[1]The present invention relates to a cold-rolled steel sheet and a manufacturing method for a flux-cored wire.
[2]
BACKGROUND
[3]For the material for the electrode can, a steel plate is applied to the development and Flux material is combined in order to correspond to various uses. In typical use is the development of a variety of special-purpose welding members made of such as abrasion resistance is superior and Mn Steel welding member, the welding member for extremely low temperature is excellent toughness at cryogenic temperature, anti-vibration performance is superior dust STEEL welding member. Accordingly, there is a welding materials developed for progress to meet these special welding steel.
[4]
[5]
Typical welding method of welding productivity is highest and a welding method, welding is easy in various positions has a flux-cored welding (FCW, Flux Cored Welding) method. Weld materials used in the welding method is a flux cored wire (Flux Cored Wire), which from about 5% to 50% machining a strip (Strip) drawing a general cold-rolled steel sheet into a U-shape, and the ratio of weight to the processed U-tube level of the welding operation manganese in accordance with the object to ensure the characteristics suitable for use purpose of the flux components and the electrode for gender secured (Mn), nickel (Ni) in followed by the addition of a mixture of the alloying elements, such as in powder form circular electrode It is prepared for the material.
[6]
The core to be added in powder form through the kind and amount of change in the alloy component will ensure the various properties required for the electrode material. Accordingly, to be charged in order to produce a welding member which is the low temperature toughness requirements, such as welding member for extremely low temperature additionally, the elements for improving the low temperature toughness by the alloying elements to be added to the flux core wire.
[7]
[8]
On the other hand, the flux-cored wire for cold-rolled steel surrounding the core wire used for the manufacture is generally a regular carbon steel is used alloying elements are not added much, there is a stainless steel is used for some special applications.
[9]
The steel product for a wire of normal carbon steel base for many purposes because of advantages such elongation is excellent and does not generate a tearing phenomenon of the pull-out when the steel material also is continuous production is possible without passing through a separate heat treatment step from the lower molding degree of work hardening to a final wire manufacturing It has been widely applied. However, the same carbon steel weld steel material, so in order to ensure in order to ensure the characteristics of the electrode requires the addition of the flux and the core the alloy element which filled inside the wire, but the welding operability by low alloy basically flux amount is the need adequacy sikineunde upward within the core alloying elements that is the fact that the limit. That is, a large amount of oxidizing agent in the center portion of the steel wire (Ti, Mn, Zr, Al, etc.), slag forming agents (TiO 2 , SiO 2 , Al 2 O 3 , ZrO 2, MnO, etc.), an arc stabilizer (K, Na, etc.), alloy components (Si, Mn, Ni, Zr, Cr, etc.), etc. are all one must be added, including the flux in the wire of steel filled with yongjeokryang of approximately 30 to 60% to limit a difference in the powder to be filled, but the weight ratio is about 15 to 25% level known as the threshold. When such a case is to increase the content of alloying elements to secure the properties there is a problem that a limited amount of flux components such as a making it difficult to secure a stable welding characteristics. In addition, these alloying elements are raised for welding the welding portion of the core component segregation during melting operation as added in powder form was also a problem that also acts as a weld defect factors.
[10]
In the case of a steel product for welding wire utilizing stainless steel it has essentially a nickel present in the carbon steel component, compared to general carbon steel (Ni) or chromium (Cr) Because of the high amounts of alloying elements, such as the core alloying elements that are added with the flux the amount can be reduced, but because it is basically a high-alloy reality that applies only to the original materials such as high prices for special purposes. Not only the case of these stainless steel welded disk There is another problem of extracting the heat treatment to be carried out separately between the manufacturing process increases the risk caused by work hardening is disconnected when the electrode wire processing served as increase of the manufacturing cost factors.
