JPH0679762A - Cylinder for molding machine and production thereof - Google Patents

Abstract

PURPOSE:To obtain a cylinder for a molding machine excellent in fatigue strength, corrosion resistance and abrasion resistance without being attended by evils such as an increase in cost or the like by constituting the cylinder of a cylinder matrix composed of alloy steel and the lining material excellent in abrasion resistance and corrosion resistance present on the inner surface of the matrix and forming the lining material from a specific Fe-base alloy. CONSTITUTION:A cylinder 1 for a molding machine has a hollow cylinder matrix 2 composed of alloy steel and the lining material 3 excellent in abrasion resistance and corrosion resistance present on the inner surface of the cylinder matrix 2. The lining material 3 is formed from an Fe-base alloy containing 1.0-3.0wt.% of C, 0.2-2.0wt.% of Si, 2.0wt.% or less of Mn, 2.0-7.0wt.% of Ni and 0.5-2.0wt.% of B and substantially composed of the remainder of Fe and inevitable impurities. By this constitution, the abrasion resistance and corrosion resistance of the lining material 3 can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical cylinder used in a plastic molding machine and a method for manufacturing the same, and more particularly to an inexpensive molding machine cylinder excellent in wear resistance and corrosion resistance and a method for manufacturing the same.

[0002]

2. Description of the Related Art Cylinders for molding machines such as plastics have a hollow cylindrical shape made of steel in order to prevent corrosion or wear caused by resin or additives added to the resin during heat molding. A structure in which an alloy material having wear resistance and corrosion resistance is lined on the inner surface of the cylinder base material by centrifugal casting is used. In the cylinder for a molding machine having such a structure, in recent years, in order to improve productivity, it is desired to shorten the injection molding cycle and increase the injection pressure resistance. Since the small lining material made of the above-mentioned alloy material is repeatedly subjected to expansion and contraction stresses and cracks are easily generated, it is necessary to have high strength so that the cylinder base material does not expand or contract as much as possible.

However, since the base material of the above-mentioned molding machine cylinder is mainly composed of pearlite and a small amount of ferrite, it does not have sufficient strength for a high-speed and high-pressure injection molding cycle. There is a problem that the lining material causes fatigue fracture due to expansion and contraction and cracks occur.

Therefore, as a method of improving these performances, as shown in FIG. 6, the reinforcing member 4 is joined to the molding machine cylinder 1 composed of the lining material 3 and the cylinder base material 2 by a shrink fitting method. A method can be considered. However, according to this method, there is a problem that the manufacturing cost increases, and there is a problem that the manufacturing procedure becomes long because it takes time and labor.

Therefore, an object of the present invention is to provide an inexpensive cylinder for a molding machine, which is excellent in fatigue strength, corrosion resistance and wear resistance, without any adverse effects such as cost increase. Another object of the present invention is to provide a method for manufacturing such a cylinder for a molding machine.

[0006]

As a result of intensive studies in view of the above problems, the present inventor has lined a hollow cylindrical cylinder base material made of alloy steel with an alloy having wear resistance and corrosion resistance by centrifugal casting. When forming a cylinder for a molding machine, the cylinder base material is made into a desired structure, and by applying an appropriate heat treatment for this purpose, it is inexpensive and excellent in wear resistance and corrosion resistance without adverse effects such as cost increase. The present invention has been accomplished by discovering that a cylinder for a molding machine can be obtained.

That is, the cylinder for the molding machine of the present invention is
It has a hollow cylinder-shaped cylinder base material made of alloy steel and a lining material existing on the inner surface of the cylinder base material and having excellent wear resistance and corrosion resistance, and the lining material is C 1.0 to
3.0 wt%, Si 0.2-2.0 wt%, Mn 2.0 wt% or less,
It is characterized in that it is composed of 2.0 to 7.0% by weight of Ni, 0.5 to 2.0% by weight of B, and the balance being an Fe-based alloy consisting essentially of Fe and inevitable impurities.

Further, in the method for producing a cylinder for a molding machine of the present invention, the lining material is put into the cylinder base material and centrifugally cast, and then a temperature range in which bainite transformation occurs at a cooling rate of 20 to 200 ° C./min. It is characterized in that it is cooled to room temperature, held there for 10 minutes or more, then heated to an annealing temperature of 550 to 650 ° C. at a heating rate of 1 to 10 ° C./minute, and cooled to room temperature after annealing.

