JPH0339453A - Production of cast aluminum alloy bar for vtr cylinder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for making an aluminum alloy cast rod for a VRT cylinder.

[Conventional technology] Conventionally, forged products made from extruded aluminum alloy rods have often been used for vRT cylinders, but in order to reduce costs, it has been desired to switch to cast rods that do not require an extrusion process, and this is currently being implemented. be. However, unlike extruded rods, cast rods cannot improve the workability of the material through extrusion processing, and therefore have the problem of being susceptible to cracking and cracking during forging. In addition, when cold forging a material into a product shape, conventionally, the material is forged twice, that is, forged twice to bring the material closer to the product shape, and then the work-hardened material during forging is annealed, making it easier to forge. Previously, a method was used in which the forging was re-forged and finished into the product shape, but in order to streamline the process, single-step forging was desired, and as VTR cylinders were becoming lighter and cheaper, , product shapes are becoming thinner and more complex, and the forgeability required of materials is becoming more demanding.

For this reason, when a cast bar is forged, cracks and cracks are likely to occur, which is a major problem in using the cast bar.

For this reason, when a cast bar is forged, cracks and cracks are likely to occur, which is a major problem in using the cast bar.

[Problems to be Solved by the Invention] Under these circumstances, an object of the present invention is to provide a method for manufacturing an aluminum alloy cast rod for a VTR cylinder that is less likely to crack or break during forging.

[Means for Solving the Problems] The present invention solves the above problems and provides a VTR with good forgeability.
The present invention provides a method for manufacturing an aluminum alloy cast rod for cylinders, and its gist is that Cu 3
~4.5% by weight, MgO03~Il1% by weight, NiO,
5-2.5% by weight, SLo, 1-0.9% by weight, Fe
An aluminum alloy cast rod for a VTR cylinder, characterized in that an aluminum alloy containing 0,1 to 0.7 ffl amount% and the remaining aluminum and impurities is cast to a diameter of 80 m5+ or less at an average cooling rate of 50 ° C / sec or more. It's in the manufacturing method.

The reasons for limiting the alloy components and manufacturing method in the present invention are as follows.

Cu: Cu is an element originally added to increase the strength of the VTR cylinder through processing (T6 quenching, tempering) performed after forging, but it has the following effects during forging.

That is, Cu present in AI mainly forms particles and precipitates, and a portion is dissolved in solid solution in AI. Among these, crystallized substances are coarse compounds formed together with other elements during casting, and become the starting point of forging cracks. Therefore, after casting, as much crystallized material as possible is injected (solid solution) through homogenization treatment.
It is desirable to Precipitates can be broadly divided into two types depending on their function.

One is the stable phase (θ: A12 C
u, S: A12 CuMg), and one is a metastable phase or G that improves hardness and strength.

It is P band. Among these, the G and P bands are formed in a short period of time even when the material is left naturally due to the supersaturated solid solution of Cu after casting or homogenization treatment, increasing the hardness of the material. The forgeability of the material improves as the hardness decreases, so before forging, a softening treatment is used to convert Cu, which was supersaturated as a solid solution during casting and homogenization, into a stable phase rather than a G, P band or metastable phase. It is desirable to precipitate a large amount. Therefore, it is desirable to reduce the amount of crystallized substances and increase the number of stable phases in order to improve forgeability.

However, when the content exceeds 4.5 wt%, the amount of crystallized substances that become the starting point of forging cracks increases significantly, and when this is infiltrated by homogenization treatment, the amount of Cu dissolved in supersaturated solid solution increases significantly. For this reason, it becomes difficult to precipitate most of it in the form of a stable phase during the softening treatment, resulting in insufficient reduction in hardness. In addition, if it is less than 3vt%, metastable phases and G precipitate during processing (T6 quenching, tempering).

Due to the small amount of P band, sufficient strength cannot be obtained.

Therefore, the range is 3 to 4.5 vL%.

Mg: Like Cu, Mg is an element added to increase the strength of VTR cylinders during the T6 process, but before forging, a softening process precipitates a large amount of stable phase to reduce the hardness of the material. can improve sex.