[11]
[12]
As of workability, in particular the drawing workability and the steel product for welding wire for extremely low temperature required for the low temperature toughness is to prepare a high-priced alloying element as a pure powder form in order to take advantage of the common carbon steel to secure the sheet entrance low temperature toughness after Tube Mill flux other flux While improving the low temperature toughness by charging with ingredients, and in this case the alloy powders to be added, even there is a problem according to a restriction on the addition conditions of the flux component to secure the welding stability in accordance with the high days input Fair as well as highly purified . There was also the problem that expensive alloying elements be added to this time deterioration of the welding operability causes a segregation phenomenon in the flux.
[13]
[14]
For example, in Patent Document 1 as a method for manufacturing a steel sheet for use in a flux cored wire, Mn: 1.4 ~ 2.4%, Si: 0.2 ~ 0.4%, Ni: Cr in the steel containing 2.8 ~ 6.4%, Mo, addition of Ti, such as a method for producing a steel having excellent electrode for impact toughness and strength properties are disclosed by. However, Patent Document 1 has a problem in that manufacturing cost is increased because many of the addition of expensive alloying elements, there is also a difficult problem to secure the drawing workability by the addition of alloying elements, but high strength can be secured, the flexible lower.
[15]
Further, in Patent Document 2, and by the addition of Ti, Mg, etc. in the flux material discloses a technique for reducing welding defects to facilitate deoxygenation reaction of the molten metal. However, many alloys it is necessary to add an element, thus when the addition of many alloying elements to the flux of fine particles during welding going out around the spatter (spatter) developing the flux more in order to obtain sufficient deoxidizing effect of the molten metal the welding operability such as occurring, there is a problem to be lowered.
[16]
[17]
Therefore, it is possible to obtain an excellent low-temperature toughness of the weld in a cryogenic environment for, the welding workability and drawing workability is excellent flux cored wire for cold-rolled steel sheet and development of a method of manufacturing the same situation that is desired.
[18]
[19]
(Prior art document)
[20]
[Patent Document 1] Korea Patent Laid-open No. 2006-107910 No.
[21]
(Patent Document 2) Japanese Unexamined Patent Publication Sho No. 60-46896
[22]
Detailed Description of the Invention
SUMMARY
[23]
One aspect of the present invention is to provide a welding workability and drawing workability is excellent flux cored wire for cold-rolled steel sheet and a method of manufacturing the same.
[24]
[25]
On the other hand, object of the present invention is not limited to the above-described information. An object of the present invention will be understood from the overall context of the present specification, Those having ordinary skill in the art will not have any difficulty to understanding an additional object of the present invention.
[26]
Problem solving means
[27]
In one aspect% by weight of the present invention, C: 0.01 ~ 0.15%, Mn: 0.1 ~ 0.5%, Si: 0.05% or less (0% excluded), P: 0.0005 ~ 0.01%, S: 0.008% or less (0 contains 0.5 to 2.0%, remainder Fe and unavoidable impurities,% is excluded), Al: 0.005 ~ 0.06%, N: 0.0005 ~ 0.003%, Ni
[28]
Microstructure relates to a ferrite area fraction to 93-98% and comprising, acicular bainite with cementite is excellent in low temperature toughness, containing 2-7% tight in that the total flux cored wire for cold-rolled steel sheet.
[29]
[30]
Further, another aspect of the present invention in weight%, C: 0.01 ~ 0.15%, Mn: 0.1 ~ 0.5%, Si: 0.05% or less (0% excluded), P: 0.0005 ~ 0.01%, S: 0.008% or less (excluding 0%), Al: 0.005 ~ 0.06%, N: 0.0005 ~ 0.003%, Ni: 0.5 ~ step of heating the slab containing 2.0%, remainder Fe and unavoidable impurities to 1100 ~ 1300 ℃;
[31]
Phase is finished the heated slab hot rolling temperature to obtain a hot rolled steel sheet by hot rolling such that the 880 ~ 950 ℃;
[32]
Step for winding the hot-rolled steel sheet in a temperature range of 550 ~ 700 ℃;
[33]
To obtain a cold-rolled steel sheet to the take-up the hot-rolled steel sheet cold-rolled to a reduction ratio of 50 to 85% step; And
[34]
A method of manufacturing a cold-rolled steel sheet for use in a flux cored wire including a; step of continuous annealing the cold-rolled steel sheet.
