JP2990214B2 - Alloyed molten Zn-plated steel sheet of ultra-low C-base thin hot rolled sheet excellent in workability and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is intended to improve fuel efficiency by reducing the weight of automobiles and to reduce the manufacturing cost of automobile parts.
The present invention relates to an alloyed molten Zn-coated steel sheet of a hot-rolled thin sheet having a tensile strength of 35 kgf / mm ² or more and excellent in workability and, in a preferred embodiment, excellent in vertical cracking resistance, and a method for producing the same. .

[0002]

2. Description of the Related Art From the viewpoint of protection of the global environment and the like, there is a growing need for improving fuel efficiency of automobiles, and weight reduction of vehicle bodies is becoming important. In terms of materials, further thinning and improvement of workability are pursued, and members and the like have a tensile strength of 35%.
There is an increasing demand for extremely low-C thin hot rolled steel sheets of kgf / mm ² or more and Zn-plated steel sheets using the same as base sheets.

In the production of a hot-rolled steel sheet for processing, which emphasizes elongation characteristics, hot rolling is generally performed in the γ region in order to obtain fine grains. For steel with a significantly reduced carbon content, it is necessary to further raise the hot rolling finish temperature. This has been addressed by slab ripening during the slab heating stage, shortening the time required for finish rolling, and increasing the rolling speed. However, for example, in the case of a thin material having a thickness of 1.4 mm or less, a sufficient temperature cannot be secured due to an increase in the rolling time, and the workability of the product may be deteriorated. Such problems become more serious when the direct casting of the continuous casting / hot rolling process and the reduction of the slab heating temperature, which are currently being promoted by material manufacturers, are achieved. The establishment of fine-graining technology for hot rolling of thin hot-rolled steel sheets is an urgent issue to be solved at present.

[0004] First, the problem of the material in the prior art will be described. Extremely low C-Ti steel (0.0014% C-0.15%
Mn-0.028% Al-0.060% Ti) and general automotive mild steel (low C-Al killed steel, 0.05% C-0.21)
% (Mn-0.040% Al) after hot rolling is shown in FIG. When the low C-Al killed steel is transformed during the cooling process after hot rolling, the transformation from γ to α occurs at a temperature of about 820 ° C. or less, while the extremely low C-T
In i-type steel, transformation starts at a temperature of about 870 ° C.

In the hot rolling of a thin material as described above, the finishing temperature is usually 880 ° C. due to an increase in the time required for hot rolling.
The actual situation is as follows. When a very low C steel is rolled at such a temperature, the degree of γ + α dual phase rolling increases, and as shown in FIG. 2, the structure of the product becomes coarse mixed grains or coarse grains with residual strains, and elongation occurs. Significantly deteriorates. It should be further noted that, as shown in FIG. 1, since the transformation start point of the steel is further raised by being processed just above the transformation point, it is necessary to sufficiently secure the finishing temperature of the extremely low C steel. It is necessary to take this temperature rise into consideration, and it is difficult to produce a thin steel sheet having excellent workability.

In particular, in the ultra-low CP added steel having a tensile strength of 35 kgf / mm ² or more, which is the object of the present invention,
The addition of P, which is a ferrite-forming element, further increases the transformation point of steel from γ to α, so that the problem in hot rolling of thin materials becomes large. There has been no report on the production of a thin hot-rolled steel sheet using an extremely low-C steel grade containing 0.04% or more of P.

In recent years, a method of hot rolling in the α region has been proposed as a hot rolling technique for ultra-low C steel, but in order to stably generate a fine-grained structure having excellent workability while hot rolling. Has many issues to be solved. At present, no case of α-range rolling has been reported in steels which have been strengthened by adding Si, Mn, P or the like. Further, it is known that steel to which a large amount of P is added is easily embrittled and, in particular, is often broken when deformed at a low temperature after pressing. This crack is a characteristic one that occurs linearly and is called a vertical crack. In addition, the more embrittlement is, the more it cracks even at a high temperature. The temperature at which a vertical crack occurs is called a vertical crack transition temperature. When a pressed part manufactured from a steel sheet having a high vertical crack transition temperature is used in an automobile, the cold part is used in an environment at a temperature equal to or lower than the vertical crack transition temperature, and there is a possibility that the part may be damaged during traveling. For this reason, it is necessary to lower the vertical crack transition temperature. However, there has been no report of such an attempt made in an ultra-low C steel to which a large amount of P is added.

