JP2984138B2 - Continuous cast slab of Fe-Cu alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a Cu-containing material of 20 to 90% by weight.
The present invention relates to a continuous cast slab of a contained Fe-Cu alloy. The continuous cast slab of this Fe-Cu alloy can be rolled into a thin plate and used as a material for electronic and magnetic parts, for example, a lead frame material.

[0002]

2. Description of the Related Art For example, Japanese Patent Application Nos. 2-93440 and 3-73265 are inventions filed by the present inventors and describe Fe-Cu alloy thin plates using continuous cast slabs. Have been. That is, by specifying an alloy component, a continuous cast slab having a fine metal structure and a thickness of 2.2 to 10 mm is manufactured and cold-rolled to manufacture an Fe-Cu-based alloy thin plate.

According to the knowledge of the present inventors, the slab of the Fe-Cu alloy immediately after casting has a low strength, and therefore, cracks are formed on the surface of the slab due to thermal stress generated in the slab during cooling. There is a problem that it easily occurs. If the components of the molten metal are selected within the ranges described in Japanese Patent Application Nos. 2-93440 and 3-73265, this problem is slightly improved, and the production of continuous cast slabs having a thickness of 10 mm or less is possible. Becomes

[0004] However, it is difficult to sufficiently prevent cracks only by selecting the components. Therefore, a slab having a thickness of more than 10 mm, which generates a large thermal stress when cooling the slab, has many cracks. Conventionally, it has not been manufactured.

[0005]

The Fe-Cu based alloy as a material for electronic and magnetic parts is often used as a thin plate having a thickness of 0.5 mm or less. Therefore, the thickness is 2.2-
It can also be manufactured by rolling a 10 mm slab. When producing a thin slab, the casting speed (m / min) is increased and continuous casting is performed at a high speed. However, since the thickness is small even when cast at a high speed, the productivity (ton / min) of the continuous casting is small with a conventional slab having a thickness of 2.2 to 10 mm, and the continuous casting is performed with high productivity. Things are difficult.

If a slab having a thickness of more than 10 mm can be produced without causing cracks during cooling, the productivity of continuous casting is greatly improved. The present invention relates to F
An object of the present invention is to provide a cast slab of an e-Cu-based alloy, in which cracks are less likely to occur during cooling.

[0007]

According to the present invention, (1) Cu is 2
0% by weight or more, Cr is 1 to 10% by weight, Fe is 10% by weight
% Or more, and is a continuous cast slab having a thickness of more than 10 mm to 80 mm, wherein the surface layer portion of the slab is formed of a columnar structure having a thickness of 1/3 or more of the thickness of the slab. , Fe
-A continuous cast slab of a Cu-based alloy. (2) Cu
20% by weight or more, 1 to 10% by weight of Cr, 10% by weight of Fe
Mo, Al, La, Si, Ti, Z
one or more elements selected from r, C and B in total
Contains not more than 10% by weight and has a thickness of more than 10 mm to 80 mm
A continuous cast slab, wherein the surface layer of the slab has a thickness of 1
It is characterized by being formed of a columnar structure with a thickness of / 3 or more
It is a continuous cast slab of an Fe-Cu alloy.

[0008] The Fe-Cu alloy of the present invention contains at least 20% by weight of Cu in order to improve electric conductivity and heat dissipation as materials for electronic and magnetic parts. Fe in alloy
The minutes impart strength to the alloy . The content of F e is too small
And, the strength becomes insufficient. The ratio of the content of Cu to the content of Fe is selected according to the application based on the balance between electric conductivity and the like, but the content of Fe is 10% by weight or more.

[0009] Cr is added to impart corrosion resistance to the alloy. If the content is less than 1% by weight, the effect of improvement is small, so that the content is 1% by weight or more. However, when Cr is contained, coarse crystal grains are likely to be generated in the slab. Therefore, the content is set to 10% by weight or less.

