CA1133365A - Method and apparatus for cooling steel strips to effect continuous annealing - Google Patents
Method and apparatus for cooling steel strips to effect continuous annealingInfo
- Publication number
- CA1133365A CA1133365A CA354,549A CA354549A CA1133365A CA 1133365 A CA1133365 A CA 1133365A CA 354549 A CA354549 A CA 354549A CA 1133365 A CA1133365 A CA 1133365A
- Authority
- CA
- Canada
- Prior art keywords
- cooling
- steel strip
- rollers
- water
- strip
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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
- C21D9/573—Continuous furnaces for strip or wire with cooling
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A steel strip heated to a temperature above recrystal-lization temperature is passed through a cooling unit including a plurality of cooling rollers cooled by cooling water flowing through the interior thereof. The steel strip is caused to pass alternately about upper and lower surfaces of the cooling rollers. By raising and lowering alternate cooling rollers, the contact area, i.e., the contact time between the strip and the cooling rollers is varied to change the cooling rate. When the cooling rollers are separated from the strip, cooling water is filled into the cooling unit to directly cool the strip.
Cooling gas may be ejected against the strip before it enters into the cooling unit. Where the strip is cooled indirectly, so that it is passed about a series of cooling rollers cooled by water flowing through their interior, it is possible to cool the strip without forming oxide films thereon. The type of cooling is selected according to the type of the steel strip.
With this method and apparatus it is easy to adjust the cool-ing rate of a steel strip.
A steel strip heated to a temperature above recrystal-lization temperature is passed through a cooling unit including a plurality of cooling rollers cooled by cooling water flowing through the interior thereof. The steel strip is caused to pass alternately about upper and lower surfaces of the cooling rollers. By raising and lowering alternate cooling rollers, the contact area, i.e., the contact time between the strip and the cooling rollers is varied to change the cooling rate. When the cooling rollers are separated from the strip, cooling water is filled into the cooling unit to directly cool the strip.
Cooling gas may be ejected against the strip before it enters into the cooling unit. Where the strip is cooled indirectly, so that it is passed about a series of cooling rollers cooled by water flowing through their interior, it is possible to cool the strip without forming oxide films thereon. The type of cooling is selected according to the type of the steel strip.
With this method and apparatus it is easy to adjust the cool-ing rate of a steel strip.
Description
11333~5 This invention relates to a method and an apparatus for cooling steel strips in order to effect continuous anneal-ing thereof.
Methods of cooling steel strips (this term also in-cludes plates) to effect continuous annealing thereof are classified into two types, one is the so-called gas jet type and the other is the water cool type. Although each type has an inherent advantage, it has certain defects.
More particularly, according to the gas jet system, a cooling gas is blasted at high speed against a steel strip heated to a temperature of about Al transition point to cool the strip to about 400C and then the strip is subjected to a super aging treatment for 3 to 5 minutes. The cooling effic-iency of a gas is inferior to that of a liquid because of its small thermal capacity. Although the liquid has a larger ' thermal capacity than the gas, the vapour film formed on the surface of the strip decreases the cooling efficiency. For this reason, in a modern high speed large processing line, the cooling equipment is large, expensive and requires a high running cost.
However, the gas jet type has an advantage in that its cooling speed can be adjusted at will, which is suitable for soft steel strip, and the heat cycle of this type is economical because, contrary to the water cooling type, it is not necessary to first cool the coolant to room temperature and then heat it to a super aging temperature.
Among the water cooling types, i.e., the water quench-ing systems, are included a method in which a liquid coolant is ejected upon a uniformly heated steel strip and a method in which a heated steel strip is dipped in a liquid coolant. To eject the liquid, not only a special ejection equi~ment is necessary but also the pattern of the ejected cooling liquid ~ ~33~65 varies, thlls failing to give uniform cooling and a homogeneous product.
The heat cycle of each cooling system is fast. This is particularly true with the dip method since the cooling speed is extremely high, i.e., of the order of 1000 - 2000C/
sec., as compared with 10 - 30C/sec. for the gas jet method.
The dip method is suitable for manufacturing high tension steel materials having a mixed structure of ferrite and marten-site and not containing any other special elements. As pointed out above since this method ensures a high speed cooling, the cooling equipment for a high speed steel strip processing line is extremely compact. Moreover, since it is sufficient to merely pass the steel strip through cooling water, the running cost can be greatly reduced.
In spite of the advantages described above, since the cooling speed is too rapid, even when the cooling water is heated to its boiling point, it is impossible to subject the steel strip to the super aging temperature during cooling.
Furthermore, since the temperature of the steel strip subjected to cooling goes down to about 100C or normal temperature, if a super aging treatment is performed subsequent to quenching, it is necessary to reheat the steel strip which has been cooled to such a low temperature, that the treatment requires addi-tional process steps and equipments resulting in a poor thermal efficiency.
It is an object of this invention to provide an im-proved method and apparatus for cooling a continuously running steel strip capable of readily adjusting the cooling rate of a steel strip.
Another object of this is to provide a method and apparatus for cooling, at any cooling rate, a steel strip which has ~een heated to a recrystallization temperature without ~L333~iS
forming oxide films.
Still another object of thls invention is to provide an improved cooling unit in which the strip can be cooled in-directly by passing it about a series of cooling rollers through which cooling water is passed, or directly by passing it through a body of cooling water.
According to one aspect of this invention, there is provided a method of cooling a steel strip which has been heat-ed to a temperature above its recrystallization temperature during a continuous annealing treatment, characterized by the steps of passing the steel strip about a plurality of cooling rollers and varying the contact time of the steel strip with the cooling rollers so as to vary the cooling rate.
