JPH09263906A - Iron-nickel-chrome-alum. ferritic alloy and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an Fe-Ni-Cr-Al ferritic alloy excellent in molten metal erosion resistance and having extremely good workability and to provide a method for producing the same. SOLUTION: This alloy has a compsn. contg., by weight, <=0.05% C, <=2% Si, <=2% Mn, 2 to <15% Ni, 15 to <20% Cr, 2 to 8% Al and one or >= tow kinds among Ti, Zr, Hf, V, Nb, Y and rare earth metals by 0.05 to 1.0%, and the balance substantial Fe with inevitable impurities. Furthermore, as for the method for producing the same, this alloy stock is formed into a prescribed shape, which is held under heating in an oxidizing atmosphere heated at 800 to 1,300 deg.C, then, a film essentially consisting of the oxide of aluminum is formed on the surface of the member, and after that, cooling is executed at a rate of that in air cooling or above.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a mold and its parts,
The present invention relates to a Fe-Ni-Cr-Al-based ferrite alloy used as a metal melt contact member such as an insert, an abrasion resistant member, and a method for producing the same.

[0002]

2. Description of the Related Art Usually, Fe, Ni, Co, Al, Zn,
When casting a melt of a metal material such as Cu, Mg, or an alloy mainly composed of these metals, a metal melt contact member such as a mold is conventionally formed of hot die steel, high speed steel, stainless steel, or the like. Steel has been used. In the portion where the molten metal comes into contact with the above-mentioned steel materials, these steel materials have the drawbacks of being damaged by the molten metal, increasing the iron content in the molten metal, and degrading the quality of cast parts. Furthermore, melting damage of these molds causes various inconveniences in operation, such as poor skin of cast products and poor mold releasability due to welding between the cast product and mold, resulting in early deterioration of the function of members. However, there was a problem of a short life.

In order to solve these problems, conventionally,
On the surface of the member manufactured from the steel material, carburization, in addition to the method of performing a surface treatment such as nitriding to form a hard layer, nitride,
Carbides, borides (eg TiN, TiC, BN, Si
Proposal to coat the surface of C, Si ₃ N ₄ , TiB ₂ , Al ₂ O ₃ ) etc. by physical vapor deposition method represented by plasma chemical vapor deposition method or sputtering method, or by fusion bonding method or shrink fitting method. (JP-A-56-111560, JP-A-59-21416, JP-A-59-33128, JP-A-60-178017, JP-A-61-33734).
issue). On the other hand, ceramic-based materials that hardly react with molten metal, W alloys and Mo alloys that are less likely to cause melting loss, and the like are partially used.

[0004]

Since the surface treated layer obtained by carburizing and nitriding the member manufactured from the above steel material is a diffusion treatment, not only a deep treated layer can be obtained, but there is no problem of peeling. It has come to be often used in combination with a material developed on the assumption that these treatments are carried out. Also, the greatest advantage of these surface treatments is that they are very inexpensive. However, in recent years, as the strength of cast parts has increased, the use of high melting point aluminum alloys and zinc alloys has increased as compared with conventional aluminum alloys and zinc alloys as casting material.

Therefore, in the case where the surface of the mold has been conventionally carburized or nitrided, C and N in the surface treatment layer are reversely diffused into the molten metal due to the temperature rise during the work. However, there has been a problem that the original melting resistance function is deteriorated. Further, when the ceramic hard material is coated by a chemical vapor deposition method or a physical vapor deposition method, fine cracks are recognized in the coating layer, and the molten metal permeates through the cracks as a route to form a mother layer directly under the coating layer. There is a drawback that volume expansion occurs due to the reaction with iron in the material to form an alloy, resulting in the phenomenon of peeling the coating layer. further,
Ceramic-based materials, W alloys, and Mo alloys are very expensive, and when used as a nest, various problems due to a large difference in thermal expansion coefficient from surrounding steel materials, bending, and chipping. However, there were problems such as lack of strength, toughness, and thermal shock resistance, and they were not always satisfactory.

An object of the present invention is Fe-Ni-C which is excellent in melting resistance and wear resistance and has extremely good workability based on a novel idea for solving the above problems.
An object of the present invention is to provide an r-Al ferrite alloy and a method for producing the same.