[35]
[36]
In addition, solving means of the above-described problems is, it is not enumerate all features of the present invention. The various features and advantages and effects thereof of the present invention can be understood in more detail with reference to specific embodiments below.
[37]
Effects of the Invention
[38]
According to the present invention, the welding workability and drawing workability it is effective to provide superior flux cored cold-rolled steel sheet and a manufacturing method for the wire.
[39]
Brief Description of the Drawings
[40]
Figure 1 is a picture taken from the microstructure of Honor 2.
[41]
2 is a photo photographed the microstructure of Comparative Example 6.
[42]
Best Mode for Carrying Out the Invention
[43]
Hereinafter, the preferred embodiments of the present invention. However, embodiments of the present invention can be modified in many different forms and is not limited to the embodiments and the scope of the present invention described below. In addition, embodiments of the present invention is provided in order to explain more fully the present invention to those having ordinary skill in the art.
[44]
[45]
Flux -cored wire for cold-rolled steel sheet
[46]
It will now be described in detail with respect to the flux-cored wire for cold-rolled steel sheet according to an aspect of the invention.
[47]
[48]
Cold-rolled steel sheet for use in a flux cored wire according to one aspect of the present invention in weight%, C: 0.01 ~ 0.15%, Mn: 0.1 ~ 0.5%, Si: (excluding 0%), 0.05% or less, P: 0.0005 ~ 0.01 %, S: 0.008% or less (0% excluded), Al: 0.005 ~ 0.06%, N: 0.0005 ~ 0.003%, Ni: 0.5 ~ 2.0%, remainder Fe and unavoidable including impurities, and the microstructure is a area fraction containing 93-98% ferrite, and the needle-like bainite and cementite containing 2-7% in the sum.
[49]
[50]
First, a detailed description of the alloy composition of the present invention. Units or less for each element content refers to a weight% unless otherwise specified.
[51]
[52]
C: 0.01~0.15%
[53]
Carbon (C) is generally an element to be added to improve the strength of steel, and is an element to be added in order to have similar properties to the welding heat affected portion base material.
[54]
If the C content is less than 0.01%, it is insufficient that the aforementioned effect. If, on the other hand, C content exceeds 0.15%, there may occur problems such as breakage during drawing process that occurs due to the high strength or strain hardening. In addition, there is a disadvantage that not only causes the low-temperature welding cracks or joints decreases the impact toughness due to high hardness be carried out a number of heat treatment can be processed into a final product. Therefore, C content may be 0.01 ~ 0.15% is desirable, and more preferably for a welding heat affected portion improved properties 0.02 ~ 0.13%.
[55]
[56]
Mn: 0.1 ~ 0.5%
[57]
In the case of manganese (Mn) to increase the strength of the steel as a solid solution strengthening element serves to improve the hot workability by lowering the Ar3. However, excessive addition of manganese has a large amount of - it is possible to form a sulfide (MnS) precipitates inhibit the river ductility and formability.
[58]
If the Mn content is less than 0.1%, and the red-short occurrence factor is hard to contribute to the stabilization of austenite. On the other hand, if the Mn content exceeds 0.5%, the decrease in ductility, and is a cost increase and the central segregation caused by factors in addition of large amounts of alloy elements, can result in disconnection during the drawing operation. Therefore, Mn content is preferably 0.1 to 0.5%, may be more preferably from 0.2 to 0.45%.
[59]
[60]
Si: 0.05% or less (excluding 0%)
[61]
Since silicon (Si) acts as a factor, as well as act as a break to form an oxide layer on the surface of the steel sheet by combination with oxygen deterioration of surface properties and fell corrosion resistance factors promote hard phase transformation in the weld metal decreases the low temperature toughness that It defines the amount to 0.05% or less. More preferably, the Si content can be less than 0.04%, it is possible and more preferably, 0.02% or less.