According to another aspect of this invention there is provided a method of cooling a steel strip which has been heated to a xecrystallization temperature in a continuous annealing treatment, characterized by the steps of cooling the steel strip with cooling gas and then cooling the steel strip with water.
According to still another aspect of this invention there is provided a cooling apparatus for continuously anneal-ing a steel strip which has been heated to a temperature above recrystallization temperature, characterized by the fact that it comprises a cooling unit including a plurality of cooling rollers about which the steel strip is passed, and a mechanism for varying the contact area between the steel strip and the cooling rollers, thus varying the contact time between the steel strip and the cooling rollers, a cooling medium circulating in the interior of the cooling rollers.
A gas cooling unit which ejects a cooling gas against the steel strip may be provided in front of the water cooling unit. The steel strip is passed about alternate upper and lower surfaces of the cooling rollers. When alternate cooling rollers are raised to positions away from the strip, the cool-ing unit is filled with water thus effecting direct cooling of the steel strip~ A water tank is connected to the cooling unit via a water seal and the steel strip is circulated through the cooling unit and the water tank. In this manner when water is drained from the cooling unit and the water tank, the alter-nate rollers are lowered to cause the steel strip to pass through a wavy passage while contacting the upper and lower surfaces of the cooling rollers. In this case, cooling water is passed through the interior of the cooling rollers, thus effecting indirect cooling. In this manner, the cooling unit of this invention can readily be switched between direct cool-ing and indirect cooling.
Further objects and advantages of the present inven-tion can be more fully understoo~ from the following detailed description taken in conjunction with the accompanying draw ings in which:
Figure 1 is a diagrammatic representation showing one example of a continuous annealing apparatus embodying the invention, Figure 2 is a side view of the cooling rollers shown in Figure 1, Figure 3 is a plan view of the cooling rollers shown in Figure 2, Figure 4 is a diag,rammatic representation showing another example of a continuous annealing apparatus according to this invention' Figure 5 is an enlarged side view of the cooling unit shown in Figure 4 when it is used as a direct water cooling unit' Figure 6 is a side view similar to Figure 5 showing a 1~L33.~6S
way of cooling whereby water is passed through the cooling rollers, Figure 7 is a diagrammatic longitudinal sect.ional view showing one example of the cooling unit together with a gas cooling unit' and Figure 8 is a partial view showing a modified appar- ,.
atus according to the embodiment shown in Figure 4.
In the continuous annealing apparatus shown in Fig-ure 1, a steel strip (S) payed out from either one of a plur-ality of uncoilers la and lb is continuously passed through aprocessing line by alternately connecting together the strips payed out from respective uncoilers with a shear 2a and a welder 2b. Following the welder 2b are installed in success-ion, an alkali washing tank 3, an electrolysis rinsing tank 4 and a hot water spray washing tank 5 which constitute a pre-.
treatment surface cleaning unit. After passing through this pretreatment surface cleaning unit the strip is then guided into a furnace 10 via a dryer 6 and an inlet looper 7. The furnace 10 includes a heating zone 8 for effecting recrystal-lization annealing, a uniform heating zone 9 and a cooling unit12. The strip recrystallized, annealed and cooled in this manner is then introduced into the furnace 10 again and passed through a reheating zone 13 for over aging processing, an over aging processing zone 14 and a gas cooling zone 15 The strip is then passed through an outlet looper 16, a water cooling unit 17, a dryer 18 and a refining mill 19. After passing through the refining mill 19, the strip (S) passes through a trimming width varying notcher 20, a side trimmer 21, an oiler 22, an exit shear 23 and is finally taken up by a take up reel 24.
The cooling unit utilized in the annealing apparatus is shown in Figures 2 and 3. More particularly, the strip (S) 1133;~6S
passes about four rollers 32 and 32a. A pair of rollers 32 can be raised or lowered together with their supporter 31 by means of screw or oil pressure cylinders 30. Water or other cooling fluid passes through the interior of either one or both of the rollers 32 and 32a. By varying the contact angle or length of the str;p in contact with the upper surfaces of the rollers 32 and the lower surfaces of the rollers 32a the con-tact time can be varied even under the same running speed thus varying the cooling speed and the temperature of the cooled strip, so as to send the strip to the next step while maintain-ing it at a de~inite temperature. This cooling unit can be used at any point of travel of the strip, for example, the gas cooling zone 15 and the water cooling unit 17.
The cooling unit shown in Figures 3 and 4 can also be used as a cooling unit which can be switched to a direct cool-ing depending upon the characteristi.cs of steel strip to be cooled. Steel strips not requiring an over aging treatment can be cooled at such high cooling speeds as 1000 - 2000C/sec.
where oxide films are properly removed. Especially, in a high tension steel plate or strip in which a mixed structure of fer-rite and martensite can be obtained with only a small quantity of special elements, such high speed cooling by direct contact is advantageous. Therefore, the cooling unit according to this invention can be also constructed to be switchable between in-dlrect cooling using cooled rollers and direct cooling using water.