[0008]

DISCLOSURE OF THE INVENTION The present invention relates to a method for producing an alloyed molten Zn-coated steel sheet using an ultra-low C-based thin hot-rolled steel sheet as an original sheet, even if the hot-rolling finishing temperature is 850 ° C. or less. It is an object of the present invention to provide a technique capable of imparting an excellent elongation and further imparting excellent tackiness characteristics. The alloyed molten Zn-plated steel sheet of the ultra-low C type thin hot rolled sheet having excellent workability according to the present invention is C 0.0080% or less, Si 0.6% or less, and Mn 0.2 to 0.2% by weight. 2.0%, P 0.04 to 0.15%, S 0.015% or less, and Al 0.01 to 0.10%, the balance being iron and unavoidable impurities, and
120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
Satisfies 50Si-150P ≧ 60 (%) and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), mainly consists of polygonal ferrite structure, plate thickness is 1.4mm or less, tensile strength Is 35 kgf / mm ² or more.

According to the present invention, the alloyed molten Zn-coated steel sheet of the ultra-low C type thin hot rolled sheet having excellent workability and resistance to longitudinal cracking has a C content of 0.0080% or less and a Si of 0.6. % Or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015% or less, and Al 0.01 to 0.10%, the balance being iron and unavoidable impurities Consisting of and 120 Mn
+ 100Cu + 200Ni + 100Mo + 150Ti +
100Cr + 1000Nb + 13000B-50Si-
150P ≧ 60 (%), P−80B ≦ 0 (%), and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), mainly consisting of polygonal ferrite structure, and having a plate thickness of 1 .4 mm or less and a tensile strength of 35 kgf / mm ² or more.

Further, the tensile strength according to the present invention is 35 kgf / mm.
^The method for producing an alloyed molten Zn-plated steel sheet of an ultra-low C based thin hot rolled sheet having excellent workability of ² or more is as follows: 0.0080% or less by weight, 0.6% or less of Si, 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015% or less, and Al 0.01 to 0.10%, the balance being iron and unavoidable impurities, and 120 Mn
+ 100Cu + 200Ni + 100Mo + 150Ti +
100Cr + 1000Nb + 13000B-50Si-
When hot rolling a steel satisfying 150P ≧ 60% and 0 ≦ (１ ／) Mn + Ti−P ≦ 0.22 (%), the finishing temperature is 750.
880 ° C., average cooling rate of 10-100 ° C./sec, coil winding temperature of 500 ° C. or less to mainly form a polygonal ferrite structure, pickling the hot-rolled steel sheet,
It is characterized in that the plating process is performed.

The tensile strength according to the present invention is 35 kgf / mm.
^The method for producing an alloyed molten Zn-coated steel sheet of an ultra-low C-based thin hot rolled sheet excellent in workability and longitudinal cracking resistance of ² or more,
0.0080% or less by weight of C, 0.6% or less of Si, 0.2 to 2.0% of Mn, 0.04 to 0.15% of P, 0.015% or less of S, and 0.01% of Al 0.10%, consisting of iron and unavoidable impurities, and 120M
n + 100Cu + 200Ni + 100Mo + 150Ti
+ 100Cr + 1000Nb + 13000B-50Si
-150P ≧ 60%, P-80B ≦ 0 (%), and 0 ≦ (１ ／) Mn + Ti-P ≦ 0.22 (%) When hot rolling a steel, the finishing temperature is 750.
880 ° C., average cooling rate of 10-100 ° C./sec, coil winding temperature of 500 ° C. or less to mainly form a polygonal ferrite structure, pickling the hot-rolled steel sheet,
After reheating to a temperature of 580 ° C. or higher, a plating process is performed.

The technical features of the present invention described above are as follows. 1) Reduction of coarse rolling structure by optimizing chemical composition and hot rolling conditions. 2) Stable formation of a structure mainly composed of polygonal ferrite by cooling control. 3) Ensuring quality of alloy plating by optimizing chemical components and, according to a preferred embodiment, ensuring longitudinal crack resistance.

Based on the experimental results shown in FIGS. 1 and 2, the chemical composition and the hot rolling conditions of the ultra-low C steel giving good elongation were investigated. That is, ultra-low carbon steels of various chemical components shown in Tables 1 and 2 were melted in a small melting furnace, and were forged and rough-rolled.
This was a slab for experimental rolling having a thickness of 0 mm.

[0014]

[Table 1]

[0015]

[Table 2]

In hot rolling, a slab heating temperature of 12
Rolling 6 passes at 00 ° C, final thickness 2.6mm
Steel plate. At this time, the finish rolling temperature was greatly changed in the range of 950 to 750 ° C. by changing the finish entrance temperature. After that, it was quickly cooled with steam and water (average cooling rate: 20 ° C./sec) and inserted into a furnace maintained at 450 ° C.
After 30 minutes, the coil was wound up by cooling the furnace to simulate it. Pickling the steel sheet cooled to room temperature,
The elongation and microstructure were investigated.

