JP3285055B2 - Molding machine cylinder and method of manufacturing the same - Google Patents

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 for a plastic molding machine and the like, and more particularly to a cylinder for a molding machine having excellent wear resistance, corrosion resistance and crack resistance, and a method for producing the same.

[0002]

2. Description of the Related Art In order to prevent corrosion or abrasion due to a resin or an additive added to a resin during hot molding, a hollow cylindrical member made of steel is used for a molding machine cylinder made of plastic or the like. 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. In a molding machine cylinder having such a structure, in recent years, it has been desired to shorten the injection molding cycle and increase the injection pressure resistance in order to improve productivity. Since the stress of expansion and contraction is repeatedly applied to the small lining material made of the above alloy material and cracks are easily generated, it is necessary that the cylinder base material has high strength so as not to expand and 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 are generated.

Therefore, as a method for improving these performances, as shown in FIG. 9, a reinforcing member 4 is joined to a molding machine cylinder 1 composed of a lining material 3 and a cylinder base material 2 by a shrink fitting method. A method is conceivable. However, according to this method, there is a problem that the manufacturing cost is increased, and there is a problem that the manufacturing procedure is lengthened due to the labor required.

[0005] In view of the above, the applicant of the present invention has previously described Cr 10.0 to 3
0.0 wt%, B 1.5-4.0 wt%, Si 2.0 wt% or less, Mn
2.0% by weight or less, C 0.7% by weight or less, Fe 5.0 to 20.0% by weight, the balance being a lining material obtained by dispersing 3.0 to 20.0% by weight of NbC in a Co-based alloy consisting essentially of Co, and an alloy steel A cylinder for a molding machine characterized by having a cylinder base material has been proposed (JP-A-4-28839). This molding machine cylinder has good wear resistance and crack resistance. However, it was found that large amounts of NbC could cause segregation. Also, the fluidity is poor and the castability is poor.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a molding machine cylinder excellent in fatigue strength, crack resistance, and abrasion resistance without adverse effects such as an increase in cost and an extension of a manufacturing procedure. Another object of the present invention is to provide a method for manufacturing such a molding machine cylinder.

[0007]

Means for Solving the Problems In view of the above problems, as a result of intensive studies, the present inventors lined a hollow cylindrical cylinder base material made of alloy steel with an alloy having wear resistance and corrosion resistance by centrifugal casting. When manufacturing a cylinder for a molding machine, the cylinder base material is made into a desired structure, and by performing an appropriate heat treatment for this purpose, the cost is increased, and the production procedure is lengthened without adverse effects, such as fatigue strength, especially The present inventors have found that a cylinder for a molding machine having excellent crack resistance can be obtained, and have reached the present invention.

That is, the molding machine cylinder of the present invention comprises:
A cylinder base material having a hollow cylindrical shape made of alloy steel, and a lining material having excellent wear resistance and corrosion resistance existing on the inner surface of the cylinder base material, wherein the lining material is Cr10.0 to
30.0% by weight, B 1.5-4.0% by weight, Si 2.0% by weight or less,
It is characterized by being composed of a Co-based alloy containing 2.0% by weight or less of Mn, 0.7% by weight or less of C, 5.0% to 20.0% by weight of Fe, 2.0% to 20.0% by weight of W, and the balance substantially consisting of Co and inevitable impurities.

The method of manufacturing a cylinder for a molding machine according to the present invention is characterized in that the lining material is placed in the cylinder base material, centrifugally cast, and then subjected to a temperature range in which bainite transformation occurs at a cooling rate of 20 to 200 ° C./min. After heating for 10 minutes or more, heating at a heating rate of 1 to 10 ° C / min to an annealing temperature of 550 to 650 ° C, and cooling to room temperature after annealing.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a base material of a cylinder for a molding machine according to an embodiment of the present invention will be described. In this embodiment, an 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 0.3 to 0.5% by weight of C, 0.15 to 0.35% by weight of Si, 0.3 to 1.5% by weight of Mn, 0.03% by weight or less of P, S0.03
Wt% or less, Cr 0.7-1.5 wt%, Mo 0.1-0.5 wt%
It is preferable from the viewpoint of strength. Japanese Industrial Standards (JIS G 4105)
Cr-Mo steel equivalent to SCM440 and SCM445 specified in (1) is particularly preferable in terms of strength.