[62]
[63]
P: 0.0005~0.01%
[64]
Phosphorus (P) is a case where, while present in the employed elements in steel preferably in order to maintain the rigidity of a certain level of 0.0005% or more is added as an element to raise the solid solution strengthening improve the strength of the steel and the hardness, but the content is more than 0.01% there may be caused a center segregation during casting is reduced, the ductility wire inferior processability. Therefore, P content is preferably of 0.0005 ~ 0.01%, and may be more preferably from 0.001 to 0.009%.
[65]
[66]
S: less than 0.008% (excluding 0%)
[67]
Sulfur (S) content is preferably lower as possible, so that a factor of forming the non-metallic inclusions combined with Mn in steel brittle and glowing (red shortness). Further, when the S content is high, so the problem of lowering the toughness of the base metal of the steel sheet S content is preferably not more than 0.008%, it is possible and more preferably 0.007% or less.
[68]
[69]
Al: 0.005~0.06%
[70]
Aluminum (Al) is an element advantageous for securing a flexible element to be added in order to prevent the material deterioration due to aging at a deoxidizer and an aluminum killed steel, an effect that is significantly greater than when the extremely low temperature.
[71]
If the Al content is less than 0.005%, it is insufficient that the aforementioned effect. If, on the other hand the Al content exceeds 0.06%, the aluminum-oxide (Al 2 O 3 ) and the surface inclusions is increasing by locally to deteriorate the surface properties of the hot rolled material and grain boundaries as well as the HAZ be workability is lowered as and ferrite are formed to be reduced in mechanical properties, may cause a problem that the weld bead (bead) shaped deteriorate after welding. Accordingly, it is the Al content is preferably 0.005 ~ 0.06%. Be more preferably, the Al content is in the range of 0.01 ~ 0.05%, and may be more preferably 0.01 to 0.04%.
[72]
[73]
N: 0.0005~0.003%
[74]
Nitrogen (N) is an element effective for strengthening as present in a solid solution state within the steel, the addition of more than 0.0005% is required to secure the target stiffness. On the other hand, if the N content exceeds 0.003%, the aging property by increasing the pressure as rapidly worse, not according to the denitrification step in steel production there is a problem in that the steel-making workability deteriorate. Therefore, N content is preferably 0.0005% to 0.003%. And more preferably it may be a N content of 0.001 to 0.0027%.
[75]
[76]
Ni: 0.5 ~ 2.0%
[77]
Nickel (Ni) is an element necessary for the low temperature toughness improved to form a stable organization in improving the ductility as well as effective for improving drawing formability cryogenic. If the addition of Ni to the flux component other than the steel sheet has the advantageous effect that a cost-adding the Ni because Ni to be produced in a high purity powder form as a component of the steel sheet. Further, since the fraction which can be added as a flux to the electrode is limited, it is possible to increase the amount of flux another element that affects the weldability, the addition of Ni as a component of the steel sheet can improve the weldability and the like.
[78]
If the Ni content is less than 0.5%, it is insufficient that the aforementioned effect. On the other hand, when the Ni content exceeds 2.0%, the workability may become inferior by the drawing in strength, and can lead to surface defects, Ni has a problem that the manufacturing cost increases because it is an expensive element. Therefore, the Ni content is preferably from 0.5 to 2.0%. And more preferably it may be a Ni content is 0.6 ~ 1.8%.
[79]
[80]
The remaining components of the invention are iron (Fe). However, in the conventional manufacturing process it is not intended from the raw material or the environment, because impurities may be unavoidably incorporated, it is impossible to exclude them. These impurities are, because you know if anyone skilled in the normal manufacturing process does not specifically mention that all the contents herein.
[81]
[82]
In this case, W is, as well as to satisfy the range of the content of each element, defined by the following relation 1 FC is may be 0.5 ~ 4.5. However, in relation to a unit of each element content it is weight%.
[83]
Equation 1: W FC = (25 * C + 0.4 * Mn + 26 * Al) * Ni
[84]
[85]
The relational expression 1 is designed in consideration of the relationship of the elements on the welding workability and the drawing processability.
