JPH07197144A - Production of cu or cu alloy casting product - Google Patents

Abstract

PURPOSE:To produce casting products free from crack defects by subjecting the melt of a Cu material to deoxidation by metallic deoxidizing agents contg. metals which are easier to be oxidized than the Cu material, then decreasing the concn. of the metals, etc., derived from these deoxidizing agents at a specific value of below, and then casting. CONSTITUTION:A Cu or Cu alloy is deoxidized by using >=1 kinds of the metallic deoxidizing agents contg. the metals (Ca, Al, Mg, Ti, Cr, Zr, etc.) which are easier to be oxidized than the Cu or Cu alloy in an arbitrary stage before casting at the time of casting the Cu or Cu alloy. The excessive metallic deoxidizing agents and other products of deoxidization floating on the molten metal surface in a stage for holding or transferring the molten metal are removed and the concn. of the metals and metal oxides derived from the deoxidizing agents is decreased to <=200ppm in terms of the metals if the oxygen concn. in the melt of the Cu or Cu alloy is decreased down to the equilibrium value of deoxidization. As a result, the Cu or Cu alloy casting products free from the crack defects are obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing Cu and Cu alloy cast products, and particularly to prevent ingot cracks during casting and hot work cracks thereafter, and to obtain cast products without crack defects. It is about the manufacturing method that can be done.

[0002]

2. Description of the Related Art Since Cu and Cu alloys are good conductors of electricity and heat and are excellent in corrosion resistance, workability, strength, etc., they are widely used mainly in the fields of electronics and electricity. It is used. Of these, for example, C
u-Fe alloys are widely used as materials for electronic parts such as lead frames.

By the way, a pure Cu or Cu-based alloy (hereinafter sometimes simply referred to as a Cu alloy) product is usually manufactured through the following steps. However, in the Cu alloy casting step, ingot cracking or hot working is often performed. It has been experienced that cracking occurs, and it has been confirmed that such a phenomenon is more prominent in coarser grains. Among them, in the case of Cu-Fe alloy,
It is pointed out that hot cracking tends to occur during ingot cracking during casting and subsequent hot working. Raw material → Melting → Component adjustment → Casting → Soaking → Hot rolling →
Cold rolling → heat treatment → surface treatment → product → inspection → shipping

In order to prevent such defects such as ingot cracking, miniaturization of crystal grains is effective as one means. The principle of refining crystal grains is to increase the number of crystal grains during solidification and prevent grain growth due to heating after completion of solidification, based on the fact that crystal grains are dominated by nucleation and growth. The following measures have been taken from the point where is considered effective. (1) Addition of a substance having a nuclear action of crystal grains, or generation of a new nuclear action substance by the reaction between the added substance and the molten metal, (2) rapid solidification method, (3) molten metal vibration method.

However, the above methods (2) and (3) are difficult to apply to large ingots, and
It is difficult to carry out on a practical scale and it is considered to be preferable in practice is the method of (1) above. Specifically, when Cu-based shape memory alloy is melted, 50 to 5 Ca is added to the molten metal.
In the method of refining the crystal grains by adding about 00 ppm (Japanese Patent Laid-Open No. 62-167828), or when producing a beryllium-Cu alloy, Ti is 0.05 to
A method for refining crystal grains by adding about 0.5% by weight (Japanese Patent Laid-Open No. 4-305353) has been proposed.

[0006] These methods basically use elements such as Ca and T which are more easily oxidized in the molten Cu alloy than the Cu alloy.
i and the like are added, a large number of fine oxides such as CaO and TiO ₂ are produced by the reaction with oxygen existing in the molten metal, and these are used as a nucleating agent to make the crystal grains finer. . However, when a large amount (about 100 to 5000 ppm) of these elements remains in the Cu alloy ingot, the crystal grains can be made finer, but the ingot cracks or the like due to the metal or their oxides. Surface defects such as linear defects appear, and a new problem arises in that the oxide causes plating failure during plating.

[0007]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the problems as described above.
The present invention aims to establish a technology capable of eliminating ingot cracks and other defects found in alloys and obtaining Cu and Cu alloy cast products of excellent quality without crack defects.

