Patent Publication Number: US-6340028-B1

Title: Pickling device

Description:
This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/JP99/01059 which has an International filing date of Mar. 5, 1999, which designated the United States of America. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to an acid pickling device for washing and removing oxide scale, formed on the surface of a strip plate, by acid pickling. 
     BACKGROUND OF THE INVENTION 
     FIG. 4 is a perspective side view of a conventional acid pickling device, and FIG. 5 is a sectional view taken on line V—V in FIG.  4 . 
     In the conventional acid pickling device, as shown in FIGS. 4 and 5, an acid pickling tank  101 , which is open upwards, is filled with an acid liquid L for acid pickling of a strip steel plate S. A lid  102  is attached to the top of the acid pickling tank  101  to form an inlet portion  103 , and an outlet portion  104 . To the inlet portion  103  and the outlet portion  104 , aerial deflector rolls  105 ,  106  and immersion deflector rolls  107 ,  108  are attached, respectively. 
     From a lower surface of the lid  102 , a hook  109  is suspended. From the hook  109 , a ceiling plate  111  is suspended via an engaging stop  110 . From the ceiling plate  111 , a bottom plate  113  is suspended via connecting plates  112  located at both side parts. On a lower surface of the ceiling plate  111 , many immersion guide rolls  115  rotatable via bearing portions  114  are mounted along a direction of travel of the strip steel plate S. On an upper surface of the bottom plate  113 , many skids  116  are attached at positions opposed to the immersion guide rolls  115 . 
     Thus, the strip steel plate S is guided by the aerial deflector roll  105  and the immersion deflector roll  107  at the inlet portion  103  into the acid liquid L in the acid pickling tank  101 , and travels, while being guided, between the immersion guide rolls  115  and the skids  116 . At this time, oxide scale formed on the surface of the strip steel plate S is washed with the acid liquid L and removed thereby. Then, the strip steel plate S is guided by the immersion deflector roll  108  and the aerial deflector roll  106  at the outlet portion  104 , and delivered to the outside of the acid pickling tank  101 . 
     Such a conventional acid pickling device is disclosed, for example, in Japanese Unexamined Patent Publication No. 5-78870. 
     With the foregoing conventional acid pickling device, the acid liquid L is filled into the acid pickling tank  101  which is open upwards, and the lid  102  is attached to the top of the acid pickling tank  101 . Thus, the surface area of the acid liquid L in the acid pickling tank  101  is so wide that a loss of acid becomes great as a result of evaporation. Consequently, the washing and removal of the oxide scale on the strip steel plate S by acid pickling are performed insufficiently. 
     Furthermore, the strip steel plate S travels, while being guided, between the immersion guide rolls  115  and the skids  116  in the acid pickling tank  101 . Hence, as the strip steel plate S moves, the acid liquid L follows, and a flow of the acid liquid L toward a downstream side in the direction of travel of the strip steel plate S occurs. This makes the surface of the acid liquid L beside the outlet portion  104  higher, causing an overflow of the acid liquid L from the outlet portion  104  to the outside of the acid pickling tank  101 . Besides, the many immersion guide rolls  115  and skids  116  that guide the travel of the strip steel plate S in the acid liquid L are suspended from and supported by the lid  102 . Thus, a head weight acts on the lid  102 , and may damage it. 
     SUMMARY OF THE INVENTION 
     The present invention attempts to solve the above problems. Its object is to provide an acid pickling device which suppresses a loss of an acid by decreasing a free surface of an acid liquid in an acid pickling tank, and prevents an overflow to the outside of the tank, thereby making acid pickling of a strip plate efficient. 
     The present invention is an acid pickling device for acid pickling a strip plate by causing the strip plate to travel in an acid pickling tank filled with an acid liquid while guiding the strip plate by an immersion guide roll and a skid, wherein an acid pickling tank lid for covering a top of the acid pickling tank is disposed such that a central part of the acid pickling tank lid is located at a lower position than a liquid level of the acid liquid in the acid pickling tank to cover a free surface of the acid liquid. 