[0007]

It has been well known that ceramic materials hardly react with molten metal. However, when ceramics-based materials are applied to dies, there are various problems as described above. Improving die life and cost advantages over surface treatment using diffusion by carburization and nitriding. The reality is that we cannot hope for it. Therefore, the inventor uses a steel material as a base material, and has a composition capable of producing a coating film mainly composed of aluminum oxide, which is an oxide ceramic, on the surface by high-temperature oxidation of the steel material, and the molten metal corrosion resistance The composition and the wear resistance were improved, and an appropriate composition was examined so that the workability was comparable to that of the conventional molds and wear resistant members. As a result, they have found a new alloy using the Fe-Cr-Ni-Al ferrite alloy as a basic composition. The alloy of the present invention is composed of the chemical composition shown below, and has excellent plastic workability, and by oxidation treatment after molding, at least the work surface of the member has corrosion resistance, and / or oxidation of aluminum excellent in wear resistance. One of the major characteristics is the formation of a film mainly composed of objects.

That is, in the first invention of the present invention, C: 0.05% or less, Si: 2% or less, Mn: 2% or less, Ni: 2% or more and less than 15%, Cr: 15% or more and 20% by weight.
%, Al: 2-8%, and Ti, Zr, Hf,
One or more of V, Nb, Y and REM: 0.05
Fe-Ni-Cr-Al, characterized in that the balance consists essentially of Fe and inevitable impurities.
Series ferrite alloy.

The second invention is C: 0.05% by weight.
Hereinafter, Si: 2% or less, Mn: 2% or less, Ni: 2% or more and less than 15%, Cr: 15% or more and less than 20%, Al: 2
~ 8%, and Ti, Zr, Hf, V, Nb, Y, RE
One or more of M: 0.05 to 1.0%, and one or more of W, Mo, Co: 0.2 to 2.0.
%, The balance substantially consisting of Fe and inevitable impurities, is an Fe-Ni-Cr-Al ferrite alloy. The present invention is different from the first invention in that one, two or more of W, Mo and Co are added in an amount of 0.2 to 2.0.
It is characterized by being added in the range of%.

Further, a third invention relates to a method for forming an oxide film on the above-mentioned invention alloy, which is formed by molding an alloy material having the composition of the first invention or the second invention into a predetermined shape,
Fe- characterized by heating and holding in an oxidizing atmosphere of 0 to 1300 ° C. to form a film mainly composed of aluminum oxide on the surface of the member, and then cooling at a rate of air cooling or higher.
It is a method for producing a Ni-Cr-Al ferrite alloy.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Fe-Ni according to the present invention will be described below.
The reasons and effects of limiting the chemical composition of the -Cr-Al ferrite alloy will be described.

C is Cr contained in the alloy of the present invention or Ti, Zr, Hf, V, Nb, and
It is preferably lower because it forms a carbide by combining with W, Mo, etc. and reduces the effect of addition of these elements. Also C
When the content of is increased, the CO ₂ gas generated from the surface of the base material during the oxidation treatment of the member may cause the formed film mainly composed of aluminum oxide to be broken.
However, since C is mixed in from the raw material and the cost for decarburization refining is high, the upper limit is set to 0.05%.
It is 1% or less.

Si is the Fe--Ni--Cr--Al of the present invention.
It is a very effective element for improving the melt flowability of the present alloy at the time of casting in the production of a system ferrite alloy and producing a sound ingot. Further, there is a part as oxides such as SiO ₂ in the film mainly composed of the oxide of aluminum formed on the surface of the member made of the alloy of the present invention, which reduces the denseness of the film, and the surface is oxidized by the high temperature oxidation treatment. When used as a die-casting mold, in order to make the film mainly composed of an oxide of aluminum to be porous, it improves the degassing and releasing properties of the gas generated from the molten metal during casting, and When used as a low pressure casting mold, it improves the peeling resistance of the coating agent applied to the surface of the mold. However, if the content exceeds 2%, the denseness of the coating mainly composed of aluminum oxide is significantly reduced, and the coating mainly composed of aluminum oxide is peeled off during use, resulting in use as a casting mold. Therefore, the upper limit of Si is set to 2%. The desirable range of Si is 0.
3 to 1.5%.

Mn acts as a deoxidizing and desulfurizing agent,
It is added to improve the cleanliness of the alloy. However,
If added in excess of 2%, the hot workability deteriorates, so M
The upper limit of n is 2% or less. Ni contributes to the strengthening of the matrix by forming a solid solution in the ferrite matrix, and part of it is Al.
It is an essential element for the present alloy because it precipitates an intermetallic compound of NiAl in the coexistence with and improves the hardness of the base material. To obtain the above effect, at least 2% or more of Ni is required, but conversely, if the Ni content is 15% or more,
Since the austenite phase is generated in the matrix and the strength of the base material is extremely reduced, the range of Ni is set to 2% or more and less than 15%. The desirable range of Ni is 5% or more and less than 15%.
A more desirable range is 7 to 13%.