[0008]

The structure of the manufacturing method according to the present invention, which has been able to solve the above-mentioned problems, is such that, when casting Cu or a Cu alloy, it is better than the Cu or Cu alloy at any stage before casting. After deoxidizing using one or more metal-based deoxidizing agents containing metals that are easily oxidized, the oxygen concentration in the molten Cu or Cu alloy is reduced to a deoxidizing equilibrium value, and then the metal-based deoxidizing agent is used. Which has the gist of preventing ingot cracking and hot work cracking of the ingot by casting after reducing the concentration of the metal and metal oxide derived from to 20 ppm or less for each metal element in terms of metal Is.

In carrying out the above method, Cu--Fe
When a system-based alloy is used, the oxygen concentration is reduced by deoxidation to prevent the crystallization of the Cu-Fe-O-based eutectic compound during casting, and at the same time, a fine metal oxide derived from the metal-based deoxidizer. By acting as a nucleating agent, the refinement of crystal grains during casting can be promoted to prevent ingot cracking and hot work cracking of the ingot, and Cu or Cu alloy (provided that Cu-F
(except for e-based alloys), the reduction of oxygen concentration by deoxidation and the action as a nucleating agent for fine metal oxides derived from metal-based deoxidizers make the crystal grains fine during casting. Can be improved, and ingot cracking and hot work cracking of the ingot can be prevented.

As the metal-based deoxidizing agent used at this time, an elemental metal or an alloy having Cu as a mother alloy can be used. For deoxidizing, carbon or CO gas is used for deoxidizing and metal. Deoxidation using a system deoxidizer can be used in combination.

[0011]

In order to clarify the cause of the ingot crack and the hot work crack found in the Cu-Fe alloy under the above-mentioned problems to be solved, the present inventors have made the situation of the crack occurrence part into consideration. It was observed by an optical micrograph. The results are shown in, for example, FIG. 1 (A) (ingot cracking) and FIG. 1 (B) (hot working cracking), and Cu--Fe is present in the portions where the ingot cracking and hot working cracking occur. There is an -O-based eutectic compound, and as is clear from this figure, ingot cracking and hot work cracking are caused by Cu-Fe generated in the solidification process during casting.
It was considered that the -O eutectic compound was one of the causes.

On the other hand, the present inventors have confirmed separately that Cu other than pure Cu-based or Cu-Fe-based alloys
In alloys, ingot cracks and hot work cracks due to the above eutectic compounds do not pose a problem, but ingot cracks and hot work cracks occur due to coarsening of the ingot crystal grains. There is a tendency, and this tendency is a common problem in Cu-Fe alloys.

That is, in the Cu--Fe alloy, Cu--
The formation of the Fe-O eutectic compound and the coarsening of the crystal grains adversely affect additively or synergistically to cause ingot cracks and hot work cracks, while pure Cu or the above Cu-Fe In the case of Cu alloys other than the system alloys, the coarsening of crystal grains is the main cause to cause ingot cracks and hot work cracks.

Therefore, in order to solve the above problems and to establish a method capable of stably producing a high quality Cu or Cu alloy ingot without causing ingot cracks or hot work cracks. After various investigations, as described above, Cu
Alternatively, when casting a Cu alloy, at any stage before casting, deoxidation is performed using one or more metal-based deoxidizers containing a metal that is more easily oxidized than the Cu or Cu alloy, Alternatively, after the oxygen concentration in the molten Cu alloy is reduced to the deoxidation equilibrium value, the concentration of the metal and the metal oxide derived from the metal-based deoxidizer is 20 p for each metal element in terms of metal.
It has been confirmed that ingot cracking and hot work cracking of the ingot can be effectively prevented by casting after reducing to pm or less.

At this time, when a Cu--Fe alloy is used, the oxygen concentration is reduced by deoxidation to reduce the C concentration during casting.
While preventing crystallization of the u-Fe-O-based eutectic compound,
The crystal grains during casting can be refined by acting as a nucleating agent for fine metal oxides derived from metal-based deoxidizers, and Cu or Cu alloys other than Cu-Fe-based alloys were used. In this case, by reducing the oxygen concentration by deoxidation and acting as a nucleating agent for fine metal oxides derived from a metal-based deoxidizer, it is possible to make the crystal grains fine during casting, which results in casting. It is possible to obtain a cast product with very few lump cracks and hot work cracks.