Figure 4 shows a modified continuous annealing appar-atus including the switchable type of cooling unit which is also shown in Figures 5 and 6. More particularly, the strip (S) is passed between four rollers 32 and 32a, of which the upper rollers 32a are moved in the vertical direction by a screw or oil pressure cylinder mechanism. Thus, when the upper rolle.rs 32a are raised as shown in Figure 5, the strip (S) passes directly between guide rollers 12a and 12b without contacting the cooling rollers 32 and 32a, whereas when the upper rollers 32a are lowered as shown in Figure 6, the strip (S) passes alternately about rollers 32 and 32a. The contact area of the strip against the rollers can be adjusted depending upon the degree of lowering of the upper rollers 32a. Accordingly, in the state shown in Figure 6, the cooling speed and the fina]
cooling temperature can be adjusted as desired by raising and lowering the upper rollers 32a. Where the switchable cooling unit 12 shown in Figure 4 is used as direct water cooling in the manner shown in Figure S, it is necessary to remove oxide film deposited on the strip during water cooling. For this purpose, a means for removing oxide film is provided between the cooling unit 12 and the reheating zone 13 as shown in Fig-ure 4. Thus, the strip cooled in the cooling unit 12 is passed through a pickling tank 25, a warm water washing tank 26, a neutralizing tank 27 and a dryer 28. Alternatively, as shown in Figure 8, the oxide film removing means may be installed between the outlet looper 16 and the refining mill 19, said means comprising a pickling tank 48, a warm water washing tank 49, a neutralizing tank 50, another warm water washing tank 51, a water washing tank 52 and a dryer 53. On the other hand, where the cooling unit is used as indirect cooling using rollers as shown in Figure 6 no oxide film is formed so that it is not necessary to us~j the pickling tank, the warm water washing tank and the neutralizing tank. Even in this case, only the water washing tank 52 and the dryer 53 are to be used.
As shown in Figure 7 a gas jet cooling unit 11 may be added to the cooling unit 12 described above. The gas jet cool-ing unit 11 comprises a motor driven blower 60 and a plurality of gas ejection nozzles 41 which eject cooling gas sen~ ~rom the 6~
blower 60 against the strip. The cooling gas i5 circulated in the unit 11 and is cooled by water tubes lla in front of the blower 30 down to a temperature of from 50 - 150~C from a temp-erature of 150 - 250C. As described above, the operating state of the cooling unit 12 is switched between the positions shown in Figures 5 and 6. On the right hand side o~ a cooling chamber 35 there is provided a circulating tank 36 supplemented with fresh water from a water supply pipe 46 when desired. On both sides of the water circulating tank 36 there are provided water level adjusting gates 37 and 37a to adjust the water levels in the cooling chamber 35 and in the tank 36. A strip exit port 34 is formed on the left hand side of the cooling chamber 35 to guide the strip to the pickling tank 17 or dir-ectly to the reheating zone 13. The water in the tank 36 is conveyed to water nozzles 43 via a conduit 38 including a fil-ter 33 and a pump 42 to eject cooling water against the opposite surfaces of the strips (S).
A warm water reservoir 39 is located beneath the tank 36 for receiving warm water to the left of the gate 37 and water overflown from the gate 37a. The warm water collected in the reservoir 39 is discharged through a pump 40. The reservoir 39 is connected to the tank 36 through a pipe 45 and a valve 47.
In operation, the water level in the cooling chàmber 35 is adjusted by the gate 37 while the strip is precooled by the gas blasted thereon through a plurality of nozzles 41 (for example 10 or more) and then is cooled by the water present in the cooling chamber 35. The water therein also acts as a sealing water for succeeding processing line. The warm water discharged by the pump 40 may be used in the hot water washing tank. When valve 47 is opened, the water in the cooling chamber 35 to the left of the gate 37 is completely discharged into the reservoir 39, and the strip is cooled in a state shown in Figure ~ 1 3;~;?ti5 6 by cooling rollers 32 and 32a. At this time, cooling water is passed through the interior of these rollers.
Accordingly, the switching of the cooling states be-tween Figures 5 and 6 can be readily accomplished without dis-charging the entire water content of a large tank 36 ~Ut by merely discharging a relatively small quantity of the cooling water to the left of the gate 37. Even when the water at the left of the gate 37 is discharged, the cooling gas in the gas jet cooling unit 11 is prevented from discharging to the outside by a water seal 44 disposed between the cooling chamber 35 and the tank 36.
As a consequence, with the construction shown in Fig-ures 4 - 7 it is possible to cool the strip very quickly with water to a low temperature near room temperature or relatively slowly with water cooled rollers which do not form oxide films on the strip at the time of cooling, thus smoothly effecting a series of processings including over aging processing so as to produce various types of steel strips or plates suitable for different applications.
The indirect cooling will now be described in more detail. The temperature of the steel strip supplied to the cooling unit 12 through the heating zone 8 for the recrystalliza-tion annealing and the uniform heating zone 9 varies slightly, generalLy 500 - 800C, depending upon the thickness and the com-position, and the strip is cooled by cooling rollers 32 and 32a.
The cooling water flowing through these cooling rollers may be at room temperature, and variation in the temperature of the cooling water ranging from 5C to 30C does not cause any apprec-iable change in the cooling effect. Accordingly, even when the strip is cooled by 1C or heated by 60 - 70C, such cooling and heating do not affect the cooling effect of the cooling rollers.
When the cooling rollers through which cooling water is passed i ~33.~fiS
ar~ contacted with the steel strip, and when a steel strip hav-ing a thickness of 0.6 mm and heated to 300 - 600C, for exam-ple, is contacted against the cooling rollers for about one second the strip would be cooled by about 180C, whereas when contacted for two seconds, the strip would be cooled by about 260C. When a steel strip having a thickness of 1.2 mm is con-tacted for one second it would be cooled to about 90C, whereas about 140C would be reached when the steel strip is contacted for two seconds. When a steel strip having a thickness of 0.8 mm running at a speed of 150 m/min. is contacted against rollers 32 and 32a through which water is allowed to pass, at a contact angle of 0.8 ~ after being heated to 580C by a recrystalliza-tion annealing treatment, it is cooled to about 505 - 515C by the first roller 32 and to about 465 - 480C by the second roller 32a. The strip is cooled down to 410 - 420C by the third roller 32 and then to 380C by the fourth roller 32a. The same result can be attained by reducing the contact angle as the roller diameter is reduced. Even when the strip gauge or line speed varies similar results can be obtained with a con-tact time of less than two seconds by varying other parameters.
