JP2951241B2 - Manufacturing method of cold rolled steel sheet with excellent workability and enamel properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention is workability and enameling, especially
The present invention relates to a method for stably and economically producing a cold-rolled steel sheet having excellent heat resistance .

[0002]

2. Description of the Related Art Enamel products made by firing a glassy glaze having excellent corrosion resistance and chemical resistance on the surface of a steel sheet are widely used for kitchenware, chemical equipment and the like. Since the steel sheet used for this enamel product is required to have excellent formability as well as enamel properties such as anti-sticking property and adhesiveness, an ultra-low carbon steel sheet excellent in workability is often used.

[0003] Further, conventionally, there has been proposed a technique for improving the enamel properties by performing various component adjustments on ordinary ultra-low carbon steel. For example, JP-A-59-
Japanese Patent No. 229463 describes a technique for improving the anti-sticking property by defining the oxygen content in steel. Japanese Patent Publication No. 60-51538 discloses a technique for improving the adhesion of an enamel by adding Cu.

[0004]

However, even with the techniques disclosed therein, satisfactory enamel characteristics have not yet been satisfied directly under severe enamel application conditions. Further, the technology of increasing the oxygen content in steel or containing Cu deteriorates the surface properties of the steel material in the steel plate manufacturing process, and causes a problem of increasing costs such as an increase in rework steps and a decrease in yield.

The present invention has been made in view of the above problems, and has as its object to provide a method for stably and economically producing a cold-rolled steel sheet having excellent workability and enamel characteristics.

[0006]

Means for Solving the Problems The present invention according to claim 1
How to manufacture cold rolled steel sheets with excellent workability and enamel properties
According to the method , the chemical composition is expressed by weight%, C: 0.008% or less, Mn: 0.05 to 0.5%, P: 0.02% or less, S: 0.02% or less, sol.Al: 0.01 to 0.1%, N: 0.01% or less Cu : 0.10% exceeds 0.02% or less, Ni: 0.10% exceeds 0.02% or less, Ti: contains 0.05 to .15%, the steel balance of Fe and unavoidable impurities
Continuous casting, after hot rolling, winding at 500-750 ° C
After pickling and pickling, cold rolling was performed at a draft of 60% or more.
Thereafter, annealing is performed in the range from the recrystallization temperature to Ac ₃ points.

[0007] The invention described in claim 2 is the same as the invention.
1. The method according to 1, wherein the chemical composition further comprises B:
It contains 0.002% or less.

[0008]

When a metal noble from Fe, such as Cu, is added to steel, the steel on the surface layer of the steel sheet during casting and subsequent hot rolling is added.
Is selectively oxidized, and after a descaling step by pickling, a steel sheet in which Cu is concentrated in the surface layer is obtained as a result.
Further microscopically, if there is a difference in the enrichment state at each site, this may cause fine irregularities on the steel sheet surface after the pickling treatment, which is the pretreatment for enamel firing. It is considered to be formed to produce the effect of improving the enamel adhesion.

The present inventors have investigated various component systems. As a result, it has been found that the addition of a certain amount of Cu and Ni in combination is superior to the single addition of Cu and Ni in improving the adhesion to enamel and the toughness. I found that.
In other words, by adding an appropriate amount of Cu and Ni in combination to a normal ultra-low carbon IF steel to which Ti is added, good workability and good workability can be achieved without any need for other component adjustments that increase the cost. A steel sheet having enamel characteristics can be stably manufactured.

Although the detailed mechanism is unknown at present,
There is a difference in fine irregularities on the steel sheet surface after pickling between the addition of Cu and Ni alone and the addition of a combination thereof, which is considered to contribute to the improvement of adhesion. On the other hand, with regard to the toughness, it is considered that the composite precipitates in the steel serve as hydrogen trap sites, thereby improving the effect. In addition, a feature of the present invention is that a uniform surface property can be obtained in the width and longitudinal direction of the steel sheet, but this is due to the fact that Cu and Ni are uniformly present in the molten steel during the slab stage, and thus during casting. It is supposed to be. Furthermore, the addition of Cu and Ni composites has the effect of improving the properties of the continuous casting slab and the surface layer of the steel sheet in the hot rolling stage, and has the effect of preventing an increase in the number of steps and a decrease in yield.

Hereinafter, the present invention will be described in detail. First, the reasons for limiting the components of the steel of the present invention will be described. Hereinafter, all units are wt%. C: not more than 0.008% C decreases the transformation temperature as its content increases,
Since firing distortion is likely to occur, pinholes during enamel firing increase, and further increase in precipitates causes deterioration in workability, the upper limit is made 0.008%.