The results are expressed as Ceq values (= 120 Mn + 100 C
u + 200Ni + 100Mo + 150Ti + 100Cr
+ 1000Nb + 13000B-50Si-150P)
FIG. In FIG. 3, when the steel type is constant (that is, equivalent to a constant Ceq value), any material having a high finishing temperature exhibits excellent elongation due to polygonal ferrite sizing, but has a low finishing temperature. In the material, coarse grains or mixed grains in which distortion remains are generated, and elongation is deteriorated.

The finishing temperature at the boundary where the elongation is greatly deteriorated is
Depending on the type of steel, it moves to the lower temperature side as the Ceq value increases. In other words, it can be seen that the higher the Ceq value, the lower the temperature of the steel. As described above, the Ceq value of steel that can obtain a good structure or elongation at a finishing temperature of 850 ° C. or less in ordinary thin material rolling is 60 (% by weight).
That is all.

The temperature at the boundary where the elongation is greatly deteriorated is Ceq
It is considered that the reason for the relatively good correspondence with the value is that the change in the Ceq value broadly corresponds to the change in the transformation point from γ to α during cooling or rolling of the steel. However, extremely low C
No report has been made on the transformation point of hot-rolled steel sheet from γ to α, and the Ceq formula in the present invention has been found based on the results of various experiments. The finishing temperature that gives excellent elongation is not always higher than Ar ₃ points. Tests show that a steel with a wider γ + α dual-phase temperature range can have a larger temperature range in which rolling can be performed at _three or less Ar points.

In the case of alloying molten Zn plating of steel, the degree of alloying of the plating layer greatly affects the plating adhesion of the steel sheet. The degree of alloying varies depending on the sheet temperature, Zn plating bath temperature, bath composition, heating rate for alloying, time, and the like. A large impact. Generally, P is known as an element that is difficult to alloy, and Ti is known as an element that is easily alloyed. In the case of an extremely low C steel, including these elements,
At present, it is not clear at all how the chemical composition of steel affects the alloying behavior.

In a normal production line, the above bath composition,
Switching the processing conditions for alloying in a short period of time degrades the productivity, so it is desirable to operate under the condition set as constant as possible. Accordingly, by limiting the chemical composition of steel within a range that does not adversely affect workability and the like, Zn
It would be advantageous if the adhesion of the plating layer could be secured stably.

A steel sheet having the chemical composition shown in Tables 1 and 2 (a hot-rolled steel sheet whose front and back surfaces are ground to a thickness of 2 mm) was alloyed with molten Z
An n-coating (basis weight: 80 g / m ² ) was performed, and the state of alloying and the occurrence of powdering during V-bending were investigated. FIG. 4 shows the results. In FIG. 4, the change of each state corresponds well to the change of (1/5) Mn + Ti-P (% by weight). That is, if the above expression is a value of 0 or less, the adhesion during bending is good, but the alloying is insufficient, so that corrosion resistance, spot weldability and the like become problems. On the other hand, if the value of the above equation exceeds 0.22, the alloying becomes excessive, and the plating adhesion is significantly deteriorated, causing problems such as flaking during bending. From the above, it can be seen that when the value of the above equation is in the range of 0 to 0.22, good alloying plating can be generated.

Next, improvement of the vertical cracking resistance will be described.
FIG. 6 shows the effect of the amounts of P and B added on the results of processing at −40 ° C. after the cup molding. It is apparent that longitudinal cracks can be prevented by adding B. It is unlikely that the temperature drops below -40 ° C even in a cold region. From FIG. 6, it is necessary to add B so that P−80B ≦ 0 (% by weight) in order to suppress the occurrence of vertical cracking at −40 ° C. FIG. 7 shows the effects of P-80B and the soaking temperature on the results of processing at -40 ° C. after the cup molding. From now on, in order to suppress vertical cracks, P-80B ≦ 0 and soaking temperature should be 580
It is clear that the temperature needs to be higher than or equal to ° C.

The present invention has been completed based on the above experimental results. Next, the manufacturing method according to the present invention will be described. The present invention relates to an alloyed molten Zn-plated steel sheet using an ultra-low C-based thin hot-rolled steel sheet as a base sheet, and the C content is limited to 0.008% or less. C content is 0.00
When it exceeds 8%, the decrease in elongation of the final product is large,
Not preferred.

The amount of Si is 0.6% or less. Si is a solid solution strengthening element for steel together with P, and is effective for strengthening extremely low C steel. However, Si is also a ferrite-forming element and raises the transformation point from γ to α. Therefore, excessive addition of Si deteriorates the elongation of a thin hot-rolled steel sheet. Furthermore,
In the manufacturing process from hot rolling to plating,
The upper limit is set to 0.6%, since it is easily concentrated on the surface of the steel sheet and the adhesion may be deteriorated.

