JP2000129390A - Soft high carbon steel sheet for working capable of eliminating pickling stage, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily manufacture a soft high carbon steel sheet for working, usable for the manufacture of automobile parts or parts of other industrial products. SOLUTION: This steel sheet can be manufactured by subjecting a steel, which has a composition consisting of 0.10-0.50% C, <=0.5% Si, 0.50-1.50% Mn, <=0.03% P, <=0.01% S, 0.03-0.10% sol.Al, <=0.01% N, 0.50-1.50% Cr, and the balance Fe with inevitable impurities and containing, if necessary, either or both of 0.1-1.0% Mo and 0.1-2.0% Ni, to hot rolling under the ordinary conditions and then applying annealing at temperatures ranging from 600 deg.C to the Ac1 transformation point under the condition that index Z given by equation Z= T×(20+Log t)}/1000 takes a value from 18 to 21. In the equation, T is annealing temperature (K) and (t) is annealing temperature holding time (Hr).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-processing soft carbon steel sheet capable of omitting a pickling step used for manufacturing parts of automobiles or other industrial products, and a method for producing the same.

[0002]

2. Description of the Related Art Hitherto, parts for automobiles or other industrial products have been manufactured by hot forging from bar steel or bar steel, finishing grinding, and then heat-treating. For example, parts having a thickness of about 10 mm, such as pole parking, which are parts of automatic transmissions for automobiles, are subjected to hot forging from steel bars and rods, and then subjected to grinding and heat treatment (simple quenching / tempering or carburizing, heat treatment such as nitriding). It was manufactured by applying.

In recent years, manufacturers have been reviewing the manufacturing process from the viewpoint of cost reduction. The process of streamlining the manufacturing process is considered to be the production of the above-mentioned parts as well as the production of precision punching and heat treatment (especially carburizing and quenching) from thin plates, or some of them have been put to practical use, but due to the thin plates used for part production. Various problems have arisen.

[0004] For example, in the hot-rolled steel strip having a thickness of 6.0 mm or more, there is almost no equipment capable of pickling coils in the steelmaking industry in Japan.
In some cases, precision punching is performed in the state of hot rolling with scale attached. Precision punching in such a state is very problematic in manufacturing due to severe wear of the mold or flaws in the mold due to the scale attached to the surface.

[0005] Further, when the plate thickness is 6.0 mm or more, there is a case where descaling is performed by shot blasting because there is almost no equipment capable of pickling coils in the steelmaking industry in Japan.
However, in descaling by shot blasting, the scale of the scale slightly remains or shot grains remain on the steel sheet, so that the press die is severely worn during punching. Compared to ordinary continuous pickling, descaling by shot blasting is very expensive.

[0006] Further, a method in which a plate having a thickness of 6.0 mm or more is cut and then subjected to batch pickling can be adopted. In this case, after the plate is cut, batch pickling can be performed and then annealing can be performed. However, when batch pickling and annealing are performed on a cut plate, the pickling cost becomes extremely high due to the batch processing, and punching in a coil shape cannot be performed.

[0007] Since many parts manufactured by precision punching generally have complicated shapes, manufacturing or repairing a punching die is very expensive, and manufacturing and repairing the die occupying the entire process cost. The cost for is a very large percentage. Therefore, in applications for parts manufactured by such precision punching, there is a demand for a soft material with less wear of the mold, that is, a soft material.

[0008] As a steel sheet for precision punching and its manufacturing method, C: 0.05 to 0.18%, Si: 0.40% or less, Mn: 0.60 to 1.20
%, Cr: 0.80% or less, B: 0.0005 to 0.005%, Al: 0.080% or less, if necessary, contains Ti: 0.05% or less, the balance being Fe and unavoidable impurities, precision punching steel sheet, Alternatively, a steel slab of the above composition is heated to 1100 ° C. or more, and this is precision punched by hot rolling under a temperature control of a finishing temperature of 780 to 930 ° C. and a winding temperature of 510 to 720 ° C. in a hot rolling step. Production method of steel sheet for use (JP-A-58-104160), C:
0.30 ~ 0.70%, Si: 0.01 ~ 0.50%, Mn: 0.50 ~ 2.00%, P: 0.0
3% or less, S: 0.003-0.05%, soL.Al: 0.07% or less, Cr: 0.05
~ 0.50%, N: 0.01% or less, if necessary Ni, Cu, Mo,
Contains at least one or more of Ti, B, and Ca, with the balance being Fe
And high-carbon hot-rolled steel sheet excellent in punching workability, which is composed of a mixed structure of ferrite and pearlite, or a steel having the above composition, which is composed of a mixed structure of ferrite and pearlite, is hot-rolled at a finishing temperature of the Ar3 transformation point or higher, and thereafter After cooling at an average cooling rate of 20 to 70 ° C / sec to the winding temperature, 530 to 6
A method for producing a high-carbon hot-rolled steel sheet excellent in punching workability at a temperature of 70 ° C. has been proposed (JP-A-8-337843).

