JPH05286000A - Compound cylinder for plastic molding machine - Google Patents

Abstract

PURPOSE:To provide a compound cylinder for plastic molding machine having hard quality, excellent abrasion resistance and corrosion resistance, and excellent seizure resistance. CONSTITUTION:A lining layer of a cylinder for plastic molding machine is made of a cobalt group alloy or a nickel group alloy. On the surface of the lining layer, a sulphurizing layer or nitrosulphurizing layer having a depth of 1mum or above is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite cylinder used in a plastic molding machine or the like, and more particularly to a composite cylinder for a molding machine which is excellent in wear resistance, corrosion resistance and seizure resistance.

[0002]

2. Description of the Related Art In recent years,
Plastics have come to be used in a wide variety of applications as engineering plastics and polymer alloys, and accordingly, various resins are mixed and used, and various additives are added and used. .. Therefore, the lining layer in the cylinder of the molding machine used for injection molding or extrusion molding of these resins is desired to have more excellent wear resistance and corrosion resistance.

For this reason, a cobalt-based alloy or a nickel-based alloy is used as the lining material, or a wear resistant component such as WC is blended.

By using a cobalt-based alloy or a nickel-based alloy as the lining material, or by adding a wear resistant component such as WC, the lining layer of the cylinder is hardened and wear resistance and corrosion resistance are improved. However, the problem that galling or seizure easily occurs between the cylinder and the screw has not been solved.

In particular, as shown in FIG.
The cylinder 2 has a screw 3 and a check ring (valve) 4 for preventing backflow of resin during injection.
When injection molding is performed on the mold 6 by the injection molding machine 1 in which the adapter 5 is attached to the tip end of the, the distance between the cylinder 2 and the check ring 4 is about 0.02 to 0.2 mm,
Since they are extremely small, they are constantly in contact with each other due to the weight of the screw, abnormal molding, mixing of foreign matter, or the like. Therefore, galling, seizure or the like is likely to occur between the cylinder 2 and the check ring 4, or between the cylinder 2 and the screw 3. This tendency is particularly remarkable in a horizontal injection molding machine which occupies most of the molding machine.

When galling, seizure or the like occurs between the cylinder 2 and the check ring 4 or between the cylinder 2 and the screw 3 in this way, the resin passing through the inside of the cylinder 2 is locally localized at the seizure occurrence point. Overheated. As a result, defects such as resin burning and deterioration (deterioration or carbonization of resin due to overheating) occur in the injection molded product.

In particular, in the case of a resin having a low plasticization temperature and high transparency such as polystyrene and polycarbonate, and a white resin such as polyacetal, the above-described resin burning and deterioration are remarkable.

[0008] Therefore, an object of the present invention is to provide a composite cylinder for a plastic molding machine which is hard and has excellent wear resistance and corrosion resistance as well as seizure resistance.

[0009]

As a result of earnest research in view of the above problems, the present inventor has determined that the lining layer of a cylinder for a plastic molding machine is made of a cobalt-based alloy or a nickel-based alloy, and the lining layer is By forming a sulfurized layer or sulphonitrided layer with a depth of 1 μm or more on the surface, it is hard and has excellent wear resistance and corrosion resistance.
The inventors have found that galling, image sticking, etc. can be significantly reduced, and have conceived the present invention.

That is, the composite cylinder for a plastic molding machine of the present invention is a hollow cylinder-shaped cylinder base material layer made of alloy steel and a cobalt-based alloy which is present on the inner surface of the cylinder base material layer and which is excellent in wear resistance and corrosion resistance. Alternatively, it is characterized in that it has a lining layer made of a nickel-based alloy, and a vulcanized layer or a oxynitrided layer is formed on the inner surface of the lining layer to a depth of 1 μm or more.

[0011]

First, the lining layer of the cylinder for a plastic molding machine of the present invention will be described. The lining layer is made of a Co-based alloy or a Ni-based alloy.

The chemical composition of the Co-based alloy is such that the sum of Cr, B, Si, Mn and Ni is 35 wt% or less, Fe is 20 wt% or less, and the balance is substantially Co and unavoidable impurities. In particular, Cr is 10 to 30% by weight, B1.5 to 4.0% by weight, Si is 4% by weight or less, Mn is 2% by weight or less, Ni is 5% by weight or less, Fe is 20% by weight or less, and the balance is substantially Co and inevitable impurities. Is preferred.

