improve the plate shape of large high strength steels.

As for the conversion between specifications and diversity as each specification under each variety of high-strength steel, especially the ultra-high-strength steel is used in small quantity, but the total number of specifications and kinds is large, and the transition in production with continuous heat treatment unit The shift frequency is increased, and the switching time becomes longer. This makes stable operation of large-scale continuous heat treatment units and production yields worse.

The elastic thin strip steel manufacturing line suitable for producing various high strength steels of the present invention has a remarkable superiority. Compared to conventional heat treatment units, the manufacturing line of the present invention has the following significant and remarkable features and advantages.

1. Excellent product variety

Using the most common continuous annealing units, conventional cold rolled products can be manufactured, and hot dip zinc plating and galvanized annealing products can be manufactured using the most common continuous hot dip galvanizing units.

With the recently developed dual-purpose units of continuous annealing / hot dip galvanizing, two types of products can be manufactured, such as general cold-rolled and hot-dip galvanized products. In addition, the target product of the dual purpose unit of continuous annealing / hot dip galvanizing is not high strength steel, especially ultra high strength steel. Thus, it does not have a clear superiority in product diversity.

A flexible production line for producing high strength steel according to the present invention in which a high speed, high hydrogen jet cooling device and a water quenching device are installed at the same time is used to manufacture high strength and ultra high strength steels having a small requirement but a rich specification and variety Especially useful. Such process lines can be used to produce high strength cold rolled and ultra high strength steels of various strength levels (up to 1470 MPa), as well as the highest levels and highest strength levels of up to 980 MPa, including electro galvanizing, nickel plating and zinc - Nickel alloy plating products can be manufactured. Compared to other cold-rolled strip steel process lines, such a multi-function process line is characterized by the ability to produce multiple functions and a plurality of different products.

2. Low production cost

First, in the starting material, not only the rolled cured sheet can be used as a starting material, but also a hot rolled pickled steel sheet may also be used as a starting material. In the present invention, since a new high-speed high-jet cooling apparatus and a new water quenching apparatus are used, it is possible to reduce the content of the alloy in the production of high-strength steel at the same strength level while reducing the alloy composition and lowering the production cost have. In addition, the production conditions required for steelmaking, hot rolling, pickling and cold rolling processes are reduced, thereby achieving more stable operation and lower costs in production. And because a variety of high strength steels can be produced in the process line, interconnection and movement between the manufacture of various high strength steel products is convenient and there is a great investment in other units to produce small amounts of ultra-high strength steels There is an advantage that other units are freed and the production cost is reduced overall.

3. High product quality

Since the process (production) line of the present invention is specialized in the treatment of various high strength steel products, more effective methods can be provided to improve the product quality in consideration of the process conditions necessary for the production of high strength steel. For example, in the problem of low cooling rates of a typical continuous heat treatment unit, the unit according to the present invention utilizes a new technique of high-speed, high hydrogen jet cooling and water quenching to significantly increase the cooling rate, The strength level of high strength steel can significantly reduce the content of the alloy in the chemical composition. Thus, the weldability and plating properties of high strength steel products are significantly increased with a reduction in product cost. In another example, new processes such as hot zinc plating, pickling and plating after water quenching may be used to further improve the plating properties of high strength steels, thereby increasing the surface quality and corrosion resistance of hot dip galvanized high strength steels Resistance is improved.

1 is a block diagram showing a process according to a first embodiment of the present invention.
2 is a block diagram showing a process according to a second embodiment of the present invention.
3 is a block diagram showing a process according to a third embodiment of the present invention.
4 is a block diagram showing a process according to the fourth embodiment of the present invention.
5 is a block diagram showing a process according to the fifth embodiment of the present invention.
6 is a block diagram showing a process according to a sixth embodiment of the present invention.
7 is a block diagram showing a process according to a seventh embodiment of the present invention.
8 is a block diagram showing a process according to an eighth embodiment of the present invention.
9 is a block diagram showing a process according to a ninth embodiment of the present invention.

