JPH0195837A - Manufacture of beta type titanium alloy forging - Google Patents

Abstract

PURPOSE:To reduce the manufacturing cost of a product by forming a zinc or an iron-zinc film by blasting treatment on the surface of a beta type titanium alloy, then executing cold forging at specified working speed and executing an aging treatment and a nitriding treatment of specified temp. as well. CONSTITUTION:The blasting treatment 8 by the particle adhering a zinc or iron-zinc alloy is executed on a descaled beta type titanium alloy. After executing zinc phosphate treatment and reaction type metal soap treatment 9 on this titanium alloy on which surface a zinc or iron-zinc film is formed, cold forging is executed at the working speed of <=100S<-1> strain speed and a product is obtd. If necessary, aging treatment or nitriding treatment is executed at the temp. of 400-550 deg.C. Or after executing the nitriding treatment at 730-880 deg.C an aging treatment is executed at 400-550 deg.C to improve the hardness of a product. The cold forgeability of the beta type titanium alloy is thus easily improved, moreover the hardness is increased, hence the product cost is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing at low cost a lightweight and high-strength β-type titanium alloy forged product suitable for, for example, valve retainers for automobile engines. It is.

[Conventional technology]

Conventionally, forged products for automobiles manufactured by cold forging, especially valve retainers for automobile engines, were manufactured by carburizing, quenching, and tempering case-hardened steel or structural steel.
As the demand for higher engine torque and higher engine speed increases, titanium materials are being used to make valve retainers lighter and stronger.

However, pure titanium, which has good cold forgeability, has low base material hardness for parts such as valve retainers that require wear resistance, and (α + β) type titanium alloys have high hardness but poor cold forgeability. Therefore, it can only be manufactured by hot forging, which makes it expensive.

On the other hand, β-type titanium alloy has good cold forgeability and high base material hardness, and can be further hardened by aging treatment in the post-process, making it suitable as a material for valve retainers, etc. . However, on the other hand, there are problems in that the deformation resistance is large and seizure is likely to occur during cold forging.

To prevent seizure during cold forging, steel can generally be subjected to zinc phosphate lubrication treatment, but titanium alloys are chemically inert and cannot be subjected to this treatment.

For this reason, conventionally, oxidation treatment, which is commonly performed as a lubrication treatment method for titanium, is applied to form an oxide film on the surface of the material.
Forging was performed using this oxide film as a lubricating base film.

[Problem that the invention seeks to solve]

However, although the seizure resistance of β-type titanium alloys is improved by forming an oxide film under appropriate conditions, cracks occur in the oxide film during cold forging, resulting in microcracks in the base material. This microcrank develops into macrocracks when aging treatment is performed in a post-process, resulting in deterioration of the fatigue strength of the final product. Furthermore, it is difficult to descale the oxide film, and the commonly used nitric-fluoric acid pickling causes the problem of rough skin. Furthermore, the wear resistance of the product may be required to be higher than that achieved with the titanium alloy base material.

The present invention has been made with the main purpose of overcoming these problems, and is a β material that is lightweight, has high strength, and has excellent wear resistance.
The present invention provides a method for manufacturing a molded titanium alloy forged product.

[Means for solving problems]

The first invention to solve the above-mentioned problems is to blast a β-type titanium alloy material with grains (hereinafter referred to as "iron-zinc grains") made by coating zinc or an alloy containing iron and zinc. treatment to form a zinc or iron-zinc alloy coating layer on the surface of the alloy material, followed by zinc phosphate treatment, followed by washing with water, reactive metal soap treatment, drying, and then cold treatment. The second invention is characterized by forming by forging at a processing speed of 100 s-' or less, and the second invention is characterized in that the surface lubricating film formed on the surface of the molded product obtained in the first invention is After removal, the internal hardness is increased by aging treatment at a temperature of 400 to 550°C. The third invention is characterized in that the nitriding treatment and the aging treatment are performed simultaneously at the aging temperature of the second invention. Furthermore, in the fourth invention, after removing the surface lubricating film formed on the surface of the molded product obtained in the first invention,
After nitriding at a temperature of 730-880℃, 400-5
It is characterized by hardening the surface and increasing internal hardness by aging at a temperature of 50°C.

Note that the above strain rate is defined as follows.

Generally, it is defined that the slab height is ho and the product height is h.

However, here we use 0-h Δt-h for compression as the nominal average strain.

It is defined as

[For production]

In the present invention, an iron/zinc alloy layer is physically deposited on the surface of a chemically inert β-type titanium alloy material by blasting iron/zinc particles onto the surface. As a result, subsequent lubrication treatments such as zinc phosphate treatment and reactive metal soap treatment are performed well, and seizure during cold forging is prevented.