The strip thus cooled to 350 - 380C is guided into the follow-ing heat treatment zone (13 - 15). Accordingly, fuel cost nec-essary for reheating the strip can be reduced by 25 - 30% in comparison to the cost involved in a case wherein the strip is cooled to about room temperature.
To have a better understanding of the invention the following example is given.
Example A low carbon steel strip having a thickness of 0.8 mm, and a width of 1000 mm was passed through the heating zone 8 and the uniform heating zone 9 at a speed of 150 m/min. to effect recrystallization annealing for one minute and at a il33;~6~
temperature of 700~C dnd thel-l is Sellt to the cooling unit 12 shown in Fi~ure 1. Each one of the cooling rollers 32 and 32a had a diameter of 600 mm and cooling water at 15C was passed through these rollers at a rate of 250 ~/minute. The strip ~S) was cooled by contacting it about these cooling rollers at a contact angle of from 0 to 0.9 ~. The temperature of the strip (S) was about 600C when it enters into the cooling unit and it was cooled to about 395C to 415C and the variation in the temperature of the cooled strip was less than 20C which means uniform cooling. The thus cooled strip is then over aged at a temperature of 400 - 350C for three minutes in the reheating zone 13 and the over aging processing zone 14 thereby obtaining a strip of steel having uniform mechanical properties which is suitable for use in contraction.
Methods of cooling steel strips (this term also in-cludes plates) to effect continuous annealing thereof are classified into two types, one is the so-called gas jet type and the other is the water cool type. Although each type has an inherent advantage, it has certain defects.
More particularly, according to the gas jet system, a cooling gas is blasted at high speed against a steel strip heated to a temperature of about Al transition point to cool the strip to about 400C and then the strip is subjected to a super aging treatment for 3 to 5 minutes. The cooling effic-iency of a gas is inferior to that of a liquid because of its small thermal capacity. Although the liquid has a larger ' thermal capacity than the gas, the vapour film formed on the surface of the strip decreases the cooling efficiency. For this reason, in a modern high speed large processing line, the cooling equipment is large, expensive and requires a high running cost.
However, the gas jet type has an advantage in that its cooling speed can be adjusted at will, which is suitable for soft steel strip, and the heat cycle of this type is economical because, contrary to the water cooling type, it is not necessary to first cool the coolant to room temperature and then heat it to a super aging temperature.
Among the water cooling types, i.e., the water quench-ing systems, are included a method in which a liquid coolant is ejected upon a uniformly heated steel strip and a method in which a heated steel strip is dipped in a liquid coolant. To eject the liquid, not only a special ejection equi~ment is necessary but also the pattern of the ejected cooling liquid ~ ~33~65 varies, thlls failing to give uniform cooling and a homogeneous product.
The heat cycle of each cooling system is fast. This is particularly true with the dip method since the cooling speed is extremely high, i.e., of the order of 1000 - 2000C/
sec., as compared with 10 - 30C/sec. for the gas jet method.
The dip method is suitable for manufacturing high tension steel materials having a mixed structure of ferrite and marten-site and not containing any other special elements. As pointed out above since this method ensures a high speed cooling, the cooling equipment for a high speed steel strip processing line is extremely compact. Moreover, since it is sufficient to merely pass the steel strip through cooling water, the running cost can be greatly reduced.
In spite of the advantages described above, since the cooling speed is too rapid, even when the cooling water is heated to its boiling point, it is impossible to subject the steel strip to the super aging temperature during cooling.
Furthermore, since the temperature of the steel strip subjected to cooling goes down to about 100C or normal temperature, if a super aging treatment is performed subsequent to quenching, it is necessary to reheat the steel strip which has been cooled to such a low temperature, that the treatment requires addi-tional process steps and equipments resulting in a poor thermal efficiency.
It is an object of this invention to provide an im-proved method and apparatus for cooling a continuously running steel strip capable of readily adjusting the cooling rate of a steel strip.
Another object of this is to provide a method and apparatus for cooling, at any cooling rate, a steel strip which has ~een heated to a recrystallization temperature without ~L333~iS
forming oxide films.
Still another object of thls invention is to provide an improved cooling unit in which the strip can be cooled in-directly by passing it about a series of cooling rollers through which cooling water is passed, or directly by passing it through a body of cooling water.
According to one aspect of this invention, there is provided a method of cooling a steel strip which has been heat-ed to a temperature above its recrystallization temperature during a continuous annealing treatment, characterized by the steps of passing the steel strip about a plurality of cooling rollers and varying the contact time of the steel strip with the cooling rollers so as to vary the cooling rate.
According to another aspect of this invention there is provided a method of cooling a steel strip which has been heated to a xecrystallization temperature in a continuous annealing treatment, characterized by the steps of cooling the steel strip with cooling gas and then cooling the steel strip with water.
According to still another aspect of this invention there is provided a cooling apparatus for continuously anneal-ing a steel strip which has been heated to a temperature above recrystallization temperature, characterized by the fact that it comprises a cooling unit including a plurality of cooling rollers about which the steel strip is passed, and a mechanism for varying the contact area between the steel strip and the cooling rollers, thus varying the contact time between the steel strip and the cooling rollers, a cooling medium circulating in the interior of the cooling rollers.
