JPH0759730B2 - Corrosion and wear resistant alloys for plastic injection molding and extrusion machines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has excellent corrosion resistance and wear resistance, which are used as materials for cylinders, screws, plungers and the like that make up plastic injection molding machines and extrusion molding machines. It relates to a cobalt-based alloy.

[Conventional technology]

Cylinders that make up plastic injection molding machines and extrusion molding machines, such as screws in the cylinders, plungers, etc., have wear resistance that can withstand contact with resin that is pressure-fed in the cylinder under heating, and resin. Corrosion resistance to corrosive substances generated from the melt is required. Conventionally, nitrided steel (JIS G4202SACM645) has been exclusively used as the material for the part.

[Problems to be Solved by the Invention]

In recent years, plastic injection molding and extrusion molding operations have been carried out for the purpose of improving the quality and function of molded products, for example, flame-retardant plastics containing a halogen compound such as a fluorine compound as a flame retardant, glass fiber / ceramics as a reinforcing material. There is an increasing demand for composite reinforced plastics containing fibers or the like, or molded articles such as plastic magnets containing a ferromagnetic alloy powder for imparting a special function, for example, magnetic force.

The halogen compound compounded in the resin composition has a strong corrosion action on the surface of the member, and hard materials such as glass fibers / ceramic fibers and alloy powder accelerate the wear of the surface of the member. For this reason, in the conventional forming machine made of nitrided steel, the service life is remarkably reduced due to the damage on the surface of the member, and it is difficult to cope with it as a production machine.

The present invention provides an alloy having improved corrosion and wear resistance to address the above problems associated with plastic injection molding and extrusion machines.

[Means and Actions for Solving the Problems]

The alloy of the present invention has Cr: 5 to 20%, Mo: 5 to 20%, W: 5 to 15%, B:
0.5 to 4%, Si: 0.5 to 3%, C: 1.5% or less, the balance is substantially Co
Consists of.

The reasons for limiting the components of the alloy of the present invention are as follows.

Cr: 5-20% Cr increases the hardness of the alloy by combining with C, B, etc. to form carbides, borides, etc., and brings about high wear resistance.
This effect is obtained by adding 5% or more, and is strengthened as the amount of addition increases. However, above 20%, the effect is almost saturated. Therefore, it is 5 to 20%.

Mo: 5 to 20% Mo strengthens the wear resistance of the alloy by forming carbides, borides and the like like the above-mentioned Cr. The lower limit of the amount of addition is set to 5%, because if it is less than that, the above effect is insufficient. The effect increases as the amount of addition increases, but when it exceeds 20%, it is almost saturated. Therefore, 5
~ 20%

W: 5-15% W also forms Cr, boride, etc.
Like Mo, it has the effect of increasing the wear resistance of the alloy. The effect is obtained by adding 5% or more, and is strengthened as the amount of addition increases. However, when it exceeds 15%, the effect is almost saturated. Therefore, it is 5 to 15%.

B: 0.5 to 4% B has the effect of forming a solid solution in the alloy to lower the melting point of the alloy and facilitating the alloy melting operation, and as described above, Cr, Mo, W
By forming a compound with the above, it contributes to the improvement of the wear resistance of the alloy. This effect is obtained by the addition of 0.5% or more and strengthens as the amount increases, but if it exceeds 4%, the alloy becomes brittle, so it is made 0.5 to 4%.

Si: 0.5-3% Si, like B above, lowers the melting point of the alloy to facilitate alloy melting operation, and forms a compound with Cr, Mo, W, etc. Increase wear resistance. The effect is obtained by adding 0.5% or more. The effect increases as the amount of addition increases, but if it exceeds 3%, the alloy becomes brittle, so the amount is made 0.5 to 3%.

C: 1.5% or less C, like B and Si, lowers the melting point of the alloy, facilitates its melting operation, and forms a compound with Cr, Mo, W, etc. to increase the wear resistance of the alloy. The effect is obtained by adding a trace amount, and is strengthened as the added amount increases, but if it exceeds 1.5%, the alloy becomes brittle, so it is made 1.5% or less.

The alloy of the present invention is most typically supplied as a sintering raw material powder, and by a known sintering process such as hot pressing or hot isostatic pressing (HIP),
A sintered alloy layer that covers the surface of a metal member such as a cylinder or a screw is formed, and its outstanding corrosion resistance and wear resistance effectively protect the metal member from its corrosive and wear environment. Further, it is of course possible to form a sintered product having a required member shape by using the sintering raw material powder. FIG. 1 shows that a coating layer (2) made of the alloy of the present invention is formed on the inner surface of a metal tubular body (1) to form a tubular body (1) and a coating layer (2).
2 shows an example in which a cylinder having a two-layer structure is constructed.