Mn: 0.05-0.5% Mn is added for the purpose of preventing hot embrittlement. 0.
If the amount is less than 05%, the effect is too small. On the other hand, if the amount is too large, the ductility is deteriorated. Therefore, the upper limit is made 0.5%.

P: not more than 0.02% Since a large content of P causes a decrease in enamel adhesion and secondary work brittleness resistance, the upper limit is made 0.02%.

S: 0.02% or less S combines with Ti and Mn to form a sulfide such as TiS and MnS, and contributes to the improvement of the jump-resistant property. However, Mn
Since the workability deteriorates due to the increase of the elongated inclusions in the system, the upper limit of the content is set to 0.02%.

Sol. Al: 0.01-0.1% Al is added for the purpose of deoxidizing molten steel before adding Ti. If the amount of sol. The effect is too small, Ti is oxidized, and the yield of elements is reduced. On the other hand, if it exceeds 0.1%, the deoxidizing effect is saturated and Al ₂ O ₃ inclusions increase, thereby deteriorating workability.

N: 0.01% or less N exists as an impurity in steel and forms nitrides of Ti and Al. From the viewpoint of workability and anti-sticking property, it is preferable to precipitate TiN without remaining in a solid solution state, but an increase in the amount of Ti added to fix N causes an increase in manufacturing cost. Therefore, the upper limit is made 0.01%.

Cu: more than 0.02% and not more than 0.10% By adding Cu, fine undulations are generated on the surface of the steel sheet after pickling, and the enamel adhesion is improved. Furthermore, the effect becomes remarkable by the composite addition with Ni. If it is less than 0.02%, such an effect is too small. On the other hand, the addition of a large amount deteriorates pickling properties and saturates the effect on adhesion, so the upper limit is made 0.10%. 0.06% from an economic point of view
The following is desirable.

Ni: more than 0.02% and 0.10% or less Ni is an important constituent element of the present invention together with Cu. That is, Ni concentrates in the surface layer together with Cu during the steel sheet manufacturing process, and causes fine undulations on the steel sheet surface after pickling to improve the enamel adhesion. The composite addition of Ni is Cu
Compared to a single addition, it is more effective in improving the enamel adhesion, and has the characteristic that the effect is macroscopically uniform. In addition, it also has the effect of improving the properties of the slab surface and the hot rolled sheet surface after casting. In order to bring about the effect of this composite addition, it is necessary to add more than at least 0.02%. However, if it exceeds 0.10%, the effect is saturated and the cost is increased. The upper limit is 0.1
0%. Further, considering softening, the content is desirably 0.06% or less.

Ti: 0.05 to 0.15% Ti is added to fix N and C and to form a precipitate containing P and S. By reducing solid solution elements such as C and N, workability is improved, and furthermore, the formation of precipitates improves the anti-sticking property. To do so, at least 0.
Addition of 05% is required. However, excessive precipitation due to excessive addition deteriorates the workability, so the upper limit is made 0.15%.

The steel used in the present invention is formed of the balance of Fe and unavoidable impurities, in addition to the above components, and can contain the following elements as necessary. B: 0.002% or less B is an element effective for suppressing embrittlement in secondary processing,
Also in the present invention, it can be added as needed to improve the secondary workability. However, 0.002%
If the addition exceeds 3, the effect is saturated, so the upper limit is made 0.002% from the viewpoint of economy.

Continuous casting of steel having the above chemical composition,
The obtained slab is hot-rolled by an ordinary method. That is,
The steel is heated to a temperature of about 1100-1300 ° C.
r Finish rolling at a temperature of ₃ points or more. The lower limit of the winding temperature is set to 500 ° C. in order to secure ductility and deep drawability, and the upper limit is set to 7 from the viewpoint of material deterioration at both ends of the coil and production cost.
50 ° C.

After hot rolling, cold rolling is performed after pickling. Although there is no particular limitation on the cold rolling conditions for the enameled steel sheet, the rolling reduction is set to 60% or more from the viewpoint of workability.
However, when the rolling reduction exceeds 90%, the r value (rank for-
Value) decreases and an excessive load is applied to the rolling mill, so the upper limit is preferably set to 90%.

The thus obtained cold rolled steel sheet is annealed. Annealing is performed within a temperature range from the recrystallization temperature to Ac ₃ points. A high workability steel sheet cannot be obtained by annealing below the recrystallization temperature.
When annealed at temperatures in excess of c ₃ transformation point, because the crystal orientation is randomized, workability is deteriorated. The annealing method is not limited to continuous annealing or batch annealing.