Cr is Fe-Ni-Cr-Al of the present invention.
In a ferrite ferrite alloy, it is an element important in stabilizing the ferrite phase of the base material, at the same time as having the effect of forming a uniform coating film mainly composed of aluminum oxide, which has a strong adhesion to the member. In order to obtain the above effect, Cr needs to be 15% or more. On the contrary, if the content of Cr is 20% or more, the castability and plastic workability of the alloy are significantly reduced, so the Cr range is set to 15% or more and less than 20%. To do. The desirable range of Cr is 16 to 19.5%.

Al, in the coexistence with Ni, precipitates NiAl in the ferrite matrix to improve the hardness of the base material, and at the same time, forms a uniform aluminum oxide on the surface of the member by the oxidation treatment after molding the member. It is an indispensable element for forming a coating film as a main component and improving the melt loss resistance to molten metal and the wear resistance of sliding parts. To obtain the above effect, it is necessary to add 2% or more of Al.
If the content is more than 8%, the toughness and plastic workability of the alloy are significantly reduced, so the Al content is made 2 to 8%. Al
The desirable range of is 4 to 8%. A more desirable range is 4.5 to 7%.

Ti, Zr, Hf, V, Nb, Y, REM
Is an oxide particle that is formed on the surface of the member due to the oxidation treatment that is performed after the molding of the member. Since it has the effect of remarkably improving the properties, one or more kinds are added. In order to obtain this effect, it is necessary to add at least 0.05% or more singly or in combination, but if excessively added, the oxide particles are coarsened and the adhesion of the film is deteriorated. , Hf, V, Nb, Y, and REM are 0.05 to 1.0%.

Although W, Mo and Co are not necessarily added, they have the effect of further enhancing the high temperature strength by forming a solid solution in the base material to strengthen the solid solution, and they are added as necessary. In order to obtain the above effect, it is necessary to add 0.2% or more, but if it exceeds 2%, the deformation resistance at high temperature increases and the hot workability deteriorates significantly. Further, since the above elements are expensive, there is a cost disadvantage. Therefore, the content of one or more of W, Mo, and Co that is added as necessary is set to 0.2 to 2.0%.

In the method for producing the alloy of the present invention, after melting and ingoting, hot working or plastic working of hot working and cold working and annealing are carried out, and further, if necessary, mechanical working is carried out. After that, the member is formed into a predetermined shape. Subsequently, this member is heated and held at a temperature of 800 to 1300 ° C. in an oxidizing atmosphere to form a coating film containing aluminum oxide as a main component on the surface, and then cooled by air cooling or at a higher speed. The annealing treatment performed after the plastic working of the alloy of the present invention can be performed in combination with the oxidation treatment. Moreover, according to the alloy of the present invention and the method for producing the same, since the quenching and tempering treatment which is required for steel in the conventional tool steel base is not required, the process can be greatly shortened. In the present invention, performing this oxidation treatment is an important means for improving the melt loss resistance and wear resistance of the alloy of the present invention. At this time, if the oxidizing temperature is lower than 800 ° C., the thickness of the film exhibiting the above effects cannot be obtained,
At a temperature higher than 1300 ° C., the ferrite matrix of the base material becomes brittle and the formed film mainly composed of an oxide of aluminum easily peels off. Therefore, the oxidation treatment temperature is set to 800 to 1300 ° C.

Further, if the cooling rate after the oxidation treatment becomes excessively slow, NiAl in the ferrite matrix becomes coarse and the hardness of the base material lowers. Therefore, it is preferable to cool as quickly as possible by air cooling or more. In the case of a simple shape, water cooling or oil cooling may be used. However, for example, many casting molds have complicated shapes, and in this case, extreme cooling such as water cooling or oil cooling causes deformation due to heat treatment distortion of the base material or shock thermal stress. It causes the peeling of the coating film mainly composed of the aluminum oxide. Therefore, in the case of a member having a complicated shape, it is preferable that the cooling after the oxidation treatment is allowed to cool or blow air.