[86]
W FC case is less than 0.5, there is a problem that at room temperature tissue is the welding operability deteriorates, as the side workability less amount of transformation as a hard glass, but, in order to secure the low temperature toughness, increasing the amount of alloy added to the alloying elements of the flux . Thus, W FC lower limit of is preferably 0.5, it can be a more preferable lower limit is 0.505.
[87]
On the other hand, W FC when the 4.5 exceeded, there is a problem in that manufacturing cost increases with increasing fraction of the mild microstructure with much addition of expensive alloying elements not only be a problem with the breaking of Tube Mill and drawn during welding member occurs . Thus, W FC upper limit of the, and preferably to 4.5, more preferable upper limit may be 4.0, more than the preferred upper limit can be 3.5 days.
[88]
[89]
Microstructure of the cold-rolled steel sheet according to the present invention includes a ferrite with an area fraction 93-98%, and the needle-like bainite and cementite containing 2-7% in the sum.
[90]
Ferrite fraction is less than 93% in the material is cured Tube Mill and drawing can act as a factor of breakage during processing, if it exceeds 98% is that the thickness of the flux cored wire rises because the rigidity is decreased according to the material softening there is a problem. Therefore, the ferrite fraction is preferably a 93-98%, and may be more preferably, 93.5 ~ 97.5%.
[91]
In addition, rigid needle merchant bainite and cementite shall be the sum is controlled to 2 ~ 7%. If the sum is less than 2%, depending on the rigidity is deteriorated, and a problem that increase in thickness of the flux cored wire, exceeds 7%, there is a problem in that workability is deteriorated. Thus, the bainite and cementite is preferably the sum is from 2 to 7%, and may be more preferably 2.5 to 6.5%.
[92]
[93]
At this time, a cold-rolled steel sheet is 200 ~ 300MPa yield strength according to the present invention, the elongation be at least 40%. By satisfying such properties it can be applied preferably as a material for the flux cored wires.
[94]
Is less than the yield strength of 200MPa There are concerns buckling of the tube, in the case of 300MPa exceeded, the dielectric breakdown voltage side of the tube there is a problem such as a glass single strength manufacturing cost increase according to the degree of wear increases in jogwanseong degradation and processing tool according to the increase .
[95]
If the elongation is less than 40%, the worse the workability Tube Mill can arise a problem in that a crack, such as during processing tearing occurs.
[96]
[97]
In addition, cold-rolled steel sheet according to the invention may be up to the welded portion segregation index 0.15%.
[98]
More specifically, means a segregation factor of the welding welds in the flux cored wire produced by using the cold-rolled steel sheet according to the present invention. Weld segregation index can be expressed as the ratio of the area occupied by the piece seokbu additive element in the entire area of ​​the weld.
[99]
When segregation occurs in the weld zone is the concentration of stress to the side during processing seokbu acts as breaking factor. In order to prevent the tearing of the weld zone during secondary processing segregation after welding of the welded part is preferred that the segregation index less than 0.15%.
[100]
As in the conventional flux cored wire is added an element such as nickel (Ni) as an alloying element in the flux rather than the base material in order to secure the low temperature toughness, but a problem of segregation index of the weld rise occurs, the cold-rolled steel sheet according to the invention a may be secured to these factors significantly reduce the segregation of the weld segregation index to less than 0.15% when it uses.
[101]
[102]
Flux cored for wire production method of the cold-rolled steel sheet
[103]
It will now be described in detail a manufacturing method of another aspect of a flux cored wire for cold-rolled steel sheet of the present invention.
[104]
[105]
Production method of another aspect of a flux cored wire for cold-rolled steel sheet of the present invention includes the steps of heating a slab having the above-described alloy composition to 1100 ~ 1300 ℃; Phase is finished the heated slab hot rolling temperature to obtain a hot rolled steel sheet by hot rolling such that the 880 ~ 950 ℃; Step for winding the hot-rolled steel sheet in a temperature range of 550 ~ 700 ℃; To obtain a cold-rolled steel sheet to the take-up the hot-rolled steel sheet cold-rolled to a reduction ratio of 50 to 85% step; And a; and the step of continuously annealing the cold-rolled steel sheet.