The amount of Mn is in the range of 0.2 to 2.0%. Mn
Is extremely effective in lowering the transformation point of steel from γ to α, and the effect is remarkable when the Mn content is 0.2% or more.
However, an excessive addition exceeding 2.0% is not preferable because a low-temperature transformation structure such as bainite is easily generated and elongation is deteriorated. The P content is in the range of 0.04 to 0.15%. It is known that the addition of P is effective as a strengthening element for ultra-low C steels and also effective in improving the corrosion resistance and fatigue strength of steels. Addition is highly desirable. here,
In order to ensure a stable tensile strength of 35 kgf / mm ² or more by adding P, 0.04% or more is necessary. Therefore, the upper limit of the amount of addition is 0.15%, since problems such as insufficient conversion may occur.

The amount of S is set to 0.015% or less. Local elongation of steel is greatly affected by the amount and morphology of non-metallic inclusions.
The amount is preferably reduced by reducing the amount of S, and thus the amount of S needs to be 0.015%. Al content
It is in the range of 0.01 to 0.10%. The steel of the present invention is essentially an Al-killed steel.
At least 01% of Al is required. However, too much Al
Is added, the increase in the amount of inclusions in the steel causes deterioration of elongation and also increases the production cost. Therefore, the upper limit of the amount of Al is 0.10%.

In the present invention, the above-mentioned elements form the basis of the steel of the present invention, but the following elements can be used together with the above-mentioned elements in order to stably produce higher strength steel. Cu, Ni, Cr, Mo and B are
All are effective alloying elements for lowering the transformation point of steel from γ to α and strengthening the steel. However, when any of the elements is added excessively, the formation of a structure such as bainite is promoted and the elongation of the steel is deteriorated. 1.0% or less, Cr is 1.
5% or less, Mo is 0.5% or less, and B is 0.003% or less.

As for B, as described above, in order to suppress the occurrence of vertical cracks, P-80B ≦ 0 (% by weight).
It is necessary to satisfy. Nb, Ti and V are
It has the effect of suppressing the coarsening of the microstructure of steel and is also effective as a strengthening element for steel. Nb is effective for hot rolling of an extremely low C-based thin steel sheet because the transformation point from γ to α decreases when a relatively large amount of Mn is present. Ti is Z
It is also important as an alloying promoting element for the n-plated layer. However, even if Nb, Ti, and V are excessively added, the respective effects are saturated and the manufacturing cost is increased. Therefore, the addition of Nb is 0.08% or less and Ti is added.
0.10% or less and V is 0.10% or less.

Controlling the form by addition of Ca, Zr, REM, etc. is also effective in improving the elongation of the steel. However, when these elements are added excessively,
Since the amount of inclusions is increased to deteriorate the above characteristics, Ca is 0.01% or less, Zr is 0.05% or less, REM
Is 0.05% or less. Further, according to the present invention, as described above, each element needs to satisfy the following formula in order to secure excellent elongation at a relatively low finishing temperature.

120Mn + 100Cu + 200Ni + 1
00Mo + 150Ti + 100Cr + 1000Nb + 1
3000B-50Si-150P ≧ 60 (% by weight) From the viewpoint of alloying the Zn plating layer, the following rules are required based on the experimental results described above. 0 ≦ (１ ／) Mn + Ti−P ≦ 0.22 (% by weight) Next, the limitation of the hot rolling conditions will be described.

The casting of steel may be continuous casting, ingot casting, or thin slab continuous casting. The slab after slab heating or directly carried in from continuous casting is rough-rolled, finish-rolled, and finished to a predetermined thickness. The finishing temperature is 880 ° C. or lower for the purpose of the present invention. Although the lower limit of the finishing temperature is not particularly limited as long as the structure of the final product is mainly a polygonal ferrite structure, it is usually 750 ° C. or higher.

The finish-rolled steel sheet is cooled at an average cooling rate of 10 ° C./sec or more and wound at a temperature of 500 ° C. or less. This is because the hot-rolled sheet structure is mainly made of polygonal ferrite to stably provide a high elongation and to suppress the embrittlement of steel due to segregation of P at the grain boundaries. Although the upper limit of the cooling rate is not particularly limited, it is usually 100 ° C./° C. in consideration of deterioration in flatness due to quenching of a thin steel sheet having a thickness of 1.4 mm or less and deterioration in elongation due to formation of a low-temperature transformed structure such as bainite.
Seconds or less are preferred. The lower limit of the winding temperature is usually 200 ° C., particularly from the viewpoint of flatness.

The reason why the final structure is mainly made of polygonal ferrite is to achieve a stable and high elongation.
Even if sizing is performed at the hot rolling finishing stage, elongation deteriorates when bainite is formed by rapid cooling thereafter. Accordingly, the content of bainite and the like in the final structure is set to 20% by volume or less. The thin hot-rolled steel sheet manufactured in the above process is pickled and subjected to molten Zn plating according to a conventional method, whereby the ultra-low C type thin hot-rolled steel sheet excellent in workability according to the present invention is obtained. Can be obtained. A skin pass step may be inserted before or after pickling.