     Thus, the surface area of the acid liquid in the acid pickling tank is narrower than in the earlier technology, thereby suppressing the loss of an acid due to evaporation, and ensuring reliable washing and removal of oxide scale on the strip plate by acid pickling. Moreover, the free surface of the acid liquid in the acid pickling tank is forcibly restrained, so that the liquid level of the acid liquid is held constant, thus preventing an overflow of the acid liquid to the outside of the tank. Consequently, the acid pickling of the strip plate can be performed efficiently. 
     The present invention also concerns the acid pickling device, wherein the immersion guide roll is provided on the acid pickling tank lid, and the skid is provided on a support block installed at the bottom of the acid pickling tank. 
     Thus, there is no need to suspend heavy materials from the lid, so that the lid can be decreased in rigidity, and can be made light-weight. 
     The present invention also concerns the acid pickling device, wherein the support block is provided with a bottom plate positioned below the skid and extending along a direction of travel of the strip plate. 
     Thus, as the strip plate moves in the acid pickling tank, the acid liquid follows, and is flowed downstream in the travel direction. As a result, the acid liquid is circulated, and becomes no more stagnant. 
     The present invention also concerns the acid pickling device, wherein a plurality of the immersion guide rolls and a plurality of the skids are provided, with predetermined spacing, in a direction of travel of the strip plate, the support block is provided with a bottom plate positioned below the skid and extending along the direction of travel of the strip plate, and the bottom plate is provided with acid liquid passages each located between the adjacent skids. 
     Thus, as the strip plate moves in the acid pickling tank, the acid liquid follows, generating a flow toward a downstream side in the travel direction. However, the flow of the acid liquid is circulated in the acid pickling tank through the acid liquid passages, thus eliminating stagnation of the acid liquid, and releasing the liquid pressure. Hence, it does not take place that the surface of the acid liquid suddenly becomes high, causing an overflow to the outside of the tank. In addition, the pressure imposed on the lid is also decreased, thus enabling the lid to be decreased in strength and be rendered light-weight. 
     The present invention also concerns the acid pickling device, wherein the acid liquid passages are each provided between the adjacent skids and upstream in the direction of travel of the strip plate. 
     Namely, the acid liquid passages are positioned just behind the site of passage of the strip steel plate between the immersion guide rolls and the skids. Thus, the static pressure of the acid liquid on the exit side progressively increases compared with the entrance side for the strip plate in the acid pickling tank. Hence, the acid liquid is agitated, and its circulation can be promoted. 
     The present invention also concerns the acid pickling device, wherein a plurality of the immersion guide rolls and a plurality of the skids are provided, with predetermined spacing, in a direction of travel of the strip plate, and communication holes for the acid liquid are provided in the support blocks that support the skids. 
     Thus, as the strip plate moves in the acid pickling tank, the acid liquid follows, generating a flow toward a downstream side in the travel direction. However, the flow of the acid liquid is circulated in the acid pickling tank through the communication holes, thus eliminating stagnation of the acid liquid, and releasing the liquid pressure. Hence, it does not take place that the surface of the acid liquid suddenly becomes high, causing an overflow to the outside of the tank. In addition, the pressure imposed on the lid is also decreased, thus enabling the lid to be decreased in strength and be rendered light-weight. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG.  1 ( a ) is a schematic side view of an acid pickling device according to a first embodiment of the present invention, and 
     FIG.  1 ( b ) is a graph showing the static pressure distribution of an acid pickling liquid of the acid pickling device; 
     FIG. 2 is a sectional view taken along line II—II in FIG.  1 ( a ); 
     FIG.  3 ( a ) is a schematic side view of an acid pickling device according to a second embodiment of the present invention, and 
     FIG.  3 ( b ) is a graph showing the static pressure distribution of an acid pickling liquid of the acid pickling device; 
     FIG. 4 is a schematic side view of a conventional acid pickling device; and 
     FIG. 5 is a sectional view taken along line V—V in FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A first embodiment of the present invention will now be described in detail by reference to the accompanying drawings. 