A gas cooling unit which ejects a cooling gas against the steel strip may be provided in front of the water cooling unit. The steel strip is passed about alternate upper and lower surfaces of the cooling rollers. When alternate cooling rollers are raised to positions away from the strip, the cool-ing unit is filled with water thus effecting direct cooling of the steel strip~ A water tank is connected to the cooling unit via a water seal and the steel strip is circulated through the cooling unit and the water tank. In this manner when water is drained from the cooling unit and the water tank, the alter-nate rollers are lowered to cause the steel strip to pass through a wavy passage while contacting the upper and lower surfaces of the cooling rollers. In this case, cooling water is passed through the interior of the cooling rollers, thus effecting indirect cooling. In this manner, the cooling unit of this invention can readily be switched between direct cool-ing and indirect cooling.
Further objects and advantages of the present inven-tion can be more fully understoo~ from the following detailed description taken in conjunction with the accompanying draw ings in which:
Figure 1 is a diagrammatic representation showing one example of a continuous annealing apparatus embodying the invention, Figure 2 is a side view of the cooling rollers shown in Figure 1, Figure 3 is a plan view of the cooling rollers shown in Figure 2, Figure 4 is a diag,rammatic representation showing another example of a continuous annealing apparatus according to this invention' Figure 5 is an enlarged side view of the cooling unit shown in Figure 4 when it is used as a direct water cooling unit' Figure 6 is a side view similar to Figure 5 showing a 1~L33.~6S
way of cooling whereby water is passed through the cooling rollers, Figure 7 is a diagrammatic longitudinal sect.ional view showing one example of the cooling unit together with a gas cooling unit' and Figure 8 is a partial view showing a modified appar- ,.
atus according to the embodiment shown in Figure 4.
In the continuous annealing apparatus shown in Fig-ure 1, a steel strip (S) payed out from either one of a plur-ality of uncoilers la and lb is continuously passed through aprocessing line by alternately connecting together the strips payed out from respective uncoilers with a shear 2a and a welder 2b. Following the welder 2b are installed in success-ion, an alkali washing tank 3, an electrolysis rinsing tank 4 and a hot water spray washing tank 5 which constitute a pre-.
treatment surface cleaning unit. After passing through this pretreatment surface cleaning unit the strip is then guided into a furnace 10 via a dryer 6 and an inlet looper 7. The furnace 10 includes a heating zone 8 for effecting recrystal-lization annealing, a uniform heating zone 9 and a cooling unit12. The strip recrystallized, annealed and cooled in this manner is then introduced into the furnace 10 again and passed through a reheating zone 13 for over aging processing, an over aging processing zone 14 and a gas cooling zone 15 The strip is then passed through an outlet looper 16, a water cooling unit 17, a dryer 18 and a refining mill 19. After passing through the refining mill 19, the strip (S) passes through a trimming width varying notcher 20, a side trimmer 21, an oiler 22, an exit shear 23 and is finally taken up by a take up reel 24.
The cooling unit utilized in the annealing apparatus is shown in Figures 2 and 3. More particularly, the strip (S) 1133;~6S
passes about four rollers 32 and 32a. A pair of rollers 32 can be raised or lowered together with their supporter 31 by means of screw or oil pressure cylinders 30. Water or other cooling fluid passes through the interior of either one or both of the rollers 32 and 32a. By varying the contact angle or length of the str;p in contact with the upper surfaces of the rollers 32 and the lower surfaces of the rollers 32a the con-tact time can be varied even under the same running speed thus varying the cooling speed and the temperature of the cooled strip, so as to send the strip to the next step while maintain-ing it at a de~inite temperature. This cooling unit can be used at any point of travel of the strip, for example, the gas cooling zone 15 and the water cooling unit 17.
The cooling unit shown in Figures 3 and 4 can also be used as a cooling unit which can be switched to a direct cool-ing depending upon the characteristi.cs of steel strip to be cooled. Steel strips not requiring an over aging treatment can be cooled at such high cooling speeds as 1000 - 2000C/sec.
where oxide films are properly removed. Especially, in a high tension steel plate or strip in which a mixed structure of fer-rite and martensite can be obtained with only a small quantity of special elements, such high speed cooling by direct contact is advantageous. Therefore, the cooling unit according to this invention can be also constructed to be switchable between in-dlrect cooling using cooled rollers and direct cooling using water.
Figure 4 shows a modified continuous annealing appar-atus including the switchable type of cooling unit which is also shown in Figures 5 and 6. More particularly, the strip (S) is passed between four rollers 32 and 32a, of which the upper rollers 32a are moved in the vertical direction by a screw or oil pressure cylinder mechanism. Thus, when the upper rolle.rs 32a are raised as shown in Figure 5, the strip (S) passes directly between guide rollers 12a and 12b without contacting the cooling rollers 32 and 32a, whereas when the upper rollers 32a are lowered as shown in Figure 6, the strip (S) passes alternately about rollers 32 and 32a. The contact area of the strip against the rollers can be adjusted depending upon the degree of lowering of the upper rollers 32a. Accordingly, in the state shown in Figure 6, the cooling speed and the fina]
cooling temperature can be adjusted as desired by raising and lowering the upper rollers 32a. Where the switchable cooling unit 12 shown in Figure 4 is used as direct water cooling in the manner shown in Figure S, it is necessary to remove oxide film deposited on the strip during water cooling. For this purpose, a means for removing oxide film is provided between the cooling unit 12 and the reheating zone 13 as shown in Fig-ure 4. Thus, the strip cooled in the cooling unit 12 is passed through a pickling tank 25, a warm water washing tank 26, a neutralizing tank 27 and a dryer 28. Alternatively, as shown in Figure 8, the oxide film removing means may be installed between the outlet looper 16 and the refining mill 19, said means comprising a pickling tank 48, a warm water washing tank 49, a neutralizing tank 50, another warm water washing tank 51, a water washing tank 52 and a dryer 53. On the other hand, where the cooling unit is used as indirect cooling using rollers as shown in Figure 6 no oxide film is formed so that it is not necessary to us~j the pickling tank, the warm water washing tank and the neutralizing tank. Even in this case, only the water washing tank 52 and the dryer 53 are to be used.
