JP3483529B2 - High toughness inner hardening material for cylinder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner surface hardened material such as plastic which is welded to a cylinder for an injection molding machine by using a centrifugal lining method.

[0002]

2. Description of the Related Art On the inner surface of a cylinder of an injection molding machine made of plastic or the like, an alloy having both abrasion resistance and corrosion resistance is centrifugally formed in order to prevent abrasion and corrosion due to resin or an additive material added to the resin. It is welded by the lining method.

The inner surface hardener used for this centrifugal lining has many alloys so far. As an example, the inventors of the present invention disclosed in Japanese Examined Patent Publication No. 3-56300 have a Cr content of 18 to 24% and a B. 0-3.5%, Si 1.0
~ 4.0%, Mo 0.5 ~ 5.0%, Cu 0.5 ~
5.0%, W 5% or less, Ni 3.0% or less, Fe2.
Disclosed is a composition of a Co-based inner surface hardening material for a cylinder consisting of 0% or less, C 0.5% or less, the balance Co and unavoidable impurities, and it is also shown that this lining layer has excellent wear resistance and corrosion resistance. Disclosure.

[0004]

However, in recent years, as the performance of plastic materials has improved, injection molding of plastics has a molding temperature of about 350 ° C. and a molding pressure of about 2500 k.
The operation at a higher temperature and pressure of gf / cm ² is increasing. The centrifugal lining layer on the inner surface of the cylinder for an injection molding machine used under such high temperature and high pressure has a defect that cracks may sometimes occur in the lining layer after a short period of operation.

Therefore, in the present invention, the Japanese Patent Publication No. 3-563 is used.
To provide an inner hardened material for a cylinder, which can be used under higher temperature and higher pressure, without impairing wear resistance and corrosion resistance of the Co-based inner hardened material for a cylinder disclosed in No. 00, and centrifugal lining property. Has an aim. For this purpose, there arises a problem that the toughness of the hardened material on the inner surface is increased as much as possible.

This is due to the following two reasons. First, if the toughness of the inner hardened material decreases in the molding temperature range when the injection molding machine is used, the toughness of the centrifugal lining layer formed by this alloy also decreases, and The lining layer has a higher probability of cracking. Therefore, it is desirable that the toughness at high temperature is as high as possible.

The second reason is to improve the strength of the cylinder body. Chrome cylinder molybdenum steel (JIS SCM440) is usually used for the cylinder body, but when performing centrifugal lining, it is heated to a predetermined temperature of 1050 ° C to 1200 ° C, and after the centrifugal lining treatment, about 900 ° C to
Slowly cooled to room temperature or furnace cooled. Due to such cooling conditions, the cylinder body is in an annealed state, and its strength is not sufficient for a cylinder body used under high temperature and high pressure. To improve the strength of the cylinder body,
If the cylinder body can be cooled by forced air cooling or the like from about 900 ° C. after the centrifugal lining treatment, the purpose is achieved.

However, in this case, a difference in thermal contraction occurs due to a temperature difference between the cylinder body and the lining layer, and stress is generated in the lining layer. If the lining layer cannot withstand this stress, the lining layer will crack. Therefore, in order to increase the strength of the cylinder body, it is desirable that the toughness of the inner surface hardened material at high temperature is as high as possible.

[0009]

The inventors of the present invention have variously studied from the above viewpoints to improve the toughness at high temperature of the above Co-based inner surface hardened material for a cylinder, and as a result, this Co-based inner surface hardening material for a cylinder has been obtained. It was found that the toughness of this alloy at a high temperature is remarkably improved by reducing the Ni content contained in the material as much as possible and adding a trace amount of Al. Based on this knowledge, we have completed a high toughness inner surface hardening material for cylinders for forming a centrifugal lining layer that does not crack even when used under high temperature and high pressure.

The high toughness inner surface hardening material for a cylinder according to the present invention comprises Cr 18 to 24% by weight and B 2.8 to 3.5.
%, Si 1.0 to 4.0%, Mo 0.5 to 3.0%,
Cu 0.5-3.0%, W 1.0-5.0%, Ni
0% or over 0-0.1%, Al 0.05-0.1
5%, C 0% or more than 0 to 0.5%, Fe 0% or more than 0 to 2.0%, [O] 0% or more than 0 to 0.1
It is characterized by being composed of 5%, the balance being Co and inevitable impurities.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting the alloy composition (% by weight) of the high toughness inner surface hardened material for a cylinder according to the present invention will be described below.