The alloy components of the Co-based alloy will be described below. In Co-based alloys, wear resistance as a cylinder cannot be maintained only with Co-based alloys, so Cr, B, Si, Mn and Ni
It is preferable to contain However, Cr, B, Si, Mn and
If the total amount of Ni exceeds 35% by weight, the strength and corrosion resistance decrease.

The preferable Cr content is 10.0 to 30.0% by weight, and the particularly preferable Cr content is 11.0 to 23.0% by weight. Cr forms a hardened phase due to the boride of Cr-B together with B, and improves the hardness of the alloy. If Cr is less than 10.0% by weight, the above Cr-B phase is not sufficiently formed, while if it exceeds 30% by weight, the melting point of the alloy becomes 1200 ° C or more, so that the lining on the cylinder base material layer. It is not preferable because it becomes difficult to form a layer.

The preferred content of B is 1.5 to 4.0% by weight. B has the effect of precipitating high-hardness boride in the structure and improving the hardness of the alloy, but if it is less than 1.5% by weight, its effect is not sufficient, and if it exceeds 4.0% by weight, the eutectic structure becomes coarse, In addition, brittleness increases, which is not preferable.

Si acts as a deoxidizing agent, but due to its effect the content is set to 4.0% by weight or less.

Mn acts as a deoxidizing agent, but due to its effect, the content is 2.0% by weight or less.

Ni is a mixed element, the content of which is 5.0
It is less than or equal to weight%. If the Ni content exceeds 5.0% by weight, the hardness of the alloy decreases, which is not preferable.

The preferable Fe content is 20.0% by weight.
Hereafter, the particularly preferable Fe content is 8.0% by weight or less. Even if Fe is not initially contained in the alloy, Fe penetrates from the cylinder base metal layer by a welding reaction with the cylinder base metal layer made of steel. It is necessary for a certain amount of Fe to transfer from the cylinder base material layer to the alloy in order to achieve complete welding between the lining layer and the cylinder base material layer. When Fe content increases, hardness decreases and corrosion resistance against acid decreases.
If it exceeds 0.0% by weight, its effect cannot be ignored, and thus it is not preferable.

Since Co combines with Cr and B to improve the high hardness characteristics and the corrosion resistance of the alloy, the residual weight% of the base alloy is set.

Further, in the present invention, per 100 parts by weight of the metal component of the above Co-based alloy, IVa group, Va group or VIa group is used.
Wear resistance can be further improved by dispersing 3 to 40 parts by weight of fine particles of a carbide of a group element. Examples of the carbide of the IVa group, the Va group, or the VIa group element include WC, NbC, TiC, and VC. Further, the above-mentioned carbide is preferably in the form of fine particles of 50 μm or less.

When the content of the carbide of the IVa group, the Va group or the VIa group element is less than 3 parts by weight, the sufficient effect cannot be obtained by the addition, while when it exceeds 40 parts by weight, the viscosity of the lining material is increased. It becomes large and it becomes difficult to form a uniform lining layer. A more preferable content of the carbide of the IVa group, the Va group or the VIa group element is 10 to 30 parts by weight per 100 parts by weight of the alloy component.

Next, the case of Ni-based alloy will be described. Ni
The chemical composition of the base alloy is 35 total of Cr, B, Si, Mn and Co.
% By weight, 20% by weight or less in Fe, the balance being substantially Ni
And unavoidable impurities are preferable, and especially Cr5
20 wt%, B1.5-4.0 wt%, Si4 wt% or less, Mn2
It is preferable that it is composed of not more than 10% by weight, not more than 10% by weight of Co, not more than 20% by weight of Fe, and the balance substantially consisting of Ni and inevitable impurities.

In a Ni-based alloy, the wear resistance of the cylinder cannot be maintained only by the Ni-based alloy, so Cr, B, Si,
It preferably contains Mn and Co. However, Cr, B, S
If the total amount of i, Mn, and Co exceeds 35% by weight, the strength and corrosion resistance decrease.

Preferably, the Cr content is 5.0 to 20.0% by weight, especially 7 to 15% by weight, B is 1.5 to 4.0% by weight, Si is 4.0% by weight or less, especially 3.0% by weight or less, Mn is less than 2.0% by weight.

The reason for limiting the range of the contents of Cr, B, Si and Mn is the same as in the case of the Co-based alloy described above.

Co is a mixed element, and its content is 10.0% by weight or less. When Co exceeds 10.0% by weight, the hardness decreases, which is not preferable.

A preferable Fe content is 20.0% by weight or less,
A particularly preferable Fe content is 8.0% by weight or less. The reason for limiting the range of the Fe content is the same as in the case of the Co-based alloy described above.