An elastic strip steel manufacturing line for manufacturing various high strength steel according to the present invention will be described in detail with reference to the accompanying drawings. (In the figure, the solid line arrows indicate the process used in the embodiment, and the dashed lines indicate an optional process that can be applied to other embodiments.)

As shown in FIG. 1, the process schematic diagram of this embodiment includes a starting material (1) - uncoiling and cleaning (2) - heating (3) - immersion (4) - delay cooling (5) - gas jet cooling (6) (10) - Final cooling (11) - Planarization (12) - Finishing (13) - Grinding and post treatment (14) - Coiling (15) - Final product (16) .

By using the process according to the present invention, it is possible to produce general cold-rolled steel sheets and phase-change hardened high-strength cold-rolled steel sheets, in particular cold-rolled TRIP steel and DP steels lower than the 80 kg grade, cold rolled 80 Kg- grade TRIP and 80 Kg- The process parameters for DP steel are shown in Table 1. As shown in Table 1, it is important to control the immersion temperature, the aging temperature and the respective time during the continuous annealing for the 80 Kg grade TRIP steel, and the requirements for the high cooling rate are not important not. However, with regard to the high strength DP steel of the 80 Kg grade, the soaking temperature and fast cooling rate are important process parameters in controlling continuous annealing, and there are many requirements, especially at high cooling rates. In aging, it is necessary to carry out the reaction at a low temperature, and it is necessary to perform the reaction for a short time in order to prevent the decomposition of the martensitic structure.

Pickling and reheating processes are not performed in this process, and heat treatment processes are performed at low cost. The surface quality of this product was found to be excellent.

Table 1. Process parameters for cold rolled 80 Kg-grade TRIP steel and 80 Kg-grade DP steel
Heating rate

V0
℃ / s
Immersion temperature


T1
℃
Immersion time

t1
s
Delayed cooling rate

V1
℃ / s
Final temperature of delayed cooling
T2
℃
Fast cooling rate
V2
℃ / s
Aging temperature

T3
℃
Aging time

t2
s

80K-TRIP

3-15
700-820
30-150
3-30
500-700
20-60
300-500
120-500
80K-DP

3-15
750-850
30-150
3-30
500-700
50-150
200-300
80-300

As shown in FIG. 2, the process schematic diagram of this embodiment shows that the starting material (1) - uncoiling and cleaning (2) - heating (3) - immersion (4) - delayed cooling (5) - Reheating (9) - Overshoot (10) - Final cooling (11) - Planarization (12) - Finishing (13) - Gridding and postprocessing (14) - Coiling (15) - Final product (16) .

Compared with Example 1, this process according to the present invention is characterized in that the overaging process is carried out first at a low temperature and then at a high temperature, whereby the process wrought iron with excellent anti- It utilizes an overhang process made from carbon aluminum-strip steel. Process parameters for the production of low carbon aluminum-free soft iron products with excellent anti-aging properties are shown in Table 2. As shown in Table 2, it is important to control the soaking temperature and aging process during continuous annealing in order to produce low carbon aluminum removal steel with good anti-aging properties, It is first carried out at low temperature and then at high temperature to obtain a sufficient separation of dissolved carbon. The process line of the present invention meets the requisite conditions of such a process by applying a fast cooling process in which reheating is performed.

Compared to other patents, high-power induction heaters are built on the high-hydrogen jet cooling section of the process line of the present invention, thereby enabling control of the heating rate after high-speed cooling, I never do that. The conditions of the process for manufacturing a high strength steel sheet using the equipment are satisfied.