Although not essential in the present invention, one or more elements selected from Mo, Al, La, Si, Ti, Zr, C, and B may be further contained in a total amount of 10% by weight or less. it can. Mo, like Cr, imparts corrosion resistance to the alloy, and Al, La, Si, Ti, Zr, C, B
Prevents the generation of coarse crystal grains in the slab. However, if these elements are excessively contained, the total content of Cu and Fe decreases, and the electric conductivity and the strength of the Fe—Cu alloy are impaired. Therefore, the content is 10% by weight or less in total, and preferably 5% by weight or less.

FIG. 2 is an explanatory view of an example of a twin belt type continuous casting apparatus. Reference numeral 4 denotes a metal belt stretched between the pulleys 1, 2, 3 and runs in the direction of the arrow. The metal belt 4 'also runs while being stretched between the pulleys 1', 2 ', 3'. The metal belts 4 and 4 'face each other as shown in FIG. 2, and the belts 1 and 2 and 1' and 2 'are run substantially parallel to each other.

Between the metal belts 4 and 4 'running in parallel, side dams (not shown) are provided at both ends (upper end and lower end of the paper) of the metal belt. The molten metal 7 is injected into a space formed by the metal belts 4, 4 'running in parallel and the side dam. The poured molten metal forms solidified shells 6 and 6 ′ on the metal belt, and the solidified shells 6 and 6 ′ move downward following the movement of the metal belts 4 and 4 ′ to become cast pieces 8. Taken out. When the twin-belt continuous casting apparatus of FIG. 2 is used, a continuous cast slab having a thickness of more than 10 mm to 80 mm can be manufactured with high productivity.

[0013] The slab of the present invention is characterized in that the surface layer of the slab is formed of a columnar structure having a thickness of 1/3 or more of the thickness of the slab. That is, for example, in the case of a slab having a thickness of 30 mm, a columnar structure having a thickness of 10 mm or more is formed on the surface layer of the slab. In the present invention, the columnar structure means that the cross section of the slab is polished with alumina and the polished surface is made of H ₂ O: 50.
cc, HNO ₃ : 25cc, acetic acid: 25cc solution 1
It refers to an aggregated portion of a metal structure extending from the surface of the slab toward the center of the thickness of the slab, which is observed when the surface of the slab is macro-etched and visually observed for 2 to 2 minutes.

As will be described later in detail, a slab in which the surface layer of the slab has a columnar structure having a thickness of 1/3 or more of the thickness of the slab has a Cu content of about 50%, for example. In the case of a Fe-Cu alloy having a composition of about 50% Fe and 0.5% Cr, the temperature of the molten metal injected into the twin-belt continuous casting apparatus shown in FIG. To be obtained. When the temperature of the molten metal having this composition is, for example, 1300 ° C. or less, no columnar structure is observed in the surface layer portion of the slab, and the entire cross section is a slab formed of only the granular structure.

[0015]

The present inventors manufactured Fe-Cu alloy slabs shown in Tables 1 through 4 using the twin-belt continuous casting apparatus shown in FIG.

The slab was cold-rolled, and the surface was visually inspected for cracks. According to the knowledge of the present inventors, cracks having a length of 50 mm or less have a shallow depth and can be easily removed and removed, and do not become a major obstacle in rolling in a later step, but have a length of more than 50 mm. It is difficult to remove the cracks. Therefore, in FIG. 1, a slab having no cracks having a length of more than 50 mm was obtained without cracks, and a length of 50 mm was obtained without cracks in FIG. 1.
Refers to a slab with excessive cracks.

[0017]

[Table 1]

The present inventors also took a macroetch sample of a cross section from a substantially central portion in the longitudinal direction of each slab, and examined the thickness of the columnar structure in the surface layer of the slab. FIG. 1 shows the correspondence between the thickness of the columnar structure of the slab and the observation result of cracks in the slab.