Further, the oxidation treatment time for forming the aluminum oxide on the surface of the member may be appropriately set depending on the application and size of the member, but it is sufficiently resistant to melting damage of the molten metal. Considering the formation of a coating film mainly composed of aluminum oxide having a variable thickness and the improvement of wear resistance, it is desirable to hold the member for 5 to 20 hours after reaching a predetermined temperature.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. (Example 1) No. 1 shown in Table 1 1-24 and No. 3
A material having a composition of 0 to 34 was melted in a vacuum induction melting furnace. The obtained ingot is hot forged and its cross section is 40
After being processed into a square material having a size of 15 mm × 15 mm, annealed, and then processed into a predetermined test piece to obtain a test material. At this time, with respect to the alloy whose workability was poor and hot forging was impossible, the alloy was melted again, the obtained ingot was annealed, and then a predetermined test piece was cut out. In addition, No.
Forty conventional alloys (equivalent to SKD61) were melted in the atmosphere, and the obtained ingot was hot forged to obtain a cross section of 40.
After making square pieces of mm × 15 mm, annealed,
Then, it processed into the predetermined test piece. The following test was performed on the above test materials.

In each characteristic test, the test piece cut out from each of the obtained test materials was 1-24 and No. 30-3
For No. 4, 1150 ° C., 15 in an oxidizing atmosphere furnace
After heating and holding for a period of time, it was quickly taken out of the furnace, cooled to room temperature at an average cooling rate of about 100 ° C./sec, subjected to an oxidation treatment, and then tested. No. 40 conventional alloy S
For KD61, the cut out test piece was oil-cooled at 1030 ° C., and subsequently adjusted by changing the tempering temperature to 600 to 650 ° C. so that the hardness became 40 HRC, and then subjected to the surface treatment shown in Table 2. The test was conducted. Regarding the evaluation of the plastic workability, the alloy in which the deformability was remarkably inferior at the time of hot forging and large cracks were not allowed to be forged, and the alloy having good deformability was allowed to be forged.

[0024]

[Table 1]

[0025]

[Table 2]

(1) Workability evaluation No. 1 obtained by a vacuum induction melting furnace. 1-24 and No. Hot forging was performed on 30 to 34 ingots, and workability was evaluated based on whether or not forging was performed at that time. (2) Abrasion amount The amount of abrasion is the loss of the test piece after the test, which is caused by sliding the test piece of 8 mm round x 25 mm length against the flat surface of the plate-shaped mating material for a certain period of time without pressing the end surface of the test piece The amount of wear was measured from the amount. Note that SCM415 (annealed material) was used as the mating material, the load was 30 kgf, and the sliding speed was 10 m / mi.
n, the test time was 1.5 hours, and the reciprocating motion was performed. (3) Melting resistance against molten metal The aluminum resistance test is based on aluminum alloy AC4CH at 750 ° C.
The test piece was dipped in the molten metal of No. 3 for 3 hours, and the weight loss ratio of the test piece before and after the test was compared for its melting resistance. For the zinc corrosion resistance test, the test piece was immersed in a molten zinc alloy ZAC2 at 600 ° C. for 20 hours, and its melting resistance was evaluated by the same method as in the aluminum corrosion resistance test. Table 3 shows the above results and the measurement results of the internal hardness of each test piece after the oxidation treatment.

[0027]

[Table 3]

As shown in Table 3, the alloys of the present invention have excellent workability and can be easily hot forged. On the other hand, in the case of No. 30, 3
Nos. 2 and 33, which had extremely poor plastic workability and were incapable of forging due to many cracks in the ingot during hot forging, had a relatively low Cr content. Nos. 31 and 34 had no problem in workability, and hot forging could be easily performed. Further, the internal hardness of the alloy of the present invention after the oxidation treatment is 410 H even when compared with the conventional alloy SKD61 of 380 to 400 HV.
V to 460 HV, which is sufficiently durable for use as a casting mold or a molten metal welding device. No. 3
It can be seen that the alloy No. 1 has excellent workability, but the Ni content is out of the range of the alloy of the present invention, so that the internal hardness is significantly reduced.

With respect to the wear amount of the alloy of the present invention, as the amount of Si added increases, the coating mainly composed of aluminum oxide on the surface becomes porous and the wear amount slightly increases, and the wear resistance thereof slightly decreases. However, in all cases, the wear resistance is about the same level as or higher than the wear amount of the conventional alloy, which is good. However, the wear amount of the comparative alloy is no. Regarding Nos. 31 and 32, due to insufficient hardness of the base material and insufficient adhesion of the coating film mainly composed of aluminum oxide, No. With respect to No. 33, since the denseness of the coating film mainly composed of the oxide of aluminum was extremely lowered by the excessive addition of Si, the coating film was peeled off during the abrasion test and the abrasion amount was increased. Comparative alloy No. Regarding No. 34, it is considered that the effect of improving the wear resistance by the film was not obtained because the film mainly composed of the oxide of aluminum was destroyed during the oxidation treatment by the excessive addition of C.

