• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The present invention relates to a method for producing a hot rolled low carbon steel having excellent surface scale and workability, which is, by weight, carbon: 0.02 to 0.05%, manganese: 0.10 to 0.30%, phosphorus: 0.20% or less, sulfur: 0.020% or less, balance In a slab made of iron (Fe) and unavoidable impurities, the slab is heated to a heating furnace extraction temperature of 1150 to 1220 ° C., rolled to a crude rolling exit temperature of 1000 to 1200 ° C., and the center portion and both edge portions of the rolled steel sheet. Edge heating was performed to make the temperature uniform, water cooled, followed by finishing rolling at a running speed of 640 to 680mpm, and the exit temperature of the finishing rolling was 850 to 900 ° C.
    公开号:KR20040003316A
    申请号:KR1020020037981
    申请日:2002-07-02
    公开日:2004-01-13
    发明作者:김종성；김성준
    申请人:주식회사 포스코；
    IPC主号:
    专利说明:

    Hot rolled law carbon steel plate manufacturing method for surface scale and workability excellent}
    [9] The present invention relates to a method for producing low carbon steel having excellent surface scale and workability, and more particularly, carbon (C), manganese (Mn), phosphorus (P), sulfur (S), and the balance of iron (Fe) and unavoidable impurities. The slab consisting of the heating, rough rolling, edge heating, finishing rolling, cooling by appropriately to control the low-carbon steel excellent in surface scale and workability.
    [10] In general, the process for manufacturing hot rolled steel sheet is to insert a slab having a proper ratio of the components necessary for iron (Fe) in order to manufacture the desired product in a heating furnace and heated to the appropriate temperature and time, and rough rolling, finishing rolling As the steel sheet produced by this process is recently subjected to the process of cooling, winding and winding, the quality requirements of the customer's hot rolled products have been strict, and interest in producing materials with excellent mechanical properties, surface quality, and shape has increased. In particular, the workability of the hot rolled steel sheet in the aspect of improving workability and real error rate has emerged as a big problem.
    [11] The main problem caused by poor workability is that the edge part workability of the steel sheet is deteriorated due to the material deviation in the width direction, causing the edge part cracks during cold working as shown in FIG. 2. The cause of the material deviation is due to the difference in grain growth (see FIG. 4) due to the lack of the edge temperature as shown in FIG. The nonuniformity of the structure affects the phase transformation behavior and the precipitation behavior of the alloy carbonitrides during water cooling, causing material variation.In low carbon steels, the edge temperature is high because the phase transformation start temperature (Ar3) is high and the transformation progression speed is fast. The degraded portion is transformed into phase during rolling, so that the rolled ferrite and the unrolled ferrite are coexisted, and the rolled ferrite coarsens the grain size in order to minimize the strain.
    [12] As a result, coarse grains are generated due to residual grain growth (rolled ferrite + unrolled ferrite) and abnormal grain growth in the final structure, thereby inhibiting mechanical properties and cold workability of the hot rolled steel sheet as shown in FIG. 5. will be. Such phenomena tend to be a problem, especially for thin materials (2.3 mm or less), which are relatively difficult to secure at the finishing rolling extraction temperature (hereinafter referred to as "FDT").
    [13] Conventional hot rolled steel sheet manufacturing Bangbang to solve this problem is provided in Patent Application No. 1997-072735, which is to produce a hot rolled steel sheet with a thickness of 1.3 ~ 2.3mm, carbon: 0.02 ~ 0.05wt%, Silicon: trace, manganese: 0.10 ~ 0.30wt%, phosphorus <max.0.015%, sulfur <max.0.10, aluminum 0.01 ~ 0.04wt%, nitrogen <40ppm and boron 20 ~ 30ppm added to start the transformation (Ar3) is lowered by about 20 ~ 30 ℃ compared to the prior art, but this causes the cost increase due to the addition of boron, it is difficult to manage the proper ingredient of boron during the operation, and even if the temperature of Ar3 is lowered. Securing the filament rolling extraction temperature (hereinafter referred to as "FDT") in the museum remains a difficult problem.
