JP2006283056A - Screw for injection molding machine, and assembled component thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide alloy steel having high temperature corrosion resistance, wear resistance and toughness by controlling MC type carbides in melted alloy steel which has an economical advantage as well, and having cost effectiveness since expensive Co and powder steel are not used, to provide a screw for an injection molding machine using the alloy steel, and to provide an assembled component thereof. <P>SOLUTION: The screw for injection molding machine is produced using melted alloy steel having a composition comprising, by weight, 0.9 to 1.5% C, 0.1 to 2% Si, 0.1 to 1% Mn, 3 to 14% Cr, 0.1 to 7% Mo, 0.1 to 7% W, 1 to 5% V and 0.1 to 0.2% Nb, and the balance Fe with inevitable impurities as the stock, and, among MC type carbides present on the surface of the cut face parallel to the surface layer part in the face in contact with a molding material, the diameter of an equivalent circle in the maximum grains lies in the range of 4 to 15 μm, and also, among the MC type carbides having the diameter of an equivalent circle of ≥4 μm, ≥45% of the grains are composed of relatively spherical grains in which the ratio between the major axis and the minor axis in the cross-section of the grains is ≥0.5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a screw for an injection molding machine that requires wear resistance, corrosion resistance, and high toughness, and a screw for an injection molding machine including a screw head, a check ring, a sheet, and a nozzle, and an assembly part thereof.

As new injection molding methods such as high-performance molding resin, ultra-thin molding by ultra-high-speed and high-pressure injection, and composite layer injection molding are developed one after another, even more resistance in high-temperature corrosive environments. Abrasion and toughness have been required. Also for molding materials, so-called super engineering plastics, in which a large amount of hard filler is added to improve heat resistance, have been put into practical use. In addition, molding of hard particles such as metal powder and ceramic powder has been actively performed. Conventionally, an improved material of JIS SKD11, which is an alloy steel, has been used as a component material for injection molding machines for corrosion resistance and wear resistance. As these improving materials, the materials described in Patent Document 1 and Patent Document 2 have been used. The thing of patent documents 1-3 had the subject that expensive Co was added and it was inferior to economical efficiency. Powdered steel is also used as a material to supplement wear resistance and toughness, but there are also problems in terms of price.
Japanese Examined Patent Publication No. 2-39582 Japanese Patent No. 2564657 Japanese Patent No. 2746884

However, in the recent injection molding of heat-resistant resin or the like, the conventional improved steel of SKD11 has a problem that it reaches the end of its life in a short time due to lack of corrosion resistance, wear resistance, toughness and the like at high temperature.
As a method for improving corrosion resistance, wear resistance, and toughness at high temperatures, there is a method of manufacturing an alloy steel with an increased amount of additive alloy elements by a manufacturing method in which alloy powder is hot isostatically pressed. Although the powder alloy steel can obtain high hardness and high toughness at the same time due to the fineness of the carbide, it is weak against abrasive wear due to the fine carbide, resulting in early wear of parts for injection molding machines.

  The object of the present invention is to use Co, powder steel, which has high corrosion resistance, wear resistance, toughness at high temperature and high cost by controlling MC type carbide in molten alloy steel which is economically superior. It is an object to provide a screw for an injection molding machine and an assembly part thereof using the alloy steel that is economical and has good economic efficiency and the alloy steel.

  The present invention, by weight, C: 0.9 to 1.5%, Si: 0.1 to 2%, Mn: 0.1 to 1%, Cr: 3 to 14%, Mo: 0.1 to 7%, W: 0.1 to 7%, V: 1 to 5%, Nb: 0.1 to 0.2%, a screw for an injection molding machine manufactured using a molten alloy steel consisting of Fe and inevitable impurities as a raw material, and a screw head and check ring as an assembly part thereof In a screw for an injection molding machine including a sheet, a nozzle, and an assembly part thereof, the largest particle among the MC type carbides existing on the surface layer part of the surface that contacts the molding material, that is, the surface of the part, or the surface of the cut surface parallel to the part The equivalent circle diameter (equivalent circle diameter, which is the diameter of the circle when the measured particle cross-sectional area is replaced with the area of the circle) is in the range of 4 to 15 μm, and the equivalent circle diameter is 4 μm or more. 45% or more of the type carbides have a major axis / minor axis ratio of the particle cross section The above-mentioned problems of the present invention have been solved by a screw for an injection molding machine and its assembly parts, which are characterized by comprising relatively spherical particles having a ratio of 0.5 or more.