Further, in the present invention, the wear resistance is further improved by dispersing 3 to 40 parts by weight of fine particles of a IVa group, Va group or VIa group element carbide per 100 parts by weight of the metal component of the Ni-based alloy. Can be improved. IVa above
As the carbide of the group Va group or VIa group element, the same as the above Co-based alloy can be used.

In order to line the alloys described above on the cylinder base material layer, it is common to use a metal melting method typified by a centrifugal casting method. Atomized powders of these alloys are used. A method of sinter-bonding by a HIP process may be used.

On the other hand, the cylinder base material is Cr-Mo steel,
Generally, steel materials such as Ni-Cr-Mo steel and Cr-Mn-V are used.

The composite cylinder for a plastic molding machine of the present invention is formed by forming a vulcanized layer or oxynitrided layer having a depth of 1 μm or more on the inner surface of the lining layer made of the alloy as described above.

The method for forming the sulfurized layer or the sulfurized nitrided layer will be described below. The sulfurized layer or the sulfurized nitrided layer is
It can be formed by performing a sulfurizing treatment or a sulfuritriding treatment, respectively.

The sulfurizing treatment is carried out by using an alkali base 60 such as NaOH.
˜90 parts by weight and 10 to 40 parts by weight of a sulfurizing agent such as Na ₂ S ₂ O ₃ and S at 100 to 150 ° C. are dissolved in a low temperature salt bath for 1 to 3 hours. It can be applied by dipping.

The sulfurized layer obtained by the above-mentioned sulfurizing treatment has a solid solution structure of S, and its thickness is 1 μm or more, preferably 1 μm or more.
~ 30 μm. Since the sulfurized layer significantly reduces the friction coefficient of the surface, even if the thickness is less than 1 μm,
Although it has the effect of preventing galling and seizure, a depth of 1 μm or more is required to prevent the sulphurized layer from disappearing and maintain its sufficient function even if it makes violent contact with the valve or screw. is there.

The hardness (H _RC ) of the lining layer obtained by the sulfurized layer is about 50 to 60.

Further, in order to form the above-mentioned vulcanized layer to a deeper depth and to harden the inside of the lining layer by nitriding treatment, a vulcanized sulfurizing reaction and a nitriding reaction are simultaneously carried out. You may give a process.

The sulfuritriding treatment is carried out by using 70 to 90 parts by weight of a nitrogen-containing alkaline base such as NaCN, Na ₂ S ₂ O ₃ and Na ₂ S.
It can be applied by immersing the cylinder having the lining layer in a high temperature salt bath prepared by dissolving 10 to 30 parts by weight of a sulfurizing agent such as O ₄ at 500 to 580 ° C. for 1 to 3 hours.

The sulfuritriding layer obtained by the above-mentioned sulfuritriding treatment has a structure such as an S solid solution layer, a mixed solid solution layer of S and N, an N solid solution layer, and the like in order from the surface side. Is 1 μm or more,
It is preferably 1 to 100 μm. The amount of the layer having a high sulfur concentration (corresponding to the sulfurized layer) in the sulfuritrided layer is preferably 1 to 30 μm from the surface to a depth of 1 μm or more.
The depth is μm, more preferably 1 to 20 μm. The reason for limiting the thickness range of the layer having a high sulfur concentration is the same as in the case of the sulfurized layer described above. The hardness (H _RC ) of the lining layer obtained by the sulfuritriding layer is about 50 to 60.

It should be noted that the sulfurizing treatment or the sulfuritriding treatment is not only performed on a newly made cylinder, but also when a galling or seizure occurs on the cylinder due to some abnormality during plastic molding. Good. For example, when the degree of galling or seizure is slight, the cylinder can be subjected to a sulfurizing treatment or a sulfuritriding treatment, and can be used again for molding a plastic. In addition, when the scoring and seizure are severe, the recurrence of scoring and seizure should be prevented by polishing and removing the irregularities on the inner surface due to scuffing, etc., and then applying sulphidizing treatment or sulphonitriding treatment. You can

Such a sulfurizing treatment and a sulfuritriding treatment are
This is an extremely suitable method for modifying the inner surface of the cylinder because it does not change the dimensions of the material to be treated.

The present invention will be described in more detail with reference to the following specific examples. Example 1 Equivalent to SCM440 specified in Japanese Industrial Standard (JIS G 4105)
The cylinder base material layer was formed using Cr-Mo steel.