The reason why the strain rate is set to 1005-' or less is because in β-type titanium alloys, when the strain rate increases, the deformability decreases, making it impossible to manufacture cold forged products that require large deformations.
This is because the deformability of the alloy needs to be 1003-' or less in order to fully utilize its deformability.

The reason why cold forged products are aged at 400 to 500°C is to maximize the hardness of the base material. Below 400°C, age hardening is insufficient, and above 550°C, over-aging occurs. .

The purpose of nitriding is to harden the surface and improve wear resistance, and ion blating, PVD, etc. can be applied to nitriding at 400 to 500°C. By employing a nitriding means capable of nitriding at the aging temperature, aging treatment and nitriding treatment can be performed simultaneously, which has the effect of eliminating steps. Other nitriding temperatures 7
30 to 880°C is the solution temperature of β-type titanium alloy,
and the gas nitriding temperature. In cold forging, the properties differ depending on the shape of the product due to the difference in the degree of processing, so if the product is subjected to -degree solution treatment and then aged, a product with uniform properties in each part can be obtained. If it is less than 730°C, the solution treatment is insufficient and the nitriding rate is slow, and if it exceeds 880°C, crystal grains will grow abnormally, so 730 to 880°C is the solution treatment and gas nitriding temperature.

[Specific structure of the invention]

Hereinafter, the present invention will be specifically explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing the manufacturing process of the present invention when obtaining a valve retainer.

As the β-type titanium alloy material 1 which is the starting material of the present invention,
For example, Ti-15V-3G-3Al-3Sn.

Ti -3AA -8V -6Cr -4Mo -4Z
r etc. are suitable. By cutting 2 this material, we can directly obtain the processing slag 3 shown in Fig. 2(a), or by cutting the material and lubricating its surface with MO32 oil, etc., and then performing upsetting and punching. After cold forging preforming 5 by processing and annealing 6 if necessary, shot blasting, pickling with fluoro-nitric acid, etc., and descaling treatment 7 to ensure sufficient cleanliness so that no microcracks remain on the surface, and process slag 3. obtain. Here, if the processing degree of the cold forging preform is large, the preform should be formed at a temperature of 600 to 750°C for about 30 minutes.
It is preferable to heat the material for 6 minutes and anneal it. At that time, descaling is also carried out sufficiently by the method described above.

The processing slag obtained in this way is lubricated by the blasting process 8 with iron/zinc particles described later to provide a lubricating base treatment, followed by zinc phosphate treatment, water washing, reactive metal soap treatment, and drying (bonding).・Bondalube treatment) 9. The structure of the lubricating coating on the titanium alloy slag after the lubrication treatment is as shown in Figure 3. On the β titanium alloy slag, there is an iron/zinc alloy layer β, a zinc phosphate coating layer C1, a reaction layer D, and a reactive metal soap layer. It has a structure in which E is laminated.

The processing slag thus lubricated is subjected to a cold forging main forming process 10. This actual molding has a strain rate of 100 S.
−'The machining speed is below. As a result, a valve retainer (see FIG. 2(b)) 11 as a cold forged product is obtained. Here, the strain rate is the ratio between the machining speed and the height of the slag before machining.

In the present invention, in order to further prevent wear, the lubricating coating of the molded article is removed 12 by hot water washing followed by hydrochloric acid pickling, etc., and then subjected to aging 13 at 400 to 550°C. If the material hardness is increased, it can be used as is. Furthermore, after treatment 14 such as ion nitriding which also served as aging at a temperature of 400 to 550°C, or after gas nitriding treatment 15 at a temperature of 730 to 880°C, aging 16 is performed at 400 to 550°C to improve the internal hardness. Increase it to make a finished product.

Next, the specific contents of each main step of the present invention will be explained.

Blasting using iron-zinc particles, which is the main feature of the present invention, uses iron particles as a core, as disclosed in Japanese Patent Publication No. 59-9312, and zinc is attached to the surface of the core through an iron-zinc alloy layer. This method forms an iron-zinc alloy layer on the surface of processing slag by blasting grains using a conventional method. The amount of the iron/zinc alloy layer deposited is preferably 1 to 40 glrd in consideration of zinc phosphate treatment properties in subsequent steps, lubricating oil retention, economic efficiency, productivity, and the like. That is, 1 g/
If it is less than rtf, the entire surface of the Ti alloy material cannot be covered,
Poor zinc phosphate treatment properties in the post-process, and poor retention during press working. On the other hand, if the deposition amount exceeds 40 g/nr, it will take a long time to deposit the iron-zinc alloy layer, and the workability will be poor compared to the lubricating effect.