     In an acid pickling device of the first embodiment, as shown in FIG.  1 ( a ) and FIG. 2, an acid pickling tank  11 , which is open upwards, is filled with an acid liquid L for acid pickling of a strip steel plate S. A lid  12  is attached to an upper opening of the acid pickling tank  11  to form an inlet portion  13 , and an outlet portion  14 . The lid  12  has an outer peripheral flange portion  12   a  fitted liquid-tight into a receiver portion  11   a  formed at a side part of the acid pickling tank  11 , and has a central part forming a covering portion  12   b  which is concaved downwardly. The covering portion  12   b  enters the acid liquid L in the acid pickling tank  11 , and lies below the liquid level of the acid liquid. Thus, most of a free surface of the acid liquid L in the acid pickling tank  11  is covered with the covering portion  12   b  of the lid  12 . To the inlet portion  13  and the outlet portion  14 , aerial deflector rolls  15 ,  16  and immersion deflector rolls  17 ,  18  are attached, respectively. 
     On a lower surface of the covering portion  12   b  of the lid  12 , immersion guide rolls  20   a  to  20   e  are rotatably mounted by a pair of (i.e., right and left) bearing portions  19   a  to  19   e  made of a metal (or resin, carbon or ceramic). This plurality of immersion guide rolls  20   a  to  20   e  are arranged parallel to each other, with predetermined spacing, along a direction of travel of the strip steel plate S. On a bottom surface of the acid pickling tank  11 , a plurality of support blocks  21   a  to  21   e  are arranged in parallel along the direction of travel of the strip steel plate S. To the top of the support blocks  21   a  to  21   e , a bottom plate  22  is fixed so as to connect the support blocks  21   a  to  21   e  together. To an upper surface of the bottom plate  22 , a plurality of skids  23   a  to  23   e  are fixed at positions opposed to the immersion guide rolls  20   a  to  20   e.    
     In the support blocks  21   a  to  21   e , acid liquid communication holes  24   a  to  24   e , through which the acid liquid L can flow, are formed. In the bottom plate  22 , acid liquid passages  25   a  to  25   d , through which the acid liquid L can flow, are each formed between the adjacent two of the skids  23   a  to  23   e  downstream in the direction of transport of the strip steel plate S. These acid liquid passages  25   a  to  25   d  are each in a slit, circular, or rectangular shape. 
     Thus, the strip steel plate S is guided by the aerial deflector roll  15  and the immersion deflector roll  17  at the inlet portion  13 , and led into the acid liquid L of the acid pickling tank  11 , where the strip steel plate S travels, while being guided, between the plurality of immersion guide rolls  20   a  to  20   e  and the plurality of skids  23   a  to  23   e . During this occasion, oxide scale formed on the surface of the strip steel plate S is washed with and removed by the acid liquid L. Then, the strip steel plate S is guided by the immersion deflector roll  18  and the aerial deflector roll  16  of the outlet portion  14  to the outside of the acid pickling tank  11 . 
     According to the acid pickling device of the present embodiment, the covering portion  12   b  in the central part of the lid  12  enters the acid liquid L in the acid pickling tank  11 , and lies below the liquid level of the acid liquid. As a result, most of the free surface of the acid liquid L in the acid pickling tank  11  is covered with the covering portion. Thus, the surface area of the acid liquid L in the acid pickling tank  11  becomes smaller than in the earlier technology. Hence, a loss of an acid due to evaporation is decreased to ensure the reliable washing and removal of the oxide scale formed on the strip steel plate S by acid pickling. 