  In the present invention, the composition of such alloy steel and the size, shape and area ratio of MC type carbide in the alloy steel are controlled, and a new molten alloy steel is applied to the screw for an injection molding machine and its assembly parts. Parts made from molten alloy steel, characterized by comprising spherical particles, have corrosion resistance, wear resistance and toughness at high temperatures under severe forming conditions, which cannot be achieved with conventional alloy steel parts It provides long-life and cost-effective parts without using expensive Co and powder steel. Note that the area ratio of MC type carbide was obtained by dividing the total area of each MC type carbide particle cross-section with an equivalent circular diameter of 4 μm or more appearing on the screen of the optical image measurement microscope by the area of the screen itself. Value.

Preferably, the MC type carbide having an equivalent circular diameter of 4 μm or more present on the surface layer part of the surface where the part comes into contact with the molding material, that is, on the die surface, or on the cutting surface parallel to the part surface, A screw and an assembly part having an area ratio of 0.5 to 5% in parallel particle cross sections (particle cross sections cut along the axial direction of the round steel, that is, the longitudinal direction) may be used. Screws and assembly parts for injection molding machines with improved corrosion resistance and wear resistance by applying one or more composite films of titanium-containing or chromium-containing ceramic coating by PVD to the surface in contact with the molding material It is good.
More preferably, the alloy steel is prevented from intruding gas components including O2 and N2 into the molten steel by an inert atmosphere by an electroslag remelting method, and has a melting rate of 100 to 800 kg / h. It may be manufactured from the alloy steel manufactured by controlling the size and form of the MC type carbide while maintaining the ratio of the diameter divided by the electrode outer diameter at 1.2 to 1.7.

  Preferably, by weight, C: 1.0 to 1.5%, Si: 0.4 to 1.1%, Mn: 0.3 to 0.5%, Cr: 4 to 10%, Mo: 2 to 5%, W: 0.2 to 6%, V : 1.8 to 5%, Nb: 0.1 to 0.15%, the screw for injection molding machine manufactured using molten alloy steel consisting of Fe and inevitable impurities as a raw material, and screw heads and check rings that are assembly parts thereof In the screw for an injection molding machine including a sheet, a nozzle, and its assembly parts, among the MC type carbides present on the surface layer part of the surface in contact with the molding material, that is, the part surface, or the cut surface parallel to the part, the largest particle The MC type having an equivalent circle diameter (equivalent circle diameter, which is the diameter of a circle when the measured particle cross-sectional area is replaced with a circle area) in the range of 4 to 12 μm and an equivalent circle diameter of 4 μm or more 48 to 63% or more of carbides have a long particle cross section It is more desirable to use relatively spherical particles having a diameter-minor axis ratio of 0.5 or more.

