JPS6051537B2 - Manufacturing method of aluminum killed cold rolled steel sheet with excellent hollowability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an aluminium-killed cold-rolled steel sheet having excellent enamel properties.

HA'Reima 1,, L,, Enemy HA Jinseki'K1 Jin Kogami---
n- That is, the following method is known as a method for improving nail-skipping resistance and enamel adhesion.

(1) As disclosed in Japanese Patent Publication No. 55-2446, coarse carbides are formed by increasing the hot-rolling temperature, and these carbides are destroyed during cold rolling, separated from the matrix, etc. A method of absorbing hydrogen into the resulting board to improve its resistance to nail skipping. (2) As disclosed in Japanese Patent Publication No. 55-42133, C is reduced to 0.0 by vacuum degassing method.
A method of adding B and REM to 2% or less. (3
) As disclosed in Japanese Patent Publication No. 55-12164, a method in which C is reduced to 0.02% or less by vacuum degassing, B is added, and C is decarburized and annealed to 0.005% or less.

However, in the above-mentioned methods (1) to (3), the nail-skipping resistance and enamel adhesion were not necessarily satisfactory. From the above-mentioned viewpoints, the inventors of the present application have investigated the nail-skipping resistance of aluminum-killed cold-rolled steel sheets and the enamel adhesion J.
As a result of various studies on properties, we found that by optimizing the composition and manufacturing conditions of the aluminium-killed cold-rolled steel sheet to which B is added, we can produce an aluminium-killed cold-rolled steel sheet that is inexpensive and has excellent nail-skipping resistance and enamel adhesion. We obtained the knowledge that it can be manufactured.

i This invention was made based on the above-mentioned knowledge, and the aluminum killed steel is made of aluminum with the remainder being Fe and unavoidable impurity elements, and which satisfies the following relationship: It is characterized by being wound up at ~720°C, pickled by a conventional method, and annealed after cold rolling.

The reasons for limiting each component in this invention will be explained.

(1) CC exists in the form of carbide in steel, but during cold rolling, the carbide peels off from the matrix and creates voids due to the destruction of the carbide, thereby improving the nail-skipping resistance. However, if the C content is less than 0.02%, the above-mentioned effects are lost, so the lower limit of the C content was set at 0.02%.

On the other hand, if the C content exceeds 0.10%, the product becomes hard and the press formability deteriorates, making it undesirable as a steel plate for enameling, so the upper limit was set at 0.10%. (2) M
nMn is 1 of -S amount in order to prevent hot embrittlement caused by S.
Although it is necessary to add an amount of Mn to a certain level, it is preferable to add as little Mn as possible in terms of press moldability and enamel firing distortion.

Therefore, in consideration of these points, in the present invention, the amount of h added is limited to a range of 0.05 to 0.50%.
(3) A certain amount of P, SP and S is unavoidable as impurity elements, but they affect the pickling speed in the enamel pretreatment, and if their content is less than 0.005%, the acid Washing speed becomes slow and enamel pretreatment workability deteriorates.

On the other hand, if the content is large, the press moldability deteriorates, so in this invention, the content of P and S is set to 0.005 to 0.005.
It was set to 0.030%. (4) N Since N is unavoidably contained in steel and has the effect of making the steel hard and promoting age hardening, it is preferable that its content be small.

However, it is difficult to reduce the amount to less than 0.0010%, so in this invention, the range is set to 0.0010 to 0.01%.
It was set as 00%. (5) SOlAl SOlAl makes the steel into killed steel and replaces solid solution N with A.
It is necessary to precipitate as IN and make the product non-aging, and at least 0.005% or more is essential.

On the other hand, if added in a large amount, the manufacturing cost will increase, so in this invention it is set at 0.005 to 0.100%.

(6) B B, like C, is an element necessary to improve the nail-skipping resistance, and as shown in FIG. 1, when the C content is 0.02% or more, B is added to 0. It can be seen that the occurrence of nail skipping can be prevented by adding 0.015% or more.

On the other hand, adding a large amount of B not only increases the manufacturing cost but also makes the slab properties unstable.
The addition range was 0.0015% to 0.0050%.
Furthermore, although B fixes solid solution N as BN in steel, it is thought that the entire amount of B does not become BN, but about half of that amount combines with N. Therefore, in the above composition range, solid solution N often remains in the steel, and the non-aging property, which is one of the characteristics of aluminum-killed cold-rolled steel sheets, is lost. As a result of various studies, it was found that non-aging properties can be achieved by satisfying the following conditions.