Table 2. Process parameters of low carbon aluminum-strip steel and martensitic steel Heating rate
V0
℃ / s Immersion temperature
T1
℃ Immersion time
t1
s Delayed cooling rate
V1
℃ / s Final temperature of delayed cooling
T2
℃ Fast cooling rate
V2
℃ / s Final temperature of fast cooling
T3
℃ Reheat rate
V3
℃ / s Reheat temperature
T3
℃ Aging temperature
T5
℃ Aging time
t2
s

Aluminum-removing steel


3 to 15

700
~ 800

30 to 150

3 to 30

500
~ 700

30-100

100
~ 280

10 to 80

300
~ 500

200
~ 350

100
~ 500
Martensite steel


3 to 15

700
~ 900

30 to 150

3 to 30

600
~ 700

50 to 150

100
~ 200

10 to 80

200
~ 300

200
~ 300

100
~ 500

More importantly, in this embodiment of the present invention, the strip steel is cooled to a temperature below the phase transformation point of the martensite. After the phase transformation of the martensite has taken place, the steel is tempered to cause tempering plus quenching and generates tempered martensite structure to adjust the overall performance of the steel sheet.

A high strength steel sheet having stable strength and plasticity superior to the double-phase steel product of Example 1 is thus produced. Additionally, martensitic steels with lower strength levels, but with better firing, can likewise be produced. The process parameters for making martensitic steel products are shown in Table 2. As shown in Table 2, an important point in the production of high strength martensitic steel is to control the immersion temperature and the rapid cooling rate during the continuous annealing, and the final cooling temperature and the final temperature of the rapid cooling, ≪ / RTI > is an important consideration in the production of certain martensite.

Compared with the conventional method according to the high-speed cooling method after reheating, the heating rate and temperature after the rapid cooling in the process line of the present invention can be controlled by the configuration of the high power induction heater after the high hydrogen jet cooling step . And no pickling is required. The conditions for the process for making high strength steel sheets using the equipment are thus fulfilled. Properties affecting the present process may also be one of the features of the present invention.

As shown in Figure 3, the process schematic diagram of this embodiment includes a starting material (1) - uncoiling and cleaning (2) - reheating (9) - hot dip galvanizing (or including galvanizing annealing) (11) - planarization (12) - passivation (20) - finishing (13) (or including drawing (14) - drawing and post processing (14) - coiling (15) 16).

A high strength or ultra high strength hot cold pickled steel sheet (e.g., hot rolled martensitic steel) is used as the starting material in the process of this embodiment. The high-temperature steeping zinc plating ability of high-strength steels can be improved by electroplating a very thin layer such as Ni, Fe, etc. on the surface of the starting material, and the resulting material is hot dip galvanized (or / and galvanized annealed ) Is heated from 450 ° C to 550 ° C before being injected into the zinc plating port, and then a post-process such as the planarization process is performed. Due to the short reheating and hot dip galvanizing time (within 1 minute), the decomposition of the martensitic structure is significantly reduced or avoided, leading to the manufacture of ultra-high strength hot rolled hot dip galvanized sheets with excellent surface quality at significantly lower cost . The process parameters for the production of ultra high strength hot rolled hot dip galvanized martensitic steel products are shown in Table 3. As another of the features of the present invention, the process line of the present invention can be suitably used to produce ultra high strength hot rolled hot dip galvanized steel sheets.

Table 3. Process parameters of hot rolled hot dip galvanized martensite
Reheat rate

V0, ° C / s
Reheat temperature

T1, ° C
Reheating and hot dip galvanizing
duration
t1, s
Cooling rate after galvanizing
V1, ° C / s

Martensite
steel


10-80

450-550

10-60

3-50

As shown in Fig. 4, the process schematic diagram of this embodiment shows that the starting material (1) - uncoiling and cleaning (2) - heating (3) - immersion (4) - delayed cooling (5) - water quenching (7) Cleaning (8) - Reheating (9) - Overexposure (10) - Final cooling (11) - Planarization (12) - Finishing (13) - Gridding and postprocessing (14) - Coiling (15) ).

The process of the present embodiment includes a process of water quenching and tempering and is used for producing an ultra high strength cold rolled steel sheet having excellent surface quality. If a water quenching process with a faster cooling rate than high hydrogen jet cooling is used, the strength level of the cold rolled steel sheet can be increased greatly for the same chemical composition, or the alloy content can be significantly reduced for the same strength level of high strength steel So that excellent welding characteristics can be obtained. In addition, the ferric oxide coating on the surface of the strip can be removed by pickling after water quenching, thereby producing a steel sheet with excellent surface quality.