As shown in Figure 7 a gas jet cooling unit 11 may be added to the cooling unit 12 described above. The gas jet cool-ing unit 11 comprises a motor driven blower 60 and a plurality of gas ejection nozzles 41 which eject cooling gas sen~ ~rom the 6~
blower 60 against the strip. The cooling gas i5 circulated in the unit 11 and is cooled by water tubes lla in front of the blower 30 down to a temperature of from 50 - 150~C from a temp-erature of 150 - 250C. As described above, the operating state of the cooling unit 12 is switched between the positions shown in Figures 5 and 6. On the right hand side o~ a cooling chamber 35 there is provided a circulating tank 36 supplemented with fresh water from a water supply pipe 46 when desired. On both sides of the water circulating tank 36 there are provided water level adjusting gates 37 and 37a to adjust the water levels in the cooling chamber 35 and in the tank 36. A strip exit port 34 is formed on the left hand side of the cooling chamber 35 to guide the strip to the pickling tank 17 or dir-ectly to the reheating zone 13. The water in the tank 36 is conveyed to water nozzles 43 via a conduit 38 including a fil-ter 33 and a pump 42 to eject cooling water against the opposite surfaces of the strips (S).
A warm water reservoir 39 is located beneath the tank 36 for receiving warm water to the left of the gate 37 and water overflown from the gate 37a. The warm water collected in the reservoir 39 is discharged through a pump 40. The reservoir 39 is connected to the tank 36 through a pipe 45 and a valve 47.
In operation, the water level in the cooling chàmber 35 is adjusted by the gate 37 while the strip is precooled by the gas blasted thereon through a plurality of nozzles 41 (for example 10 or more) and then is cooled by the water present in the cooling chamber 35. The water therein also acts as a sealing water for succeeding processing line. The warm water discharged by the pump 40 may be used in the hot water washing tank. When valve 47 is opened, the water in the cooling chamber 35 to the left of the gate 37 is completely discharged into the reservoir 39, and the strip is cooled in a state shown in Figure ~ 1 3;~;?ti5 6 by cooling rollers 32 and 32a. At this time, cooling water is passed through the interior of these rollers.
Accordingly, the switching of the cooling states be-tween Figures 5 and 6 can be readily accomplished without dis-charging the entire water content of a large tank 36 ~Ut by merely discharging a relatively small quantity of the cooling water to the left of the gate 37. Even when the water at the left of the gate 37 is discharged, the cooling gas in the gas jet cooling unit 11 is prevented from discharging to the outside by a water seal 44 disposed between the cooling chamber 35 and the tank 36.
As a consequence, with the construction shown in Fig-ures 4 - 7 it is possible to cool the strip very quickly with water to a low temperature near room temperature or relatively slowly with water cooled rollers which do not form oxide films on the strip at the time of cooling, thus smoothly effecting a series of processings including over aging processing so as to produce various types of steel strips or plates suitable for different applications.
The indirect cooling will now be described in more detail. The temperature of the steel strip supplied to the cooling unit 12 through the heating zone 8 for the recrystalliza-tion annealing and the uniform heating zone 9 varies slightly, generalLy 500 - 800C, depending upon the thickness and the com-position, and the strip is cooled by cooling rollers 32 and 32a.
The cooling water flowing through these cooling rollers may be at room temperature, and variation in the temperature of the cooling water ranging from 5C to 30C does not cause any apprec-iable change in the cooling effect. Accordingly, even when the strip is cooled by 1C or heated by 60 - 70C, such cooling and heating do not affect the cooling effect of the cooling rollers.
When the cooling rollers through which cooling water is passed i ~33.~fiS
ar~ contacted with the steel strip, and when a steel strip hav-ing a thickness of 0.6 mm and heated to 300 - 600C, for exam-ple, is contacted against the cooling rollers for about one second the strip would be cooled by about 180C, whereas when contacted for two seconds, the strip would be cooled by about 260C. When a steel strip having a thickness of 1.2 mm is con-tacted for one second it would be cooled to about 90C, whereas about 140C would be reached when the steel strip is contacted for two seconds. When a steel strip having a thickness of 0.8 mm running at a speed of 150 m/min. is contacted against rollers 32 and 32a through which water is allowed to pass, at a contact angle of 0.8 ~ after being heated to 580C by a recrystalliza-tion annealing treatment, it is cooled to about 505 - 515C by the first roller 32 and to about 465 - 480C by the second roller 32a. The strip is cooled down to 410 - 420C by the third roller 32 and then to 380C by the fourth roller 32a. The same result can be attained by reducing the contact angle as the roller diameter is reduced. Even when the strip gauge or line speed varies similar results can be obtained with a con-tact time of less than two seconds by varying other parameters.