The above-mentioned molten Zn plating is usually carried out by heating and soaking at a temperature of about 450 ° C. or more and then immersing the steel plate in a plating bath for the purpose of removing surface dirt on the steel plate. . However, as described above, in order to suppress the occurrence of vertical cracks, the soaking temperature needs to be 580 ° C. or higher. After plating, alloying treatment (5
(Heat treatment at 00 ° C. or more for 5 seconds or more) to obtain a product. In the case of extremely low C steel, even if the soaking in the plating line is performed at a high temperature in the α + γ two-phase region, there is no significant change in the microstructure.

The present invention relates to a hot-rolled original sheet alloyed molten Zn-plated steel sheet. The hot-rolled steel sheet according to the present invention is cold-rolled and kept in full hard or further annealed. Even if it is used after applying it, not only there is no problem on the material, but also fine-grained grains in the state of the hot-rolled sheet reduce the in-plane anisotropy of the cold-rolled steel sheet and the cold-rolled thick-plated steel sheet, It works advantageously for increasing the γ value.

[0037]

EXAMPLES Some of the materials used in the basic experiments described above were hot-rolled under various conditions, and ground by grinding the front and back surfaces.
After forming a steel plate having a thickness of mm, an alloyed molten Zn plating treatment was performed, and mechanical properties, plating adhesion and the like were investigated. The manufacturing conditions and the results of the investigation are shown in Tables 3 to 10 and FIGS. 5 to 8.

Of these, Tables 5 to 10 and FIGS. 6 to 8 relate to steel sheets for improving longitudinal cracking resistance in addition to workability.

[0039]

[Table 3]

[0040]

[Table 4]

[0041]

[Table 5]

[0042]

[Table 6]

[0043]

[Table 7]

[0044]

[Table 8]

[0045]

[Table 9]

[0046]

[Table 10]

[0047]

It is evident that the steel sheet satisfying the conditions according to the present invention has excellent elongation, good adhesion and good longitudinal cracking resistance. In the future, with the development of thin hot-rolled steel sheet manufacturing technology, for example, hot-rolled original sheet alloyed molten Zn-plated steel sheet with a thickness of 1.0 mm or less can be sufficiently used as a substitute for the conventional cold-rolled original sheet. it is conceivable that.

[0048]

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the hot rolling temperature and the transformation point from γ to α in ultra-low C-Ti steel and general mild steel for automobiles (low C-Al killed steel).

FIG. 2 is a graph showing the relationship between hot rolling finish temperature and elongation in an extremely low C-Ti steel.

FIG. 3 is a graph showing a relationship between a Ceq value, a rolling finishing temperature, and a structure.

FIG. 4 is a graph showing the relationship between the Fe concentration and the plating adhesion in the plating layer and the amount of a chemical component ((1/5) Mn + Ti-P) of steel.

FIG. 5 is a graph showing a relationship between tensile strength and elongation of steel.

FIG. 6 is a graph showing the relationship between tensile strength and elongation of steel.

FIG. 7 is a graph showing the effect of P and B on the result of processing at −40 ° C. after cup molding.

FIG. 8 is a graph showing the effect of (P-80B) and the soaking temperature on the results of processing at −40 ° C. after cup molding.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C23C 2/28 C23C 2/28 (56) References JP-A-3-44423 (JP, A) JP-A-3-253516 (JP) JP-A-4-346645 (JP, A) JP-A-4-66621 (JP, A) JP-A-2-310355 (JP, A) JP 4-53938 (JP, B2) JP-B 2-48608 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 38/00 301 C21D 9/46 C22C 38/06 C23C 2/06 C23C 2/28

Claims (20)