Furthermore, if (N%-0.5・B-B%) is less than 0.0005%, that is, the amount of solid solute N is less than 0.0005%, the steel plate is practically non-aging, so as mentioned above, No restrictions are required. Therefore, (N%-0.5・heat・B%) is 0.
0005% or more, SOlAl%(N%-0.5
- Heat/B%) was set to 2.0X10-5 or more. (7)C
U Cu is an element that affects the enamel adhesion and the pickling speed in the enamel pre-treatment.If it is less than 0.010%, the enamel adhesion will be poor, while if it is 0.050% or more, the pickling speed will be slow. , the enamel pretreatment workability deteriorates.

Therefore, in this invention, the addition range of Cu is 0.010~
It was set to 0.050%. In this invention, after hot rolling steel containing each of the above-mentioned components by normal means,
It is wound at 0'C because below 550C, carbide precipitates finely and the nail-skipping resistance decreases.
On the other hand, if the temperature exceeds 720'C, it becomes difficult to descale the hot rolled steel sheet.

The finishing temperature is not particularly limited, but is preferably 800 to 900°C. After that, it is pickled, cold rolled, and recrystallized annealed. The recrystallization annealing method may be either a normal box annealing method or a continuous annealing method, but in the case of continuous annealing, it is preferable to perform precipitation treatment of solid solution C within the line. Aluminum killed cold-rolled steel sheets manufactured by this method are suitable for double-layer enameling steel sheets that use a lower glaze, but are not suitable for direct single-layer enameling steel sheets that use a top glaze to adhere directly to the steel sheet. ,
To prevent carbon boiling, the amount of C is 0.01.
% or less. next,
Examples of this invention will be described.

Steel having the chemical composition shown in Table 1 is finished at a finishing temperature of 870°C.
After hot rolling at a coiling temperature of 560°C, pickling and 0.8T
It was cold rolled to 0n. After this, annealing (box annealing, continuous annealing, decarburization annealing) was performed, and finally 1% temper rolling was performed. Table 2 shows the results of the mechanical properties and enamel properties of the aluminum-killed steel sheets produced in this manner. In the annealing method in Table 2, BA means box annealing, CA means continuous annealing,
And DC means decarburization annealing.

In addition, the amount of nail skipping is the number of nails that occur when firing in a humidified atmosphere (D.P.: 30°C), and the adhesion of the enamel is 2. This is a value measured using a PEI adhesion tester to measure the adhesion of the lower glaze when pickling an enameled steel plate for minutes. moreover,
In the case of continuously annealed material, the hot rolling coiling temperature was 680°C.
As is clear from Table 2, Comparative Steel E has a C content that is outside the scope of the present invention, and has poor nail-skipping resistance, with a large number of nail-skippings occurring.

In addition, since comparative steel E has a small amount of C, solid solute C does not precipitate sufficiently even if it is precipitated by continuous annealing.
x) AII is high and it is not time-limited. Comparative steel F
Because the amount of B is so low that it is out of the range of the present invention, the resistance to nail skipping is poor. It is unsuitable as a copper plate for enamel.
Comparative steel G has Cu amount and SOlAl%×(N%-0.
5.,l-?・B%) is outside the scope of the present invention, and the enamel adhesion and aging resistance are poor. Furthermore, comparative steel H
is an aluminium-killed cold-worked steel sheet without the addition of B, which has poor nail-skipping resistance and enamel adhesion, and cannot be used as a steel sheet for enamel. On the other hand, in W4A to D of the present invention, no occurrence of nail skipping was observed at all,
It can be seen that this is a non-aging cold rolled steel sheet with excellent press formability and extremely good enamel adhesion. Incidentally, A-1 of the continuously annealed material of the steel A of the present invention has a value of 1.7k9/Vi, but this value is practically non-aging, and there is no problem at all with respect to aging. As explained above, according to the present invention, extremely useful effects such as being able to manufacture an aluminum killed cold-rolled steel sheet for enameling with excellent enameling properties at low cost are brought about.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the amount of B and the number of skipped nails.

Claims (1)

[Claims] 1 C: 0.02-0.10%, Mn: 0.05-0.50%, P: 0.005-0.030%, S: 0.005-0.030% , N: 0.0010-0.0100%, SolAl: 0.005-0.100%, B: 0.00
15 to 0.0050%, Cu: 0.010 to 0.050%, the balance consisting of Fe and inevitable impurity elements, and N
%-0.5・14/11・B%>0.0005%, SolAl%×(N%-0.5・14/11・%
) > 2.0 x 10^-^5 (more than % by weight) aluminum killed steel is hot-rolled and then coiled at 550 to 720°C, pickled by a normal method, and after cold rolling. A method for producing aluminum killed cold-rolled steel sheets with excellent enamel properties, which is characterized by annealing.