As shown in FIG. 5, the process schematic diagram of this embodiment shows that the starting material (1) - uncoiling and cleaning (2) - heating (3) - immersion (4) - delayed cooling (5) - post-treatment 20 (or finishing 13 and drawing) such as hot dip galvanizing 18 (or galvanizing annealing 19), final cooling 11, planarization 12 passivation, (14), etc.), winding (15), and final product (16).

Using this process of the present invention, it is possible to produce high strength, high temperature immersed galvanized steel sheets and galvanized annealed steel sheets having relatively high strength levels, which are particularly suitable for the manufacture of hot dip galvanized TRIP steels and DP steel of lower strength have. Due to the simple manufacturing process, the unit can be operated at low cost.

As shown in FIG. 6, the process of the present embodiment is characterized in that the starting material (1) - uncoiling and cleaning (2) - heating (3) - soaking (4) - delayed cooling (5) Cooling (6) - reheating (9) - hot dip galvanizing (18) (or galvanizing annealing (19)) - final cooling (11) - planarization (12) - post treatment (prefiltering, passivation (E.g., a workpiece 20, a finish 13, a drawing 14, etc.) - a coil ring 15 - a finished product 16.

By using this process of the present invention, it is possible to produce a high strength, high-temperature-dipped galvanized steel sheet having a relatively high strength level and an excellent surface quality. In the present process of the present invention, the strip steel is rapidly cooled below the phase transformation point by high hydrogen jet cooling to achieve martensitic phase transformation, and then heated to about 460 DEG C for hot dip galvanization. The requirement for the degree of cure of the steel sheet is low and some of the disadvantages of the conventional process are eliminated. In a conventional process, when a large amount of alloy components are added to steel (to improve the degree of curing of the steel sheet so as to enable phase transformation of martensite after the hot dip galvanizing step), an impact on hot galvanizing ability It is possible to increase the alloy components such as Mn and Si on the steel sheet surface. In addition to increasing the strength of the steel sheet, this process according to the invention can lower the alloy content in the substrate (substrate) to some degree. On the other hand, the content of the alloy component in the steel is very low. Therefore, plating and weldability are improved, and excellent surface and user applicability can be provided to the finally obtained high-strength hot-dip galvanized steel sheet. It should be noted, however, that the post-galvanizing capability will be enhanced to improve the effect of this embodiment. Preferably, the zinc plating cooling capacity of this embodiment is at least 1.5 times that of conventional hot dip galvanizing units to reduce decomposition of the reinforced phases.

As shown in Fig. 7, the process schematic diagram of this embodiment shows that the starting material (1) - uncoiling and washing (2) - heating (3) - immersion (4) - delayed cooling (5) - water quenching (7) (8) - reheating (9) - hot dip zinc plating (18) (or galvanizing annealing (19)) - final cooling (11) - planarization (12) - post treatment (prefiltering, passivation (Finish 20, finish 13, drawing 14, etc.) - winding 15 - final product 16.

By using this process according to the present invention, it is possible to produce a high strength, high-temperature-dipped galvanized steel sheet having excellent surface quality and higher strength than in Example 6. [ In this embodiment of the present invention, high hydrogen jet cooling can be replaced by water quenching with a faster cooling rate, and thus the steel sheet strength can be significantly improved over the same chemical composition of the substrate. Depending on the use of the pickling process, increased alloy components such as Mn, Si, etc. on the oxide coating and strip steel surface formed by water quenching can be removed. Therefore, the hot zinc plating ability in the subsequent process is improved, and a high strength, high-temperature-dipped galvanized steel sheet having an excellent surface quality can be obtained.

As shown in Fig. 8, the process schematic diagram of this embodiment shows that the starting material (1) - uncoiling and washing (2) - heating (3) - immersion (4) - delayed cooling (5) - water quenching (7) Cleaning (8) - electroplating (17) (Fe or Ni electroplating) - reheating (9) - hot dip galvanizing (18) (or galvanizing annealing (19) (Pre-phosphorescence treatment, passivation 20, finishing 13, drawing 14 and the like) -winding 15-final product 16.