(57) [Claims] C. 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015% or less in weight%. And Al 0.01 to 0.10%, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
Satisfies 50Si-150P ≧ 60 (%) and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), mainly consists of polygonal ferrite structure, plate thickness is 1.4mm or less, tensile strength Is an alloyed molten Zn-plated steel sheet of an ultra-low C-based hot rolled sheet with excellent workability of 35 kgf / mm ² or more. 2. In% by weight: (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % Or less, and 0.01 to 0.10% of Al. (B) Cu 1.6% or less, Ni 1.0% or less, Cr 1.5% or less, Mo 0.5% or less, and B 0.003% or less Contains at least one element selected from the group consisting of iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
Satisfies 50Si-150P ≧ 60 (%) and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), mainly consists of polygonal ferrite structure, plate thickness is 1.4mm or less, tensile strength Is an alloyed molten Zn-plated steel sheet of an ultra-low C-based hot rolled sheet with excellent workability of 35 kgf / mm ² or more. 3. In% by weight: (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % Or less, and Al 0.01 to 0.10%, and (b) at least selected from the group consisting of Nb 0.08% or less, Ti 0.10% or less, and V 0.10% or less Contains one kind of element, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
Satisfies 50Si-150P ≧ 60 (%) and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), mainly consists of polygonal ferrite structure, plate thickness is 1.4mm or less, tensile strength Is an alloyed molten Zn-plated steel sheet of an ultra-low C-based hot rolled sheet with excellent workability of 35 kgf / mm ² or more. 4. In weight%: (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % Or less, and 0.01 to 0.10% of Al, and (b) at least selected from the group consisting of 0.01% or less of Ca, 0.05% or less of Zr, and 0.05% or less of REM. Contains one kind of element, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
Satisfies 50Si-150P ≧ 60 (%) and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), mainly consists of polygonal ferrite structure, plate thickness is 1.4mm or less, tensile strength Is an alloyed molten Zn-plated steel sheet of an ultra-low C-based hot rolled sheet with excellent workability of 35 kgf / mm ² or more. 5. In weight%: (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % (B) Cu 1.6% or less, Ni 1.0% or less, Cr 1.5% or less, Mo 0.5% or less, and B 0.003% or less, containing at least one element selected from the group consisting of: (c) Nb 0.08% or less, Ti 0.10% or less, and V 0.10% or less Contains at least one selected element, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
Satisfies 50Si-150P ≧ 60 (%) and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), mainly consists of polygonal ferrite structure, plate thickness is 1.4mm or less, tensile strength Is an alloyed molten Zn-plated steel sheet of an ultra-low C-based hot rolled sheet with excellent workability of 35 kgf / mm ² or more. 6. In weight%, C is 0.0080% or less, Si is 0.6% or less, Mn is 0.2 to 2.0%, P is 0.04 to 0.15%, S is 0.015% or less, And 0.01 to 0.10% of Al, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
50Si-150P ≧ 60 (%), P−80B ≦ 0 (%), and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), mainly composed of polygonal ferrite structure, Is an alloyed molten Zn-plated steel sheet of an ultra-low C-base thin hot rolled sheet with excellent workability and longitudinal cracking resistance of 1.4 mm or less and tensile strength of 35 kgf / mm ² or more. 7. In weight%: (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % Or less, and 0.01 to 0.10% of Al, and (b) Cu 1.6% or less, Ni 1.0% or less, Cr 1.5% or less, Mo 0.5% or less, And B 0.0003% or less containing at least one element selected from the group consisting of iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
50Si-150P ≧ 60 (%), P−80B ≦ 0 (%), and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), mainly composed of polygonal ferrite structure, Is an alloyed molten Zn-coated steel sheet of an ultra-low-C thin hot rolled sheet with excellent workability and longitudinal cracking resistance of 1.4 mm or less and tensile strength of 35 kgf / mm ² or more. 8. In% by weight: (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % Or less, and Al 0.01 to 0.10%, and (b) at least selected from the group consisting of Nb 0.08% or less, Ti 0.10% or less, and V 0.10% or less Contains one kind of element, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
50Si-150P ≧ 60 (%), P−80B ≦ 0 (%), and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), mainly composed of polygonal ferrite structure, Is an alloyed molten Zn-coated steel sheet of an ultra-low-C thin hot rolled sheet with excellent workability and longitudinal cracking resistance of 1.4 mm or less and tensile strength of 35 kgf / mm ² or more. 9. In weight%: (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % Or less, and 0.01 to 0.10% of Al, and (b) at least selected from the group consisting of 0.01% or less of Ca, 0.05% or less of Zr, and 0.05% or less of REM. Contains one kind of element, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