An example of a method for manufacturing this projection material is the molten zinc method, in which a melt of metallic zinc or metallic zinc is alloyed with aluminum (approximately 3 to 5%) and steel (approximately 0.2 to 5%).
1%) and a predetermined particle size, preferably 1
Iron particles (solid) Y with a particle size that passes through a 0 mesh sieve,
Desirably, Y/X is mixed at a weight ratio of 10 to 90%, reacted at a reaction temperature of 400 to 500°C for a reaction time of about 2 to 10 minutes, and after cooling the obtained reaction product, mechanically, preferably This is a method of grinding to such an extent that the isolated amount of zinc or iron-zinc alloy layer in the shell portion is 30% or less of the amount in the shell portion.

Another example is the permeation zinc method, in which iron or iron alloy particles (solid) and zinc powder are mixed, or ammonium halides or chlorides are added in an amount of about 0.5 to 3%, and this mixture is mixed with iron or iron alloy particles (solid) and zinc powder. Filled in a cylindrical container made of iron or silicon carbide and sealed, zinc is diffused and penetrated by heat treatment at a temperature of 400 to 700°C for 3 to 20 minutes, forming an iron-zinc alloy phase and zinc around the iron particles. Form a shell. Here, for the heat treatment, a screw type or
Alternatively, a Psymia-type external heating closed furnace may be used.

Such a projection material may be projected onto the titanium surface using a conventional projection device.

In addition, the shell made of iron or iron alloy of the above projection material is
In addition to pure iron, an iron alloy containing C, N, St, Mn, Cr, Ni, etc. may be used. Zinc alloy is zinc with A
It is an alloy to which L, Cu, etc. are added.

The iron/zinc coating may be plated, but since the coating formed by blasting is porous, the lubricating coating retains well. Therefore, the present invention adopts a method of forming an iron-zinc alloy layer by blasting iron-zinc particles.

Next, regarding the zinc phosphate treatment conditions, the total acidity is 30 to 35.
The point is that the treatment temperature may be approximately 80°C and the treatment time may be 10 to 20 minutes. In short, the process is carried out under conditions that can ensure a deposit of 7 g/rrf, which is generally required for cold forging. After zinc phosphate treatment, perform normal water washing to prevent rust.

In addition, the conditions for reactive metal soap treatment are as follows: the amount of adhesion required for normal cold forging, that is, the reaction layer ≧1
g/nr, reactive soap adhesion amount ≧2.0 g/rrr or more, the treatment concentration may be 2 to 3 points, the treatment temperature may be about 80° C., and the treatment time may be 3 to 5 minutes, although there are no particular limitations. Note that calcium stearate or sodium stearate is preferably used as the reactive soap.

Drying after the reactive soap treatment can basically be done by natural drying in the atmosphere, but if quick drying is required, a hot air drying oven, an infrared drying oven, a high frequency induction heating oven, etc. may be used.

Note that the phosphorous-oxygen-zinc-treated material may be dried at a temperature of about 200° C., which also serves as baking, in order to solve the problem of hydrogen embrittlement.

〔Example〕

Next, an example will be explained.

(Example 1) An ingot of β-type titanium alloy having the alloy compositions (A) and (B') shown in Table 1 was melted, heated to a temperature of 1 oso℃, and rolled at 940℃ to 20wφ This wire rod is subjected to a cutting process, or a process of cutting, fluororesin lubrication, cold forging, annealing at 650°C, and fluoronitric acid descaling to produce the cutting slag and cold forging shown in Figure 2(a), respectively. Got a slug.

Next, both slags were subjected to iron/zinc particle blasting to form an iron/zinc alloy layer of approximately 10 g/rrr on the wire surface, followed by zinc phosphate coating treatment (total acidity 30 points, treatment temperature 80°C, treatment time 15 minutes). , attached piece 7.8g/rrr)
After washing with water, sodium stearate treatment (concentration approximately 2 points, treatment temperature 80℃, treatment time 5 minutes, coating amount:
Reaction summary 1.6g/rrr, reactive layer coating approx. 5.7
g/rrf and dried at about 200°C, main molding was carried out at a processing speed of 10 s-' strain rate to obtain the valve retainer shown in 2(b).

Table 2 shows the cold forgeability and hardness measurement results of this retainer.

Table 2 For comparison, both slags were oxidized at 650°C for 20 minutes, cooled in air at a cooling rate of 1.5°C/see, and then lubricated with fluorine resin. The cold forgeability and hardness measurement results of the valve retainer obtained by main forming at a processing speed of ' are also listed in Table 2.

As is clear from Table 2, the valve retainer treated with oxidation lubrication has no cracks that can be seen with the naked eye, but
Fine cracks were observed under the 00 microscope. On the other hand, in the case of the method of the present invention, no cracks were observed and good cold forgeability was exhibited. Moreover, the hardness of all of them is HV320 or higher.