The reasons for limiting the component ranges of alloy steel will be described below. Each in weight percent
C forms MC type carbide and improves wear resistance. However, if the amount of C is too large, the toughness decreases, so the C content is limited to 0.9 to 1.5% by weight. Si and Mn are added as deoxidizers, but if the amount of Si and Mn is too large, the toughness decreases. Therefore, the weight ratio of Si and Mn was limited to Si: 0.1-2% and Mn: 0.1-1%. Cr combines with C to form M7C3 carbide to improve wear resistance, and further dissolves in the base to improve corrosion resistance. Therefore, Cr is added to ensure corrosion resistance, but Cr is less than 3% The above effect is small, and if it exceeds 14%, the overall toughness is lowered, so Cr is limited to 3 to 14%. Mo and W form M6 C-type carbides and improve wear resistance. However, if less than 0.1%, the effect is small, and if the amount of Mo and W is too large, the toughness decreases, so Mo: 0.1 to 7% or less, W: Limited to 0.1-7% or less. V forms MC type carbides and remarkably enhances the wear resistance. However, if too large, the toughness and grindability are deteriorated, so V: 1 to 5%. Nb is a component that forms MC carbides, has a small amount of dissolution in the matrix due to quenching heating, and prevents coarsening of the austenite crystal grains. If less than 0.1%, the effect is small, and if it exceeds 0.2%, the effect is improved. Since it is small, the range was made into Nb: 0.1-0.2%.

  Subsequently, in the alloy steel in the surface layer portion of the surface where the screw and the assembly part are in contact with the molding material, that is the point of the present invention, that is, the surface of the component or the cut surface parallel to the surface of the component (hereinafter referred to as the component surface layer portion). Among MC-type carbides, the equivalent circular diameter of the largest particles, forging, the area ratio of MC-type carbides in the cross-section parallel to the rolling axis (the cross-section of the particles cut along the axial direction of the round steel, that is, the longitudinal direction) The reason why the diameter ratio is limited to the above will be described. Parts made of powder alloy steel whose maximum equivalent circular diameter of MC type carbide in the alloy steel existing on the surface of the part is less than 4μm are easy to wear because the MC type carbide is easily removed together with the base material due to abrasive wear. Is short. On the other hand, the area ratio of MC type carbide whose maximum equivalent circular diameter of MC type carbide in the alloy steel existing in the component surface layer exceeds 15 μm and whose equivalent circular diameter in the steel existing in the mold surface layer is 4 μm or more. If it exceeds 5%, it becomes very brittle, and it is easy to cause cracks starting from MC type carbide. In particular, when the shape of particles of more than 45% of MC type carbides are coarse and elongated squares with a major axis / minor axis ratio of less than 0.5, they are difficult to grind and are more prone to cracking, leading to early component damage. Cause. On the other hand, when the area ratio of MC type carbide is less than 0.5%, it becomes very easy to wear and the life of the part is shortened. Therefore, the maximum equivalent circular diameter of MC type carbide in the alloy steel of the part surface layer is set to 4 to 15 μm. Forging MC type carbides with an equivalent circle diameter of 4 μm or more, and limiting the area ratio in the cross section parallel to the rolling axis to 0.5 to 5%, among the MC type carbides with an equivalent circle diameter of 4 μm or more It was limited to the conditions where particles with a ratio of 0.5 or more accounted for 45% or more of the total.

The inventors previously invented a cutting tool disclosed in Japanese Patent No. 3249493, which was manufactured from a new high-speed tool steel by controlling the size, shape, and area ratio of MC type carbide in the high-speed tool steel. did. In this study, we conducted extensive research to apply new molten alloy steel with controlled size, shape, and area ratio of MC type carbide in alloy steel to screws for injection molding machines and their assembly parts. It has been found that, when controlled to a limited range, it is possible to obtain a long-life injection molding machine part that cannot be achieved by conventional alloy steels.
The best mode for carrying out the present invention is, by weight, C: 0.9 to 1.5%, Si: 0.1 to 2%, Mn: 0.1 to 1%, Cr: 3 to 14%, Mo: 0.1 to 7% , W: 0.1 to 7%, V: 1 to 5%, Nb: 0.1 to 0.2%, the screw for an injection molding machine manufactured using a molten alloy steel made of Fe and inevitable impurities as a raw material, and its assembly In a screw for an injection molding machine including a screw head, a check ring, a sheet, a nozzle as a part, and an assembly part thereof, the screw is present on the surface layer part of the surface in contact with the molding material, that is, on the surface of the part, or on the surface of the cut surface parallel to the part. Among the MC type carbides, the equivalent circle diameter of the largest particle (equivalent circle diameter, which is the diameter of the circle when the measured particle cross-sectional area is replaced with the circle area) is in the range of 4 to 15 μm and is equivalent More than 45% of the MC type carbides with a circle diameter of 4μm or more The particles consist of relatively spherical particles having a major axis / minor axis ratio of 0.5 or more.