[0009] Further, C: 0.2-1.3%, Si: 0.1-1.0%, Mn: 0.05-
2.0%, P: 0.05% or less, S: 0.05% or less, Al: 0.01 to 0.2%, N:
After heating a high carbon steel material containing 0.05% or less and the balance of Fe and unavoidable impurities to a temperature of 1000 to 1300 ° C,
Perform rough rolling with a rolling reduction of 50% or more in the temperature range of Ar3 transformation point or more and 950 ° C or less, and then reduce the rolling rate by 10% or more in the temperature range of 600 ° C or more and 600 ° C or more and less than the Ar1 transformation point.
Finish rolling at less than 0%, at this time, at least for the final stand of the finishing mill rolling at a wear coefficient μ of 0.15 or more under the conditions, and subsequently winding in a temperature range of 450 ~ 700 ° C.,
Further, there has been proposed a method for producing a high-carbon hot-rolled steel sheet excellent in punching workability by performing annealing at a temperature range of 500 to 740 ° C. for 10 seconds to 8 hours (Japanese Patent Laid-Open No. 8-269541).

[0010]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 58-104160
The steel sheet disclosed in Japanese Unexamined Patent Publication No. H8-337843 and Japanese Patent Application Laid-Open No. H8-337843 have a mixed structure of ferrite and pearlite, so when performing precision punching, the abrasion of the mold is large, and the cost of mold care is increased. Has the disadvantage that the production cost is very high.

[0011] Further, the method disclosed in JP-A-8-269541 is
When performing precision punching, there is a large possibility that cracks will occur on the punched end surface (shear surface). In the annealing treatment of this method,
The surface decarburization of the base metal can be so large that it cannot be recovered by normal carburizing.

[0012] An object of the present invention is to solve the above-mentioned disadvantages of the prior art, to soften a steel plate having a thickness of 6.0 mm or more, which cannot be continuously pickled with existing equipment, and to make parts for automobiles or other industrial products. An object of the present invention is to provide a high carbon steel sheet for processing which can be used for production and a method for producing the same.

[0013]

Means for Solving the Problems The present inventors have enthusiastically promoted research and development for overcoming the above-mentioned conventional problems and obtaining a steel material which can cope with a new manufacturing process for parts such as automobiles.
As a result, it has been found that spheroidizing annealing of carbides can be performed in a hot-rolled state by optimizing the use of chemical components, especially Cr, and the annealing method. By adding Cr, the surface scale generated at the time of hot rolling is reduced at the time of annealing to be easily formed into a foil, and thus can be easily removed in a material processing step such as slit processing. As a result, it was found that a soft steel plate for precision punching could be manufactured without performing pickling. In addition, it has been found that the addition of Cr suppresses carburization of the surface layer, thereby facilitating annealing.

[0014] The soft high carbon steel sheet for processing according to the present invention which can omit the pickling step is as follows: C: 0.10 to 0.50%, Si: 0.5% or less, Mn: 0.50 to
1.50%, P: 0.03% or less, S: 0.01% or less, sol.Al: 0.03-0.10
%, N: 0.01% or less and Cr: 0.50 to 1.50% or less, if necessary, one or two of Mo: 0.1 to 1.0%, Ni: 0.1 to 2.0%
Contains seeds, with the balance being Fe and unavoidable impurities.

[0015] The steel sheet of the present invention is characterized in that, in order to promote the reduction of scale during annealing and to suppress the decarburization of the surface layer, in particular, 0.5 to 1.5% of Cr is added as a component. As a result, the surface scale of the hot-rolled steel sheet is easily reduced to a foil shape during annealing, and as a result, can be easily removed in a material processing step such as slit processing, so that soft precision punching can be performed without performing pickling. Can be manufactured. Also, since decarburization of the surface layer is suppressed,
Annealing is facilitated, and a steel sheet having a thickness of 6.0 mm or more, which cannot be continuously pickled, can be softened, and the manufacturing cost of parts for automobiles or other industrial products can be rationalized.

[0016] The method for producing a soft high carbon steel sheet for processing capable of omitting the pickling step of the present invention is as follows: C: 0.10 to 0.50%, Si: 0.5% or less,
Mn: 0.50-1.50%, P: 0.03% or less, S: 0.01% or less, sol.Al:
0.03-0.10%, N: 0.01% or less and Cr: 0.50-1.50%, Mo: 0.1-1.0%, Ni: 0.1-2.0% as required
A hot-rolled steel strip obtained by hot rolling a steel slab containing one or two types, the balance being Fe and unavoidable impurities, under normal conditions, in a temperature range of 600 ° C or higher and A _C1 transformation point or lower. And annealing is performed so that the range of the index Z obtained by the following equation (1) is 18 or more and 21 or less. Z = {T × (20 + Log t)} / 1000 Equation (1) where T: annealing temperature (K), t: annealing temperature holding time (Hr)

[0017] As described above, a hot-rolled steel sheet obtained by hot-rolling a steel slab having a defined chemical composition under normal conditions is heated to 600 ° C.
Above the temperature range of the _C1 transformation point or less, and by performing the annealing to the range of the index Z obtained in the above formula (1) is 18 or more and 21 or less, without pickling, soft and after annealing It is possible to manufacture a steel sheet for precision punching excellent in the removability of reduced scale.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the chemical components of a steel sheet are specified for the following reasons. C is an effective element for increasing the strength and hardenability of steel, but 0.1%
If it is less than 0.5%, the hardness of the core of the material is insufficient, and if it exceeds 0.5%, the hardness after annealing becomes high, and the precision punching property deteriorates.

[0019] Si is an element useful not only for improvement of hardenability but also for deoxidation. However, if it exceeds 0.5%, the hardness of the steel sheet increases, and it is economically disadvantageous. .

Mn is added to improve hardenability and prevent brittleness during hot rolling by fixing S, but if it is less than 0.5%, it is sufficient for both hardenability and prevention of brittleness reduction. If the effect is not obtained, and if it exceeds 1.50%, not only the effect is saturated, but also the alloy addition cost becomes very expensive, so the content was set to 0.50 to 1.50%.

[0021] If the content of P exceeds 0.03%, the toughness, particularly the toughness after the heat treatment is reduced, so the content of P is set to 0.03% or less.

S is an element effective for improving the punching property.
If it exceeds 0.01%, the cleanliness becomes poor, and the brittleness during hot rolling worsens.

Sol.Al is used to fix N in the deoxidizing material and steel as AlN. If it is less than 0.03%, its effect is not sufficient, and if it exceeds 0.10%, the effect is only saturated. However, since the cost of alloy addition increases, 0.03-0.10
%.

N forms AlN and is effective in refining austenite, but when it exceeds 0.01%, it causes embrittlement of the steel sheet,
Further, in order to reduce the effect of Cr by forming CrN, the content is set to 0.01% or less.

[0025] Cr is usually added to improve the strength and hardenability, but if it is less than 0.50%, when annealing is performed with the surface scale adhered, the decarburization of the surface layer portion is suppressed and the reduced scale after annealing is reduced. The effect of improving peelability is not sufficient,
Further, when the content exceeds 1.5%, not only the effect is saturated, but also the alloy addition cost increases, so the content is set to 0.50 to 1.50%.

The reasons for limiting the amounts of the essential components have been described above. In order to further improve the mechanical properties, the following elements can be added as necessary in addition to the alloy elements.

Mo is an element for improving the tempering softening resistance.
Even if tempering is performed at a temperature around 0 ° C., high toughness can be obtained while maintaining a certain degree of hardness, which also contributes to improvement of wear resistance.However, if it is less than 0.1%, the effect is not sufficient. .
If it exceeds 0%, the effect is saturated, and not only the alloy addition cost increases, but also the base metal hardness increases, so that it is added as needed in the range of 0.1 to 1.0%.

[0028] Ni has the effect of increasing the hardenability and the toughness, but if it is less than 0.1, the effect is not sufficient, and if it exceeds 2.0%, the effect is saturated, the base metal hardness increases, and 0.1-2.0% due to increased alloy addition cost
It is added as needed within the range.

[0029] The hot rolling under ordinary conditions in the present invention is as follows.
This means that a steel slab having the specified chemical composition is heated to 1050 to 1300 ° C., then hot-rolled at a finishing temperature equal to or higher than the Ar3 transformation point, and wound at a winding temperature of 500 ° C. to 700 ° C.

[0030] The degree of softening during annealing is determined by a combination of annealing temperature and annealing time. When annealing a hot-rolled steel sheet in the present invention, since the hot-rolled steel sheet is annealed as it is, there is a surface scale generated during the hot rolling, and it is necessary that this scale can be easily removed after the annealing. If the annealing temperature is too low or the annealing time is too short, not only does not sufficiently soften, but because the scale remains in close contact with the steel sheet surface, it is difficult to remove the scale on the surface after annealing. . Conversely, if the annealing temperature is too high or the annealing time is too long,
Softening occurs sufficiently, and the scale of the steel sheet surface is reduced and the removability is improved, but decarburization occurs near the surface of the steel sheet, and when machine parts are created, the fatigue strength decreases,
It causes important problems such as reduced wear resistance. These effects appear as a combined effect of the annealing temperature and the annealing time as described above.

As a result of various studies by the present inventors, the annealing temperature of the hot-rolled steel sheet in the present invention is set to a temperature range of 600 ° C. or more and A _C1 transformation point or less, and an index Z obtained by the above equation (1) is obtained. It has been found that the combined effect of the annealing temperature and the annealing time can be unitarily expressed by using. Therefore, as a result of organizing the test data using this index Z, as shown in FIG. 1,
When the index Z is less than 18, the hardness is high without sufficient softening, and it is difficult to remove the scale from the surface after annealing while the scale remains in close contact with the steel sheet surface. Further, the index Z is 21
If the ratio exceeds the above range, the decarburized layer on the surface of the steel sheet becomes large, causing significant problems such as a decrease in fatigue strength and a decrease in wear resistance when machine parts are produced. Therefore, the index Z is 18-21,
It has been concluded that a steel sheet that is soft and has excellent removability of reduced scale after annealing can be produced by controlling the thickness to desirably in the range of 19 to 20.

[0032] When the annealing temperature of the hot-rolled steel sheet is lower than 600 ° C, not only the sufficient softening does not occur, but also the scale on the steel sheet surface remains in close contact. Further, when the temperature exceeds the _AC1 transformation point, decarburization occurs near the surface of the steel sheet, and when a mechanical part is produced, important problems such as a decrease in fatigue strength and a decrease in wear resistance are caused.

Therefore, in the annealing of the hot-rolled steel sheet, the annealing temperature is selected from a temperature range of 600 ° C. or more and A _C1 transformation point or less,
And, the annealing temperature (K) in the above formula (1), K = annealing temperature
(° C.) +273.15, the index Z in the above formula (1) is 18
The annealing time may be determined so as to be 21 to 21, preferably 19 to 20.

[0034]

Example After steels of the present invention having the chemical components shown in Table 1 were melted, the steels were continuously cast to form slabs, and each slab was heated to 1050 to 1300 ° C. and then transformed into Ar3. Hot rolling was performed at a finishing temperature of not less than the point, and the film was wound at a winding temperature of 500 to 700 ° C. to produce a hot-rolled steel sheet having a thickness of 10 mm. Each hot-rolled steel sheet, without pickling, in the temperature range shown in Table 2, and, as shown in Table 2, the index Z obtained from the above formula (1) is controlled in the range of 19 to 21 to anneal. did. A test piece was collected from each of the obtained annealed hot-rolled steel sheets, and the base metal hardness (Hv10kg) was measured according to the Vickers hardness test method specified in JIS Z 2244,
The decarburized layer depth on the surface was measured according to the method for measuring the decarburized layer depth of steel specified in JIS G 0558. The results are shown in Table 2.

[0035]

【table 1】

[0036]

[Table 2]

As shown in Tables 1 and 2, the steel sheets of Test Nos. 1 to 28 manufactured from Steel Nos. 1 to 28 satisfying the component composition of the present invention and satisfying the annealing conditions are the base metals. Hardness (Hv10kg) 140-180
And the depth of the decarburized layer on the surface is suppressed to 37 μm or less.

[0038]

[Comparative Example] After smelting comparative steels of steel Nos. 31 to 51 having the chemical components shown in Table 3, continuous casting was performed to form slabs. Each slab was heated to 1050 to 1300 ° C, and then the Ar3 transformation point was obtained. Hot rolling at the above finishing temperature, winding at a winding temperature of 500 to 700, sheet thickness of 10
mm hot rolled steel sheet was manufactured. Each hot-rolled steel sheet, without pickling, in the temperature range shown in Table 4, and annealed by controlling the index Z obtained from the above formula (1) to a range of 17 to over 22 as shown in Table 4. did. A test piece was collected from each of the obtained annealed hot-rolled steel sheets, and the base metal hardness (Hv10 kg) and the depth of the decarburized layer on the surface were measured in the same manner as in the example. The results are shown in Table 4.

[0039]

[Table 3]

[0040]

[Table 4]

As shown in Tables 3 and 4, the test N using steel No. 31
o.29 has a low C content, so the base metal hardness required for precision punching applications where this steel material is used is 140 to 180 Hv10
kg was not obtained. In test No. 30 using steel No. 32, since both the annealing temperature and the index Z were out of the range of the present invention, a base material hardness of 140 to 180 Hv 10 kg required for precision punching applications could not be obtained. Test No. 31 using steel No. 33 was Ni
Although the aim was to improve the toughness after heat treatment by the addition, the objective could not be achieved because the amount of Ni added was outside the range of the present invention. In test No. 32 using steel No. 34, the toughness after heat treatment was deteriorated because P was too high. In Test Nos. 33 and 37 using steel Nos. 35 and 39, the amount of C was too large, so that the base material hardness exceeded 180 Hv10 kg, and the precision punching property deteriorated.

[0042] In test No. 34 using steel No. 36, the S content was too large, so that the hot workability was lowered and surface flaws were frequently generated during hot rolling. In test No. 35 using steel No. 37, since the amount of Si was too large, the base metal hardness exceeded 180 Hv10 kg, and the precision punching property deteriorated. In test No. 36 using steel No. 38, since the amount of Cr was small, the surface scale did not peel off after annealing, which was a great obstacle during punching. Test No.38 using steel No.40
However, although the amount of Mo added was larger than the range of the present invention, there was no problem in performance, but the cost was high. Test No.39 using steel No.41
Has an insufficient amount of sol.Al, resulting in insufficient deoxidation. In test No. 40 using steel No. 42, since the annealing conditions were excessive (index Z ≧ 22), the depth of the surface decarburized layer exceeded 100 μm, and the performance as a part could not be satisfied. steel
In test No. 41 using No. 43, the quenchability was insufficient because the amount of Mn was too small, and sufficient hardness was not obtained at the center of the plate thickness of a 10 mm thick part. Test No. 42 using steel No. 44,
Although the aim was to improve the toughness after tempering by adding Mo, the purpose could not be achieved because the amount of Mo added was too small. In test No. 43 using steel No. 45, the amount of Cr added was larger than the range of the present invention, and there was no problem in performance, but the cost was high.

In test No. 44 using steel No. 46, the N content was larger than the range of the present invention, microcracks occurred in the slab stage, and surface flaws occurred frequently on the steel plate. Test No. 45 using steel No. 47 was Mn
The amount was larger than the range of the present invention, the base material hardness exceeded 180 Hv10 kg, and the precision punching property was deteriorated. Test N using steel No. 48
In o.46, the amount of Sol.Al added was larger than the range of the present invention, and there was no problem in performance, but the cost was high. In test No. 47 using steel No. 49, since the annealing temperature exceeded the _AC1 transformation point, the depth of the surface decarburized layer exceeded 100 μm, and the performance as a part could not be satisfied. Test No. 48 using steel No. 50 was Ni
The addition amount is more than the range of the present invention, there is no problem in performance,
Cost was high. Test No. 49 using steel No. 51 had a base material hardness of 180 Hv10 kg because the annealing temperature was too low at less than 600 ° C.
And the precision punching property deteriorated.