[0009]

Embodiments and Functions First, a base material of a molding machine cylinder according to an embodiment of the present invention will be described. In this embodiment, alloy steel is used as a cylinder base material for coating a lining material having wear resistance and corrosion resistance.

When Cr-Mo steel is used as the alloy steel, the content of chemical components is C 0.3 to 0.5% by weight, Si 0.15 to 0.35% by weight, Mn 0.3 to 1.5% by weight, P 0.03% by weight or less, S0.03
Weight% or less, Cr 0.7 to 1.5% by weight, Mo 0.1 to 0.5% by weight
It is preferable in terms of strength. Japanese Industrial Standard (JIS G 4105)
Cr-Mo steels equivalent to SCM440 and SCM445 specified in 1) are particularly preferable in terms of strength.

When Ni-Cr-Mo steel is used as the alloy steel, the content ratio of chemical components is 0.3 to 0.5% by weight of C and 0.15 to 0.15 of Si.
0.35% by weight, Mn 0.3-1.5% by weight, P0.03% by weight or less,
From the viewpoint of strength, it is preferable that S is 0.03% by weight or less, Ni is 3.0% by weight or less, Cr is 0.7 to 1.5% by weight, and Mo is 0.1 to 0.5% by weight.
SNCM439 equivalent to Japanese Industrial Standard (JIS G 4103)
Ni-Cr-Mo steel is particularly preferable in terms of strength.

Further, in this embodiment, in order to improve the strength of the cylinder base material, 20% or more of the structure is made of bainite and the rest is made of sorbite. If the bainite of the structure is less than 20%, sufficient strength cannot be obtained, which is not preferable. In order to have the organizational structure shown above,
In the present embodiment, the lining material described above is put into the cylinder base material described above, centrifugally cast, and then subjected to heat treatment.
This heat treatment method will be described with reference to the heat treatment pattern shown in FIG.

Here, the horizontal axis of FIG. 1 represents time, the vertical axis represents temperature, and A on the heat treatment pattern is a centrifugal casting step, B is a cooling step, C is a holding step, D is a heating step, and E is an E step. Indicates an annealing step, and F indicates a cooling step to room temperature.

In this embodiment, a cylinder for a molding machine is formed by a centrifugal casting process shown in A, and then in a cooling process shown in B, the temperature is cooled to a temperature range where bainite transformation occurs. The cooling rate at this time is 20-200 ° C / min. If the cooling rate is less than 20 ° C / min, troostite is generated, and if it exceeds 200 ° C / min, cracks are likely to occur on the inner surface of the lining material.

Next, as shown in C, in the holding step,
The region where bainite transformation occurs is 300 to 600 ° C. If the region where bainite transformation occurs is less than 300 ° C, the expansion of the base material at low temperature tends to cause cracks on the inner surface of the lining material, and if it exceeds 600 ° C, pearlite occurs. In addition, the holding time in the holding step needs to be 10 minutes or more. If the holding time is less than 10 minutes, the amount of bainite in the cylinder base material is less than 20%, and sufficient strength cannot be obtained.

Next, as shown in D, heating is performed up to the annealing temperature, at this time, the heating rate is 1 to 10 ° C./minute.
If the heating rate is less than 1 ° C / min, the amount of bainite in the cylinder base material becomes excessive, and cracks are likely to occur on the inner surface of the lining material. On the other hand, if it exceeds 10 ° C / min, the amount of bainite is insufficient and strength cannot be obtained.

Next, as shown in E, annealing is performed.
At this time, the annealing temperature is 550 to 650 ° C. If the annealing temperature is lower than 550 ° C, the purpose of annealing, that is, residual stress relief, will not be achieved, and if it exceeds 650 ° C, the metal structure will be affected. The annealing time is 1 to 5 hours. If the annealing time is less than 1 hour, the residual stress cannot be removed sufficiently, and if it exceeds 5 hours, the effect is not significantly changed.

Finally, as shown in F, the temperature is cooled to room temperature.

The cylinder for a molding machine in this embodiment formed as described above has a structure having excellent wear resistance and corrosion resistance because the strength of the cylinder base material is remarkably improved.

Next, the alloy components constituting the lining material having wear resistance and corrosion resistance used in this embodiment will be described.

The C content is 1.0 to 3.0% by weight. C
Is an element essential for forming carbides and maintaining the hardness and strength of the matrix. If it is less than 1.0% by weight, hardness is insufficient and wear resistance is reduced. On the other hand, if it exceeds 3.0% by weight, the degree of eutecticity increases to make it brittle, resulting in a decrease in mechanical strength and a decrease in corrosion resistance, which is not preferable.

