JPS59229463A - Steel for enamel with superior workability - Google Patents

Abstract

PURPOSE:To obtain a steel sheet fit to undergo single enameling and double enameling and having superior workability and suitability to enameling by continuous casting by specifying the amounts of C, Mn, N and O contained in steel. CONSTITUTION:This steel sheet obtd. by continuous casting consists of <=0.0050% C, <=0.6% Mn, <=0.0050% N, 0.016-<0.030% O and the balance Fe or further contains <=0.05% Cu and 0.0001-0.0050% B and/or 0.003-0.080% Nb. The steel sheet is fit to undergo single enameling and double enameling, and the calcining temp. range is extended because of the high A1 transformation point. The steel sheet gives enamel having high adhesive strength and free from fish scale and bubbles.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel for enamel, which is made of specific components and obtained by continuous casting, and is characterized by excellent workability and aging properties.

Enamel steel plates are used for kitchen utensils, sanitary utensils, bathtubs, etc., and as a basic property, they first need to have nail-skipping resistance. Nail skipping is a clear phenomenon in which water dissolved in the original plate during enamel firing reduces its solubility due to the temperature drop after firing, collects at the interface between the enamel and the original plate, and destroys the enamel with its pressure. In order to obtain a good enamel steel plate, it is necessary to improve the Suigun@Kurano of the original plate.

Furthermore, since enameled steel sheets are often used for exploration drawing, they must have good deep drawing properties and other formability.

Furthermore, since enamel is finished by firing at 800-900℃, if the transformation point is busy during this period, firing distortion will occur due to transformation distortion, and if there is a large amount of C in the FC original plate, workability will deteriorate. CO gas is generated in the wafer, causing bubbling defects.

Therefore, the steel plate for enamel is required to have an extremely low C content and to have abundant hydrogen storage sites through addition of inclusions, TI, and rare earth element g (REV).

In order to meet these demands, steel plates for enamel are made by decarburizing annealing molten steel, or by vacuum degassing treatment of molten steel.
The steel used is annealed steel with a lower hydrogen content and the addition of Ti, REM, etc. to increase the number of hydrogen storage sites.

However, continuous casting is difficult with rimmed steel due to rimming action during casting, and with steel plates containing elements such as TI and REM that are highly reactive with oxygen, the surface quality deteriorates.

With the remarkable development of steel manufacturing methods and continuous casting methods in recent years, interest in manufacturing steel for enamel by continuous casting has increased. ・Prior art regarding the manufacturing method of steel for enamel by continuous casting is JP-A-53 -7531, Special Publication No. 57-490
There is a technique described in No. 89.

The technology described in JP-A-53-7531 is to continuously cast steel that has been decarburized and deoxidized by vacuum degassing.
B, Zr, rare earth elements, etc. are added using wires, and there is no difference in principle from the core-killed method in the agglomeration method.Therefore, the problem is that there are few hydrogen storage places in the slab surface layer, and nail skipping occurs. have The technology described in Tokko No. 57-49089 is C,
Due to the high O content, slumming axes are unavoidable during continuous casting, and in addition, workability is low, and ζ etc. cause nail skipping, bubbles, etc.
In terms of firing distortion, etc., it cannot be said to be strong enough as a steel for enamel.

The inventors of the present invention have conducted various studies with the aim of producing a steel for enameling that can be cast once or twice by continuous casting, and has excellent enamel properties.
The inventor invented a steel for enamel obtained by continuous casting of an ultra-low C-O system.

That is, the gist of the present invention is that IC:0.
00504 or less, Mn: 0.64 or less, N: 0.005
0 or less, O: 0.016 or more and 0, less than 030, as necessary, B: O, 0O01 to O, OO50%,
A steel for enamel having excellent workability, characterized in that it contains one or two of Nb: 0.003 to 0.080, the remainder being Fe and unavoidable impurities, and is obtained by continuous casting.

2C: 0.005011-/lower% Mn: o
, 6'16 or less, N: 0.00501JN or less,
O: 0.0161 or more and less than 0.0301, Cu: 0.0
In addition to 51 or less, B: 0, 0001 to O, as necessary.
OO50 excellent, Nb: 0.003 to 0, one type of 0801 or 21B'e is included, the balance is Fs and inevitable impurities, and the steel is obtained by continuous casting.For enamel with excellent workability. It is steel.

The reason for limiting the components of the present invention will be explained in detail below.

It is an element that has a serious effect on the workability, firing strain, bubbles, etc. of steel sheets for carbon enamel, and when continuously casting non-deoxidized steel, if there is a large amount of carbon, the IJ forming process will occur in the mold. This makes it impossible to cast. The upper limit of C is 0.0050 in order to obtain a steel for enamel which has good workability and does not cause defects such as firing distortion and bubbles by continuous casting. Furthermore, if C is extremely lowered, it is impossible to lower the oxygen level in the steel without using a large amount of deoxidizing agent (5), and bubbles are generated during solidification, so the lower limit of C is 0.0010%. degree is preferred.