Cr (18 to 24%) Cr dissolves in a matrix containing Co as a main component to improve the corrosion resistance of the alloy. The corrosion resistance to nitric acid is improved by increasing the amount of added Cr, but less than 18% is less effective.
On the other hand, if it exceeds 24%, the crystallized amount of chromium boride increases and the solid-liquid coexisting region of the alloy expands, which is not preferable when centrifugal lining is performed. Therefore, its content should be 18-24.
Set to%.

B (2.8-3.5%) B forms a high-hardness boride mainly composed of Co and Cr, which increases the hardness of the alloy and improves the wear resistance. Also,
The eutectic reaction between the boride and the Co solid solution also serves to lower the melting point of the alloy. If the B content is less than 2.8%, the hardness of the alloy becomes insufficient and the composition becomes a hypoeutectic composition, so that the solid-liquid coexistence region of the alloy expands, which is not preferable. On the other hand, if it exceeds 3.5%, the hardness of the alloy is excessively increased, the toughness is lowered and the composition becomes a hypereutectic composition, and the solid-liquid coexistence region of the alloy is widened, which is not preferable. Therefore,
Its content was set to 2.8-3.5%.

Si (1.0 to 4.0%) Si forms a solid solution in Co to increase the hardness of the alloy, improving wear resistance and corrosion resistance. If the Si content is less than 1.0%, the effect is not sufficient. On the other hand, if the Si content is more than 4.0%, the hardness of the alloy increases and the toughness decreases, which is not preferable. Therefore, the content thereof is set to 1.0 to 4.0%.

Mo (0.5-3.0%), Cu (0.5
˜3.0%) Mo and Cu both form a solid solution in Co to improve the corrosion resistance of the alloy, especially the corrosion resistance to hydrochloric acid. Mo and Cu are both 0.5
If it is less than%, the effect of improving the corrosion resistance to hydrochloric acid is insufficient,
On the other hand, if it exceeds 3.0%, no improvement effect is recognized for the added amount, and the solid-liquid coexistence region of the alloy is widened, which is not preferable. Therefore, their contents are both set to 0.5 to 3.0%.

W (1.0 to 5.0%) W forms a solid solution in Co to enhance the strength of the alloy and also contributes to the improvement of corrosion resistance and wear resistance. If the W content is less than 1.0%, the effect is not sufficient. On the other hand, if the W content exceeds 5.0%, a boride containing W as a main component is formed and the toughness of the alloy is reduced, which is not preferable. Therefore, its content is 1.0 to 5.0%
Stipulated in.

Ni (0% or more than 0 to 0.1%) Since Ni is often contained in Co in a small amount, the influence of Ni was investigated. In FIG. 1, Cr 21%, B 3.0%, Si
2.0%, Mo 1.0%, Cu 1.0%, W 4.
Sample obtained by heating and melting a Co-based alloy having a composition of 0%, C 0.08%, Fe 1.5%, and the balance of Co and an alloy containing a small amount of Ni to 1200 ° C., and casting. Shows the Charpy impact value of.

As can be seen from FIG. 1, the samples obtained from the 0% Ni alloy have higher Charpy impact values than those from the Ni-containing alloys, and the impact values increase with increasing temperature. . On the other hand, the sample obtained from the alloy containing Ni has a higher Ni content,
The impact value decreases and the impact value at high temperature does not increase.

The decrease in impact value due to the inclusion of Ni is considered to be because the boride containing Ni as a main component is formed in the alloy and the boride is fragile, thus lowering the toughness of the alloy. Thus, Ni impairs the toughness of the alloy, so 0%
Is most preferred. However, in consideration of the purity of Co, which is the raw material of this alloy, etc., if Ni exceeds 0 to 0.1%, it is acceptable as a range that does not substantially impair the toughness. Therefore, its content is defined as 0% or over 0 to 0.1%.

Al (0.05-0.15%) Al is used when the alloy is melted in the centrifugal lining process.
It acts as a deoxidizer and contributes to the improvement of the toughness of the lining layer.