Si has the function of maintaining deoxidation and fluidity of the molten metal when it is made into a bimetal by centrifugal casting.
It has the effect of improving castability. If it is less than 0.2% by weight, the effect is not sufficient, and if it is more than 2.0% by weight, the toughness of the alloy decreases, so the content rate is 0.2 to 2.0% by weight.
And

Mn not only acts as a deoxidizing agent, but is also effective in preventing the adverse effect of S mixed in as an impurity. Due to this effect, the content is 2.0% by weight or less.

Ni has the effect of improving the hardness and wear resistance as well as the corrosion resistance by making the matrix of the metal structure into bainite or martensite. If it is 2.0% by weight or less, a large amount of pearlite is precipitated and the hardness is lowered. On the other hand, if it is 7.0% by weight or more, it becomes an austenite base, and conversely the hardness decreases. Therefore, the content rate is 2.0-
7.0% by weight

The B content is 0.5 to 2.0% by weight. B
Has the function of precipitating a high-hardness boride in the structure, improving the hardness of the alloy, lowering the melting point of the alloy, and promoting the adhesion between the alloy layer and the base metal.
If it is less than 2.0%, the effect is not sufficient, and if it exceeds 2.0% by weight, the supereutectic structure becomes coarse and brittleness increases, which is not preferable.

Since Fe improves the high hardness characteristics and corrosion resistance of the alloy, it is the balance as the matrix of the alloy.

The present invention will be described in detail with reference to the following specific examples. The heat treatment cycle will be described with reference to FIG.

Example 1 SCM440 equivalent to the Japanese Industrial Standard (JIS G 4105)
The cylinder base material was formed using Cr-Mo steel. Then
In order to form an alloy for a lining material, alloys having the compositions shown in Table 1 are blended. Once the alloy for lining materials blended in this way is heated and melted, it is formed into a plate-shaped alloy casting, and this alloy casting is crushed and put into the cylinder through the opening for the hopper, and the opening is completely sealed. Then, it was centrifugally cast at 1200 ° C. (A shown in FIG. 1).

Next, after cooling at a cooling rate of 40 ° C./min to a temperature at which bainite transformation of 480 ° C. occurs (B shown in FIG. 1), it is held for 20 minutes (C shown in FIG. 1), and then a heating rate of 5 After being reheated at 630 ° C./min to the annealing temperature of 630 ° C. (D shown in FIG. 1), it was held for 5 hours for annealing (E shown in FIG. 1) and cooled to room temperature (F shown in FIG. 1). ).

The structure of the lining material of the cylinder for the forming machine formed as described above is composed of 80 or more bainite and martensite structures as shown in the metal structure of FIG. As shown in the metal structure of FIG. 5, the cylinder base material structure of the cylinder for the molding machine is approximately 50% baylite.
%, And the balance was sorbite.

With respect to the lining material of the molding machine cylinder of Example 1 described above, the hardness and the average bending strength were measured and Table 2
Shown in. A tensile test was conducted on the strength of the cylinder base material, and 0.2% proof stress at 450 ° C was measured.

Table 1 Sample name Lining material Alloy chemical composition (% by weight) C Si Mn Ni B Cr Fe Example 1 2.02 0.82 1.06 3.74 0.94 0.15 Bal.

Table 2Lining material Cylinder base material Hardness transverse rupture strength 0.2% proof stress (450 ℃)Sample name (HRC) (kg / mm ² ) (HSC) (kg / mm ² )  Example 1 61 88 38 59

Samples having a size of 10 mm × 15 mm × 10 mm were prepared from the cylinder for a molding machine of the above-mentioned Example 1 and the nitrided steel (obtained by air-cooling SACM 645 steel specified in JIS G 4202). , # 400 abrasive paper was pressed with a load of 2.0 kg and slid for a distance of 480 m, after which the amount of wear of the lining material was examined.
Fig. 2 shows the results of evaluation of wear resistance by relative values when the result of nitriding steel was set to 10. The wear resistance of the lining material of Example 1 has a relative value of 4, and the wear amount is reduced to half or less.
The wear resistance is greatly increased.

Further, a sample having a size of 1.5 mm × 4 mm × 10 mm was prepared from the above-mentioned Example 1 and the cylinder for the forming machine of the nitrided steel, and after dipping in a 10% HCl aqueous solution at 50 ° C. for 24 hours,
The corrosion weight loss rate of the lining material was investigated. The result of nitriding steel is 1
Fig. 3 shows the results of evaluation of the corrosion resistance by the relative value when The relative corrosion resistance of the lining material of Example 1 to acid was 0.9, the corrosion weight loss rate was decreased, and the corrosion resistance was increased.