[106]
[107]
Slab heating step
[108]
Heat the slab having the above-described alloy composition to 1050 ~ 1300 ℃. This is to perform the subsequent hot rolling process smoothly, and the process for homogenizing the slab.
[109]
The slabs from problems that the heating temperature is subsequently increased rapidly load during hot rolling of less than 1050 ℃, and the other hand, if it exceeds 1300 ℃ as well as energy costs increase, the amount of the surface scale may increase to lead to loss of material have.
[110]
[111]
Hot rolling step
[112]
Wherein the finish hot rolling, the slab heating temperature, hot-rolled so that the 880 ~ 950 ℃ to obtain a hot-rolled steel sheet.
[113]
If the finish rolling temperature is lower than 880 ℃ has been honrip the grain upset proceeds rapidly as the hot rolling is finished at a low temperature area, results in a reduction in the hot rolling resistance and workability. On the other hand, if the finish rolling temperature exceeds 950 ℃ has become a grain size not support a uniform hot-rolled made insufficient throughout the thickness can receive a reduction in the impact toughness due to coarsening of crystal grains.
[114]
[115]
Winding steps
[116]
The hot-rolled steel sheet is wound at a temperature of 550 ~ 700 ℃. At this time, the cooling of the winding former hot rolled steel sheet after hot rolling is run-can be carried out at a table (ROT, Run-out-table) - out.
[117]
If the coiling temperature is less than 550 ℃ there gives an adverse effect on formability by causing the material to create a difference image shows a variation of the behavior of the low temperature the precipitate by the temperature unevenness in the width direction during cooling and keeping. On the other hand, if the coiling temperature exceeds 700 ℃ there arises a problem of deteriorating the surface material and the softened jogwanseong as the dialog is in the final product tissue bath.
[118]
[119]
Cold rolling step
[120]
Cold-rolling the hot-rolled steel sheet to a take-up reduction ratio of 50 to 85% to obtain a cold-rolled steel sheet.
[121]
Rolling reduction is less than 50%, it not only difficult to ensure a uniform material such as a low recrystallization driving force localized tissue growth occurs, in consideration of the thickness of the finished product should work by lowering the thickness of the hot-rolled steel sheet hot-rolling workability there is a significantly worse problems. On the other hand, if the reduction ratio exceeds 85%, the material is a hardened, as well as the risk of cracking during drawing, there is a problem of lowering the cold-rolling workability of a mill load.
[122]
Therefore, the reduction rate is preferably 50 to 85%, and may be more preferably from 65 to 80%.
[123]
[124]
At this time, it may further comprise the step of pickling the hot-rolled steel sheet before cold rolling the winding.
[125]
[126]
Continuous annealing step
[127]
And continuous annealing the cold-rolled steel sheet to ensure the workability and stiffness. From the state in which the intensity increases by a variation introduced in the cold rolling, to secure the strength and workability of the target by performing a stress-relief annealing.
[128]
[129]
In this case, the continuous annealing can be carried out at a temperature range of 700 ~ 850 ℃.
[130]
The annealing temperature lower than 700 ℃ according to deformation is not sufficiently removed have significantly less workability problems. On the other hand, the annealing temperature exceeds 850 ℃ may cause problem in tongpan to continuous annealing in accordance with the high-temperature annealing.
[131]
[132]
At this time, the continuous annealing the cold-rolled steel sheet may be cooled at a cooling rate of 30 ~ 60 ℃ / sec. If when the cooling rate is 60 ℃ / sec are exceeded needle bainite and cementite a large amount can be produced here Tube Mill and may act as a factor of breakage during the drawing process, the cooling rate is 30 ℃ / sec is less than according to the material softening since the rigidity can be lowered because this may cause a problem that the thickness of the flux cored wire increases.