If the amount of Mn increases, it impairs workability, so it should be kept at a coefficient of 0.60 or less. In order to further improve processability, it is preferable that the Mn content is 0.30% or less.

Since the steel of the present invention does not contain elements such as At that combine with N and reduce solid solution N, it is highly desirable to reduce N, which causes aging properties, as much as possible. From this point, set Nil to O
, OO504 or less, but for slow aging at room temperature, O
,0O15% or less.

This is the most important nine points of the present invention. That is, O combines with 81 and Mn in the steel to form an oxide, which increases the number of inclusions in the steel and provides storage sites for hydrogen in the steel. However, its amount is closely related to C in steel, porosity, and workability, so if C6 is lowered, 0 increases, and bubbles are generated when molten steel solidifies, making continuous casting impossible. As a result of various studies, the inventors of the present invention found that by adjusting C within the above range and setting O to (6) 150 ppm or more and less than 300 ppm, bubbles do not occur during continuous casting and hydrogen storage is abundant. It has been found that it is possible to produce steel for enamel having a certain area.

If the zero amount is less than 150 ppm, there will not be enough hydrogen storage space and skipping will occur.

Furthermore, if aging due to solid solution C and N becomes a problem, B
, 1s or 2 types of Nb are added as necessary. B fixes solid solution N, but if it is less than 0.00011, it is ineffective, and if it exceeds 50% of 0.0 O, defects such as slab damage 11 will occur. Also, Nb fixes solid solution C, but O,
If it is less than OOB, there is no effect, and if it exceeds 0.08%, the effect will be saturated and it will be economically disadvantageous.

In addition, when high adhesion of the enamel is required, such as when applied once, Cu is added. In that case, if the amount of Cu added exceeds 0.051'e, the pickling properties will deteriorate.
The upper limit is set at 0.05%. Further, in order to obtain a stable improvement in adhesion, it is recommended that the amount added be 0.02'1 or more.

In addition, S as an unavoidable impurity is very important from the viewpoint of processability.
．． Although it is preferable that the amount is 0.01011 g or less, it is also possible to contain it at 0.04% t for the purpose of further increasing the hydrogen storage locations in the steel and further improving the enamel properties. However, when S exceeds 0.04, the workability deteriorates significantly.

Steel having such components is melted in a converter, and the converter may be top-blown, bottom-blown, or top-bottom blown.

Next, C00 is lowered to a predetermined level by vacuum degassing treatment, and the treatment method used at that time is RH.

Any method such as DH may be used. After that, it is made into a slab by continuous casting. Next, hot rolling is carried out, which may be done by heating and hot rolling in the usual manner, heating from a hot piece slab, or directly hot rolling a hot piece slab. The turbidity may be at a low temperature of about 1100 to 1150°C.

Although it is preferable that the finishing temperature be higher than the Ar5 transformation point, rolling at a temperature lower than the partial transformation has little effect on the material of the cold-rolled annealed ridge.

The winding temperature may be the usual 550 to 680'C, but in order to completely precipitate Nb carbonitride when Nb is added, K is preferably about 680 to 750'C.

Next, the steel is pickled and cold-rolled, but since the steel of the present invention has extremely good pickling properties, there is no need to pour a particular amount during the pickling process. In addition, cold rolling is about 50 to 8
Approximately 5% is sufficient.

This cold-rolled steel sheet is annealed and used as a base plate for enamel.Since the steel of the present invention has an extremely low C content of less than 501 O, OO, there is no need to perform decarburization annealing using an open coil, and box annealing using a normal tight coil. , or continuous annealing. Furthermore, in the case of steel with addition of sulfur, continuous annealing is preferable because high-temperature annealing can be performed economically without temperature unevenness. The annealing temperature is 580 to 750°C for box annealing and 650°C for continuous annealing.
The temperature is usually about 850°C. The presence or absence of overaging treatment during continuous annealing and the method of cooling from the annealing temperature do not matter.

Enamel can be applied once or twice, and since the AI transformation point of wood-like material is as high as about 870° C. or higher, the firing temperature range can be wide.

Next, examples of the present invention will be described.

