JPS6333522A - Production of raw plate for t-1 to t-3 class soft quality surface treatment for di works - Google Patents

Abstract

PURPOSE:To obtain a raw plate for soft quality surface treatment having uniform quality and excellent deep drawability by containing the specific quantities of C, Mn, P, Al, and N in an Al killed steel, hot-rolling this Al killed steel at the specific temp. and next executing the over-ageing treatment after recrystallizing annealing by the continuous annealing method. CONSTITUTION:The low carbon Al killed steel is contained by wt% of 0.01-0.06% C, 0.05-0.60% Mn, <=0.02% P, 0.005-0.008% acid soluble Al, <=0.0070% N and remaining part of Fe with inevitable impurities. The Al killed steel is hot-rolled, wound at 600-700 deg.C and cold-rolled. Next, by the continuous annealing method, the recrystallizing annealing is executed at the temp. range of >=recrystallizing temp. and <=850 deg.C for 5sec-5min. After that, it is cooled at 5-250 deg.C/sec cooling velocity and the over-ageing treatment at 300-500 deg.C for 30-180sec is executed. Further, the Al killed steel is cooled to Ar3 the transformation point or below and next after heating, it may be executed by the same method as the above. In this way, T-1 to T-3 class surface treating steel plate having excellent uniformity for quality and high strength to pressure is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a surface-treated original plate such as tinplate,
The present invention relates to a method for producing a soft surface treatment original plate which has superior formability and practical properties than conventional box annealed materials by a continuous annealing method, particularly a soft surface treatment original plate having a temperature of T-1 to T-3.

[Prior art] Tin plated steel plate made of tin-plated steel plate or tin-free steel plated with chromic acid (hereinafter referred to as T, F,
Surface-treated steel sheets such as steel sheets (referred to as S) are often used for food cans, aerosol cans, and easy-open cans.

These surface-treated steel sheets have different strengths depending on their use.

The degree of tempering (temper once) is specified as a guideline for selecting ductility and other properties as appropriate, and this temper once is expressed in Rockwell surface hardness (HR30T), ranging from soft to T-1 (I ( R30T: 46-52), T
-2 (HR30T: 50-56), T-3(I(R3
0T: 54-60), T-4 (HR30T: 58-6
4), T-5 (HR30T: 62-68), T-6 (H
R30T: 67-73), DR-8, DR-9, and DR-1o, but in continuous annealing with rapid heating and short-time heating, when continuous casting material is bound, the soft original plate Conventionally, soft surface-treated base plates T-1 to T-3 were manufactured by box annealing. However, compared to continuous annealing, box annealing has the disadvantages of inferior shape, nonuniform mechanical properties in the longitudinal direction of the coil, and inferior productivity.
Moreover, manufacturing costs are high.

[Problems to be solved by the invention] For these reasons, continuous annealing is applied to soften soft materials such as T.
Methods for manufacturing class-3 tin plates have been studied, and for example, Japanese Patent Publication No. 11290/1983 proposes a manufacturing method using continuous annealing in which Al-killed steel with reduced C and N is subjected to over-aging treatment. Although this method may have some effect, the reality is that it has not yet been possible to stably obtain soft tin plate in an actual production line.

In recent years, tinplate, T, F, and S have been subjected to severe processing such as multi-stage drawing processing or DI processing (iron processing is applied after deep drawing processing), and they are not only corrosion resistant but also have excellent workability. Soft materials for DI processing (once tempered T-1 to T-
For grade 3), only box annealed materials were applied.

The reason for this is that box-annealed materials have better elongation and deep drawability, and are generally considered to be more suitable for DI processing applications.

As a result of various studies on the various characteristics required for DI cans, the present inventors found that surface-treated steel sheets for DI cans have a DI
The present invention was completed based on the new finding that continuously annealed materials are actually superior in terms of formability and practical characteristics of DI cans.