  In the present invention, the composition of such alloy steel and the size, shape and area ratio of MC type carbide in the alloy steel are controlled, and a new molten alloy steel is applied to the screw for an injection molding machine and its assembly parts. Parts made from molten alloy steel, characterized by comprising spherical particles, have corrosion resistance, wear resistance and toughness at high temperatures under severe forming conditions, which cannot be achieved with conventional alloy steel parts It provides long-life and cost-effective parts without using expensive Co and powder steel. Note that the area ratio of MC type carbide was obtained by dividing the total area of each MC type carbide particle cross-section with an equivalent circular diameter of 4 μm or more appearing on the screen of the optical image measurement microscope by the area of the screen itself. Value.

  Next, Example 1 of the present invention will be described. Table 1 shows the chemical composition in the steel of the test piece made of steels of the present invention 1, 2, 3, 4, 5, and comparative steels 6, 7, and 8 and the surface of the part, that is, the part surface or a cut parallel to the part surface. The maximum equivalent circle diameter (the area of the particle cross section measured for the largest MC type carbide is the area of the circle) Equivalent circle diameter (μm) which is the diameter of the circle when replaced, equivalent circle diameter (equivalent circle diameter which is the diameter of the circle when replacing the measured particle cross-sectional area as the area of the circle) Area ratio of 4 μm or more (Forging, area ratio% in cross section parallel to rolling axis, that is, particle cross section cut along the axial direction of round steel, ie, longitudinal direction), major axis / minor axis ratio of MC type carbide with equivalent circle diameter of 4 μm or more 0.5 or more Shows the composition ratio of each particleIn the actual optical image measurement microscope, the area ratio of the MC type carbide is the value obtained by adding all the cross-sectional areas of the MC type carbide particles that have an equivalent circular diameter of 4 μm or more that appears on the screen of the optical image measurement microscope. The value was divided by the area of the screen itself, and the maximum equivalent circular diameter (μm), area ratio, and major axis / minor axis ratio of the MC type carbide were measured with a microscope image of an optical image measurement microscope. The observation target of MC carbide was an equivalent circular diameter of 0.15 μm or more. MC type carbide was electrolytically corroded with 10% chromic acid on a test piece cut out from the surface of the component, and measured with an optical image measurement microscope.

  Further, the alloy steel of the present invention prevents invasion of gas components including O2 and N2 into the molten steel by an inert atmosphere by the electroslag remelting method, and the melting condition: melting rate: 100 to 800 kg / h, steel ingot A ratio obtained by dividing the outer diameter by the outer diameter of the electrode was maintained at 1.2 to 1.7, and a steel ingot was manufactured by controlling the size and the major axis / minor axis ratio of the MC type carbide grains. The steel ingot was made into a steel bar having a diameter of 30 mm by hot working such as forging and rolling. The specimen was manufactured from this steel bar with a diameter of 30 mm and was heat-treated to 60 HRC by quenching and tempering.

Table 2 shows the corrosion of specimens made from steels of the present invention 1, 2, 3, 4, 5, and comparative steels 6, 7, 8 when they are rotated for 100 hours in PPS resin while applying pressure to the specimens. This is an index of wear loss. The test conditions are a test temperature of 300 ° C., a rotation speed of 200 rpm, and a pressing pressure of 10 Mpa / mm 2. Table 3 shows a list of results of actual machine tests on an injection molding machine.
As shown in Table 3, the conventional steel screws and nozzles were worn out in 3 months, whereas the screw and nozzle parts of the steel of the present invention had no wear even after 6 months. Was secured. Further, the check ring of the conventional steel cracked in one month, whereas the check ring of the steel of the present invention showed good results without cracking even after 2 months. In addition, even when the steel of the present invention is coated with CrN, the service life is more than twice that of the conventional steel, and the service life is further improved.