However, if it exceeds 8% by weight, the reduction in hardness will be insufficient, and if it is less than 0.3% by weight, sufficient strength will not be obtained after T6 treatment. Therefore, the content should be in the range of 0.3 to 1.8% by weight.

St: Like Cu5Mg, Sl is also an element added to increase the strength of VTR cylinders during T6 treatment.
Before forging, a softening treatment is performed to precipitate a large amount of stable phase, thereby reducing the hardness of the material and improving forgeability.

However, if it exceeds 0.9% by weight, the reduction in hardness will be insufficient, and if it is less than 0.1% by weight, sufficient strength will not be obtained after T6 treatment. Therefore, 0.1-0.9 ffi amount%
The range shall be .

Ni: The amount of Ni dissolved in solid solution in AI is extremely small, and most of the added amount remains in AI as a crystallized substance, making it almost impossible to dissolve it even in a homogenization treatment. This crystallized material improves the wear resistance of VTR cylinders and the forged materials.
Although it contributes to improving the machinability when cutting the TR cylinder, it acts as a starting point for cracks during forging, leading to a decrease in forgeability. If it is less than 0.5% by weight, its contribution to wear resistance and machinability is small, and if it exceeds 2.5% by weight, forgeability is significantly reduced.

Therefore, the content should be in the range of 0.5 to 2.5% by weight.

Fe: Fe combines with Nt during casting to form a Fe-Ni compound, which contributes to the wear resistance of the VTR cylinder. However, since the Fe-N1-based compound hardly dissolves in the homogenization process, it becomes a starting point for cracks during forging.

Q: If it is less than 1% by weight, sufficient wear resistance cannot be obtained;
If it exceeds 7% by weight, forgeability will be significantly reduced. Therefore,
The range is 0.1-0.7111ffi%.

When the cooling rate binary alloy solidifies, the primary crystal A1 grows in a dendritic shape, and then a compound mainly consisting of alloying elements crystallizes between the dendrites. This compound is very brittle and the dendritic spacing (D
AS), so the larger the DAS, the lower the forgeability. In particular, when the average value of DAS exceeds 15 μm, forgeability is significantly reduced. By the way, DAS has a relationship with the cooling rate as shown in the following formula. 7,8X 10', m-2-
It is 7. Therefore, in order to make the average DAS value 15 μm or less, a cooling rate of 50° C./SOC or more is required on average.

Casting size: In order to achieve an average cooling rate of 50@C/sec or more, the casting size must be φ80 mm or less.

If the diameter exceeds φ80mm, the average cooling rate should be reduced to 50℃/sec.
This is because it becomes difficult to do so.

In order to obtain a forging material from the above-mentioned cast rod, it is desirable to use the following manufacturing process.

A. Molten metal treatment and casting When melting and casting the aluminum alloy having the above composition,
The molten metal is filtered and degassed, and a refining agent is added to make the crystal grains finer to produce an ingot. If coarse inclusions are mixed into the ingot or the amount of H2 gas in the ingot is large, forgeability will decrease, so molten metal filtration is performed to reduce the thickness to 10 μm.
After removing the above inclusions, the amount of H2 gas is 0.25cc/1
It is desirable to degas so that the amount is 00g or less.

As the refining agent, Al-Ti or AI-Ti-B intermediate alloy is preferable, with 0.005 to 0.20% by weight of Ti;
It is effective to add BO,001 to 0.04% by weight.

Further, it is desirable that the casting speed be 450+n/s1n or more and the amount of cooling water be 3017 sin or more.

B. Homogenization Treatment The ingot is heated in order to homogenize the ingot structure and infiltrate the crystallized substances in the ingot. Treatment at 450-520°C for 8-48 hours is desirable.

C1 The homogenized ingot is heated and then gradually cooled in order to coarsely precipitate a large amount of the main hardening fraction dissolved in the softened ingot and reduce the hardness of the ingot. After maintaining the temperature at 330 to 390°C for 2 to 48 hours, it is desirable to gradually cool the mixture at a cooling rate of 20°C/hr or less.

After passing through the above steps, the cast material is forged into a predetermined shape for a VTR cylinder, subjected to T6 treatment to increase strength and hardness, and finally finished into a product by cutting.