(Example 2) Cutting slag manufactured from sample material B of Example 1 was used in Example 1.
Table 3 shows the cold forgeability and hardness measurement results of the valve retainers obtained by performing zinc phosphate-soap treatment and lubrication using the method described above, followed by main forming at various strain rates. Shown below.

Table 3 Strain rate = Machining speed / Initial slag height (1/S-') 3rd
From the table, it can be seen that when the strain rate exceeds 100 s-', cracks occur and the deformability decreases.

(Example 3) After removing the lubricating film from the molded product (valve retainer) of specimen B produced in Example 1 with hot water and 5% hydrochloric acid,
Table 4 shows the nitriding depth and hardness measurement results after nitriding of products subjected to ion nitriding treatment at the temperatures shown in the table for 20 hours.

Table 4 Table 4 shows that at temperatures below 400°C, a sufficiently thick nitrided layer cannot be obtained, and at temperatures above 550°C, the inside of the retainer softens due to overaging. Also,
A comparison with Table 2 shows that the hardness of the base material increases with aging.

(Example 4) After removing the lubricating film from the molded product (valve retainer) of test material B manufactured in Example 1 with hot water and 5% hydrochloric acid,
Table 5 shows the nitriding depth and hardness measurement results of products that were subjected to gas nitriding and solution treatment at 0° C. for 15 hours and then aged at the temperatures shown in Table 5.

Table 5 Comparing Tables 2 and 5, it is found that at temperatures below 400°C, the hardness is the same as that of cold forging, and at temperatures above 550°C, the highest hardness is obtained due to overaging. It turns out that there isn't. It is well known that the hardness of solution-aged materials is uniform across the cross section of the product, and that the nitrided surface has better wear resistance than the base material.

〔Effect of the invention〕

As described above, according to the present invention, a β-type titanium alloy forged product with better cold forgeability than β-type titanium alloy slag can be manufactured at a low cost. Not only retainers but also gears,
It is now possible to apply β-type titanium alloy numbers to various forged products such as shafts and bolts, which has the great effect of expanding its use not only to automobile parts but also to aircraft parts. It is.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the manufacturing process of the present invention, Fig. 2(a), (bl is a longitudinal cross-sectional view showing the processing slag of the valve retainer and the shape of the valve retainer, and Fig. 3 is a longitudinal cross-sectional view showing the processing slag of the valve retainer. It is a figure which shows the lubricating film structure applied to.

Claims (4)

[Claims] (1) Descaled β-type titanium alloy material is blasted with particles coated with zinc or iron-zinc alloy to form a zinc or iron-zinc coating on the surface of the alloy material, and then zinc phosphate After processing, followed by washing with water, treatment with reactive metal soap, and drying, the strain rate is 1 by cold forging.
A method for manufacturing a β-type titanium alloy forged product, characterized by forming at a processing speed of 00s^-^1 or less. (2) Descaled β-type titanium alloy material is blasted with particles coated with zinc or iron-zinc alloy to form a zinc or iron-zinc coating on the surface of the alloy material, and then zinc phosphate After processing, followed by washing with water, treatment with reactive metal soap, and drying, the strain rate is 1 by cold forging.
β characterized by molding at a processing speed of 00s^-^1 or less, followed by removing the surface lubricating film formed on the surface of the obtained molded product, and then aging at a temperature of 400 to 550 ° C. Method for manufacturing molded titanium alloy forged products. (3) Descaled β-type titanium alloy material is blasted with particles coated with zinc or iron-zinc alloy to form a zinc or iron-zinc coating on the surface of the alloy material, and then zinc phosphate After processing, followed by washing with water, treatment with reactive metal soap, and drying, the strain rate is 1 by cold forging.
Molding is performed at a processing speed of 00s^-^1 or less, and then the surface lubricating film formed on the surface of the obtained molded product is removed, and then aged at the same time as surface treatment by nitriding at a temperature of 400 to 550°C. A method for manufacturing a β-type titanium alloy forged product, characterized by: (4) Descaled β-type titanium alloy material is blasted with particles coated with zinc or iron-zinc alloy to form a zinc or iron-zinc coating on the surface of the alloy material, and then zinc phosphate After processing, followed by washing with water, treatment with reactive metal soap, and drying, the strain rate is 1 by cold forging.
After molding at a processing speed of 00s^-^1 or less, then removing the surface lubricating film formed on the surface of the obtained molded product, and nitriding at a temperature of 730~880℃,
A method for producing a β-type titanium alloy forged product characterized by aging at a temperature of 550°C.