When Ni-Cr-Mo steel is used as the alloy steel, the content of the chemical component is C 0.3-0.5% by weight, Si 0.15-
0.35 wt%, Mn 0.3-1.5 wt%, P 0.03 wt% or less,
S is preferably 0.03% by weight or less, Ni 3.0% by weight or less, Cr 0.7 to 1.5% by weight, and Mo 0.1 to 0.5% by weight in terms of strength.
SNCM439 equivalent of Japanese Industrial Standard (JIS G 4103)
Ni-Cr-Mo steel is particularly preferred in terms of strength.

In this embodiment, in order to improve the strength of the cylinder base material, at least 20% of the structure is formed of bainite, and the remainder is formed of sorbite. If the bainite in the structure is less than 20%, it is not preferable because sufficient strength cannot be obtained. To achieve the organizational structure shown above,
In this embodiment, after the centrifugal casting of the lining material described above in the cylinder base material described above, heat treatment is performed.
This heat treatment method will be described with reference to a heat treatment pattern shown in FIG.

Here, the horizontal axis in FIG. 1 indicates time, and the vertical axis indicates temperature. A in 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 a heating step. Indicates an annealing step, and F indicates a cooling step to room temperature.

In this embodiment, a molding machine cylinder is formed by a centrifugal casting process shown in A, and then cooled in a cooling process shown in B to a temperature range in which bainite transformation occurs. 20-200 ° C / min. When the cooling rate is less than 20 ° C./min, troostite is generated, and when the cooling rate is more than 200 ° C./min, cracks easily occur on the inner surface of the lining material.

Next, as shown in C, in the holding step,
The area where bainite transformation occurs is 300-600 ° C. If the area where bainite transformation occurs is less than 300 ° C, cracks are likely to occur on the inner surface of the lining material due to transformation expansion of the base material at a low temperature, and pearlite occurs when the temperature exceeds 600 ° C. The holding time in the holding step is required to be 10 minutes or more. If the holding time is less than 10 minutes, the bainite amount of the cylinder base material will be less than 20%, and sufficient strength cannot be obtained.

Next, as shown in D, heating is performed to the annealing temperature, at which time the heating rate is 1 to 10 ° C./min.
When the heating rate is less than 1 ° C./min, the bainite amount of the cylinder base material becomes excessive, and cracks are easily generated on the inner surface of the lining material. On the other hand, if the temperature exceeds 10 ° C./min, the amount of bainite is insufficient, so that strength cannot be obtained.

Next, annealing is performed as shown in E,
At this time, the annealing temperature is 550 to 650 ° C. If the annealing temperature is lower than 550 ° C, the purpose of annealing to remove residual stress 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 sufficiently removed, and if it exceeds 5 hours, there is no significant change in the effect.

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

The molding machine cylinder according to the present embodiment formed as described above has a structure having excellent fatigue strength, particularly crack resistance, since the strength of the cylinder base material is significantly improved.

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

The Cr content is 10.0 to 30.0% by weight, and a particularly preferred Cr content is 11.0 to 23.0% by weight. Cr
If the content is less than 10.0% by weight, when the alloy of this example is sulfided, the sulfide scale is contained in a matrix composed of Co ₂ S _4.
It forms a structure in which Cr ₂ S ₃ is dispersed, and this scale is not preferable because it does not suppress the sulfidation reaction. When Cr exceeds 10.0% by weight, the sulfide scale forms a structure in which Co ₂ S ₄ is dispersed in a matrix composed of Cr ₂ S ₃ , and this scale suppresses the sulfidation reaction. However, when the Cr content exceeds 30.0% by weight, the sulfidation resistance is improved, but the melting point of the alloy of this example is 1200
C. or more, which is not suitable for centrifugal casting.

The B content is 1.5 to 4.0% by weight. B
Has the effect of increasing the hardness of the alloy by precipitating high-hardness borides in the structure, but if the content is less than 1.5% by weight, the effect is not sufficient, and if it exceeds 4.0% by weight, the hypereutectic structure becomes coarse, In addition, it is not preferable because brittleness is increased.

The relationship between the amount of Cr and the amount of B is such that when the amount of Cr is increased, the amount of B is reduced, and when the amount of Cr is reduced, the amount of B is increased. Become. That is, when the content of Cr is 30% by weight, the content of B is 1.5% by weight, and when the content of Cr is 10% by weight, the content of B is 4.0% by weight.

Although Si acts as a deoxidizing material, its content is set to 2.0% by weight or less from the effect.

Mn acts as a deoxidizer, but its content is set to 2.0% by weight or less from the effect.

The content of C is 0.7% by weight or less. C has the effect of improving the hardness and strength of the matrix. However, if it exceeds 0.7% by weight, the eutectic degree increases and becomes brittle, and the strength decreases, which is not preferable.

The Fe content is between 5.0 and 20.0% by weight. Fe
Even if is not initially contained in the alloy, it enters from the cylinder base material by a welding reaction with the cylinder base material made of steel.
It is necessary for a predetermined amount of Fe to transfer from the cylinder base material to the alloy in order to perform complete welding between the lining material and the cylinder base material. However, if Fe is less than 5.0% by weight, the effect is not exhibited. Further, when Fe is increased, the hardness is reduced, and the corrosion resistance to acids is reduced. When the content exceeds 20.0% by weight, the effect cannot be ignored, so that it is not preferable.

The W content is 2.0 to 20.0% by weight. W
Forms an extremely hard boride and carbide with B and C, and has an effect of improving abrasion resistance. If the amount is less than 2.0% by weight, the amount of the boride is small and the effect is not exhibited. If it exceeds 20% by weight, the amount of boride becomes excessive,
As it becomes excessively hard and the mechanical strength is significantly reduced,
2.0 to 20.0% by weight.

Since Co is combined with Cr and B to improve the high hardness properties and corrosion resistance of the alloy, Co is left as a matrix of the alloy.

In this embodiment, Ni may be contained. In this case, the preferred content of Ni is 5.0% by weight.
It is as follows. If Ni exceeds 5.0% by weight, the hardness of the alloy is lowered, which is not preferable.

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 The equivalent of SCM440 specified in Japanese Industrial Standard (JIS G 4105)
A cylinder base material was formed using Cr-Mo steel. Then
In order to form the alloy for the lining material, an alloy having a composition shown in Table 1 was blended. However, Fe was transferred from the cylinder base material during casting.

The alloy for lining material thus mixed is once melted by heating and then formed into a plate-like alloy casting.
This alloy casting was crushed and put into a cylinder through an opening for a hopper, and all the openings were sealed, followed by centrifugal casting at 1200 ° C. (A shown in FIG. 1). Then, at a cooling rate of 40 ° C./min,
After cooling to a temperature at which the bainite transformation takes place at 480 ° C. (B in FIG. 1), it is held for 20 minutes (C in FIG. 1) and then reheated at a heating rate of 5 ° C./min to an annealing temperature of 630 ° C. Thereafter (D shown in FIG. 1), the sample was annealed while holding for 5 hours (E shown in FIG. 1), and cooled to room temperature (F shown in FIG. 1).

The structure of the lining material of the molding machine cylinder formed as described above is composed of light-colored WB, dark-colored CrB, and gray Co base, as shown in the metallographic structure of FIG. As shown in the metallographic structure of FIG. 8, the base metal structure of the molding machine cylinder contained about 50% bainite, and the remainder was composed of sorbite.

Example 2 SNCM 439 equivalent to the Japanese Industrial Standard (JIS G 4130)
Using Ni-Cr-Mo steel, form a cylinder base material,
A lining material was formed with the composition shown in Table 1 in the same manner as in Example 1.

The above-mentioned lining material is added to the above-mentioned cylinder base material for 12 minutes.
A cylinder for a molding machine was produced by centrifugal casting at a temperature of 00 ° C. (A shown in FIG. 1), and then subjected to heat treatment. The heat treatment was performed at a cooling rate of 20 ° C./min (B shown in FIG. 1). ), Bainite transformation temperature 450 ° C, holding time 20 minutes (C shown in Fig. 1), heating rate 5 ° C / min (D shown in Fig. 1), annealing temperature 600 ° C, annealing time 5 hours (shown in Fig. 1). E), and the other conditions were the same as in Example 1. The structure of the lining material of the molding machine cylinder formed as described above has a relatively light-colored WB as shown in the metal structure of FIG.
And dark CrB and gray Co base.

Comparative Example 1 A cylinder base material was formed using the same Cr-Mo steel as in Example 1, and then an alloy having the composition shown in Table 1 was used.
A lining material was formed in the same manner as described above.

The lining material is added to the cylinder base material by 11
A cylinder for a molding machine was prepared by centrifugal casting at a temperature of 00 ° C. (A shown in FIG. 1), and then subjected to a heat treatment. The heat treatment was performed at a cooling rate of 60 ° C./min (B shown in FIG. 1). ), Cooled to a temperature of 620 ° C just before bainite transformation, holding time 20 minutes (C shown in Fig. 1), heating rate 5 ° C / min (D shown in Fig. 1), annealing temperature 630 ° C, annealing time 5 hours ( E) shown in FIG. 1, and the other conditions were the same as in Example 1.