In FIG. 2, Cr 21%, B 3.0%, Si
2.0%, Mo 1.0%, Cu 1.0%, W 4.0
%, C 0.08%, Fe 1.5%, the balance of Co, and a Co-based alloy containing 0.10% of Al contained therein are heated and melted to 1200 ° C. and cast. The Charpy impact value of the obtained sample is shown. As can be seen from FIG. 2, the sample obtained from the alloy containing Al has a higher Charpy impact value and less variation than that from the alloy not containing Al. This is considered to be because the toughness of this sample was improved because fine inclusions in the molten metal were removed by the deoxidizing action of Al during melting during sample preparation. If the Al content is less than 0.05%, the effect is insufficient. On the other hand, if the Al content is more than 0.15%, excessive Al causes oxidation of the alloy, which hinders melting in the centrifugal lining treatment step, which is not preferable. Therefore, its content is set to 0.05 to 0.15%.

C (0% or more than 0 to 0.5%), Fe
(0% or more than 0 to 2.0%) Even if neither C nor Fe is contained in the alloy, the performance as the alloy of the present invention can be exhibited. However, since the raw materials and impurities may be mixed in as impurities during melting, the influence of C and Fe was investigated. As a result, when C exceeds 0.5%, the hardness of the alloy increases and the toughness tends to decrease, and when Fe exceeds 2.0%, the corrosion resistance tends to decrease. However, the effect was not particularly observed at C 0 excess-0.5% and Fe 0 excess-2.0%. Therefore, the content thereof is C 0% or more than 0 to 0.5%,
Fe was set to 0% or more than 0 to 2.0%.

[O] (0% or more than 0 to 0.15%) [0] can exhibit its performance as the alloy of the present invention even if it is not contained in the alloy. However, when this alloy is used in the centrifugal lining treatment step, since it is in the form of powder or granules, [O] is contained as an unavoidable oxide on the surface thereof. Therefore, the influence of [O] was investigated.
As a result, when [O] exceeds 0.15%, the melting of the alloy in the centrifugal lining treatment process tends to be inhibited.
However, no particular effect was observed when [O] exceeded 0 to 0.15%. Therefore, its content is set to 0% or more than 0 to 0.15%.

[0024]

EXAMPLES AND COMPARATIVE EXAMPLES First, as shown in Table 1, the alloy of the present invention (Sample Nos. 1 to 4), a Co-based alloy conventionally known as Samples (Sample Nos. 5 to 7), and a conventionally known Ni were used as comparative examples. A Charpy impact test (400 ° C. and 600 ° C.) and a quench cracking test after centrifugal lining were conducted on the base alloy (Sample No. 8).

In each sample, the raw materials are Co, Cr, Co-B,
Si, Mo, Cu, W, Ni, Al, Fe, Mn, Cr
-C was blended so as to have the composition shown in Table 1, heated and melted to 1450 ° C. in an Ar atmosphere in a high frequency melting furnace, and powdered by an N ₂ gas atomizing method. The sample
As the raw materials Co and Co-B used in Nos. 1 to 6, high purity products were used. Further, Al of Sample Nos. 1 to 4 and 6 was added in a predetermined amount to the molten metal immediately before atomization. Furthermore, among the alloy compositions in Table 1, Al and [O] are analysis values of the obtained powder, and the others are compounding values. A Charpy impact test piece was prepared using the obtained powder.

150 g of the powder of each sample was heated and melted to its liquidus temperature + 30 ° C. in an Ar atmosphere furnace, and 12 mm
Cast into a shell mold of × 12 mm × 75 mm, the cast piece is 10 mm × 10 mm × 55 mm, JI with U notch
Finished into S3 test piece. The test piece is 400 ° C and 6
After soaking in an electric furnace maintained at 00 ° C, a Charpy impact test was performed.

As can be seen from Table 2, the alloy of the present invention has a higher Charpy impact value than the alloy of the comparative example,
The characteristic is that the temperature at 600 ° C. is higher than that at 0 ° C.

Outer diameter 100 mm, inner diameter 24 mm, length
200mm chrome molybdenum steel (JIS SCM44
250 g of each sample powder was placed in the tube of 0), and steel lids were welded to both ends of the tube to prepare a test material for centrifugal lining. It should be noted that one of the lids of this test material has a hole with a diameter of 6 mm in the center. This test material was heated and heated in a furnace to the liquidus temperature + 30 ° C of the sample powder contained therein. During the heating and heating, Ar gas was flown in through the hole provided in the lid of the test material to prevent oxidation inside.