    [14] In addition, a specific methodology for rolling above the transformation temperature has not been proposed, which causes a problem of causing surface scale defects as shown in FIG. 6 by inducing excessive crude rolling extraction temperature (hereinafter referred to as “RDT”) during actual operation. .
    [15] In addition, in order to secure the workability, it is important to secure the rolling temperature in the width direction of the steel sheet, in particular, the edge part, so it is appropriate to use a coolant spray between stands, a method of using a high pressure descaler, and a number of rough rolling passes. The control method should suggest an operation method to minimize the temperature difference between the center and the edge of the steel sheet, which was not considered at all.
    [16] The present invention has been invented to solve this problem in view of the above problems, the object of which is to roll the slab made of carbon, manganese, phosphorus, sulfur, the balance iron (Fe) and unavoidable impurities, first in the heating furnace Providing low carbon steel with excellent surface scale and processability by appropriately controlling heating time and extraction temperature, crude rolling pass number and extraction temperature in rough rolling, edge heating of steel sheet, progress rate of finishing rolling and descaling Is in.
    [1] 1 is a schematic view showing a hot rolled low carbon steel manufacturing process according to the present invention,
    [2] Figure 2 is a photograph and texture photograph showing an example of poor processing and crack generation of hot rolled low carbon steel,
    [3] 3 is a graph showing an example of occurrence of deviation of the filament rolling exit temperature;
    [4] 4 is a graph and a tissue photograph showing an example of occurrence of tissue deviation according to filament rolling extraction temperature;
    [5] Figure 5 is a tissue photograph showing the mechanism of coarse grain and hybridization of hot rolled low carbon steel,
    [6] Figure 6 is a photograph showing the form after the rolling in the high temperature rough rolling exit temperature operation,
    [7] 7 is a block diagram showing an automation system for surface scale and material improvement;
    [8] 8 is a graph showing a width direction temperature system,
    [17] Characteristic technical features of the present invention for achieving the above object, by weight% carbon: 0.02 ~ 0.05%, manganese: 0.10 ~ 0.30%, phosphorus: 0.20% or less, sulfur: 0.020% or less, the balance is iron (Fe) And a slab made of unavoidable impurities, wherein the slab is heated to a heating furnace extraction temperature of 1150 to 1220 ° C., rolled to a crude rolling exit temperature of 1000 to 1200 ° C., and uniformly temperatured at the center and both edges of the rolled steel sheet. Edge heating, water cooling and finishing rolling at a running speed of 640 to 680mpm and the exit temperature of the finishing rolling were made to be 850 to 900 ° C.
    [18] The slab heating time in the heating furnace is 180 to 220 minutes, the number of R2 rough rolling passes of the rough rolling mill is three times, and the water cooling method before the edge heating and entering the finishing mill includes two sprays. Only one of the devices is operated to cool the rolled steel sheet. During finishing rolling, descaling is performed and no cooling water is injected.
    [19] Process for producing hot rolled low carbon steel having excellent surface scale and workability of the present invention having the above characteristics, first, by weight% carbon: 0.02 ~ 0.05%, manganese: 0.10 ~ 0.30%, phosphorus: 0.20% or less, sulfur : 0.020% or less, the remainder is charged into the heating furnace 10, as shown in Fig. 1, a conventional slab made of iron (Fe) and unavoidable impurities and heated to an extraction temperature of 1150 to 1220 ° C for 180 to 220 minutes.
    [20] The reason why the slab stagnation time in the heating furnace is maintained at 180 to 220 minutes is that when the stagnation time is short, there is no sufficient heat treatment, and thus temperature deviation occurs in the width direction and the longitudinal direction, thereby affecting the flowability. However, if it is maintained for a long time, the surface scale due to the reduction in rolling productivity and the overproduction of the primary scale is a problem, it is preferable to maintain within 180 ~ 220 minutes.
    [21] In addition, the reason for maintaining the furnace extraction temperature at 1150-1220 ° C. is advantageous to maintain 1150 ° C. or higher in order to secure an optimum rough rolling exit temperature and finishing rolling exit temperature, but if the exit temperature is too high, it is appropriate. The crude rolling exit temperature and the finishing rolling exit temperature can be easily secured, but are disadvantageous in terms of surface scale generation. Therefore, it is preferable to limit the range to 1150 ° C to 1220 ° C.