The strip thus cooled to 350 - 380C is guided into the follow-ing heat treatment zone (13 - 15). Accordingly, fuel cost nec-essary for reheating the strip can be reduced by 25 - 30% in comparison to the cost involved in a case wherein the strip is cooled to about room temperature.
To have a better understanding of the invention the following example is given.
Example A low carbon steel strip having a thickness of 0.8 mm, and a width of 1000 mm was passed through the heating zone 8 and the uniform heating zone 9 at a speed of 150 m/min. to effect recrystallization annealing for one minute and at a il33;~6~
temperature of 700~C dnd thel-l is Sellt to the cooling unit 12 shown in Fi~ure 1. Each one of the cooling rollers 32 and 32a had a diameter of 600 mm and cooling water at 15C was passed through these rollers at a rate of 250 ~/minute. The strip ~S) was cooled by contacting it about these cooling rollers at a contact angle of from 0 to 0.9 ~. The temperature of the strip (S) was about 600C when it enters into the cooling unit and it was cooled to about 395C to 415C and the variation in the temperature of the cooled strip was less than 20C which means uniform cooling. The thus cooled strip is then over aged at a temperature of 400 - 350C for three minutes in the reheating zone 13 and the over aging processing zone 14 thereby obtaining a strip of steel having uniform mechanical properties which is suitable for use in contraction.
Claims (17)
1. A method of cooling a steel strip which has been heated to a temperature above recystallization temperature in a continuous annealing treatment, said method comprising the steps of passing said steel strip about a plurality of cooling rollers and allowing varying contact time of said steel strip with said cooling rollers so as to vary cooling rate.
2. The method according to claim 1 wherein an over aging treatment is applied to said steel strip after said steel strip is cooled by said cooling rollers.
3. The method according to claim 1 wherein contact angles between said steel strip and said cooling rollers are varied thereby varying the contact time.
4. The method according to any one of claims 1 - 3 wherein a coolant is passed inside said cooling rollers.
5. The method according to any one of claims 1 - 3 wherein said steel strip is passed alternatively about upper and lower surfaces of said cooling rollers.
6. The method according to claim 1 which further compris-es the step of cooling the steel strip with cold gas before the steel strip is cooled by said cooling rollers.
7. An apparatus for cooling a steel strip which has been heated to a temperature above recrystallization temperature during a continuous annealing treatment, said apparatus com-prising cooling rollers about which the steel strip is passed, and a mechanism for varying contact area between the steel strip and the cooling rollers, thus varying contact time between the steel strip and the cooling rollers.
8. The apparatus according to claim 7 wherein cooling water is passed inside said cooling rollers.
9. The apparatus according to claim 7 wherein said means for varying the contact area between said steel strip and said cooling rollers are adapted to cause said strip to pass alternately about upper and lower surfaces of said cool-ing rollers.
10. The apparatus according to claim 7 which further comprises means for raising or lowering alternate cooling rollers with respect to remaining rollers so that when said alternate rollers are raised said steel strip passes without contacting said cooling rollers whereas when said alternate cooling rollers are lowered said steel strip passes alternately about upper and lower surface of said plurality of cooling rollers.
11. The apparatus according to claim 10 wherein when said alternate cooling rollers are raised away from said steel strip said cooling unit is filled with cooling water to cool said steel strip with said cooling water.
12. The apparatus according to claim 7 which further com-prises means for cooling said steel strip with cooling gas before it enters into said cooling unit.
13. The apparatus according to claim 12 wherein said means for cooling said steel strip with cooling gas comprises a plur-ality of nozzles for ejecting cooled gas against said steel strip, a blower for circulating said gas through said nozzles and a water cooler for cooling the circulating gas.
14. The apparatus according to claim 7 which further comprises a water tank connected to said cooling unit through a water seal, a reservoir connected to said water tank, and a water circulating pump for supplying water in said water tank to said cooling unit.
15. The apparatus according to claim 14 which further com-prises water nozzles disposed in said cooling unit on the opposite sides of said steel strip, said water nozzles being connected to an outlet side of said circulating pump.
16. The apparatus according to claim 14 which further comprises a gate at an intermediate point of said water tank and said reservoir is connected to said water tank at a point between said gate and said water seal through a valve.