The hardness was measured for the lining materials of the molding machine cylinders of Examples 1 and 2 and Comparative Example 1 and Table 2 was obtained.
Shown in

Table 1 Sample name Lining material alloy chemical composition (% by weight) CB Si Mn Cr Ni Co Fe W Example 1 0.1 2.6 1.0 1.0 18 0.5 Remainder 9.5 3.0 Example 2 0.2 2.8 1.0 1.0 20 0.7 Remainder 10.5 8.5 Comparative Example 1 0.2 2.5 2.7 1.0 6.3 67.4 10.0 10.0-

Table 2 Lining material hardness (HRC) Cylinder base material hardness (HSC) Example 1 50 37 Example 2 57 37 Comparative example 1 53 to 58 30 to 32

For the molding machine cylinders of Examples 1 and 2 and Comparative Example 1, the tensile strength of the lining material (value calculated from the bending strength and the Weibull value) and the yield stress of the cylinder base material were measured. . Since substantially the same results were obtained for Examples 1 and 2, the results for Example 1 and Comparative Example 1 are shown in FIG.

The pressure resistance of the molding machine cylinders of Examples 1 and 2 and Comparative Example 1 was measured. In Examples 1 and 2, almost the same results were obtained.
The results for Example 1 and Comparative Example 1 are shown in FIG.

Further, a sample having a size of 10 mm × 15 mm × 10 mm was prepared from the molding machine cylinders of Examples 1 and 2 and Comparative Example 1, and pressed against # 400 abrasive paper with a load of 2.0 kg. 48
After sliding at a distance of 0 m, the wear amount of the lining material was examined. The results were expressed by a relative value when the result of Comparative Example 1 was set to 10, and the wear resistance was evaluated. In Example 2, the same results as in Example 1 were obtained.
The results are shown in FIG.

Further, samples were prepared from the molding machine cylinders of Examples 1 and 2 and Comparative Example 1 described above, immersed in a 10% HCl aqueous solution at 50 ° C. for 24 hours, and the corrosion loss rate of the lining material was examined. . The results were expressed by a relative value when the result of Comparative Example 1 was set to 1, and the corrosion resistance was evaluated. Example 1,
Since the same result was obtained for No. 2, the results for Example 1 and Comparative Example 1 are shown in FIG.

As is clear from FIG. 2, the tensile strength of the lining material forming the molding machine cylinder of Example 1 was remarkably improved about twice or more as compared with the molding machine cylinder of Comparative Example 1. .

Further, the yield point stress of the cylinder base material of Example 1 was improved by 80% or more as compared with Comparative Example 1.

Further, as is apparent from FIG.
The pressure resistance of the molding machine cylinder of Example 1 was improved by about 80% compared to the molding machine cylinder of Comparative Example 1.

As described above, in the molding machine cylinder of the present embodiment, the lining material has a sufficient strength, and the strength of the cylinder base material is remarkably improved, so that the crack resistance is remarkably improved.

With respect to the wear resistance of the lining material of Example 1, as shown in FIG.
The relative value when is 10 is 5, the wear amount is reduced by about half, and the wear resistance is greatly increased. Nitride steel (SAC specified in JIS G 4202
When a similar test was performed on a sample obtained by nitriding M645 steel, the relative value was 35 as shown in FIG. 4, and the amount of wear was significantly reduced as compared with this. It can be said that abrasion was obtained.

As for the corrosion resistance of the lining material of Example 1 to acid, as shown in FIG. 5, the relative value when Comparative Example 1 was set to 1 was 1.3, indicating an increase in the corrosion weight loss rate.
Corrosion resistance is slightly reduced. However, nitrided steel that has been widely used for cylinders (SACM specified in JIS G 4202)
When the same test was performed on a sample obtained by nitriding 645 steel, the relative value was 20, as shown in FIG. 5, and in comparison with this, the corrosion weight loss rate was significantly reduced. It can be said that excellent corrosion resistance was obtained.