[Means for solving the problems] The present invention provides (1) weight% 1? , C: 0.01-0.06
%, Mn: 0.05-0.60%, P: 0.02% or less, acid-soluble Al: 0.005-0.08%, N: 0°0
A low carbon Afl killed steel billet consisting of 0.070% or less and the balance Fa and unavoidable impurities is hot rolled and then 600%
It is rolled at a temperature of ~710°C, then cold rolled, and then recrystallized by continuous annealing at a temperature above the recrystallization temperature and below 850°C for 5 seconds to 3 minutes. Cool, then 30-1 at a temperature of 300-500 °C
This is a method for producing a T-1 to T-3 grade soft surface treatment base plate for DI processing, which is characterized by performing an over-aging treatment for 80 seconds, and (2) C: 0.01 to 0. 06%, Mn:
0°05-0.60%, P: 0.02% or less, acid soluble A
Low carbon Al consisting of l: 0.005 to 0.08%, N: 0.0070% or less, and the balance is Fe and unavoidable impurities.
Cooling the killed steel piece to a temperature below the A r 3 transformation point,
Then (T)℃=6875/(3,865-1og[Al%
+0.015])-250, hot rolled,
After rolling and cold rolling at a temperature of 0 to 710°C, and then recrystallization annealing for 5 seconds to 3 minutes at a temperature above the recrystallization temperature and below 850°C by continuous annealing method, 5 to b 300 T-1 or T-2 for DI processing, characterized by performing overaging treatment for 30 to 180 seconds at a temperature of ~500°C
The manufacturing method for grade soft surface treatment blanks.

[Properties required for DI cans include good workability and low processing energy during DII processing, excellent stretch flange formability after DII processing, and high pressure resistance as a can body. This is required. In recent years, the plate thickness of DI cans has been becoming increasingly thinner, and among the above three points, the demand for increasing pressure resistance is becoming very strong.

The pressure resistance of the can body is determined by (plate thickness) x (strength), and making the material thinner requires increasing the strength of the material, but increasing the strength increases the likelihood of galling during DI molding, and also reduces processing energy. Increased disadvantages arise. In addition, box annealed materials require relatively high alloy components, resulting in poor DII workability.

On the other hand, in the case of continuously annealed materials, the present inventors have found that the strength of the can body is significantly increased by painting and baking after DI processing, and as a result, the pressure resistance is also increased (hereinafter this property is referred to as BH property). . In other words, when continuously annealed material is used, D
It has been found that during II processing, the material is soft and therefore has excellent DII workability, and when painted and baked, the post-compressive strength can be made equal to or higher than that of box annealed material. This means that if the strength of the material is the same, the pressure resistance of the can body can be higher with the continuously annealed material, so this industrial value is extremely large.

Stretch flange forming is then performed by flan extraction after DI processing, and good stretch flange formability is extremely important, and the defective rate must be suppressed to several tens of ppm or less. For this reason, box-annealed materials that elongate as steel plates, have excellent r-values, and have little solid solution C in the steel have been conventionally used.

As a result of deep research on the stretch flange formability after DII processing, the present inventors found that the stretch flange formability after DII processing, that is, after significant processing, is different from the stretch flange formability of the steel sheet itself, and is rather contrary to conventional knowledge. It has been newly discovered that continuously annealed materials have better stretch flangeability after DII processing despite having solid solution C.

The present invention will be explained in detail below. First, the steel components constituting the present invention will be explained.

Since C hardens steel, its upper limit is set at 0.06%. Reducing C is effective for softening, but C
When BH is reduced to 0.01% or less, solute C decreases significantly and BH
Since the lower limit is set to 0°01%. Mn is 0 to prevent hot embrittlement caused by S, which is an unavoidable impurity.
．． It is necessary to contain 0.05% or more, but if it exceeds 0.60%, the steel becomes hard like C, and the characteristics of the present invention are lost.

The preferred range is 0.1-0.3%. Al acts as a deoxidizing agent to reduce oxide inclusions that are harmful to workability, and also to suppress hardening due to strain aging during surface treatment by fixing N in the steel. It is necessary to contain o, o o s% gold. But 0
．． If it exceeds 0.8%, the steel becomes hard and surface flaws increase. The preferred range is 0.015-0.06%. P
and N are elements that significantly harden steel, and by lowering both P and N, a more pronounced softening effect than previously thought can be obtained. Temper once T-1 or T-
In order to obtain a grade 3 surface treatment original plate, the upper limit of P should be set to 0.
02%, and the upper limit of N is 0.0070%. The preferred range of N is 0.0030% or less. Since S becomes inclusions in the steel and causes surface defects in the surface-treated steel sheet and cracking during processing, it is preferably 0°015% or less. In particular, when manufacturing a soft surface treatment base plate once tempered to T-1 grade, C: 0.01 to 0.03%, Mn: 0.
．． 05-0.20%, acid soluble AI2: 0.04-0.
07%.

It is preferable that P: 0.01% or less and N: 0.0025% or less.

Next, hot rolling conditions will be explained. Hot rolling is a soft surface treatment by continuous annealing that is soft and has excellent DII workability, and also has appropriate BH properties, by specifying the coiling temperature in the first sense and the slab heating temperature in the second sense. It is possible to manufacture original plates. When the winding temperature becomes low, the stretch flangeability deteriorates.