17. The apparatus according to claim 16 wherein a water supplement pipe is connected to said water tank on one side of said gate on the opposite side of said water seal.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP80808/1979 | 1979-06-28 | ||
| JP54080808A JPS5937335B2 (en) | 1979-06-28 | 1979-06-28 | Steel strip cooling equipment for continuous annealing |
| JP8149079A JPS5842254B2 (en) | 1979-06-29 | 1979-06-29 | Continuous annealing equipment |
| JP81490/1979 | 1979-06-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1133365A true CA1133365A (en) | 1982-10-12 |
Family
ID=26421788
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA354,549A Expired CA1133365A (en) | 1979-06-28 | 1980-06-23 | Method and apparatus for cooling steel strips to effect continuous annealing |
Country Status (10)
| Country | Link |
|---|---|
| AU (1) | AU530384B2 (en) |
| BR (1) | BR8003901A (en) |
| CA (1) | CA1133365A (en) |
| DE (1) | DE3023571C2 (en) |
| FR (1) | FR2460333B1 (en) |
| GB (1) | GB2054661B (en) |
| IT (1) | IT1174291B (en) |
| NL (1) | NL8003647A (en) |
| SE (1) | SE448308B (en) |
| SU (1) | SU1139376A3 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2499591A1 (en) * | 1981-02-12 | 1982-08-13 | Stein Heurtey | DEVICE FOR QUICK COOLING AND CONTROLLED IN AN ANNEAL OR REDUCING ATMOSPHERE OVEN |
| JPS58120748A (en) * | 1982-01-13 | 1983-07-18 | Nippon Steel Corp | Continuous heat treatment installation for cold-rolled steel strip for working and high tensile cold-rolled steel strip |
| DE3330394A1 (en) * | 1983-07-29 | 1985-02-14 | Josef Gartner & Co, 8883 Gundelfingen | DEVICE FOR TEMPERATURE SPACES OF A BUILDING |
| JPS60128220A (en) * | 1983-12-15 | 1985-07-09 | Mitsubishi Heavy Ind Ltd | Method for controlling temperature of strip in cooling zone of continuous annealing furnace |
| JPH0796686B2 (en) * | 1986-09-09 | 1995-10-18 | 川崎製鉄株式会社 | Metal strip meandering prevention method |
| JP4840518B2 (en) | 2010-02-24 | 2011-12-21 | Ｊｆｅスチール株式会社 | Method for producing grain-oriented electrical steel sheet |
| DE102011117572A1 (en) * | 2011-01-26 | 2012-08-16 | Salzgitter Flachstahl Gmbh | High-strength multiphase steel with excellent forming properties |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3186698A (en) * | 1963-06-14 | 1965-06-01 | Midland Ross Corp | Heat treating apparatus |
| DE1608164B1 (en) * | 1967-11-23 | 1971-11-11 | Hoesch Ag | Use of a steel for the production of high-strength packaging tape |
| JPS5280208A (en) * | 1975-12-27 | 1977-07-05 | Chugai Ro Kogyo Kaisha Ltd | Method and apparatus for temperature control of material in heat treatment of metal strip |
| JPS5458609A (en) * | 1977-10-20 | 1979-05-11 | Nippon Steel Corp | Cooler and controlled cooling method for strip of high temperature |
-
1980
- 1980-06-18 AU AU59384/80A patent/AU530384B2/en not_active Ceased
- 1980-06-23 CA CA354,549A patent/CA1133365A/en not_active Expired
- 1980-06-23 IT IT49043/80A patent/IT1174291B/en active
- 1980-06-23 BR BR8003901A patent/BR8003901A/en not_active IP Right Cessation
- 1980-06-24 NL NL8003647A patent/NL8003647A/en not_active Application Discontinuation
- 1980-06-24 DE DE3023571A patent/DE3023571C2/en not_active Expired
- 1980-06-25 FR FR8014122A patent/FR2460333B1/en not_active Expired
- 1980-06-26 SU SU802937833A patent/SU1139376A3/en active
- 1980-06-27 SE SE8004780A patent/SE448308B/en not_active IP Right Cessation
- 1980-06-30 GB GB8021345A patent/GB2054661B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3023571A1 (en) | 1981-01-15 |
| AU530384B2 (en) | 1983-07-14 |
| AU5938480A (en) | 1981-01-08 |
| GB2054661B (en) | 1983-03-16 |
| IT1174291B (en) | 1987-07-01 |
| DE3023571C2 (en) | 1991-09-12 |
| SU1139376A3 (en) | 1985-02-07 |
| FR2460333B1 (en) | 1986-07-04 |
| SE8004780L (en) | 1980-12-29 |
| GB2054661A (en) | 1981-02-18 |
| FR2460333A1 (en) | 1981-01-23 |
| NL8003647A (en) | 1980-12-30 |
| SE448308B (en) | 1987-02-09 |
| IT8049043A0 (en) | 1980-06-23 |
| BR8003901A (en) | 1981-01-13 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US6054095A (en) | Widthwise uniform cooling system for steel strip in continuous steel strip heat treatment step | |
| DE69611033T2 (en) | PRIMARY COOLING PROCEDURE FOR STEEL STEEL | |
| US4596615A (en) | Method of cooling hot steel plates | |
| KR910004610B1 (en) | Method for producing non-aging hot-dip galvanized steel strip | |
| CN109097534B (en) | Very thin precise stainless steel strip busbar bright annealing technology | |
| DE69324566T2 (en) | COOLING DEVICE AND METHOD FOR METAL STRIP | |
| CA1133365A (en) | Method and apparatus for cooling steel strips to effect continuous annealing | |
| JP2008019505A (en) | Method and facility for cooling steel strip | |
| US4422623A (en) | Apparatus for cooling steel strips to effect continuous annealing | |
| US4704167A (en) | Method and apparatus for cooling steel strip | |
| CA1177371A (en) | Process and apparatus for cooling a cold rolled steel strip | |
| US2565855A (en) | Plural station quenching device for elongated objects | |
| CA1174460A (en) | Continuous gold rolling and annealing apparatus for steel strip | |
| CA1272431A (en) | Method and apparatus of cooling steel strip | |
| US4580353A (en) | Apparatus and method for air cooling hot rolled steel rod | |
| JPS5842254B2 (en) | Continuous annealing equipment | |
| US2459674A (en) | Continuous tinplate brightening apparatus | |
| JPS6111299B2 (en) | ||
| JPS5822525B2 (en) | Sealing device in cooling section of steel strip | |
| KR910001608B1 (en) | Support device for moving metal strip | |
| JP4145606B2 (en) | Steel plate lower surface cooling device, steel plate and method for producing the same | |
| JPS6234811B2 (en) | ||
| JPS6354446B2 (en) | ||
| JPS6240086B2 (en) | ||
| JPH09263991A (en) | Cooler for electrolytic tin plated strip |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |