JP3144228B2 - Method for producing high-chromium cold-rolled steel strip excellent in ridging resistance and workability and method for producing hot-rolled steel strip for the material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high chromium cold-rolled steel strip (including a steel sheet) having less ridging and excellent workability and a method for producing a hot-rolled steel strip for the material. It is intended to provide a low-cost production method by making annealing of steel continuous.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 3-48250, Japanese Patent Application Laid-Open No. Sho 60-24325, and Japanese Patent Publication No. 60-24243 disclose a method for producing a high chromium steel strip which is excellent in workability by a continuous annealing process of a hot-rolled steel strip and has little ridging. No. 59-43978.

[0003] Japanese Patent Publication No. 3-48250 is intended to improve the microstructure of a hot-rolled steel strip by recrystallization at the time of continuous annealing by utilizing the strain accumulating effect under strong rolling under hot rolling and to improve ridging resistance. . Although this technology is intended for ferritic stainless steels in general, Al is substantially reduced to 0.02%.
~ 0.2%, causing surface flaws, possibly high M
It has been proposed to change to o, and there was a problem in terms of cost.

[0004] In addition, in this technique, the rolling temperature in the latter stage of the finish hot rolling is 800 ° C or less, and the hot-rolled steel strip annealing is performed at 700 ° C.
To 1100 ° C, preferably 900 to 1100 ° C. However, generally, when ferritic stainless steel is annealed at a high temperature such as 900 to 1100 ° C., a martensite phase is generated, which causes surface roughness during pickling and deteriorates surface properties.

Japanese Patent Application Laid-Open No. 60-24325 has a problem of workability without addition of V and a problem of corrosion resistance without addition of Mo or Cu. In addition, from the examples, the hot-rolled finishing temperature is substantially 780 ° C. or more and the hot-rolled steel strip
The test was carried out at 0 to 950 ° C., so that the average r value of the workability index was low, and the surface was roughened during pickling to deteriorate the surface properties. In addition, there is no disclosure of the winding temperature of hot rolling.

[0006] Japanese Patent Publication No. 59-43978 also improves ridging resistance by a combination of hot rolling conditions and hot rolled steel strip annealing conditions. There were flaws, there was no addition of V, there was a problem of workability, and there was no addition of Mo or Cu, which was a problem in terms of corrosion resistance.

[0007] In addition, there is no disclosure of the finishing temperature and the winding temperature of the hot-rolled steel, and the annealing of the hot-rolled steel strip is substantially reduced to 850-9.
The test was carried out at 00 ° C., so that the average r
The value was low, and the surface was roughened during pickling, and the surface properties were deteriorated.

[0008]

There has been a strong demand for inexpensively producing a high chromium cold-rolled steel strip which is free from surface flaws and surface roughness during pickling, and has excellent ridging resistance and workability.

[0009]

According to the first invention, C: 0.01 to 0.08%, Si: 0.1 to 0.5% by weight%,
Mn: 0.4-1.0%, Cr: 15-19%, Ni:
0.25% or less, Mo: 0.25% or less, Cu: 0.2
5% or less, V: 0.25% or less, Sol. Al: 0.0
A continuously cast slab of high chromium steel containing less than 1% and N: 0.005 to 0.08% was heated to a heating temperature of 1100 to 125
A hot-rolled steel strip is obtained by hot rolling at 0 ° C., a hot-rolling finishing temperature of 650 to 780 ° C., and a winding temperature of 650 ° C. or lower, and the steel strip is subjected to an annealing temperature of 700 to 800 ° C. and an annealing time of 0.1. ~
Ridging resistance characterized by continuously annealing under an annealing condition of 8 minutes, further performing pickling, and subsequently performing cold rolling, annealing and pickling, or, in some cases, further performing temper rolling. It is a method of manufacturing a high chromium cold rolled steel strip having excellent workability.

In the second invention, C: 0.01% by weight.
0.08%, Si: 0.1 to 0.5%, Mn: 0.4 to
1%, Cr: 15 to 19%, Ni: 0.25% or less, M
o: 0.25% or less, Cu: 0.25% or less, V: 0.
25% or less, Sol. Al: less than 0.01% , N: 0.
A hot-rolled slab of high chromium steel containing 005 to 0.08% is hot rolled under the conditions of a heating temperature of 1100 to 1250 ° C, a hot rolling finish temperature of 650 to 780 ° C, and a winding temperature of 650 ° C or less. A steel strip was obtained and the steel strip was subjected to an annealing temperature of 7
For high-chromium cold-rolled steel strip material excellent in ridging resistance and workability, characterized by continuously annealing under an annealing condition consisting of 00 to 800 ° C and an annealing time of 0.1 to 8 minutes, and further performing pickling. This is a method for producing a hot-rolled steel strip.

[0011]

The present invention has an exquisite overall structure for producing a high-chromium cold-rolled steel strip excellent in ridging resistance and workability at low cost while preventing surface flaws and surface roughness during pickling. The conditions are as follows.

The reasons for limiting the components (% by weight) of the present invention and the production conditions are described below. C: C has a significant effect on the mechanical properties of the high chromium steel, and if it exceeds 0.08%, it tends to harden,
0.08% is made the upper limit. Conversely, if it is less than 0.01%, ridging tends to occur. Further, to less than 0.01% C
Decreasing the steelmaking cost also increases the steelmaking cost and eliminates the economic benefits of high chromium steel. Therefore, 0.
01 to 0.08%.

Si: Si must be 0.1% or more for deoxidation. If it exceeds 0.5%, the ductility after cold rolling annealing is reduced, so 0.5% is made the upper limit.

Mn: Mn is an austenite forming element,
If the addition is less than 0.4%, the generation amount of the austenite phase during hot rolling is small, and reduction of ridging cannot be expected. Also, 0.4% or more is required for deoxidation. If it is added in excess of 1%, the hot-rolled steel strip hardens, is unlikely to soften during the subsequent short-time annealing, and may hinder cold rolling. Therefore, Mn is set to 0.4 to 1%.

Cr: Cr is an essential element for ensuring the corrosion resistance of high chromium steel. If it is less than 15%, the corrosion resistance is poor, and the hot-rolled steel strip hardens and is hardly softened during subsequent short-time annealing, which may hinder cold rolling. 19
%, Corrosion resistance is sufficient, but ridging tends to occur. Therefore, Cr is set to 15 to 19%.

Ni: Ni is an austenite-forming element and is effective in reducing ridging. However, 0.25%
If it is added in excess of, a large amount of the hard phase will remain after hot-rolled coil annealing, causing surface roughening during pickling. Also,
The ridging reduction effect is also saturated. Therefore, Ni is set to 0.
25% or less.

Mo: Mo is an element that improves the corrosion resistance of high chromium steel. However, Mo is an expensive element,
Additions above 0.25% result in increased material costs. One of the objects of the present invention is to produce a high chromium steel having excellent properties at low cost, and the addition of excessive Mo does not meet the purpose of the present invention. Therefore, Mo is 0.2
5% or less.

Cu: Cu is an element that improves the corrosion resistance of high chromium steel. However, Cu is an expensive element,
Additions above 0.25% result in increased material costs. Therefore, Cu is 0.25 for the same reason as Mo.
% Or less.

V: V fixes C and N as carbonitrides,
Since C and N in the parent phase are reduced, it is effective in improving workability. However, the effect saturates even if it exceeds 0.25%. Therefore, V is set to 0.25% or less.

Sol. Al: Al is a strong deoxidizer. However, on the other hand, a very hard spherical oxide is easily formed, and when it appears on the surface, it becomes a cause of surface flaws. Therefore, Sol. Not 0.01% as Al
Full (however, 0 is not included) .

Further, Sol. By setting the Al content to less than 0.01% and performing the hot-rolled steel strip annealing at a low temperature of 700 to 800 ° C., the ridging height can be reduced to 6.5 μm or less, which is not a practical problem. This saves energy and reduces manufacturing costs.
Good quality high chromium cold rolled steel strip can be produced.

N: Like N, N has a great effect on the mechanical properties of high chromium steel. If it exceeds 0.08%, it becomes easy to harden, so 0.08% is made the upper limit. On the other hand, N should be reduced to improve ridging resistance,
Reducing N to less than 0.005% will increase steelmaking costs and defeat the economic benefits of high chromium steel. Therefore, N is set to 0.005 to 0.08%.

Heating temperature for hot rolling: To reduce the ridging, the heating temperature is preferably lower in order to keep the structure finer. However, when the heating temperature is lower than 1100 ° C., the load at the time of hot rolling increases, and problems such as the inability to roll to a predetermined thickness and the occurrence of surface flaws due to the increase in rolling load occur. Conversely 12
If the temperature exceeds 50 ° C., the tissue becomes coarse during heating, and ridging becomes remarkable. In addition, since the steel is softened, warping occurs during heating due to the weight of the slab and rolling cannot be performed. Therefore, the hot rolling heating temperature is 1100 to 1250.
° C.

FIG. 1 shows the results of treating steel having the above-mentioned specific component range, which is one of the characteristics of the present invention, with various hot-rolling finishing temperatures and hot-rolled steel strip (sheet) annealing conditions. It can be seen that by setting the content within the range of the present invention, a high chromium cold-rolled steel strip having excellent ridging resistance and workability can be manufactured while preventing surface flaws and surface roughness during pickling.

Hot-rolling finishing temperature: The hot-rolling finishing temperature greatly affects ridging resistance and workability after cold rolling annealing. FIG. 2 shows 0.06% C, 0.3% Si, 0.5% within the scope of the present invention.
% Mn, 16.4% Cr, 0.003% Sol. Al,
A high chromium steel having a composition of 0.03% N is hot rolled at various finishing temperatures, and is heated at 790 ° C. for 3 minutes,
Anneal hot-rolled steel strip (plate) for 3 minutes at
5 shows the relationship between the hot-rolling finishing temperature, the r-value, and the ridging height when cold rolling and final annealing are performed.
As shown in FIG. 2, when the hot-rolling finishing temperature is lower than 780 ° C., the average r value which is an index of workability is greatly improved, and excellent characteristics are exhibited. However, hot rolling finishing temperature is 650
If the temperature is lower than ℃, the load of hot rolling increases and flaws are apt to be generated on the surface. Therefore, the hot rolling finish temperature is 650-78.
0 ° C.

Winding temperature: The winding temperature is 650 ° C. in order to suppress the recovery after winding by accumulating strain in low-temperature hot rolling.
The following is assumed. This is to promote the recovery in a short time during the subsequent annealing of the hot-rolled steel strip.

Annealing temperature of hot-rolled steel strip (plate): The annealing temperature also greatly affects ridging resistance and workability after cold rolling annealing. FIG. 3 shows 0.06% C, 0.3% Si, 0.5% Mn,
6.4% Cr, 0.003% Sol. The hot-rolling finishing temperature of a high chromium steel in which Al is the basic component and N is changed to two levels of 0.03% and 0.008% is constant at 750 ° C. It shows the relationship.

As shown in FIG. 3, the hot-rolled steel strip annealing temperature was 8
If the temperature is lower than 00 ° C., the ridging height decreases (improves),
The r value increases. Even when annealing is performed at 850 ° C. or more, the ridging height is reduced, but the r value is also reduced and workability is deteriorated. Therefore, annealing should be performed at 800 ° C. or less. This means
It can also be evaluated from the viewpoint of saving energy and reducing manufacturing costs.

On the other hand, if the annealing temperature is lower than 700 ° C., although not shown, the pickling property is reduced, and surface defects due to scale residue are likely to occur. Therefore, the annealing temperature is 700-
800 ° C., preferably 700 to 790 ° C.

As shown in FIG. 3, the ridging resistance is improved when N is reduced. Therefore, a lower N content is desirable.

Hot rolled steel strip (plate) annealing time: Annealing time is 0.1
If the time is shorter than 1 minute, sufficient recovery does not occur, and decomposition of the hard second phase existing as hot rolled does not occur. In this case, since good workability cannot be obtained, the annealing time is set to 0.1.
1 minute or more. As the annealing time increases, the production efficiency decreases and the production cost increases. In the case of the target steel of the present application, sufficient recovery of the parent phase and decomposition of the hard second phase existing as hot rolled occur by annealing for up to 8 minutes, thereby improving workability after cold rolling annealing. Therefore, the annealing time is set to 0.1 to 8 minutes.

As the component composition of the present invention, Ca, T
Even if i, Nb, Zr, etc. are further added as required, the effect of the present invention is not changed.

The present invention includes a method of manufacturing a hot-rolled steel strip for a raw material of a high chromium cold-rolled steel strip, including a hot-rolled steel strip until hot rolling, continuous annealing, and pickling. Further, predetermined surface finish, to perform temper rolling or tension leveler treatment after pickling of the hot-rolled steel strip to obtain better shape characteristics,
Alternatively, this includes performing a coil grinder process.

Similarly, in order to obtain a predetermined surface finish, better shape characteristics and mechanical characteristics, temper rolling or tension leveler treatment after pickling of the cold-rolled steel strip, or coil coiler treatment. Is included.