First, in the present invention, oxygen, which is a generation source of a Cu—Fe—O eutectic compound that causes cracking of a Cu alloy product, is added at any stage until casting, for example, melting, holding or transferring of raw materials. Metals that are more easily oxidized than the Cu alloy in the process (for example, Ca, Al, Mg, Ti, Cr, Zr)
The oxygen concentration in the molten Cu alloy is reduced to a deoxidation equilibrium value (usually about 60 ppm or less, preferably 15 ppm or less) by deoxidation using one or more metal-based deoxidizing agents containing. By this deoxidizing treatment, the production amount of the Cu—Fe—O eutectic compound, which is one of the causes of ingot cracking and hot work cracking in a Cu—Fe alloy, is remarkably reduced.

By the way, FIG. 2 shows the results of the investigation of the relationship between the oxygen concentration in the molten Cu-2% Fe-based alloy and the area ratio of the Cu-Fe-O-based eutectic compound in the ingot cross section when casting the molten Cu-2% Fe-based alloy. (However, the casting adopts a semi-continuous casting method, the casting speed is 40 mm / min), and although there are some differences depending on the casting speed, in both cases, when the oxygen concentration in the molten metal exceeds 60 ppm, the ingot is ingot. The area ratio of the Cu-Fe-O-based eutectic compound in the inside rapidly increases, but the oxygen concentration is 60 ppm.
If the amount is suppressed below, the amount of Cu—Fe—O eutectic compound produced during casting can be reduced to zero.

FIG. 3 is a graph showing the results of examining the relationship between the oxygen content in the molten Cu-2% Fe alloy immediately before casting and the oxygen content in the ingot, which is also clear from this figure. Thus, the amount of oxygen in the molten metal and the amount of oxygen in the ingot almost correspond to each other, and it can be seen that the oxygen in the molten metal is taken into the ingot almost as it is. And as is clear from this figure and FIG. 3, oxygen of 60 ppm or less contained in the molten metal hardly participates in the formation of the Cu—Fe—O eutectic compound during solidification of the ingot, Therefore, it does not seem to cause cracking. However, since it is undeniable that the trace amount of oxygen contained in the molten metal becomes a generation source of oxide-based inclusions,
Particularly, in the case of Cu-Fe alloy products such as ultrafine wire rods and ultrathin plates, it is desired that the oxygen concentration in the molten metal be suppressed to 15 ppm or less.

The timing of the above deoxidation is not particularly limited, and it may be performed at any stage before casting, for example, in a melting furnace, a holding furnace, a degassing apparatus, or at any place such as when transferring molten metal between them. Therefore, it is possible to deoxidize at a single point to the target oxygen concentration at once, and it is of course possible to carry out deoxidation stepwise at two or more points if necessary.

Further, as the deoxidizing agent, a metal deoxidizing agent (reducing agent) as described above or a gas reducing agent such as carbon or carbon dioxide gas is used. It also has an important meaning as a nucleating agent production step for refining the crystal grains of, and in order to produce the nucleating agent in the molten metal,
It is necessary to use at least one metal-based deoxidizing agent as the deoxidizing agent. As the metal-based solid reducing agent, Ca, Al, Mg, Ti, Cr, Zr, which has a low free energy of formation of the oxidation reaction and a small density of the product, and which is easy to float and separate
Etc. are exemplified as preferable ones, and these may be used alone or in combination of two or more kinds.

At this time, it is of course possible to use charcoal powder or CO gas as another deoxidizing agent (reducing agent) to accelerate deoxidizing. As a general gas reducing agent, H ₂ is used.
Are also known gas, so when using H ₂ gas concentration of H ₂ in the melt cause the resulting blister defects in the cast product to rise, the use of H ₂ gas should be avoided. Cu-Fe, which is one of the causes of ingot cracking and hot work cracking particularly observed in Cu-Fe alloys, is caused by the above deoxidation treatment.
The formation of the —O-based eutectic compound is effectively prevented, but ingot cracks and the like related to crystal grains are unsolved.

Therefore, in the present invention, the metal-based deoxidizing agent or its deoxidizing product used in the above deoxidizing step is effectively utilized as a nucleating agent to achieve finer crystal grains. As described above, the metal-based deoxidizing agent and its deoxidation product (particularly the metal oxide produced by deoxidation) effectively act as a nucleating agent for grain refinement. It makes it easier to cause ingot cracks.

In the present invention, as a means for effectively exhibiting the action as a nucleating agent without causing such a negative effect as impure inclusions, the molten metal is held or transferred after the above deoxidation treatment. Removes excess metal-based deoxidizer or its deoxidation product that floats on the surface of the molten metal during the process,
The concentration of metal and metal oxide derived from the metal-based deoxidizer is reduced to 20 ppm or less for each metal element in terms of metal. By this treatment, most of the metal oxides present in the molten metal are separated and removed, and the adverse effects as impure inclusions hardly occur, but extremely fine metal oxides of about 1 μm or less are kept in the molten metal as they are. Remain in a uniformly dispersed state, and this acts as a nucleating agent during casting to refine the crystal grains.

Incidentally, FIG. 4 shows Ca as a metal-based deoxidizer.
The results of examining the Ca concentration in the molten metal and the crystal grain size and the oxygen concentration in the molten metal when using Cu are shown. When Ca is added to the Cu alloy molten metal, deoxidation is performed as the amount of addition increases. The reaction reduces the amount of oxygen in the molten metal, and the grain size of the ingot cast using the molten metal becomes finer.
In FIG. 4, deoxidation and refinement of crystal grains proceed as the Ca content increases up to a Ca concentration of 300 ppm.
If the amount of Ca is further increased, deoxidation and grain refinement will not proceed any further. The reason why such a tendency is obtained is considered as follows.

That is, Ca added to the molten metal becomes an oxide (CaO) by a reaction (deoxidation reaction) with oxygen existing in the molten metal. Of these, coarse CaO and the like are melted relatively quickly. Ascend to the surface. However, extremely fine CaO or the like having a size of about 1 μm or less hardly floats and remains in a dispersed state in the molten metal, and thus the remaining deoxidized products such as the fine CaO and the like contribute to the refinement of crystal grains. To do. This is because this reaction naturally comes to equilibrium at the deoxidation equilibrium point of the deoxidation reaction (the balance point between the amount of deoxidation and the amount of oxygen absorbed from the atmosphere).

When the molten metal having a Ca content of about 400 ppm and reaching the deoxidation equilibrium point is preferably maintained in a stationary state, the deoxidized product is further floated and separated and does not participate in the deoxidation reaction. The unreacted Ca remaining in step 2 floats above the surface of the molten metal, leaving only a fine deoxidation product and a fine residual deoxidizing element in the molten metal. At this time, the absolute amounts of the deoxidation product and the residual deoxidation element decrease as the standing time is lengthened. However, as will be made clear in Examples below, when Ca is used as the deoxidizing agent, Of course, even when other metal deoxidizing agents such as Al, Mg, Ti, Cr, and Zr are used, the deoxidizing products in the melt and the residual deoxidizing elements are added until the total amount thereof becomes 20 ppm or less in terms of the metal. If floating separation is performed, ingot defects etc. due to coarse deoxidation products etc. will not be seen at all, and moreover, countless fine deoxidation product particles etc. dispersed in the molten metal without floating It became clear that the crystal grain of the ingot is remarkably miniaturized by the action as a nucleating agent and the ingot crack and the like caused by the coarse crystal grain are surely prevented.

From the viewpoint of preventing ingot cracking due to grain refinement, the object can be achieved by performing levitation separation to 20 ppm or less, but the levitation separation can be promoted to 10 ppm or less. This is preferable because the following advantages can be obtained. That is, especially C
In the case of u-Fe-based alloy, etc., when the final product is made into a wire having a small diameter, Ni, Ag,
Although plating treatment with Sn or the like is often performed, if the amount of metal oxide in the ingot is large, surface defects may occur in the product due to defective plating. However, if the content of the metal oxide, which is a deoxidation product, is reduced to about 10 ppm or less, such a problem of defective plating does not occur at all.