[Example] The present invention will be explained in more detail by giving examples below.

Example 1 After melting an alloy having the chemical components shown in Table 1 below, the melt was treated to remove inclusions and degas, and 0.02ffi and 0.004ffi of Ti5B were added, respectively, and cast. Casting was performed at a diameter of 65 mm at a speed of 510 mm/m1n. After homogenizing this cast rod at 480°C for 16 hours,
As a softening treatment, the temperature was maintained at 380°C for 6 hours, and the cooling rate was reduced to 10
It was slowly cooled to 150°C at a rate of °C/hr to obtain a cast rod. A forging test was conducted using this softened material. The results are shown in Table 2 together with the casting conditions of the cast bar and the DAS after casting. In addition, the material after softening is subjected to T6 treatment (500°C x 1 hr - water cooling -
175°C x 8hr) L, the results of examining the wear resistance and hardness are also listed in Table 2.

Among the alloys in Table 1, Nos. 1 to 5 are alloys having the chemical components of the present invention, and Nos. 6 to 8 are comparative materials. No,
Nos. 1 to 5 are excellent in forgeability, wear resistance after T6 treatment, and hardness.

However, No. 6 has a large amount of Cu and Mgjl, so the hardness after softening is high, and there are also many coarse pieces that become the starting point of forging cracks, resulting in poor forgeability.

No. 7 has a large amount of N1m, so there are many coarse pieces that become the starting point of forging cracks, and the forgeability is poor. In addition, No. 8 has a small amount of CuSMg and Ni, and the hardness after T6 treatment,
Poor wear resistance.

In addition, forgeability and wear resistance were evaluated by the following method.

Forgeability: A 20X L 30mm cylindrical test piece was compressed in various molds at a compression rate of 10mm/sin while both bottoms were restrained, and the forgeability was evaluated based on the deformation rate (critical deformation rate) at which cracks occur on the sides. did. If the critical deformation rate is 50% or more, forging into a VTR cylinder is fully possible.

Abrasion resistance: Abrasion resistance was evaluated by Okoshi type abrasion test.

00m2, Hm/5ec 2.1kg 850C (Ilv-750) φ30XL3mm Test conditions are: Friction distance, friction speed, final load, mating material without lubrication. If the specific wear amount is 8 mm/kg or less and the Vickers hardness is 120 or more, the wear resistance and hardness as a VTR cylinder are sufficient.

Table 1 Chemical composition (vL%) of the alloy used in Example 1 Table 2 Characteristics of the cast rod obtained in Example 1 Example 2 Cu 4.0% by weight, Mg 1.5% by weight, Si 0.3% by weight %, 1.9% by weight of Ni, 25% by weight of F e O, and the remaining aluminum and impurities. A cast bar was produced. After homogenizing this cast rod at 480°C for 18 hours,
As a softening treatment, the temperature was maintained at 380°C for 6 hours, and the cooling rate was reduced to 10
The mixture was slowly cooled to 150°C at a rate of °C/hr. The results of a forging test conducted using this material are shown in Table 3 along with the casting conditions and DAS of the material.

Among the alloys in Table 3, No. 1 to G are examples of the present invention, No.
, 7 to 9 are comparative examples. No, compared to 1-B.

Samples Nos. 7 to 9 have a large DAS due to a low cooling rate, and as a result, there are many coarse crystallized substances that serve as starting points for cracks, resulting in poor forgeability.

Note that the evaluation method for forgeability is the same as in Example 1.

Table 3 Characteristics of the cast rod obtained in Example 2 [Effects of the invention] As explained above, according to the present invention, the rod has excellent forgeability, wear resistance, and hardness, and is extremely suitable for use in VTR cylinders. Aluminum alloy cast bars can be obtained.

Claims (1)

[Claims] Cu: 3-4.5% by weight, Mg: 0.3-1.8% by weight
, Ni; 0.5 to 2.5% by weight, Si; 0.1 to 0.9
Aluminum for VTR cylinders, characterized in that an aluminum alloy containing 0.1 to 0.7 wt% Fe and the remainder aluminum and impurities is cast to a diameter of 80 mm or less at an average cooling rate of 50° C./sec or more. Method for manufacturing alloy cast rods.