     In addition, as stated above, the covering portion  12   b  of the lid  12  enters the acid liquid L in the acid pickling tank  11 , thereby forcibly restraining the free surface of the acid liquid L in the acid pickling tank  11 , so that the liquid level of the acid liquid L can be kept constant. 
     Besides, the acid liquid communication holes  24   a  to  24   e , through which the acid liquid L can flow, are formed in the support blocks  21   a  to  21   e . In the bottom plate  22 , the acid liquid passages  25   a  to  25   d , through which the acid liquid L can flow, are formed. Thus, when the strip steel plate S travels, while being guided, between the immersion guide rolls  20   a  to  20   e  and the skids  23   a  to  23   e , the acid liquid L follows the strip steel plate S as it moves. As a result, a downstream flow of the acid liquid L in the traveling direction of the strip steel plate S occurs. However, the acid liquid L does not wave, since its liquid level is restrained by the covering portion  12   b  of the lid  12 . This flow of the acid liquid L moves downward through the acid liquid passages  25   a  to  25   d , passes through the communication holes  24   a  to  24   e , and is returned to an upstream side in the traveling direction of the strip steel plate S. In this manner, the acid liquid L circulates within the acid pickling tank  11 . There is no stagnation of the acid liquid L, and the liquid pressure is released. 
     Hence, as shown in FIG.  1 ( a ), a differential pressure Δp occurs in the acid liquid L between its pressure at the inlet portion  13  and that at the outlet portion  14  of the acid pickling tank  11 . Hence, circulation of the acid liquid L is promoted, and it does not occur that the surface of the acid liquid L beside the outlet portion  14  suddenly rises, causing overflow of the acid liquid L to the outside of the acid pickling tank  11 . Moreover, the liquid pressure in the acid pickling tank  11  is released, and does not increase. Thus, the strength of the lid  12  can be reduced. 
     Opposite the plural immersion guide rolls  20   a  to  20   e  suspended from the lid  12 , the plural skids  23   a  to  23   e  are fixed to the bottom plate  22  on the plural support blocks  21   a  to  21   e  fixed to the bottom surface of the acid pickling tank  11 . Thus, there is no need to suspend heavy materials from the lid  12 , so that the rigidity of the lid  12  can be decreased, and it can be made lightweight. 
     Next, a second embodiment of the present invention will be described in detail by reference to the accompanying drawings. Members having the same functions as those explained in the aforementioned embodiment will be assigned the same numerals or symbols, and overlapping explanations will be omitted. 
     In an acid pickling device according to the second embodiment, as shown in FIG.  3 ( a ), an acid pickling tank  31 , which is open upwards, is filled with an acid liquid L for acid pickling of a strip steel plate S. A lid  32  is attached to an upper opening of the acid pickling tank  31  to form an inlet portion  33 , and an outlet portion  34 . The lid  32  has a central part forming a covering portion  32   b  which is concaved downwardly. The covering portion  32   b  enters the acid liquid L in the acid pickling tank  31 , and lies below the liquid level of the acid liquid. Thus, most of a free surface of the acid liquid L in the acid pickling tank  31  is covered with the covering portion  32   b  of the lid  32 . To the inlet portion  33  and the outlet portion  34 , aerial deflector rolls  35 ,  36  and immersion deflector rolls  37 ,  38  are attached, respectively. 
     On a lower surface of the covering portion  32   b  lid  32 , immersion guide rolls  40   a  to  40   e  are rotatably mounted by bearing portions  39   a  to  39   e . On a bottom surface of the acid pickling tank  31 , a plurality of support blocks  41   a  to  41   e  are arranged in parallel along the direction of travel of the strip steel plate S. To the top of the support blocks  41   a  to  41   e , a bottom plate  42  is fixed to connect the support blocks  41   a  to  4 l e  together. To an upper surface of the bottom plate  42 , a plurality of skids  43   a  to  43   e  are fixed at positions opposed to the immersion guide rolls  40   a  to  40   e.    