[0028]

EXAMPLES Next, the constitution and effects of the present invention will be described more specifically with reference to examples, but the present invention is not limited by the following examples, and may be adapted to the gist of the preceding and following. It is needless to say that the range is changed and carried out, and all of them are included in the technical scope of the present invention.

Example 1 A 10 ton high frequency induction furnace (1 KHZ) was charged with electrolytic copper metal and 2
1 wt% Fe powder is charged and the surface is covered with charcoal powder 1
After heating and dissolving at 300 ° C. (standard), a deoxidizing equilibrium amount of Mg (200 ppm) was added thereto, and the mixture was stirred for 20 minutes.
The molten metal surface covered with charcoal powder was transferred from the transfer trough to a holding furnace, and the deoxidized products were floated and separated by holding at the same temperature for 30 minutes, and then 200 × 500 × 50
Two pieces of 00 mm × 2 were taken and semi-continuous casting was performed at a casting speed of 40 mm / min. The oxygen content in the cast slab is 8 ppm, and the content of the remaining deoxidized product (MgO) in terms of Mg is 8 pp.
m, the crystal grain size was 100 μm, and internal and surface defects such as cracks did not occur at all in the cast slab.

The slab was soaked at 800 ° C. for 4 hours, and then at 800 ° C., the thickness was 200 mm to 10 mm.
Hot rolling up to, then 10mm to 0.5m thick
When cold rolling was performed up to m, no defects such as hot work cracks were observed.

Example 2 A 10 ton capacity LNG-fired shaft furnace was fitted with electrolytic copper metal 10
0% + 2% by weight of an iron plate was charged, the surface was covered with charcoal powder, and the mixture was heated and melted at 1300 ° C. With the surface of this molten metal covered with charcoal powder, it was transferred from the transfer gutter to a holding furnace, 20 kg of charcoal powder and 0.1% by weight of Mg and Al were added to the weight of the molten metal, and Ar gas injection was also used. Then, deoxidation is performed, and then the product is kept at the same temperature for 30 minutes to deoxidize the product (Al ₂ O
₍₃ , MgO) and the like were floated and separated, and then semi-continuous casting was performed in the same manner as in Example 1. The oxygen content in the obtained slab obtained by semi-continuous casting was 8 ppm, and the content of residual deoxidized products (CaO) and the like in terms of Mg was 5 ppm, A
The 1-equivalent content was 8 ppm, the crystal grain size was 150 μm, and no internal defects such as cracks and surface defects were observed in the cast slab. Further, when this slab was subjected to soaking, hot rolling and cold rolling under the same conditions as in Example 1, defects such as hot work cracks did not occur at all.

Example 3 An electric Cu ingot was charged into an induction melting furnace (1 KHZ) having a capacity of 9 tons, the entire surface was covered with charcoal powder and melted at 1200 ° C. Ca (200 pp
m) After adding, hold at 1200 ° C. for 30 minutes to remove CaO and the like floating on the surface, and then 1000 mm × 300
mm slab was semi-continuously cast at a casting speed of 40 mm / min.
The oxygen content in the slab was 8 ppm, the Ca equivalent content of CaO and Ca was 8 ppm, the crystal grain size was 200 μm, and no internal defects such as cracks and surface defects were observed in the slab. When this slab was subjected to soaking, hot rolling and cold rolling under the same conditions as in Example 1, no products such as hot work cracks were observed.

As a metal-based deoxidizing agent replacing Ca, A
Semi-continuous casting, hot rolling, in exactly the same manner as above except that deoxidizing equilibrium amounts of l, Mg, Ti, Cr, Zr and the like were added, respectively, or the same amount of Cu-Ca alloy was used in terms of Ca.
As a result of the cold rolling and the cold rolling, no ingot cracks, hot work cracks, etc. were observed, and a product having neither internal nor surface defects could be obtained.