Steel having the components shown in Table 1 was melted in a converter. (9) For items A-J, C is lowered by a predetermined amount [7] by vacuum degassing treatment, and if necessary, At? The O level was adjusted, B, Nb, and Cu were added as appropriate, and a slab was made by continuous casting. Regarding the material K, after melting in a converter, it was vacuum degassed, further deoxidized with At, and then continuously cast. During this continuous casting, Zr and REV were added in the form of a wire inside the mold. As the REV, I used Shemetal. The code is rimmed steel for decarburization annealing, and after reducing C to 0.024 by melting in a converter, it is made into an ingot by the addition method, and it is made into a slab by blooming.The 0 analysis value is after decarburization annealing. is the value of

Preliminary deoxidation with At in the ladle of molten steel in M-shaped converter furnace.
After i was set to 0.015 or less, it was poured into a mold, left for 1 minute, TI and REM Th were added and solidified, and then a slab was formed by blooming. The analytical values are the values after decarburization annealing.

In Table 1, the symbols A and F-J are steels according to the present invention, the symbols B are steels in which C0O exceeds the upper limit of the scope of the present invention, the symbols C and 0 are outside the lower limit of the scope of the present invention, and the symbols (10 ) The number is those whose Mn exceeds the upper limit of the range of the present invention, code E
If FiN exceeds the upper limit of the scope of the present invention, the sign is L
, M is comparative steel other than the method of the present invention.

These slabs were then hot rolled under the conditions shown in Table 1. The thickness of all plates after hot rolling is 40 knots, pickled and then cold rolled to 0.8 tt.
rm cold-rolled copper strip.

(11) <Example of continuous annealing> Among the cold rolled steel sheets manufactured in this way, steel codes A-J
After continuous annealing under the conditions shown in Table 2 using the same method, the samples were temper rolled at an elongation of 1.0, and their mechanical properties and enamel properties were investigated. Tensile test was conducted based on the method specified in JIS Z 2241 using a No. 5 test piece specified in JIS Z 2201. The occurrence rate of nail skipping was measured after being left for 24 hours after firing. A case where no bubbles were generated at all was marked with an ○, a case with a small amount was marked with a Δ, and a case with a medium to large degree was marked with an X. Judging by PEI test for adhesion, if the residual rate is 95 coefficients or more, mark ○, if it is 80 coefficient or more and less than 95 coefficient, mark Δ, 80 coefficient.
Items below the limit were marked with an X. Also, the water penetration time is 25℃
It was measured with

The mechanical test values are shown in Table 2, and the enamel properties are shown in Table 3.

(13) As is clear from Tables 2 and 3 of Table 3, both the material before enameling and the enameling properties are excellent. In particular, the effect is remarkable in Graves 8 to 13 to which B1Nb5Cu and the like are added. On the other hand, in S4, where C10 is outside the range of 1 of the present invention, the deterioration of workability and aging properties is large, and the generation of bubbles is also significant. In flat 5, where 0 is outside the lower limit of the range of the present invention, hydrogen permeation The time decreases significantly, and the incidence of nail skipping increases.A6, where Mn is outside the range of the present invention, has poor workability.A7, where N is outside the range of the present invention, has poor workability and aging. In flat 14 to which Zr and REMi wires were added, the occurrence of nail skipping was high because there were few water bed occlusion sites in the surface layer.

<Example of box annealing> Box annealing was performed under the conditions shown in Table 4 using A, C, H, I, L, M (7) steels indicated by w1iK. L.

Regarding M, decarburization annealing was performed using an open coil in an 804H2, 20% N2 atmosphere. After that, it was subjected to temper rolling of 1.0 or better, and the mechanical properties were improved using the same method as continuous annealing.
0 Mechanical properties investigated for enamelability are shown in Table 4, and enamelability is shown in Table 5.

Table 5 As is clear from Tables 4 and 5, the steel of the present invention can be annealed for a short time and has mechanical properties and enamel properties equivalent to decarburized annealed materials. The added ones are T1,
It has properties equivalent to REM-added decarburized annealed material. That is, the present invention makes it possible to create a steel plate for enamel with good workability that is efficient and economical in a shorter time than conventional methods.

As is clear from the above examples, the present invention makes it possible to manufacture enameled steel with excellent workability and enameling properties by continuous casting, and it is clear that this invention will contribute widely to the industrial world. be.

(18) The use of the steel of the present invention is not limited to cold-rolled steel sheets, but can also be used as hot-rolled enameled steel sheets.

(19) 285-

Claims (1)

[Claims] IC: 0.00501 or less, Mn * 0.6 or less, N: O, OO50 or less, O: 0.016 or more and 0, less than 0301, and if necessary, B: 0,
OOO1~O, OO50, Nb:0.003~o,
A steel for enamel having excellent workability, characterized in that it contains 1 or 2 s of o so o ratio, the remainder is Fe and inevitable impurities, and is obtained by continuous casting. 2 C: 0.00501 or less, Mn: 0.6 or less,
N: 0.0050'1 or less, o: o, 016 or more and 0, less than 0301, Cu: '0.05'i or less, and as necessary, B: O, 0OO1 to O, OO50, Nb: A steel for enamel with excellent workability, characterized in that it is a steel obtained by continuous casting, containing one or two of the following: 0.