[0024]

EXAMPLES Steel having the components shown in Table 1 and having symbols A to L was continuously cast to obtain a slab having a weight of about 20 tons. After cooling this slab and examining the defects on the front and back, remove the defect,
Hot rolling was performed at a heating temperature of 1150 ° C, a finishing temperature of 920 ° C, and a winding temperature of 680 ° C. The hot rolled sheet after the pickling was also examined for surface defects, and then cold rolled at a rolling reduction of 80% to a sheet thickness of 0.8 mm. Further soaking temperature: 8
Perform continuous annealing at 30 ° C. for 60 seconds, and then elongation: 1.
A 0% temper rolling was performed to obtain a cold-rolled steel sheet (steel strip).

[0025]

[Table 1]

In Table 1, symbols A to E are steel grades of the present invention. The symbol F is a steel having a high oxygen content by reducing Al as a deoxidizing agent, the symbol G is a steel in which Ti is out of the lower limit of the present invention,
The symbol H is a steel in which Cu and Ni are out of the lower limit of the range of the present invention. The symbol I is a steel in which Ni is out of the lower limit of the present invention, the symbol J is a steel in which Cu is out of the lower limit of the present invention, and the symbol K is Cu
Is a steel out of the upper limit of the present invention, and symbol L is a steel in which Ni is out of the upper limit of the present invention.

Table 2 shows the surface quality characteristics of the slab and the hot-rolled sheet and the mechanical properties of the annealed sheet. The mechanical properties are the results measured by the JIS No. 5 tensile test. The surface characteristics of the slab were determined by investigating the area requiring care for about 20 m ² of the front and back surfaces per slab, and dividing the area by the survey area. The surface properties of the hot-rolled sheet were determined by examining the locations where defects such as scabs and slivers were generated over the entire length of the hot coil, and dividing the weight of the portion requiring truncation by the total weight.

[0028]

[Table 2]

According to Table 2, the code F has many inclusions and is inferior in the surface quality of the slab. Therefore, slab care is indispensable, resulting in an increase in cost and poor mechanical properties. Further, the codes F and G have no elongation El, r value and the like because Ti is not added, and are inferior in workability. As for the signs I and K, a large number of barbed defects causing a reduction in yield occurred on the surface of the hot-rolled sheet. Further, the symbols K and L decrease the El and r values due to the addition of a large amount of alloying elements, resulting in deterioration of workability.

The enamel characteristics of the cold rolled steel sheet were examined. The enamel properties such as adhesion are as follows. After degreasing a 100 × 150 mm steel sheet sample, the weight loss is 30 g / 15% in 15% sulfuric acid.
After pickling, so as to obtain m ² , Ni treatment and neutralization,
It was assessed after firing the enamel of thickness 100μm by directly one seat of Ti Keishiro釉(Nippon Fe B over Corp. 1553C). The adhesion rate was evaluated by a PEI test after ten samples were taken from an arbitrary portion of the steel strip and baked with enamel. On the other hand, the state of occurrence of jumping was evaluated by enamelling 10 samples in the same manner, leaving the sample to stand for 1 week, and then evaluating the total number of jumping points generated on both sides of the sample.
Table 3 shows the adhesion and the occurrence of jumps.

[0031]

[Table 3]

According to Table 3, symbols G, H, and J have low adhesion rates, and symbol G has a very large number of jumps. Regarding the reference signs H, I, and J, the jumpiness is not good. The symbol I having a very small Ni content indicates a moderate adhesion rate on average, but a significant decrease in the adhesion rate is observed at 88 to 90 depending on the portion in the steel strip.

[0033]

As described above, the cold rolled steel sheet produced according to the present invention containing a predetermined amount of Cu and Ni not only has good tongue and adhesive enamel properties, but also has a good manufacturing process. Also, since the surface properties of the steel sheet can be kept good, the yield can be improved,
Excellent industrial productivity.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-277742 (JP, A) JP-A-59-182923 (JP, A) JP-A-51-27812 (JP, A) JP-A-59-1982 35631 (JP, A) JP-A-3-6330 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21D 9/46 C22C 38/00 301 C22C 38/16

Claims (2)

(57) [Claims] 1. The chemical composition is% by weight, C: 0.008% or less, Mn: 0.05 to 0.5%, P: 0.02% or less, S: 0.02% or less, sol.Al: 0.01 to 0.1%, N: 0.01% The following steel contains Cu: more than 0.02% and 0.10% or less, Ni: more than 0.02% and 0.10% or less, and Ti: 0.05 to 0.15%, with the balance being Fe and unavoidable impurities.
Continuous casting, after hot rolling, winding at 500-750 ° C
After pickling and pickling, cold rolling was performed at a draft of 60% or more.
After that, it is characterized by annealing in the range of recrystallization temperature to Ac ₃ points.
Of cold rolled steel sheet with excellent workability and enamel properties
Law. 2. The refrigeration system according to claim 1, which contains the component described in claim 1 and further contains B: 0.002% or less.
Manufacturing method of rolled steel sheet.