Example 4 Cu-2% Fe was placed in an induction melting furnace (1 KHZ) having a capacity of 9 tons.
Charge the alloy scraps and cover the entire surface with charcoal powder.
After melting at 0 ° C, deoxidized equilibrium amount of Ca (40
0 ppm) and then hold at 1300 ° C for 10 minutes,
After removing CaO etc. floating on the surface, 1000 mm x
A 300 mm slab was semi-continuously cast at a casting speed of 50 mm / min. The oxygen content in the slab is 6 ppm, the Ca equivalent content of CaO and Ca is 2 ppm, and the crystal grain size is 150 μm.
m, and internal and surface defects such as cracks were not recognized at all in the cast slab. When this slab was subjected to soaking, hot rolling and cold rolling in the same manner as in Example 1, no defects such as hot work cracks were observed, and high quality products without internal or surface defects. I was able to get

In addition, the method of the present invention is applied to the melting and deoxidizing of pure Cu and various Cu alloys before casting, including the above-mentioned examples, and the equivalent amount of deoxidized metal remaining in the molten metal before casting and the product When the correlation of defects (ingot cracks, ingot surface defects, hot work cracks, product surface defects, product plating defects, etc.) was examined, as shown in Table 1 below, conversion of deoxidized metal in the molten metal before casting was performed. It was confirmed that the above-mentioned defects can be eliminated by suppressing the amount to 20 ppm or less.

[0036]

[Table 1]

[0037]

The present invention is constructed as described above, and C
To deoxidize a molten metal when casting a u or Cu alloy by using a metal-based deoxidizer to reduce the oxygen concentration in the molten metal and to leave a very fine deoxidized product in the molten metal in a trace amount. As a result, ingot cracking and hot work cracking can be eliminated, and a Cu or Cu alloy casting product free from cracking defects can be provided.

[Brief description of drawings]

FIG. 1 is an enlarged view exemplifying a cross-sectional state of a Cu—Fe based alloy in which ingot cracking has occurred.

FIG. 2 is a graph showing the relationship between the O ₂ concentration in the molten Cu—Fe alloy and the area ratio of the Cu ₂ O eutectic compound in the ingot.

FIG. 3 is a graph showing the relationship between the amount of oxygen in the molten Cu—Fe alloy immediately before casting and the amount of oxygen in the ingot.

FIG. 4 Ca addition amount and Ca in molten metal during deoxidation treatment
It is a graph which shows the relationship of the amount and oxygen concentration, and the crystal grain size of an ingot.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Joji Masuda 14-1 Nagafu Minatomachi, Shimonoseki City, Yamaguchi Prefecture Kobe Steel Works, Ltd. Chofu Works (72) Inventor Kiyomasa Oga 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo No. 5 Inside Kobe Research Institute of Kobe Steel, Ltd. (72) Inventor Motohiro Arai 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Inside Kobe Research Institute of Kobe Works (72) Inventor Kazutaka Kunii Hyogo 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Kobe Prefecture Kobe Steel Works, Ltd. Kobe Research Institute

Claims (5)

[Claims] 1. When casting Cu or Cu alloy,
At any stage before casting, deoxidation is performed using at least one metal-based deoxidizing agent containing a metal that is more easily oxidized than the Cu or Cu alloy to adjust the oxygen concentration in the molten Cu or Cu alloy. After reducing to the deoxidation equilibrium value, the concentration of the metal and metal oxide derived from the metal-based deoxidizing agent is reduced to 20 ppm or less for each metal element in terms of metal, and then casting is performed, ingot cracking and casting A method for producing a Cu or Cu-based alloy casting product, which is characterized by preventing hot work cracking of a lump. 2. A Cu—Fe based alloy is used, which prevents decrystallization of a Cu—Fe—O based eutectic compound at the time of casting by reducing the oxygen concentration by deoxidation, and is derived from a metal based deoxidizer. The manufacturing method according to claim 1, wherein the grain size during casting is miniaturized by reducing the metal concentration. 3. Cu or Cu alloy (provided that Cu--Fe
The production method according to claim 1, wherein the crystal grains at the time of casting are miniaturized by reducing the oxygen concentration by deoxidation and the metal concentration derived from the metal-based deoxidizing agent by using (except for system alloys). 4. The method according to claim 1, wherein a simple metal or an alloy having copper as a master alloy is used as the metal-based deoxidizer. 5. The method according to claim 1, wherein deoxidation of the molten alloy is carried out in combination with deoxidation using carbon or CO gas and deoxidation using a metal-based deoxidizer.