[133]
Mode for the Invention
[134]
The present invention the following examples will be described in detail. However, the following examples are to be noted in that not intended to limit the may make the scope of the present invention to be described in more detail by illustrating the invention. The scope of the present invention is because it is determined by what is a reasonable inference from this information and set forth in the claims.
[135]
To prepare a cold-rolled steel sheet according to the manufacturing conditions described in the after heating the slab having the composition components shown in Table 1 to 1250 ℃, Table 2 below. After continuous annealing, the cooling rate was set to 40 ℃ / sec.
[136]
[137]
To measure the tongpan Castle, yield strength, elongation, workability and microstructures of the cold rolled steel sheet are shown in Table 3.
[138]
Further, to measure the segregation index of a welding portion welded to the low-temperature toughness of the flux cored wire produced by using the cold-rolled steel sheet are shown in Table 3. Utilizing a laboratory pilot (Pilot) was set-welding flux cored entire alloy component composition of the flux so that the Ni content is 1.5% of the wire to produce a wire having a diameter of 1.4mm for each of the case where the voltage 29V, current 150 ~ 180A , the welding speed is a result of the welding test targets for shipbuilding steel strip in conditions of 14cm per minute.
[139]
Yield strength shown in Table 3, the elongation were 200 and when the yield strength of more than 40% elongation and segregation index of 300MPa range satisfying the respective target criteria of less than 0.15% expressed as "O", satisfying the respective characteristics based on If it is not expressed as "X".
[140]
Further, if the workability when the end face processing defects such as tears caused during the drawing process to a cold-rolled steel sheet reduction ratio of 45% "bad", the machining deteriorated not occur was indicated as "good".
[141]
If tongpan castle if there is no rolling load during cold and hot rolling defects such as during continuous annealing heat buckle (Heat buckle) does not occur was indicated by "O", the rolling load occurs or occurrence of defects, such as during continuous annealing heat buckle It was represented by "X".
[142]
[143]
TABLE 1
[144]
TABLE 2
[145]
TABLE 3
[146]
Examples 1 to satisfying all the alloy compositions and manufacturing conditions presented in this invention meets the material 9 was based on the yield strength of 200 ~ 300MPa and an elongation more than 40% of the target, the drawing workability and tongpan property was good. In addition, because the side seokji may tear or crack at the time of secondary processing weld zone to less than 0.15% of the weld does not occur could be obtained a good processability.
[147]
As the microstructure of the invention example 2 be found in Figure 1 taken, by satisfying the alloy composition and the production conditions of the present invention could obtain the microstructure of the invention.
[148]
[149]
Comparative Examples 1 to 4 but the alloy composition was satisfactory in the present invention, a high yield strength to failure to satisfy the manufacturing condition was inferior elongation can be confirmed that even for drawing workability column. In addition, Comparative Example 1 and the case 2 has been poor tongpan. Also, in Comparative Example 1, if the microstructure has been formed by deformation ribs, that is ferrite (deformed ferrite) of interruption of the re-crystallization, compared to areas other than the 42.3% in Example 2 is modified It was observed in the ribs.
[150]
[151]
Comparative Examples 5 to 10 are, if not satisfied, but the production conditions in the present invention is satisfied, the alloy composition. A drawing process and a weld secondary tear or crack during processing of the wire has occurred, depending on in all cases fails to satisfy the work material and the weld segregation index.
[152]
In addition, out of the 200 ~ 300MPa level it does not ensure the tongpan sex or (Comparative Example 10), the yield strength who want to get the present invention or (Comparative Example 5 and Comparative Examples 7 to 10) and did not meet the elongation of the target level (compare examples 6 to 10) was the processability and low temperature toughness to meet the target properties of a cold-rolled steel sheet for use in a flux cored wire is required for an.
[153]
In the Comparative Example 62 is also recorded in the microstructure, it can be confirmed that ferrite is formed by more than 98% by area.