[0036]

In the cylinder for the molding machine of the present invention,
A hollow cylinder-shaped cylinder base material made of alloy steel is centrifugally cast with a lining material formed of a wear-resistant alloy to produce a cylinder for a molding machine.The cylinder for a molding machine is heat-treated according to the method of the present invention. By applying 20% or more of the structure of the cylinder base material by bainite,
The rest is formed by sorbite. As a result, even when the lining material is subjected to expansion and contraction stresses in order to respond to high-speed, high-pressure injection cycles, the cylinder base material has excellent strength and suppresses distortion that occurs in the lining material, and therefore wear resistance. A cylinder for a molding machine having corrosion resistance can be obtained without any adverse effects such as cost increase.

[Brief description of drawings]

FIG. 1 is a pattern diagram showing a heat treatment process of a molding machine cylinder according to an embodiment of the present invention.

FIG. 2 is a graph showing relative values of wear amounts of Example 1 and nitrided steel.

FIG. 3 is a graph showing relative values of corrosion weight loss rates of Example 1 and nitrided steel,

FIG. 4 is a photomicrograph showing the metal structure of the lining material of the cylinder of Example 1.

5 is a micrograph showing a metal structure of a base material of a cylinder of Example 1. FIG.

FIG. 6 is a schematic cross-sectional view showing an example of a molding machine cylinder.

[Explanation of symbols]

 1 Cylinder for molding machine 2 Cylinder base material 3 Lining material 4 Reinforcement member

Claims (6)

[Claims] 1. A hollow cylinder-shaped cylinder base material made of alloy steel, and a lining material existing on the inner surface of the cylinder base material and having excellent wear resistance and corrosion resistance, wherein the lining material is C 1.0 to 3.0. Wt%, Si 0.2-2.0 wt%, Mn
A cylinder for a molding machine, which is made of an Fe-based alloy containing 2.0% by weight or less, Ni 2.0 to 7.0% by weight, B 0.5 to 2.0% by weight, and the balance substantially Fe and inevitable impurities. 2. The cylinder for a molding machine according to claim 1, wherein the structure of the base material of the cylinder is 20% or more of bainite and the balance is sorbite. 3. The molding machine cylinder according to claim 1, wherein the alloy steel forming the cylinder base material is C.
0.3-0.5 wt%, Si0.15-0.35 wt%, Mn0.3-1.5
% By weight, P0.03% by weight or less, S0.03% by weight or less, Cr 0.7
A cylinder for a molding machine, which is characterized in that it is a Cr-Mo steel consisting of ~ 1.5 wt%, Mo 0.1-0.5 wt% and the balance substantially Fe and inevitable impurities. 4. The forming machine cylinder according to claim 1, wherein the alloy steel forming the cylinder base material is C.
0.3-0.5 wt%, Si0.15-0.35 wt%, Mn0.3-1.5
% By weight, P0.03% by weight or less, S0.03% by weight or less, Ni3.0
Ni-Cr containing less than 1% by weight, Cr 0.7 to 1.5% by weight, Mo 0.1 to 0.5% by weight, and the balance substantially Fe and inevitable impurities.
-Cylinder for a molding machine, which is made of Mo steel. 5. A hollow cylinder-shaped cylinder base material made of alloy steel and a lining material existing on the inner surface of the cylinder base material and having excellent wear resistance and corrosion resistance, wherein the lining material is C 1.0 to 3.0. Wt%, Si 0.2-2.0 wt%, Mn
In a method for producing a cylinder for a molding machine, which comprises 2.0% by weight or less, Ni 2.0 to 7.0% by weight, B 0.5 to 2.0% by weight, and the balance substantially consisting of Fe and an inevitable impurity, a Fe-based alloy, wherein the lining material is the cylinder. After putting into the base metal and centrifugal casting, cool it to a temperature range where bainite transformation occurs at a cooling rate of 20 to 200 ° C / min, hold it there for 10 minutes or more, then 1 to 10
A method characterized by heating to an annealing temperature of 550 to 650 ° C at a heating rate of ° C / min, and cooling to room temperature after annealing. 6. The method of manufacturing a cylinder for a molding machine according to claim 5, wherein the region in which the bainite transformation occurs is 3
A method characterized in that the temperature is 00 to 600 ° C.