Then, the test material was attached to a high-speed rotating machine,
Centrifugal lining was performed by applying a rotation of about 2000 rpm. Cooling is performed by cooling the centrifugal lining temperature to about 900 ° C, and then forcibly air-cooling the outside with a blower for about 50 ° C.
It was cooled to 0 ° C. and then left to cool.

The test material thus finished with the centrifugal lining was cut to examine the crack generation state in the lining layer. As can be seen from Table 2, in the alloy of the present invention, no cracking occurred at all, whereas in the alloy of the comparative example, there was some difference in the number of cracks, but cracking occurred in any of the samples. From this, it was confirmed that the alloy of the present invention has excellent toughness at high temperature, and therefore can sufficiently withstand the stress generated when the steel pipe of the cylinder body is cooled relatively quickly.

Next, using the alloy sample No. 1 of the present invention, a cylinder for an actual injection molding machine was produced and an actual machine test was conducted. The outer diameter of the steel pipe used as the cylinder body is 120
A chromium molybdenum steel (JIS SCM440) having a diameter of 32 mm, an inner diameter of 32 mm and a length of 1000 mm was used. 4.5 kg of the powder of sample No. 1 was placed in this tube, and steel lids were welded to both ends of the tube to prepare a tube for centrifugal lining. A hole with a diameter of 6 mm is formed in the center of one side of this lid. The tube for centrifugal lining thus obtained was subjected to centrifugal lining.

The centrifugation line was performed under the same conditions as described above. The tube with the centrifugal lining finished is machined to have an outer diameter of 106 mm, an inner diameter of 28 mm, and a length of 807 m.
finished to m. It was confirmed by endoscopic observation that the inner lining layer was not cracked by color check.
An injection molding actual machine test was conducted using the cylinder thus finished.

The molding material is PPS resin and glass fiber 50.
%, And the molding temperature was 350 ° C. and the molding pressure was 2500 kgf / cm ² . As a result of investigating the condition of the cylinder after about 300,000 shots, no crack was observed in the lining layer and no abnormality was found in the shape of the cylinder body. Further, the wear of the surface of the lining layer was 15 μm or less even in the largest portion, there was no problem in use, and no corrosion was observed at all.

This result shows that the durability is significantly improved as compared with the conventional centrifugal lining layer of Co-based and Ni-based inner surface hardened material, which often cracks after tens of thousands of shots or less. It indicates that

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

As described in detail above, the alloy of the present invention is excellent in toughness, especially at high temperature, and is also excellent in wear resistance and corrosion resistance. Therefore, a cylinder for an injection molding machine, which has a centrifugal lining layer formed on the inner surface using the alloy of the present invention, has dramatically improved durability when used under high temperature and high pressure, and its economic effect is also extremely large. . The inner hardened layer can also be formed by the HIP method using the alloy powder of the present invention.

[0038]

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a Ni content and a Charpy impact value in an alloy of the present invention.

FIG. 2 is a diagram showing the relationship between the Al content and the Charpy impact value in the alloy of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-1-139737 (JP, A) JP-A-60-13043 (JP, A) JP-A-5-84592 (JP, A) JP-A-53- 85712 (JP, A) JP 60-200937 (JP, A) JP 61-26739 (JP, A) JP 5-131289 (JP, A) JP 7-88912 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C22C 19/07 B29C 45/17

Claims (2)

(57) [Claims] 1. Cr 18 to 24% by weight, B 2.8 to
3.5%, Si 1.0-4.0%, Mo 0.5-3.
0%, Cu 0.5 to 3.0%, W 1.0 to 5.0%,
A high toughness inner surface hardened material for a cylinder, which comprises 0.05 to 0.15% Al, the balance Co, and unavoidable impurities. 2. Cr 18 to 24% by weight, B 2.8 to
3.5%, Si 1.0-4.0%, Mo 0.5-3.
0%, Cu 0.5 to 3.0%, W 1.0 to 5.0%,
Ni 0 excess-0.1%, Al 0.05-0.15%,
C 0 over ~ 0.5%, Fe 0 over ~ 2.0%, [O]
A high toughness inner surface hardening material for cylinders, which comprises 0 to 0.15% and the balance Co and unavoidable impurities.