Further, since the hardness is also high, the temperature is set at 600°C or higher. On the other hand, if the temperature is too high, the pickling properties will deteriorate, so the temperature is set at 710°C or lower.

]-Figure shows C: 0.015-0.025%, Mn:
0.15-0.25%, P: 0.006-0.010%
, Al: 0.03-0.08%, N: 0.004%
For the following steels, hot rolling heating temperature (T) °C - (6875
/ (3,865-1og [A 0%+0.01.5
])-250), the hardness of the tin plate, and the DI processability.

The manufacturing conditions shown in FIG. 1 are as follows.

(Hot rolling finishing temperature) 870 to 910°C (Hot rolling winding temperature) 550 to 710°C (Cold rolling reduction) 87 to 9
1% (annealing conditions) 700℃ x 30 seconds + 400℃ x 60 seconds (
-Next cooling rate = 10 to 40℃/sec) (Temper rolling) 1.0% (Plating) In Figure 1 of electric plating, hardness is defined as the surface hardness after electric plating (
III + 307) was set at 811, and DI processability was determined by processing a plated product plate using a laboratory DI forming machine to obtain the tube expansion rate ((D
-D, )/D,)X 1o % was measured.

As shown in Figure 1, the hot rolling heating temperature (T) is (T)
°C≦6875/(3,865-1og[Al%+0.0
151')-250 and the winding temperature is in the range of 600 to 710℃, the hardness (HR3oT) will be low and once tempered T-1
It is possible to produce a surface-treated steel sheet with a grade of T-2 to T-2 and excellent DI workability.

FIG. 2 shows C: 0.01-0.06%, Mn:Q.

10-0.40%, P: 0.006-0.020%.

Al: 0.01-0.07%, N: 0.0015-0.
For 0070% steel, hot rolling heating temperature (T) - (68
75/(3,865-1og [Al%10.015])
-250), the hardness of the tin plate, the compressive strength of the DI processed product, and the stretch flange processing rate.

The manufacturing conditions shown in FIG. 2 are as follows.

(Hot rolling finishing temperature) 870 to 910°C (Hot rolling winding temperature) 600 to 710°C (Cold rolling reduction) 87
~91% (Annealing conditions) (600~800℃) x (30~1
80 seconds) + (400℃) surface hardness(
HR30T) was measured, and the compressive strength and stretch flange processing rate were measured using a DI can manufacturing machine in a laboratory. In Figure 2 (
T)-(6875/(3,865-1og[AN+0.
O15] ) -250) Q marks at the positions of 50, 100 and 150 vary the annealing conditions over a wide range, and only the data where the hardness corresponds to T-1 or T-2 class once tempered are shown. plotted inside. Also, in Figure 2,
For comparison, the data of an example in which a material manufactured by the conventional box annealing method was tempered once and was used as equivalent to T-1 or T-2 class is plotted with an X mark.

As can be seen from FIG. 2, the surface-treated steel sheet according to the present invention is softer than the conventional box-annealed material at the stage of a plating product, so it can be easily processed before DI. Also, since the BH effect in the baking process after DI processing is large,
The compressive strength after DI processing is equal to or higher than that of box annealed material.

It also has better stretch flange formability than box annealed materials.

And hot rolling heating temperature (T)”C≦6875/ (3°8
In the range of 65-1og[Al%+0.015])-250, the highest grade surface-treated steel sheet for DI processing which is the softest and has excellent stretch flange workability can be obtained. Here, (T)”C50875/(3,865-1og[A 0
%+0.0151) -250 is a significant relationship between the steel composition, hot rolling conditions, hardness of the tin plate, DI workability, and compressive strength, and is an equation determined experimentally for the Al content and heating temperature. .

When manufacturing a soft surface treatment original plate with a tempering level of T-1 to T-3, the thermal history before hot rolling does not matter. That is, after casting the steel billet, it may be immediately rolled while being held at a temperature above the Ar transformation point, or it may be cooled to a temperature below the Ar3 transformation point and then reheated and rolled. However, when manufacturing a soft surface treatment original sheet with a tempering of T-1 or T-2, it is necessary to use Ar after casting the billet.
After cooling to a temperature below the transformation point, it is necessary to reheat to a temperature (T) that satisfies T°C≦6875/(3,865-1og[Al%+0°0151)-250.