    [22] The reason why the rough rolling exit temperature is 1000 to 1200 ° C and the number of R2 rough rolling passes of the rough rolling mill is 3 times is to maintain the surface scale while securing the finishing rolling exit temperature, which is a key factor for securing the hot rolling gutter. In order to suppress the production, the reason of the R2 3 Pass of the rough rolling is that, if it is more than that causes a problem in the plateability due to the temperature drop of the rolled steel sheet.
    [23] In addition, the reason why the edge heating of the rough-rolled rolled steel sheet is for making the temperature of the center part and both edge parts of a rolled steel plate uniform. However, the temperature difference between the center portion and both edge portions of the rough rolled rolled steel sheet is 20-30 ° C higher in temperature than both edge portions, because the cooling of both edge portions is performed quickly.
    [24] The reason why the water is cooled before the edge heating and entering the finishing mill is to maintain the drawing temperature of the finishing rolling, and the moving speed of the rolling steel sheet during finishing rolling is 640 to 680mpm. There is a possibility of pinching at the tip, and below it will cause a faulty mailing.
    [25] In addition, when the rolled steel sheet exits the last rolling mill, if the uniform sheet speed of the sheet is not secured and falls from the fast sheet speed to the low sheet speed, the rolling load increases due to the temperature drop and the plate breakage is likely to occur. It is important to maintain a uniform plate speed. Therefore, in order to maintain the most stable sheet flowability, it is very important to maintain the optimum acceleration pattern of the finishing mill which can prevent the rolling load increase due to the thickness accumulation.
    [26] On the other hand, the exit temperature of finishing rolling is set to 850 to 900 ° C. If the holding temperature is kept higher or lower, the rolling load increases due to an increase in the deformation resistance, and the thickness control becomes uneven. In addition, the reason for descaling during finishing rolling is to make the surface of the rolled steel sheet beautiful.
    [27] In the present invention manufactured by the above method, it is necessary to first select the main factors affecting the workability, and to derive the appropriate level of the factors to minimize scale generation.
    [28] In order to secure the workability of general low carbon steel, it is important to secure not only the exit temperature of the steel plate center portion but also the exit temperature of the edge portion as described above.If the processability of the edge portion is secured, the finishing rolling exit temperature (hereinafter referred to as "FDT") profile Due to the properties of (Profile), it is possible to ensure the full width direction temperature and workability of the rolled steel sheet (see Fig. 3).
    [29] Therefore, the main point of analysis is derivation of hot rolling process factors affecting edge temperature, heating time of heating furnace, extraction temperature (SRT), steel plate thickness, crude rolling pass number, crude rolling exit temperature, edge heater use Presence, cooling, initial rolling plate initial speed, inter-stand cooling water spray, finishing rolling descaling, etc. may be considered.
    [30] First, as a result of analyzing the correlation between workability of edge part and rolling operation condition (cold rolling (1.8 → 0.56mm) and analysis of edge machining result and process condition) crude rolling pass number, presence of edge heater, and finishing rolling descaling (Descaling) ) Recovery, initial rolling speed was found to be an important factor, in particular, whether the use of edge heaters, finishing rolling descaling times, plate speed was a big influence on the edge workability as shown in Table 1 below.
    [31]
    [32] In addition, as a result of the spray ON / OFF test between each stand, the temperature of the steel sheet edge portion was dropped sharply relative to the center portion, and thus, it was determined that the use of the spray between stands was a significant influence factor on the workability of the edge portion as shown in Table 2 below.
    [33]
    [34] Based on the above analysis results, the experiment was conducted to set the factor level for improving the scale and workability as shown in Table 3 below. The test method had a great effect on the surface scale such as the use of edge heaters, plate speed, and spray off between stands. Factors that affect the processability without using them are used as the fixed factor of the processability securing level, and by classifying the number of crude rolling pass, crude rolling exit temperature, finishing rolling descaling, etc. which affect both surface scale and processability. The influence of surface scale and workability was determined.