This process of the present invention is similar to the process of Example 7, with the following exceptions. That is, an Fe or Ni electroplating process is added after pickling, during which the Fe or Ni layer is electroplated onto the steel sheet surface. With this configuration, the conditions of the surface of the steel sheet can be changed prior to hot dip galvanizing. The problem of poor zinc plating of some ultra high strength steels can be completely solved. According to the process of this embodiment, it is possible to produce a double coated ultra high strength hot dip galvanized steel sheet having excellent corrosion resistance and high surface quality. This is one of the features of the present invention.

As shown in Fig. 9, the process schematic diagram of this embodiment shows the starting material (1) - uncoiling and cleaning (2) - heating (3) - immersion (4) - delayed cooling (5) - water quenching (7) Cleaning (8) - electroplating (17) (Zn or Ni electroplating) - post-treatment (pre-phosphating, passivation (20), finishing (13), drawing (14) (16).

In accordance with one example of the process of this embodiment, the sequential annealing sequence and the electroplating sequence for making cold rolled, zinc or nickel electroplated steel sheets are integrated into a single unit to effect continuous annealing and electroplating. By doing so, it not only reduces capital expenditure, increases production efficiency, but also reduces the quantity cut off from both ends of the steel sheet and increases the yield. In another aspect, by utilizing the process of delay cooling and water quenching, high strength cold rolled, zinc or nickel electroplated steel sheets can be produced using steel containing low content of alloy components and having very good stamping properties Zinc or nickel electroplated soft steel products.

1: Starting material 2: Uncoiling and cleaning
3: heating 4: immersion
5: delayed cooling 6: gas jet cooling (high-hydrogen jet cooling)
7: water quenching 8: pickling
9: Reheating 10: Overheating
11: final cooling 12: planarization
13: Finishing 14: Gridding
15: Coil 16: Final product
17: electroplating 18: hot dip zinc plating
19: Galvanized annealing 20: Passivation

Claims (6)

In a production line of an elastic band steel suitable for the production of steel,
An uncoiling and washing station, a heating station, a soaking station and a retarding cooling station in sequence, followed by a hydrogen jet cooling station and a water quenching station arranged side by side;
The hydrogen jet cooling station includes a reheat station, an overfiring station, a final cooling station, a flattening station, a finishing station, a drawing station and a winding station in succession behind the hydrogen jet cooling station;
A pickling station and an electroplating station are successively arranged behind said water quenching station; In addition,
A hot dip zinc plating station is disposed behind the reheating station;
A galvanizing annealing station is disposed behind the hot dip galvanizing station and is connected to the final cooling station via a connecting passage;
A hot dip zinc plating station is disposed behind the reheating station;
A galvanizing annealing station is disposed behind the hot dip galvanizing station and is connected to the final cooling station via a connecting passage;
The reheating station is also connected to a back-end process station via a movable bypass pathway, and when the continuously annealed product is produced at the step of connecting the reheating station, the movable bypass path is connected to the over- , And when the hot dip galvanized product or the galvanized annealed product is produced, the movable bypass passage is separated from the sealed coupling nozzle.
The process of claim 1, wherein the manufacturing line comprises a passivation station disposed to be connected to the front of the finishing station via connection channels as well as connected to the electroplating station and the planarizing station via connection channels, Wherein the elastic band steel is manufactured by a method comprising the steps of:
The production line for an elastic band steel according to claim 1, wherein an induction heater is disposed as a means for the reheating station, which is a process after the hydrogen jet cooling station.
The production line for an elastic band steel according to claim 3, wherein the induction heater has a frequency of 1000 Hz or more.
2. The method according to claim 1, wherein the bypass passage is an airtight passageway in an atmosphere filled with a protective gas made of a mixture of nitrogen and hydrogen, wherein hydrogen accounts for 2 to 7 vol% Manufacturing line.
The production line for an elastic band steel according to claim 1, wherein the gas for cooling the hydrogen jet is a mixture of nitrogen and hydrogen in which hydrogen occupies a volume of 20% or more.

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