Next, continuous annealing conditions will be explained. Annealing is performed not by the conventional box annealing method but by a continuous annealing method. In the annealing cycle, first, short-time recrystallization annealing is performed for 5 seconds to 3 minutes in a temperature range of recrystallization temperature to 850 ° C. The preferred temperature range is 680 to 720 °C.
℃ 6 Next, cooling is performed, but if the cooling rate is high, the supersaturated solid solution C before overaging treatment becomes excessive, and the driving force for overaging progress becomes large, so that a moderate amount of solid solution C remains after overaging treatment. Therefore, the upper limit is set to 250° C./sec. If the cooling rate is low, the BH property increases for the opposite reason, but the product board hardness also becomes hard, so the lower limit is 5°C/sec. ). If the overaging treatment temperature is lowered, the diffusion rate of C will slow down and the overaging treatment will take a long time, so the lower limit is set to 3.
If the temperature is increased, the solid solubility limit of C will increase and the amount of solid solubility C after over-aging will increase and the steel plate will become hard, so the upper limit should be set at 50°C.
The temperature shall be 0°C. If the overaging treatment time is short, the overaging treatment will be insufficient and the steel plate will become hard, so the lower limit is set to 30 seconds.
If it is too long, the solid solution C after over-aging treatment will be significantly reduced and BH properties will not be obtained, so the upper limit is set to 180 seconds. Preferred overaging treatment conditions are (350-450°C) x (60-120 seconds)
It is.

Finally, I will explain about tempering once. Once tempered, if it becomes hard, galling is likely to occur during DI processing and the processing energy is also large, so it is classified as T-E or T-3 grade.

[Examples] Table 1 shows examples of the present invention in comparison with comparative materials. 1st
The steel shown in the table was melted in a converter, and the continuously cast steel slabs were hot rolled to a thickness of 3 mm under the conditions listed in Table 1, pickled, and then cold rolled to a thickness of 0.32 mm.

Then, it was annealed under the annealing conditions listed in Table 1 and then 1°0%
Temper rolling was carried out and electric tin plating was carried out.

Table 1 also shows the as-product hardness (HR30T), compressive strength after DI processing, and stretch flange processing rate of the electric tin plated products manufactured under each condition.

Coil Nos. 1 to 12 manufactured within the scope of the present invention are DI
It can be seen that this is a surface-treated steel sheet of once tempered T-1 to T-3 grade with excellent workability and compressive strength.Coil Nos. 13 to 15 of comparative materials manufactured outside the scope of the present invention have high hardness. However, the pressure resistance is low and the stretch flange processing rate is also poor.

[Effects of the Invention] The present invention is a T that has low material and manufacturing costs, excellent uniformity of product material, is soft and easy to mold during DI processing, and has cutting performance that improves pressure resistance through baking treatment after processing. -1 to T-3 grade surface-treated steel sheets can be provided, and the industrial effects thereof are enormous.

[Brief explanation of drawings]

Figure 1 shows the hot rolling heating temperature (T)”C-(6875/(3,
865-1og[Al%10.0153)-250)
Figure 2 shows the relationship between hardness and DI workability of tin plate, stratified by hot rolling winding temperature.
865-1og [A 0% + 0.015ko) -250
), the hardness of the tin plate, the pressure resistance strength of the DI processed product, and the stretch flange processing rate.

Claims (2)

[Claims] (1) In weight%, C: 0.01-0.06% Mn: 0.05-0.60% P: 0.02% or less Acid-soluble Al: 0.005-0.08% N: 0. A low carbon Al killed steel piece consisting of 0.070% or less balance Fe and unavoidable impurities is hot rolled, rolled at a temperature of 600 to 710°C, cold rolled, and then continuously annealed to a temperature above the recrystallization temperature and below 850°C. After performing recrystallization annealing for 5 seconds to 3 minutes at a temperature of
A method for manufacturing a T-1 to T-3 grade soft surface treatment original plate for DI processing, which comprises performing an overaging treatment at a temperature of ~500°C for 30 to 180 seconds. (2) In weight%, C: 0.01-0.06% Mn: 0.05-0.60% P: 0.02% or less Acid-soluble Al: 0.005-0.08% N: 0. A low carbon Al-killed steel piece consisting of 0.070% or less Fe and unavoidable impurities is cooled to a temperature below the Ar_3 transformation point, and then (T)℃=6875/(3.865-log[Al%+
0.015])-250 and hot rolled to a temperature (T) that satisfies 60
Rolling and cold rolling at a temperature of 0 to 710°C, then continuous annealing at a temperature of not less than the recrystallization temperature and not more than 850°C.
After recrystallization annealing for seconds to 3 minutes, 5 to 250℃/
Cooled at a cooling rate of seconds, at a temperature of 300-500℃
A method for producing a T-1 or T-2 grade soft surface treatment original plate for DI processing, which comprises performing an over-aging treatment for ~180 seconds.