50Si-150P ≧ 60 (%), P−80B ≦ 0 (%), and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), mainly composed of polygonal ferrite structure, Is an alloyed molten Zn-coated steel sheet of an ultra-low-C thin hot rolled sheet with excellent workability and longitudinal cracking resistance of 1.4 mm or less and tensile strength of 35 kgf / mm ² or more. 10. In weight%: (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % (B) Cu 1.6% or less, Ni 1.0% or less, Cr 1.5% or less, Mo 0.5% or less, and B 0.003% or less, containing at least one element selected from the group consisting of: (c) Nb 0.08% or less, Ti 0.10% or less, and V 0.10% or less Contains at least one selected element, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
50Si-150P ≧ 60 (%), P−80B ≦ 0 (%), and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), mainly composed of polygonal ferrite structure, Is an alloyed molten Zn-coated steel sheet of an ultra-low-C thin hot rolled sheet with excellent workability and longitudinal cracking resistance of 1.4 mm or less and tensile strength of 35 kgf / mm ² or more. 11. The composition according to claim 1, wherein C is 0.0080% or less, Si is 0.6% or less, Mn is 0.2 to 2.0%, P is 0.04 to 0.15%, S is 0.015% or less. And 0.01 to 0.10% of Al, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
When hot rolling a steel satisfying 50Si-150P ≧ 60% and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), the finishing temperature is 750.
880 ° C., average cooling rate of 10-100 ° C./sec, coil winding temperature of 500 ° C. or less to mainly form a polygonal ferrite structure, pickling the hot-rolled steel sheet,
35kgf / mm tensile strength characterized by plating
^A method for producing an alloyed molten Zn-plated steel sheet of an ultra-low C-base thin hot rolled sheet having excellent workability of ² or more. 12. In weight%: (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % Or less, and 0.01 to 0.10% of Al, and (b) Cu 1.6% or less, Ni 1.0% or less, Cr 1.5% or less, Mo 0.5% or less, And B 0.0003% or less containing at least one element selected from the group consisting of iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
When hot rolling a steel satisfying 50Si-150P ≧ 60% and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), the finishing temperature is 750.
880 ° C., average cooling rate of 10-100 ° C./sec, coil winding temperature of 500 ° C. or less to mainly form a polygonal ferrite structure, pickling the hot-rolled steel sheet,
35kgf / mm tensile strength characterized by plating
^A method for producing an alloyed molten Zn-plated steel sheet of an ultra-low C-base thin hot rolled sheet having excellent workability of ² or more. 13. In% by weight: (a) 0.0000% or less of C, 0.6% or less of Si, 0.2 to 2.0% of Mn, 0.04 to 0.15% of P, 0.015% of S % Or less, and Al 0.01 to 0.10%, and (b) at least selected from the group consisting of Nb 0.08% or less, Ti 0.10% or less, and V 0.10% or less Contains one kind of element, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
When hot rolling a steel satisfying 50Si-150P ≧ 60% and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), the finishing temperature is 750.
880 ° C., average cooling rate 10-100 ° C./sec, coil winding temperature 500 ° C. or less, thereby mainly forming a polygonal ferrite structure, and pickling the hot-rolled steel sheet,
35kgf / mm tensile strength characterized by plating
^A method for producing an alloyed molten Zn-plated steel sheet of an ultra-low C-base thin hot rolled sheet having excellent workability of ² or more. 14. In weight%: (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % Or less, and 0.01 to 0.10% of Al, and (b) at least selected from the group consisting of 0.01% or less of Ca, 0.05% or less of Zr, and 0.05% or less of REM. Contains one kind of element, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
When hot rolling a steel satisfying 50Si-150P ≧ 60% and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), the finishing temperature is 750.
880 ° C., average cooling rate of 10-100 ° C./sec, coil winding temperature of 500 ° C. or less to mainly form a polygonal ferrite structure, pickling the hot-rolled steel sheet,
35kgf / mm tensile strength characterized by plating
^A method for producing an alloyed molten Zn-plated steel sheet of an ultra-low C-base thin hot rolled sheet having excellent workability of ² or more. 15. In weight%, (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % (B) Cu 1.6% or less, Ni 1.0% or less, Cr 1.5% or less, Mo 0.5% or less, and B 0.003% or less, containing at least one element selected from the group consisting of: (c) Nb 0.08% or less, Ti 0.10% or less, and V 0.10% or less Contains at least one selected element, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
When hot rolling a steel satisfying 50Si-150P ≧ 60% and 0 ≦ (1/5) Mn + Ti−P ≦ 0.22 (%), the finishing temperature is 750.
880 ° C., average cooling rate of 10-100 ° C./sec, coil winding temperature of 500 ° C. or less to mainly form a polygonal ferrite structure, pickling the hot-rolled steel sheet,