[154]
[155]
Also significantly improved the segregation generation of the weld according to the present invention through the control of the alloy composition and the production conditions as described above and as well as can increase the other flux element content through a reduction in Ni content of the flux low-temperature toughness and welding workability is excellent We were able to obtain the properties of a flux cored welding cold-rolled steel sheet. Therefore, it is possible to reduce the Ni content in the flux is a factor in the case of using a cold-rolled steel sheet of the present invention processes the non-rising, as well as to reduce the weld cracking as significantly reduced my segregation weld, stable workability ensure product It is possible because it was effective in improving workability and cost reduction side can reduce a material deviation in product.
[156]
[157]
Above embodiment has been with reference to describe, understand that without departing from the spirit and scope of the invention defined in the claims below are those skilled in the art can make various modifications and variations to the present invention It will be.

Claims

[Claim 1]By weight%, C: 0.01 ~ 0.15%, Mn: 0.1 ~ 0.5%, Si: 0.05% or less (0% excluded), P: 0.0005 ~ 0.01%, S: (excluding 0%) 0.008%, Al : 0.005 ~ 0.06%, N: 0.0005 ~ 0.003%, Ni: 0.5 ~ 2.0%, remainder Fe and unavoidable including impurities, and the microstructure is comprising 93-98% ferrite with an area fraction, and the needle-shaped bay tight Knight and cementite 2 to 7% contained flux cored wire for cold-rolled steel sheet, which as a total.
[Claim 2]
According to claim 1, wherein the cold-rolled steel sheet is the following relation W 1 defined by the FC 0.5 to 4.5 in that, characterized in flux cored wire for cold-rolled steel sheet. Equation 1: W FC (a single unit of each element content in the above relational expression 1 is% by weight.) = (25 * C + 0.4 * Mn + 26 * Al) * Ni
[Claim 3]
The method of claim 1, wherein the cold-rolled steel sheet has a yield strength is 200 ~ 300MPa, an elongation of not less than 40% flux-cored wire for cold-rolled steel sheet.
[Claim 4]
The method of claim 1, wherein the cold-rolled steel sheet is welded portion segregation index flux core, characterized in that less than 0.15%, the cold-rolled steel sheet for Dwyer.
[Claim 5]
By weight%, C: 0.01 ~ 0.15%, Mn: 0.1 ~ 0.5%, Si: 0.05% or less (0% excluded), P: 0.0005 ~ 0.01%, S: (excluding 0%) 0.008%, Al : 0.005 ~ 0.06%, N: 0.0005 ~ 0.003%, Ni: 0.5 ~ step of heating the slab containing 2.0%, remainder Fe and unavoidable impurities to 1100 ~ 1300 ℃; Phase is finished the heated slab hot rolling temperature to obtain a hot rolled steel sheet by hot rolling such that the 880 ~ 950 ℃; Step for winding the hot-rolled steel sheet in a temperature range of 550 ~ 700 ℃; To obtain a cold-rolled steel sheet to the take-up the hot-rolled steel sheet cold-rolled to a reduction ratio of 50 to 85% step; Method of producing a cold-rolled steel sheet for use in a flux cored wire including a; and the step of continuously annealing the cold-rolled steel sheet.
[Claim 6]
The method of claim 5, wherein the slab W to be defined by the following relation 1 FC process for producing a cold-rolled steel sheet for use in a flux cored wire, characterized in that 0.5 to 4.5. Equation 1: W FC (a single unit of each element content in the above relational expression 1 is% by weight.) = (25 * C + 0.4 * Mn + 26 * Al) * Ni
[Claim 7]
The method of claim 5, wherein the continuous annealing is from 700 to process for producing a cold-rolled steel sheet for use in a flux cored wire, characterized in that performing at a temperature range of 850 ℃.
[Claim 8]
6. The method of claim 5, for the manufacture of a winding hot-rolled steel sheet characterized in that it further comprises the step of pickling the cold-rolled steel sheet for flux cored wire before the cold rolling.
[Claim 9]
The method of claim 7, wherein the method of manufacturing a flux-cored wire for cold-rolled steel sheet, characterized in that for cooling the continuous annealing the cold-rolled steel sheet at a cooling rate of 30 ~ 60 ℃ / sec.