    [35]
    [36] As a result of the experiment as described above, as shown in the following Table 4 and Table 5, rough rolling R2 3 PASS, rough rolling exit temperature 1040 ℃, finishing rolling descaling was the best workability, the processing degree is 1.80mm rolled material up to 0.30mm Cold work did not produce any processing cracks, and it was confirmed that the rolling work did not have a significant effect on the surface scale.
    [37]
    [38]
    [39] Based on the above results, the conditions for securing workability without generating surface scale are as follows: crude rolling exit temperature: 1000 to 1200 ° C, crude rolling R2 3 PASS, finishing rolling descaling once, using edge heaters, plate speed 680mpm In addition, simultaneous control is required such as cooling water spraying off between stent rolling stents, and in order to perform the control as described above, an operator synchronization system (FIG. 7) and a widthwise temperature control system (FIG. 8) for improving materials are constructed.
    [40] Hereinafter, the present invention will be described with reference to Examples.
    [41] (Example)
    [42] By weight% Carbon: 0.02 ~ 0.05%, Manganese: 0.10 ~ 0.30%, Phosphorus: 0.20% or less, Sulfur: 0.020% or less, the remainder of the slab composed of iron (Fe) and unavoidable impurities in the furnace for 180 ~ 220 minutes After heating, the extraction temperature is 1190 ℃, and at the same time as the R2 3 PASS in the crude rolling mill, the exit temperature is 1040 ℃, edge heating is performed by using the edge heater, and the two heaters are installed between the edge heater and the finishing mill. Cooling water spray device Cools the rolled steel by operating only the spraying device in front of it.The hot rolled low carbon steel material (1.8 ~) is controlled by one time of finishing rolling descaling, 680mpm of finishing rolling, and cooling water spray off between finishing rolling stands. As a result of the production of less than 2.3t), it was possible to secure the surface scale and the cold workability as desired.
    [43] In summary, the surface and material properties of the present invention are superior to those of the prior art as shown in Table 6 below.
    [44]
    [45] In the present invention as described above, in rolling a slab having a conventional composition, the heating time and extraction temperature in the heating furnace, the crude rolling pass number and extraction temperature in the rough rolling, the edge heating of the steel sheet, water cooling, the progress of finishing rolling By appropriately controlling the speed and descaling, there is an effect of producing a low carbon steel excellent in surface scale and workability.
    权利要求:
    Claims (5)
    [1" claim-type="Currently amended] % By weight of carbon: 0.02% to 0.05%, manganese: 0.10% to 0.30%, phosphorus: 0.20% or less, sulfur: 0.020% or less, the balance of which is composed of iron (Fe) and unavoidable impurities
    The slab is heated to an extraction temperature of 1150 to 1220 ° C. in a heating furnace, rolled to a crude rolling exit temperature of 1000 to 1200 ° C., and edge-heated in order to uniformize the temperature of the center and both edges of the rolled steel sheet, followed by water cooling. And then rolling at a running speed of 640 to 680mpm and the exit temperature of the finishing rolling to be 850 to 900 ° C.
    [2" claim-type="Currently amended] The method for producing a low carbon steel for rollers according to claim 1, wherein the slab heating time in the heating furnace is 180 to 220 minutes.
    [3" claim-type="Currently amended] The method for producing low carbon steel for rollers according to claim 1, wherein the number of R2 rough rolling passes of the rough rolling mill is three times.
    [4" claim-type="Currently amended] The method of claim 1, wherein the water-cooling method before the edge heating and entering the finishing mill is performed by using only one of two spray apparatuses to cool the rolled steel sheet. .
    [5" claim-type="Currently amended] The method of claim 1, wherein descaling is performed during the finishing rolling and cooling water is not injected.
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    同族专利:
    公开号 | 公开日
    KR100829943B1|2008-05-16|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2002-07-02|Application filed by 주식회사 포스코
    2002-07-02|Priority to KR1020020037981A
    2004-01-13|Publication of KR20040003316A
    2008-05-16|Application granted
    2008-05-16|Publication of KR100829943B1
    优先权:
    申请号 | 申请日 | 专利标题
    KR1020020037981A|KR100829943B1|2002-07-02|2002-07-02|Hot rolled law carbon steel plate manufacturing method for surface scale and workability excellent|
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