35kgf / mm tensile strength characterized by plating
^A method for producing an alloyed molten Zn-plated steel sheet of an ultra-low C-base thin hot rolled sheet having excellent workability of ² or more. 16. In terms of% by weight, C is 0.0080% or less, Si is 0.6% or less, Mn is 0.2 to 2.0%, P is 0.04 to 0.15%, S is 0.015% or less, And 0.01 to 0.10% of Al, the balance being iron and unavoidable impurities, and
n + 100Cu + 200Ni + 100Mo + 150Ti
+ 100Cr + 1000Nb + 13000B-50Si
-150P ≧ 60%, P-80B ≦ 0 (%), and 0 ≦ (１ ／) Mn + Ti-P ≦ 0.22 (%) When hot rolling a steel, the finishing temperature is 750.
880 ° C., average cooling rate of 10-100 ° C./sec, coil winding temperature of 500 ° C. or less to mainly form a polygonal ferrite structure, pickling the hot-rolled steel sheet,
After reheating to a temperature of 580 ° C. or higher, a hot-rolled sheet of ultra-low C based material with excellent workability and longitudinal cracking resistance having a tensile strength of 35 kgf / mm ² or more, characterized by being subjected to plating treatment. A method for producing an alloyed molten Zn-plated steel sheet. 17. In weight%: (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % Or less, and 0.01 to 0.10% of Al, and (b) Cu 1.6% or less, Ni 1.0% or less, Cr 1.5% or less, Mo 0.5% or less, And at least one element selected from the group consisting of B and 0.003% or less, with the balance being iron and unavoidable impurities, and
0Mn + 100Cu + 200Ni + 100Mo + 150
Ti + 100Cr + 1000Nb + 13000B-50
When hot rolling a steel satisfying Si-150P ≧ 60%, P−80B ≦ 0 (%), and 0 ≦ (１ ／) Mn + Ti−P ≦ 0.22 (%), the finishing temperature is 750.
880 ° C., average cooling rate of 10-100 ° C./sec, coil winding temperature of 500 ° C. or less to mainly form a polygonal ferrite structure, pickling the hot-rolled steel sheet,
After reheating to a temperature of 580 ° C. or higher, a hot-rolled sheet of ultra-low C based material with excellent workability and longitudinal cracking resistance having a tensile strength of 35 kgf / mm ² or more, characterized by being subjected to plating treatment. A method for producing an alloyed molten Zn-plated steel sheet. 18. In% by weight: (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % Or less, and Al 0.01 to 0.10%, and (b) at least selected from the group consisting of Nb 0.08% or less, Ti 0.10% or less, and V 0.10% or less Contains one kind of element, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
When hot rolling a steel satisfying 50Si-150P ≧ 60%, P−80B ≦ 0 (%), and 0 ≦ (１ ／) Mn + Ti−P ≦ 0.22 (%), the finishing temperature is 750.
880 ° C., average cooling rate of 10-100 ° C./sec, coil winding temperature of 500 ° C. or less to mainly form a polygonal ferrite structure, pickling the hot-rolled steel sheet,
After reheating to a temperature of 580 ° C. or higher, a hot-rolled sheet of ultra-low C based material with excellent workability and longitudinal cracking resistance having a tensile strength of 35 kgf / mm ² or more, characterized by being subjected to plating treatment. A method for producing an alloyed molten Zn-plated steel sheet. 19. In weight%: (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % Or less, and 0.01 to 0.10% of Al, and (b) at least selected from the group consisting of 0.01% or less of Ca, 0.05% or less of Zr, and 0.05% or less of REM. Contains one kind of element, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
When hot rolling a steel satisfying 50Si-150P ≧ 60%, P−80B ≦ 0 (%), and 0 ≦ (１ ／) Mn + Ti−P ≦ 0.22 (%), the finishing temperature is 750.
880 ° C., average cooling rate of 10-100 ° C./sec, coil winding temperature of 500 ° C. or less to mainly form a polygonal ferrite structure, pickling the hot-rolled steel sheet,
After reheating to a temperature of 580 ° C. or higher, a hot-rolled sheet of ultra-low C based material with excellent workability and longitudinal cracking resistance having a tensile strength of 35 kgf / mm ² or more, characterized by being subjected to plating treatment. A method for producing an alloyed molten Zn-plated steel sheet. 20% by weight (a) C 0.0080% or less, Si 0.6% or less, Mn 0.2 to 2.0%, P 0.04 to 0.15%, S 0.015 % (B) Cu 1.6% or less, Ni 1.0% or less, Cr 1.5% or less, Mo 0.5% or less, and B 0.003% or less, containing at least one element selected from the group consisting of: (c) Nb 0.08% or less, Ti 0.10% or less, and V 0.10% or less Contains at least one selected element, the balance being iron and unavoidable impurities, and 120Mn + 100Cu + 200Ni + 100Mo + 1
50Ti + 100Cr + 1000Nb + 13000B-
When hot rolling a steel satisfying 50Si-150P ≧ 60%, P−80B ≦ 0 (%), and 0 ≦ (１ ／) Mn + Ti−P ≦ 0.22 (%), the finishing temperature is 750.
880 ° C., average cooling rate of 10-100 ° C./sec, coil winding temperature of 500 ° C. or less to mainly form a polygonal ferrite structure, pickling the hot-rolled steel sheet,
After reheating to a temperature of 580 ° C. or higher, a hot-rolled sheet of ultra-low C based material with excellent workability and longitudinal cracking resistance having a tensile strength of 35 kgf / mm ² or more, characterized by being subjected to plating treatment. A method for producing an alloyed molten Zn-plated steel sheet.