[0044]

According to the present invention, a soft high-carbon steel sheet for processing that can omit the pickling step of the present invention is C: 0.10 to 0.50%, Si: 0.5% or less, Mn:
0.50-1.50%, P: 0.03% or less, S: 0.01% or less, sol.Al: 0.03
0.10%, N: 0.01% or less and Cr: 0.50-1.50%, Mo: 0.1-1.0%, Ni: One or two of 0.1-2.0% if necessary, with the balance Fe And unavoidable impurities. As described above, by containing 0.50 to 1.50% of Cr, the surface scale of the hot-rolled steel sheet is reduced at the time of annealing and easily becomes a foil strip, so that it can be easily removed in a material processing step such as slit processing. In addition, a soft steel plate for precision punching can be manufactured without performing pickling. In addition, since decarburization of the surface layer is suppressed, annealing becomes easy, and a steel plate having a thickness of 6.0 mm or more that cannot be continuously pickled can be softened, and parts for automobiles or other industrial products are used. Of the manufacturing cost can be reduced.

[0045] The method of the present invention for producing a soft high-carbon steel sheet for processing capable of omitting the pickling step comprises: , 600
℃ in a temperature range of more than A _C1 below the transformation point, and, by applying the annealing to a range of indices Z to give a 18 to 21 by the above formula (1), without performing the pickling, soft and and annealing It is possible to manufacture a steel sheet for precision punching that is excellent in the removability of reduced scale afterwards.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between an index Z value and hardness (Hv10kg) of the present invention.

Continued on the front page (72) Inventor Yoji Yanami 1850 Minato, Wakayama-shi, Wakayama Sumitomo Metal Industries, Ltd.Wakayama Works F-term (reference) 4K032 AA01 AA05 AA11 AA12 AA16 AA19 AA21 AA23 AA24 AA27 AA29 AA03 BA01 CA02 CC03 CE01 CE02 CF02

Claims (4)

[Claims] (Claim 1) C: 0.10 to 0.50%, Si: 0.5% or less, Mn: 0.50 to
1.50%, P: 0.03% or less, S: 0.01% or less, sol.Al: 0.03-0.10
%, N: 0.01% or less and Cr: 0.5-1.50%, the balance being F
A soft high carbon steel sheet for processing that can omit the pickling process consisting of e and unavoidable impurities. 2.C: 0.10 to 0.50%, Si: 0.5% or less, Mn: 0.50 to
1.50%, P: 0.03% or less, S: 0.01% or less, sol.Al: 0.03-0.10
%, N: 0.01% or less and Cr: 0.5-1.50%, and Mo: 0.
A soft high-carbon steel sheet for processing that contains one or two of 1 to 1.0% and Ni: 0.1 to 2.0% and can omit the pickling step consisting of Fe and unavoidable impurities. 3.C: 0.10 to 0.50%, Si: 0.5% or less, Mn: 0.50 to
1.50%, P: 0.03% or less, S: 0.01% or less, sol.Al: 0.03-0.10
%, N: 0.01% or less and Cr: 0.5-1.50%, the balance being F
e and a hot-rolled steel strip obtained by hot rolling a steel slab consisting of unavoidable impurities in a temperature range of 600 ° C. or more and A _C1 transformation point or less, and by the following formula (1) A method for producing a soft high carbon steel sheet for working, which can omit the pickling step, characterized by performing annealing so that the range of the obtained index Z is 18 or more and 21 or less. Z = {T × (20 + Log t)} / 1000 Equation (1) where T: annealing temperature (K), t: annealing temperature holding time (Hr) 4.C: 0.10 to 0.50%, Si: 0.5% or less, Mn: 0.50 to
1.50%, P: 0.03% or less, S: 0.01% or less, sol.Al: 0.03-0.10
%, N: 0.01% or less and Cr: 0.5-1.50%, and Mo: 0.
Hot rolling obtained by hot rolling a steel slab containing 1 to 1.0%, Ni: 0.1 to 2.0%, one or two of which are Fe and inevitable impurities, under normal conditions. Steel strip at 600 ℃
In a temperature range of not less than the A _C1 transformation point, and for a soft working which can omit the pickling step, characterized in that annealing is performed so that the range of the index Z obtained by the following formula (1) is 18 to 21. Manufacturing method of high carbon steel sheet. Z = {T × (20 + Log t)} / 1000 Equation (1) where T: annealing temperature (K), t: annealing temperature holding time (Hr)