Next, regarding the molten metal erosion resistance of each test material, the test pieces obtained by subjecting the alloy of the present invention to an oxidation treatment to form a film mainly composed of an oxide of aluminum are aluminum alloy and zinc alloy. In comparison with conventional alloy No. It can be seen that even when compared to the SKD61 of 40-6 subjected to the salt bath sulfuritriding, it is very excellent. On the other hand, in the comparative alloy, the workability and the internal hardness are the same as those of the alloy of the present invention in the comparative alloy No. 34
In the case of C, since the coating mainly composed of the oxide of aluminum was destroyed during the oxidation treatment due to the excessive addition of C, the protective effect of the coating could not be obtained, and the molten metal corrosion resistance thereof was significantly lowered. Further, since hot forging was impossible, Comparative Alloy No. 30 is
The internal hardness and wear resistance were similar to those of the alloy of the present invention, but molten metal penetrated due to defects in the test piece due to poor solidification, resulting in melting loss.

In the alloy of the present invention, a coating film containing aluminum oxide as a main component and aluminum oxide as a main component is formed on the surface by oxidation treatment, and the base material is shielded from the molten metal to improve the melt damage resistance. However, the conventional alloy No. 1 in which alumina having almost the same composition as the coating was coated by the plasma chemical vapor deposition method was used. In No. 40-1, it was confirmed that the molten metal penetrated from the cracks in the film, which are presumed to have occurred during the coating step, and the SKD61 of the base material and the molten metal reacted with each other to cause melting loss. In this embodiment,
The results of erosion resistance tests for aluminum alloys and zinc alloys are shown.Generally, erosion of molds, etc. due to molten metal progresses due to the formation of compounds due to contact between the molten metal and the base metal of the mold, etc. To do. Therefore, the material of the casting mold or the molten metal welding equipment of the present invention is similarly excellent in the corrosion resistance to other molten metals, for example, iron-based or copper-based alloys, as well as aluminum-based or zinc-based materials. It has been confirmed.

[0032]

As described above, Fe-Ni-C of the present invention
The r-Al ferrite alloy has a high strength, high adhesion aluminum oxide film as a main component formed on the surface of the base material by using an oxidation treatment in consideration of the balance of the chemical composition. It is possible to improve molten metal erosion resistance and wear resistance without requiring special surface treatment, and it is possible to greatly improve the service life of metal melt contact members such as casting dies and wear resistant members. it can. In addition, SKD61, which has been used more often than before, is subjected to surface treatment such as nitriding treatment after processing into a predetermined member shape, quenching and tempering heat treatment, and then melt resistance and wear resistance. Whereas the product of the present invention had to be increased, the product of the present invention did not need to be subjected to complicated surface treatment or heat treatment after processing, and the desired characteristics could be obtained only by performing a simple oxidation treatment.
It is possible to significantly reduce the manufacturing process of the member and the manufacturing cost.

Claims (3)

[Claims] 1. C: 0.05% or less by weight, Si: 2
% Or less, Mn: 2% or less, Ni: 2% or more and less than 15%,
Cr: 15% or more and less than 20%, Al: 2 to 8%, and one or more of Ti, Zr, Hf, V, Nb, Y, and REM: 0.05 to 1.0%, the balance being substantially Fe, which is characterized by comprising Fe and unavoidable impurities
-Ni-Cr-Al ferrite alloy. 2. C: 0.05% or less by weight ratio, Si: 2
% Or less, Mn: 2% or less, Ni: 2% or more and less than 15%,
Cr: 15% or more and less than 20%, Al: 2 to 8%, and one or more of Ti, Zr, Hf, V, Nb, Y and REM: 0.05 to 1.0%, further W, Mo, Co
1 or 2 or more: 0.2 to 2.0%, and the balance substantially consisting of Fe and inevitable impurities, Fe-Ni-Cr-Al ferrite alloy. 3. The alloy material having the composition according to claim 1 or 2 is molded into a predetermined shape and then heated and held in an oxidizing atmosphere at 800 to 1300 ° C., and the surface of the member is mainly composed of an oxide of aluminum. Fe-Ni-Cr-Al characterized by cooling at a rate higher than air cooling after forming a film
Of manufacturing a ferrite ferrite alloy.