〔Example〕

Example 1 Corrosion tests and abrasion tests were performed on the matchmakings having the component compositions shown in Table 1, and the results shown in the right column of the table were obtained. In the table, sample numbers (No.) 1 to 10 are inventive examples, and No. 101 to 109 are comparative examples. Among the comparative examples, No. 101 to 108 have the same component system as the invention example, but the content of any element (with an underline) is an example deviating from the definition of the present invention,
No. 109 is an example of a conventional material, nitrided steel.

[I] Corrosion test The test piece was immersed in the following four types of corrosive liquids (liquid temperature: 50 ° C) for 24
Measure the corrosion weight loss (g / m ² h) over time. In Table 1, (a) to (d) show the results of the corrosion test with the corrosive liquids (a) to (d), respectively.

Corrosion solution (a): 10% hydrofluoric acid solution Corrosion solution (b): 10% hydrobromic acid solution Corrosion solution (c): 50% hydrochloric acid solution Corrosion solution (d): 50% sulfuric acid solution [II ] Abrasion test Ogoshi type rapid abrasion tester
10 ^-8 mm ³ / mm ² · kg).

(I) Counterpart material (rotating wheel): SUJ 2, hardness (H _RC ): 58-60 (ii) Pressing load: 6.3 kg / cm ² (iii) Sliding contact speed: (a) 1.93 m / sec (c) ) 3.35m / sec (iv) Sliding contact distance: 400m In the table, (a) and (b) in the "Abrasion reduction" column indicate the measurement results when the sliding contact speed is (a) and (b), respectively. ing.

As is clear from the test results in Table 1, invention examples (No. 1 to
Compared with the conventional material, nitrided steel (No.109), 10) has significantly superior corrosion resistance and wear resistance. Incidentally, even if it has a similar component system as the invention examples, Comparative Examples No. 101 to 108 whose composition ratio deviates from the definition of the present invention, invention examples (No. 1 to 10) in terms of corrosion resistance. Although it is almost at the same level as, but the abrasion resistance is not sufficient.

Example 2 (Manufacture of injection molding machine cylinder and actual machine test) [A] Manufacturing of injection molding machine cylinder: Cr-Mo alloy steel (JIS SCM 435) pipe body (inner diameter: Φ28, wall thickness: 21 t, pipe length) Using 650 ^L (mm) as the base material, insert the core metal (M) into the base material tube body (1) as shown in FIG. The alloy powder (P) having the component composition of the present invention is filled as a sintering raw material.

Alloy powder composition (wt%) Cr: 14.6, Mo: 15.1, W: 9.52, B: 1.11, Si: 1.88, C: 0.028, Bal:
Co.

Next, the inside of the alloy powder packed layer was degassed in vacuum, the lid material (C, C) was welded and joined to the pipe end, and then subjected to hot isostatic pressing sintering, temperature: 1200 ° C, pressure: 1000kgf / cm ² , holding time:
Sintering is completed under the condition of 2 hours.

After the completion of sintering, the core metal (M) is removed, and appropriate machining is applied to the base material pipe body (1) as shown in Fig. 1 and the sintering bonding of the layer thickness of about 3 mm covering the inner peripheral surface thereof. A two-layer tubular body composed of the gold layer (2) was obtained.

[B] Experimental use test Using the above two-layer tube as a cylinder of an injection molding machine, injection molding of fiber reinforced plastic was performed, and the result was compared with a nitride steel cylinder of a conventional injection molding machine under the same use conditions.
Conventional cylinders made of nitrided steel have been scrapped after about 2 to 3 months of use due to damage due to wear and corrosion on the inner surface, whereas the cylinders of the invention example have been discarded after 12 months of continuous use. However, it was confirmed that there was almost no abnormality on the inner surface and that it could still be used continuously.

〔The invention's effect〕

Since the alloy of the present invention has wear resistance and corrosion resistance that greatly surpass those of nitrided steel and the like, a plastic injection molding machine
By using it as a material for parts such as extruder cylinders, screws and plungers, it is more stable than conventional parts not only in ordinary plastic molding but also in injection and extrusion molding operations of fiber reinforced plastics and flame retardant plastics. It guarantees a long service life and contributes to stable and efficient injection / extrusion molding operations.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example in which the alloy of the present invention is used as a coating layer on the inner surface of a cylinder, and FIG. 2 is a sectional view showing an example of a method of forming a coating layer made of the alloy of the present invention on the inner surface of a cylinder. 1: Metal tube, 2: Coating layer, P: Alloy powder, M: Core bar.

Claims (1)

[Claims] 1. Cr: 5 to 20%, Mo: 5 to 20%, W: 5 to 15%, B: 0.5
~ 4%, Si: 0.5 ~ 3%, C: 1.5% or less, the balance consisting essentially of Co is a corrosion and wear resistant alloy for plastic injection molding and extrusion molding machines.