Then, in order to form a lining layer,
Co-based alloys having the compositions shown in Table 1 were blended. In addition, Fe is
Since Fe migrates from the cylinder base material layer during casting, the amount of Fe that migrates was taken into account in the composition.

The alloy for the lining layer thus blended is once melted by heating and then formed into a plate-shaped alloy casting,
This alloy casting was crushed and charged into a cylinder through an opening for a hopper, and after sealing all the openings, centrifugal casting was performed at 1200 ° C.

After slow cooling, tempering was performed at 630 ° C. for 5 hours to obtain a composite cylinder material. This material is finished to the specified dimensions, and then this cylinder is NaCN8
5 parts by weight, Na ₂ S ₂ O ₃ 10 parts by weight, Na ₂ SO ₄
It was immersed in a high-temperature salt bath containing 5 parts by weight at 560 ° C. for 3 hours, subjected to nitrosulfurization treatment, and air-cooled.

Then, it was washed with warm water and dried to obtain a sulfurized layer having a depth of about 30 μm. Table 2 shows the hardness (H _SC ) of the cylinder base material layer and the hardness (H _RC ) of the lining layer of this cylinder.

The cylinder thus obtained is incorporated into an injection molding machine together with a screw (YPT4: manufactured by Hitachi Metals Co., Ltd.) and a valve (YPT42: manufactured by Hitachi Metals Co., Ltd.) to inject polystyrene resin. When molding was carried out for one month, there was no galling, seizure, etc. between the cylinder, the screw and the valve, and no burning or stain of the resin was observed.

Further, from the surface of the lining layer to the inside (1000
FIG. 1 shows the measurement results of the Knoop hardness (H _K ) over μm) and the concentrations of sulfur (S) and nitrogen (N).

As is apparent from FIG. 1, in the lining layer of the cylinder for the plastic molding machine of Example 1, the sulfur (S) component is present in a high concentration within the range of 30 μm from the surface, and Nitrogen maintains its concentration in a wide area from about 30 μm to the deep part, and 10% from the surface.
High hardness is maintained up to about 0 μm. From these facts, the sulfuritriding layer is formed to have a thickness of about 100 μm, and the sulfurizing layer that contributes to the improvement of seizure resistance is formed to have a thickness of about 30 μm from the surface layer among the above-mentioned sulfuritriding layers. I understand.

Example 2 SNCM439 equivalent to the Japanese Industrial Standard (JIS G 4103)
The cylinder base material layer was formed using Ni-Cr-Mo steel.

Then, a Ni-based alloy having the composition shown in Table 1 was mixed to form a lining layer. In addition, Fe is
Since Fe migrates from the cylinder base material layer during casting, the amount of Fe that migrates was taken into account in the composition.

The lining layer alloy thus blended was centrifugally cast at 1100 ° C. in the same manner as in Example 1.

After slow cooling, tempering was carried out at 600 ° C. for 5 hours to obtain a composite cylinder material. This material is finished to the specified dimensions, and then this cylinder is
3 parts by weight and 37 parts by weight of Na ₂ S ₂ O ₃ were dissolved at 150 ° C. for 3 hours in a low temperature salt bath for sulphidation and air cooling.

Then, it was washed with warm water and dried to obtain a sulfurized layer having a depth of about 3 μm. Table 2 shows the hardness (H _SC ) of the cylinder base material layer and the hardness (H _RC ) of the lining layer of this cylinder.

The cylinder thus obtained was assembled into an injection molding machine together with a screw (YPT4: Hitachi Metals Co., Ltd.) and a valve (YPT62: Hitachi Metals Co., Ltd.) to prepare a polyacetal resin. When injection molding was carried out for one month, there was no galling, seizure, etc. between the cylinder, the screw and the valve, and no burning or stain of the resin was observed.

Example 3 The same cylinder base material made of Cr-Mo steel as in Example 1 was used,
An average particle diameter of 5 to 30 μm with respect to 100 parts by weight of the alloy atomized powder having the composition shown in Table 1
20 parts by weight of WC are uniformly dispersed and sealed, and the HIP device has the structure shown in FIG. 2 (in the figure, 10 indicates the HIP device, 11 indicates the cylinder, and white arrows indicate the pressure). And filled with HIP. HIP conditions are 950 ℃, 1000at
m 2 and Ar gas atmosphere for 4 hours.

The obtained composite cylinder was subjected to finishing processing to a predetermined size, and then this cylinder was subjected to Example 1
The same sulphidizing and nitriding treatment was performed to obtain a composite cylinder for a plastic molding machine. The thickness of the sulfurized layer of the obtained cylinder was about 20 μm. Table 2 shows the hardness (H _SC ) of the cylinder base material layer and the hardness (H _RC ) of the lining layer of this cylinder.