     In the support blocks  41   a  to  41   e , acid liquid communication holes  44   a  to  44   e , through which the acid liquid L can flow, are formed. In the bottom plate  42 , acid liquid passages  45   a  to  45   d , through which the acid liquid L can flow, are each formed between the adjacent two of the skids  43   a  to  43   e  upstream in the direction of transport of the strip steel plate S. 
     Thus, the strip steel plate S is guided by the aerial deflector roll  35  and the immersion deflector roll  37  at the inlet portion  33 , and led into the acid liquid L of the acid pickling tank  31 , where the strip steel plate S travels, while being guided, between the plurality of immersion guide rolls  40   a  to  40   e  and the plurality of skids  43   a  to  43   e . During this occasion, oxide scale formed on the surface of the strip steel plate S is washed with and removed by the acid liquid L. Then, the strip steel plate S is guided by the immersion deflector roll  38  and the aerial deflector roll  36  of the outlet portion  34  to the outside of the acid pickling tank  31 . 
     According to the acid pickling device of the present embodiment, the covering portion  32   b  of the lid  32  enters the acid liquid L in the acid pickling tank  31 , and lies below the liquid level of the acid liquid. As a result, most of the free surface of the acid liquid L in the acid pickling tank  31  is covered with the covering portion. Thus, the surface area of the acid liquid L becomes small. Hence, a loss of the acid due to evaporation is decreased to ensure the reliable washing and removal of the oxide scale formed on the strip steel plate S by acid pickling. In addition, the free surface of the acid liquid L in the acid pickling tank  31  is forcibly restrained, so that the liquid level of the acid liquid L can be kept constant. 
     Besides, when the strip steel plate S travels, while being guided, between the immersion guide rolls  40   a  to  40   e  and the skids  43   a  to  43   e , the acid liquid L follows the strip steel plate S as it moves. As a result, a downstream flow of the acid liquid L in the traveling direction of the strip steel plate S occurs. However, this flow of the acid liquid L moves downward through the acid liquid passages  45   a  to  45   d , passes through the communication holes  44   a  to  44   e , and is returned to an upstream side in the transport direction of the strip steel plate S. In this manner, the acid liquid L circulates within the acid pickling tank  31 . This eliminates stagnation of the acid liquid L, and releases the liquid pressure. Hence, as shown in FIG.  3 ( a ), a differential pressure Δp occurs in the acid liquid L between its pressure at the inlet portion  33  and that at the outlet portion  34  of the acid pickling tank  31 . Also, the differential pressure progressively increases owing to a load pressure Δp + , thus promoting circulation of the acid liquid L. This is because the acid liquid passages  45   a  to  45   d  are located at positions just behind the site of passage of the strip steel plate S between the immersion guide rolls  40   a  to  40   e  and the skids  43   a  to  43   e . Thus, agitation of the acid liquid L is promoted. On the other hand, it does not occur that the surface of the acid liquid L beside the outlet portion  34  suddenly rises, causing overflow of the acid liquid L to the outside of the acid pickling tank  31 . Moreover, the liquid pressure in the acid pickling tank  31  is released, and does not increase. Thus, the strength of the lid  32  can be reduced. 
     In each of the above-described embodiments, the central part of the lid  12  or  32  was rendered concaved downwardly to form the covering portion  12   b  or  32   b . However, a separate member may be provided on the lower surface of the lid  12  or  32  to form the covering portion  12   b  or  32   b . Furthermore, the numbers of the immersion guide rolls  20   a  to  20   e  or  40   a  to  40   e , and the skids  23   a  to  23   e  or  43   a  to  43   e  are not restricted to those described in the embodiments. 
     As described above, the acid pickling device of the present invention immerses a strip plate in an acid pickling tank to wash and remove oxide scale, formed on the surface of the strip plate, by acid pickling. This device is preferred for use in a surface treating device for treating a continuously traveling strip plate at a high speed.