[0035]

Embodiments of the present invention will be described below. Steel with the chemical composition shown in Table 1 obtained by melting and casting high chromium steel
1 to 5 were subjected to hot rolling, hot rolling steel strip annealing, and cold rolling steel strip annealing under the conditions shown in Table 2. After the cold rolling annealing, the average r value and the ridging height were measured. The average r value is an average value of r values in three directions of a rolling direction, a direction perpendicular to the rolling direction, and a 45 ° direction of the rolling.
Is defined by Average r value = (r ₀ + r ₉₀ + 2r ₄₅ ) / 4 Equation 1 where r x represents the r value in the direction of x degrees from the rolling direction.

[0036]

[Table 1]

The ridging height was measured with a roughness meter when the steel strip was plastically deformed by 15%.

The results are shown in Table 2. The steel strip manufactured under the conditions according to the present invention has an average r value of 1.0 or more and a low ridging height of 6.5 μm or less. In the present invention, the surface properties were also good.

On the other hand, in the steel strip manufactured without adopting the conditions of the present invention, the average r value does not reach 1.0, and many of the steel strips have a high ridging height.

The conditions A1 to A4 correspond to the steels having the compositions of A and D in Tables 1 and 3 described in Examples of Japanese Patent Publication No. 3-48250 cited as the prior art, Hot rolling,
This is the result for the steel strip obtained by annealing. In Japanese Patent Publication No. 3-48250, steel sheets D and A are shown as typical examples of ferritic stainless steel. However, these steels contain 0.02 to 0.03% of Al, and the balance between the components and the manufacturing conditions is poor. Therefore, any of the defects such as poor average r value, poor ridging height, and surface flaws This is a cold-rolled steel strip that easily occurs.

[0041]

[Table 2]

[0042]

According to the present invention, the addition of the basic element contained in the high chromium steel is mainly adjusted and the conditions of hot rolling and annealing of the hot-rolled steel strip are specified, so that the occurrence of ridging is small and the workability is excellent. It is possible to manufacture a high-chromium cold-rolled steel strip and a hot-rolled steel strip of the material at low cost.

[Brief description of the drawings]

FIG. 1 is a view showing a range of a hot-rolling finishing temperature and a hot-rolled sheet annealing temperature that provide good characteristics.

FIG. 2 is a diagram showing a relationship between a hot rolling finish temperature, an average r value after cold rolling annealing, and a ridging height.

FIG. 3 Annealing temperature of hot-rolled sheet (steel strip) and average r after cold-rolling annealing
It is a figure showing the relation between a value and ridging height.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Satoshi Ishijima 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) C21D 9/46 -9/48 C21D 8/02-8/04 C22C 38/00-38/60

Claims (2)

(57) [Claims] C. 0.01 to 0.08% by weight of C, S
i: 0.1 to 0.5%, Mn: 0.4 to 1%, Cr: 1
5 to 19%, Ni: 0.25% or less, Mo: 0.25%
Hereinafter, Cu: 0.25% or less, V: 0.25% or less, S
ol. Al: less than 0.01% , N: 0.005 to 0.0
A continuous casting slab of high chromium steel containing 8% was subjected to a heating temperature of 1100 to 1250 ° C and a hot rolling finish temperature of 650 to 78.
A hot-rolled steel strip is obtained by hot rolling at 0 ° C. and a winding temperature of 650 ° C. or lower, and this steel strip is subjected to an annealing temperature of 700 to 800.
C., annealing is continuously performed under annealing conditions of annealing time of 0.1 to 8 minutes, and further pickling is performed, and then cold rolling and annealing / pickling are performed or, in some cases, temper rolling is further performed. A method for producing a high chromium cold-rolled steel strip having excellent ridging resistance and workability. 2. C: 0.01 to 0.08% by weight, S
i: 0.1 to 0.5%, Mn: 0.4 to 1%, Cr: 1
5 to 19%, Ni: 0.25% or less, Mo: 0.25%
Hereinafter, Cu: 0.25% or less, V: 0.25% or less, S
ol. Al: less than 0.01% , N: 0.005 to 0.0
A continuous casting slab of high chromium steel containing 8% was subjected to a heating temperature of 1100 to 1250 ° C and a hot rolling finish temperature of 650 to 78.
A hot-rolled steel strip is obtained by hot rolling at 0 ° C. and a winding temperature of 650 ° C. or lower, and this steel strip is subjected to an annealing temperature of 700 to 800.
Hot rolling for high-chromium cold-rolled steel strip material with excellent ridging resistance and workability, characterized by continuous annealing under annealing conditions of 0.1 ° C. and 0.1 to 8 minutes, followed by pickling. Steel strip manufacturing method.