Further, the cylinder thus obtained was assembled into an injection molding machine together with a screw (YPT7: Hitachi Metals Co., Ltd.) and a valve (YPT7: Hitachi Metals Co., Ltd.) to obtain nylon 66 When injection molding of a composition containing glass fibers by weight was carried out for one month, there was no galling, seizure, etc. between the cylinder, the screw and the valve, and no burning or stain of the resin was observed.

Table 1 Chemical composition of alloy for lining layer (% by weight) Example No. C B Si Mn Cr Ni Co Fe Example 1 0.2 2.7 0.9 1.0 18.0 − 70.2 7.0 Example 2 0.2 2.5 2.7 1.0 7.0 70.6 9.0 7.0 Example 3 ^* 0.2 2.9 2.5 0.5 9.0 74.5 10.0 0.4 Note) *: 20 parts by weight of WC was added to 100 parts by weight of the metal component.

Table 2 Hardness of Lining Layer Hardness of Cylinder Base Material Example No. (H _RC ) (H _SC ) Example 1 50 to 55 37 to 38 Example 2 50 to 55 30 to 31 Example 3 60 ~ 65 31 ~ 32

Example 4 A cylinder for a twin-screw extruder was manufactured from the same material as in Example 3 (no sulphonitriding treatment was applied), and finished to a predetermined size, and then this cylinder was left as it was. When the polyphenylene sulfide (PPS) resin was kneaded by incorporating it into a twin-screw extruder together with a screw (made of stainless steel), severe galling and seizure occurred between the screw and the valve in 1 hour.

Then, after pulling out the twin-screw extruder cylinder and grinding and removing the scuffing-generated inner surface, the same sulphidizing and nitriding treatment as in Example 1 was performed, the screw was re-installed, and the extrusion molding was restarted. Problems such as galling between the cylinder, screw and valve, and seizure were resolved.

[0063]

As described above in detail, in the present invention, the vulcanized layer having a depth of 1 μm or more is formed on the surface of the lining layer of the composite cylinder for the plastic molding machine having the liner made of the cobalt-based alloy or the nickel-based alloy. Alternatively, since the oxynitriding layer is formed, it is possible to prevent galling, seizure, etc. between the screw or valve and the cylinder, which greatly increases the frequency of resin burning and abnormal molding of plastic molded products. Can be reduced.

Further, the service life of cylinders, screws, valves, etc. can be greatly improved.

[Brief description of drawings]

FIG. 1 is a graph showing hardness after sulfuritriding of a lining layer of a cylinder for a plastic molding machine of Example 1, sulfur concentration, and nitrogen concentration.

FIG. 2 is a schematic view showing a HIP device for manufacturing a cylinder for a plastic molding machine according to a third embodiment.

FIG. 3 is a partial cross-sectional view showing an example of an injection molding machine.

[Explanation of symbols]

 1 ... Injection molding machine 2 ... Cylinder 3 ... Screw 4 ... Check ring 5 ... Adapter 6 ... ······Mold

Claims (4)

[Claims] 1. A hollow cylinder-shaped cylinder base material layer made of alloy steel, and a lining layer made of a cobalt-based alloy or a nickel-based alloy excellent in wear resistance and corrosion resistance existing on the inner surface of the cylinder base material layer. A composite cylinder for a plastic molding machine, wherein a vulcanized layer or oxynitrided layer is formed to a depth of 1 μm or more on the inner surface of the lining layer. 2. The composite cylinder for a plastic molding machine according to claim 1, wherein the cobalt-based alloy is Cr,
A composite cylinder for a plastic molding machine, characterized in that the total amount of B, Si, Mn and Ni is 35% by weight or less, Fe is 20% by weight or less, and the balance is substantially composed of Co and inevitable impurities. .. 3. The composite cylinder for a plastic molding machine according to claim 1, wherein the nickel-based alloy is Cr,
A composite cylinder for a plastic molding machine, characterized in that the total content of B, Si, Mn and Co is 35 wt% or less, Fe is 20 wt% or less, and the balance is substantially Ni and inevitable impurities. .. 4. The composite cylinder for a plastic molding machine according to claim 2 or 3, wherein the lining layer contains 3 to 3 parts by weight of carbide particles of an IVa group, Va group or VIa group element per 100 parts by weight of a metal component. A composite cylinder for a plastic molding machine characterized by being dispersed in 40 parts by weight.