As shown in FIG. 1, when the columnar structure is thin and {(columnar structure thickness) / (slab thickness) × 100} is 20 or less, all the slabs have cracks, and in extreme cases, Is broken. On the other hand, {(columnar structure thickness) / (slab thickness) × 100} is 3
When it was 0 or more, no crack was generated on the slab.

The present inventors have further investigated the metallographic structure of these slabs and have obtained the following findings. That is, in the vicinity of the crack of the slab where the crack has occurred, a huge abnormal structure having a size of about 3000 μ or more is scattered in the surface layer portion of the slab within 1/3 of the thickness of the slab. This huge abnormal structure is not observed in the columnar structure, but is scattered exclusively in the structure of granular crystals. Therefore, the surface layer of the slab is 1/3 of the slab thickness.
The cast slab having the columnar structure having the above thickness does not have a huge abnormal structure in the surface layer portion of the cast slab, and the cast slab does not cause breakage or cracks.

The reason why the huge abnormal structure is generated exclusively in the structure of the granular crystal and not in the columnar structure is not necessarily elucidated, but the present inventors have conceived as follows.
As already described, Cu: about 50%, Fe: about 50%, C
When the molten metal of r: 0.5% is cast at 1300 ° C., the whole becomes a slab having a granular crystal structure, and a large number of huge abnormal structures are observed on the surface layer of the slab.

FIG. 5 is a state diagram of a known Fe-Cu.
A melt having a composition of Cu: about 50%, Fe: about 50%, Cr: 0.5% and a temperature of 1300 ° C. is shown as a state a in FIG. That is, the molten metal of (a) is in a state of (melt + γ), and the molten metal before casting contains already solidified γ particles in a floating state. In this molten metal, each of the floating γ particles becomes a nucleus at the time of solidification, and the crystal grows. Therefore, the whole structure has a free crystal structure.

The molten metal reaches around 1080 ° C. and completes solidification. However, since the molten metal (a) is a mixture of γ particles and a melt, the melt fills the gaps between the γ particles during solidification and is interconnected. Then, the ε phase becomes a huge abnormal structure and is scattered also in the vicinity of the surface layer of the cast slab.

As described above, when this molten metal is cast at a temperature of 1450 ° C. or higher, a cast slab having a columnar structure is obtained.
No giant abnormal structure is observed in the surface layer of this slab. FIG. 5B shows an example of this molten metal. This molten metal is γ before casting.
After the injection without containing the particles of, the temperature reaches near the liquidus line and nuclei of γ are generated. The molten metal is cooled most quickly at the contact portion with the metal belt and reaches a temperature near the liquidus line.
Accordingly, the nucleus of γ is first generated in a portion corresponding to the surface layer of the slab, and when the temperature is lowered, the nucleus of γ grows in a dendritic manner toward the center in the thickness direction of the slab.

For this reason, a columnar structure having directionality is obtained. As the nucleus of γ grows in dendrites, the melt is trapped between dendrites and reaches around 1080 ° C and solidifies,
The melt trapped between the dendrites is fine, so the solidified ε-phase is fine and does not become a giant abnormal structure.

In a slab having an insufficient columnar crystal thickness, a huge abnormal structure is scattered on the surface layer of the slab, and this huge abnormal structure has a high Cu content and a low strength ε phase. Therefore, the slab generates cracks starting from the abnormal structure. The slab having sufficiently thick columnar crystals has no huge abnormal structure in the surface layer, and the ε phase is finely and uniformly dispersed. Accordingly, the material strength is uniform, and there is no defect serving as a starting point of cracks, so that cracks are unlikely to occur.

In FIG. 5, Cu: about 50%, Fe: about 50%
In the case of molten metal of other components, if a molten metal having a temperature equal to or higher than the temperature of the liquidus line is poured into a pool of a continuous casting apparatus, the surface layer of the slab becomes 1/3 of the thickness of the slab. A cast piece having a columnar structure having the above thickness can be obtained.