Claims (6)

  C: 0.9 to 1.5%, Si: 0.1 to 2%, Mn: 0.1 to 1%, Cr: 3 to 14%, Mo: 0.1 to 7%, W: 0.1 to 7%, V: 1 to% 5%, Nb: 0.1-0.2% inclusive, screw for injection molding machine manufactured with molten alloy steel consisting of Fe and inevitable impurities as a raw material, and screw heads, check rings, sheets, nozzles that are assembly parts thereof In the injection molding machine screw and its assembled parts, the equivalent circular diameter of the largest particles among the MC type carbides present on the surface layer part of the surface in contact with the molding material, that is, the part surface, or the cut surface parallel to the part Among the MC-type carbides having an equivalent circle diameter (equivalent circle diameter when the measured particle cross-sectional area is replaced with a circle area) in the range of 4 to 15 μm and an equivalent circle diameter of 4 μm or more 45% or more of particles have a major axis / minor axis ratio of 0.5 or more. Relatively spherical injection molding machine screw and its assembly, characterized in that it consists of particles of consisting.   MC type carbide having an equivalent circular diameter of 4 μm or more existing on the surface layer portion of the surface where the screw for injection molding machine and its assembly parts come into contact with the molding material, that is, on the surface of the screw and assembly part, or on the cut surface parallel to the part surface The forging, the area ratio in the particle cross section parallel to the rolling axis, that is, the particle cross section cut along the axial direction of the round steel, that is, the longitudinal direction, is 0.5 to 5%. Screws for injection molding machines and their assembly parts.   By weight%, C: 1.0-1.5%, Si: 0.4-1.1%, Mn: 0.3-0.5%, Cr: 4-10%, Mo: 2-5%, W: 0.2-6%, V: 1.8- 5%, Nb: 0.1 to 0.15% inclusive, screw for injection molding machine manufactured using molten alloy steel consisting of Fe and inevitable impurities as raw materials, and screw heads, check rings, sheets, nozzles that are assembly parts In the injection molding machine screw and its assembled parts, the equivalent circular diameter of the largest particles among the MC type carbides present on the surface layer part of the surface in contact with the molding material, that is, the part surface, or the cut surface parallel to the part Among the MC type carbides having an equivalent circle diameter of 4 to 12 μm and an equivalent circle diameter of 4 μm or more (equivalent circle diameter when the measured particle cross-sectional area is replaced with a circle area) 48 to 63% of particles have a major axis / minor axis ratio of 0.5. A screw for an injection molding machine and an assembly part thereof, comprising the relatively spherical particles as described above.   MC type carbide having an equivalent circular diameter of 4 μm or more existing on the surface layer portion of the surface where the screw for injection molding machine and its assembly parts come into contact with the molding material, that is, on the surface of the screw and assembly part, or on the cut surface parallel to the part surface The forging, the area ratio in the particle cross section parallel to the rolling axis, that is, the particle cross section cut along the axial direction of the round steel, that is, the longitudinal direction, is 0.7 to 4.9%. Screws for injection molding machines and their assembly parts.   The surface of the injection molding machine screw and its assembly part in contact with the molding material is provided with one or more composite films of titanium-containing or chromium-containing ceramic coating by PVD. The screw for an injection molding machine according to claim 1 or claim 3 and an assembly part thereof. The electroslag remelting method prevents gas components containing O ₂ and N ₂ from entering the molten steel due to the inert atmosphere, and the melting rate is 100 to 800 kg / h, and the outer diameter of the steel ingot is divided by the outer diameter of the electrode. 4. The injection according to claim 1, wherein the injection is produced from the molten alloy steel produced by controlling the size and form of the MC type carbide while maintaining a ratio of 1.2 to 1.7. Screws for molding machines and their assembly parts.