[0053]

As described in detail above, in the molding machine cylinder of the present invention, a lining material formed of a wear-resistant alloy is centrifugally cast on a cylinder base material having a hollow cylindrical shape made of alloy steel. A cylinder for a molding machine is manufactured. By subjecting the cylinder for a molding machine to heat treatment according to the method of the present invention, at least 20% of the structure of the cylinder base material is formed of bainite, and the remainder is formed of sorbite. I have. As a result, even when the lining material is subjected to expansion and contraction stresses in order to cope with a high-speed, high-pressure injection cycle, the cylinder base material has excellent strength, and the strain generated in the lining material is suppressed. A molding machine cylinder having strength and crack resistance can be obtained without adverse effects such as an increase in cost and an extension of a manufacturing procedure.

[Brief description of the drawings]

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

FIG. 2 is a graph showing the tensile strength of the lining material of Example 1 and Comparative Example 1 and the yield point stress of the cylinder base material.

FIG. 3 is a graph showing the pressure resistance of Example 1 and Comparative Example 1.

FIG. 4 is a graph showing relative values of the amount of wear in Example 1 and Comparative Example 1.

FIG. 5 is a graph showing the relative values of the corrosion weight loss rates of Example 1 and Comparative Example 1,

FIG. 6 is a micrograph showing a metal structure of a lining material of a cylinder of Example 1.

FIG. 7 is a micrograph showing a metal structure of a lining material of a cylinder of Example 2.

FIG. 8 is a micrograph showing a metal structure of a base material of the cylinder of Example 1.

FIG. 9 is a schematic 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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/00-45/84 C22C 19/00-19/07

Claims (8)

(57) [Claims] 1. A cylinder base material having a hollow cylindrical shape made of an alloy steel, and a lining material having excellent wear resistance and corrosion resistance existing on an inner surface of the cylinder base material. 30.0% by weight, B 1.5-4.0% by weight, Si
2.0% by weight or less, Mn 2.0% by weight or less, C 0.7% by weight or less, Fe 5.0 to 20.0% by weight, W 2.0 to 20.0% by weight, the balance being substantially a Co-based alloy consisting essentially of Co and unavoidable impurities. And molding machine cylinders. 2. The cylinder for a molding machine according to claim 1, wherein the structure of the cylinder base material is composed of at least 20% of bainite and the balance of sorbite. 3. The cylinder for a molding machine according to claim 1, wherein the lining material has a Cr content of 11.0 to 23.0% by weight.
A cylinder for a molding machine. 4. The cylinder for a molding machine according to claim 1, wherein the lining material contains 5.0% by weight or less of Ni. 5. The molding machine cylinder according to claim 1, wherein the alloy steel forming the cylinder base material is C 0.3-0.5 wt%, Si 0.15-0.35 wt%, Mn
Cr-Mo steel consisting of 0.3-1.5% by weight, P0.03% by weight or less, S0.03% by weight or less, Cr 0.7-1.5% by weight, Mo 0.1-0.5% by weight, and the balance substantially consisting of Fe and unavoidable impurities A cylinder for a molding machine. 6. The molding machine cylinder according to claim 1, wherein the alloy steel forming the cylinder base material is C 0.3-0.5 wt%, Si 0.15-0.35 wt%, Mn
0.3-1.5 wt%, P0.03 wt% or less, S0.03 wt% or less, Ni3.0 wt% or less, Cr 0.7-1.5 wt%, Mo 0.1-
A molding machine cylinder characterized by being a Ni-Cr-Mo steel consisting of 0.5% by weight and the balance substantially consisting of Fe and unavoidable impurities. 7. A cylinder base material having a hollow cylindrical shape made of an alloy steel, and a lining material having excellent wear resistance and corrosion resistance existing on an inner surface of the cylinder base material, wherein the lining material has a Cr content of 10.0 to 1.0. 30.0% by weight, B 1.5-4.0% by weight, Si
2.0% by weight or less, Mn 2.0% by weight or less, C 0.7% by weight or less, Fe 5.0 to 20.0% by weight, W 2.0 to 20.0% by weight, the balance being a Co-based alloy consisting essentially of Co and unavoidable impurities In the method for manufacturing a cylinder, the lining material is put into the cylinder base material, and centrifugally cast, and then 20 to 200
Cooling to the temperature range where bainite transformation occurs at a cooling rate of ℃ / min, holding for 10 minutes or more, heating at a heating rate of 1-10 ℃ / min to an annealing temperature of 550-650 ℃, and annealing to room temperature A method comprising cooling. 8. The method for manufacturing a cylinder for a molding machine according to claim 7, wherein the region in which the bainite transformation occurs is 3 regions.
A method wherein the temperature is from 00 to 600 ° C.