FIG. 3 shows a slab having a columnar structure having a thickness of 1/3 or more of the slab thickness in the surface layer, which was prepared by the present inventors for an Fe-Cu-based alloy containing 3% of Cr. FIG. 5 is a diagram showing an example of the temperature of the molten metal at the time of casting. By using a molten metal having a higher temperature than that indicated by the dotted line, a cast piece having a columnar structure of the present invention can be obtained. FIG. 4 shows Fe-containing 6% Cr.
Using a Cu-based alloy as an example in the same manner as in FIG. 3, a cast slab having a columnar structure of the present invention is obtained.

As described with reference to FIGS. 3 to 5, when the composition of the molten metal changes, the lower limit temperature of the molten metal required for manufacturing the cast slab having the columnar structure of the present invention changes. It is easy to grasp in advance by an experiment or the like, and by maintaining the temperature of the molten metal at a temperature higher than the lower limit temperature, the cast slab having the columnar structure of the present invention can be easily obtained.

Although the present invention has been described with reference to the slab manufactured by the twin-belt continuous casting apparatus shown in FIG. 2, the effect of the slab of the present invention is controlled by controlling the casting temperature based on the new metallurgical knowledge of the present invention. By doing so, it can be easily obtained in other continuous casting apparatuses. Therefore, the present invention is not limited to the slab by the twin-belt continuous casting apparatus, and the present invention includes all slabs of the Fe—Cu-based alloy having the properties limited by the present invention.

[0031]

By using the continuous cast slab of the Fe-Cu alloy of the present invention, it is possible to prevent the occurrence of cracks or breakage when transported to a coiler after winding or when wound up by a coiler. it can.

[Brief description of the drawings]

FIG. 1 is a view showing the relationship between the columnar structure of a slab and cracks / breaks, FIG. 2 is an explanatory view of a twin-belt continuous casting apparatus, and FIG.
FIG. 4 is a diagram showing an example of the temperature of a molten metal suitable for producing a slab of the Fe—Cu-based alloy of the present invention containing 3% of r, and FIG. 4 is a diagram of the Fe—Cu-based alloy of the present invention containing 6% of Cr. FIG. 5 is a view showing an example of a melt temperature suitable for manufacturing a slab, and FIG.
FIG.

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kazumi Yasuda 20-1 Shintomi, Futtsu City, Chiba Prefecture Nippon Steel Corporation Technology Development Division (72) Inventor Satoshi Nishimura 20-1 Shintomi, Futtsu City, Chiba Prefecture New Nippon Steel Corporation Technology Development Division (72) Inventor Hirosaku Shioda 20-1 Shintomi, Futtsu City, Chiba Prefecture Nippon Steel Corporation Technology Development Division (72) Inventor Kenichi Miyazawa 1 Kimitsu, Kimitsu City, Chiba Prefecture Nippon Steel Corporation Kimitsu Works (56) References JP-A-2-251345 (JP, A) JP-A-4-333538 (JP, A) JP-A-3-243244 (JP, A) JP-A-5-138301 (JP, A) JP-A-5-277652 (JP, A) Patent 2614381 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B22D 11/06 340 B22D 11/00 C22C 9/00 C22C 38/00 302

Claims (2)

(57) [Claims] (1) Cu is 20% by weight or more and Cr is 1 to 10 weights.
%, Fe is 10% by weight or more, and the thickness is more than 10 mm to 8 %.
A continuous cast slab of 0 mm, wherein the surface layer of the slab is formed of a columnar structure having a thickness of 1/3 or more of the thickness of the slab. Cast slab. 2. Cu is 20% by weight or more, and Cr is 1 to 10 weight%.
%, Fe is 10% by weight or more, and Mo, Al, L
1 or 2 selected from a, Si, Ti, Zr, C and B
10% by weight or less of the above elements in total, and a thickness of 10%
A continuous cast slab of more than 80 mm to 80 mm, and the surface layer of the slab
The part is formed with a columnar structure with a thickness of 1/3 or more of the thickness of the slab.
Continuous casting of Fe-Cu alloy
Slab.