JPH0455571B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a composite structure screw for an injection molding machine. [Prior Art] In recent years, resins processed by injection molding machines and extrusion machines have tended to be diversified, and screws have also come to be used under harsh conditions. Examples include flame-retardant plastics that generate highly corrosive gases when heated and melted during processing, and composite plastics containing glass fibers, carbon fibers, magnetic powders, and the like. Furthermore, recently, injection molding machines have come to be used to mold powder materials with high abrasiveness such as ceramics and metal powder, and a highly durable screw is desired. In other words, the material used for the screw must not only have sufficient mechanical strength to withstand the load applied during operation, but also have excellent corrosion and abrasion resistance. Conventionally, in order to increase the durability of screws, steel materials such as maraging steel and cold work tool steel (for example, JIS SKD-11) have been used as screw materials, and in the longitudinal direction of screws, integral materials have been used. Manufactures screws using [Problems to be Solved by the Invention] The screw is damaged differently depending on its longitudinal parts (FIG. 4). In other words, if you observe a screw after use, you will notice that in the longitudinal direction, there is a part that is mainly worn (feeding part), a part that is subject to both wear and corrosion (compression part), and a part that is mainly corroded (melting part). Divided. In other words, the performance that the screw should have is considered to be different depending on each part. Although maraging steel and cold work tool steel have high strength, they do not necessarily have sufficient corrosion resistance or wear resistance. Especially when molding resins or ceramics containing glass fiber, etc., wear is significant and the service life is shortened. is short. To compensate for these drawbacks of steel screws, thermal spray coating treatment of Co-based alloys or Ni-based alloys containing high-hardness particles such as tungsten carbide, or composite material screws to which such sintered alloys are attached, have been proposed. (For example, JP-A-61-
183430) has been proposed. However, although alloys containing tungsten carbide particles have excellent wear resistance, they have the disadvantage that they tend to wear out the material that comes into contact with them (in this case, the inner wall of the cylinder). In the present invention, the composite cylindrical material shown in FIG. 1 is manufactured using a material that has higher corrosion resistance and wear resistance than maraging steel or cold work tool steel, which has been conventionally used as a screw material. , which relates to a manufacturing method for screws that are combined as shown in Figure 3, and is characterized by not only being able to deal with damage that differs in the longitudinal direction of the screws, but also minimizing the amount of expensive materials used. Therefore, the service life of the screw is not reduced. [Means for solving the problem] The composite cylindrical material shown in Fig. 1 has an outer periphery B made of a hard alloy with excellent wear resistance and corrosion resistance, and a core metal part A made of steel having the strength and toughness necessary for screws. It is a composite material made of materials, and the interface between the hard alloy B and the core metal A exhibits a high-strength metallurgical bonding state.
The material of the hard alloy B used in the present invention is an alloy having the above-mentioned characteristics, and specifically, iron-based complex boride hard alloy (hereinafter referred to as the hard alloy), Co-based alloy, Ni-based alloy, and alloy tool steel, etc., and in this case, it is most preferable to use the hard alloy. The hard alloy is a material proposed by the present inventors (for example, Japanese Patent Publication No. 54-27818, Japanese Patent Publication No. 56-8904,
It is an alloy that not only has excellent corrosion and wear resistance, but also high strength and high-temperature oxidation resistance. Especially glass fiber
It has been revealed that it has excellent wear resistance against highly abrasive materials such as resins containing carbon fibers and magnetic powder, ceramics, and metal powder, and corrosion resistance against fluorine gas. The hard alloy has a metal structure in which fine hard grains are uniformly dispersed in the alloy, and the hard grains include iron-based borides, iron-based borides,
The bonding phase is Fe, Cr, Mo, W, Ti, V, Nb, Ta,
The main component is one or more metals or alloys selected from Hf, Zr, Ni, Cu, Co, and Mn. The hard particles are B-Fe type, B-X-Fe type, B-X-Y-Fe type (X, Y are Cr, Mo, W, Ti, V, Nb, Ta, Hf,
Zr, Ni, Cu, Co, Mn) borides, such as Fe ₂ B, (Fe, Cr) ₂ B, Mo ₂ FeB ₂ , Mo ₂ (Fe,
Cr) _B2 (Mo,W) ₂ (Fe,Cr) _B2 , the hard grains of which are contained in the alloy in an amount of 25-96%, preferably 35-96%. The B content of the hard alloy is 2 to 20%, preferably 3
~15%, Fe content is at least 10%,
Furthermore, when one or more of Cr, Mo, and W are included, the range is 0.1 to 50% each. Also Ti, V, Nb,
If one or more of Ta, Hf, Zr, Ni, Cu, Co, and Mn is included, each should be within the range of 0.01 to 15%. Other elements that are unavoidably contained include Al below 3%, O below 2.5%, C within the range of 0.01 to 1%, and it is particularly desirable that Al and O be 0%, but if they are within the above ranges, the strength will be increased. , does not significantly reduce toughness. The hardness of the hard alloy can be varied within the HRA range of 80 to 92 by changing the quantitative ratio of the hard particles to the binder phase within the above range. Furthermore, the binder phase can be changed to martensite, ferrite, austenite, or a mixed structure thereof by adjusting the type and amount of additive metals such as Cr and Ni.
It is possible to design alloys that take into account hardness, strength, and even corrosion resistance and heat resistance. The raw material powder for the hard alloy includes FeB or Fe ₂ B-based boride powder prepared by water or gas atomization, or ferroboron powder, as well as Ni,
Boride powders such as Cr, W, Ti, Mo, etc., or B
Using single powder, these and Fe, Cr, Mo, W,
Ti, V, Nb, Ta, Hf, Zr, Ni, Cu, Co, Mn
Metal powders such as or alloy powders containing these as main components are used. These raw material powders are blended to have a predetermined chemical composition, the mixed powder is wet-pulverized in an organic solvent using a vibrating ball mill, and then dried and granulated to create a green compact. The powder compact is formed into a cylindrical shape by a powder compaction method such as cold isostatic pressing (CIP), but the method for forming the compact is not necessarily limited. When using the CIP method, a rigid, straight round rod is placed in the center of a rubber cylinder, filled with powder, then covered with a rubber lid and pressure-molded. After molding, the central round rod is removed to obtain a cylindrical green compact. Since the powder compact shrinks during sintering, the inner diameter of the cylindrical powder compact needs to be dimensioned in consideration of the amount of shrinkage. That is, the composite structure cylindrical material shown in FIG. 1 is manufactured by a sinter bonding method, which utilizes the contraction of the compacted powder of the hard alloy during sintering to firmly bond the hard alloy to material A. It is.
In other words, if the gap between the compact body diameter and material A before sintering is too small, cracks will occur in the hard alloy during sintering, and conversely, if the gap is too large, the material A and the hard alloy will join after sintering. This is because gaps remain on the surfaces and a good bonding state cannot be obtained. The amount of shrinkage of the hard alloy compact during sintering varies depending on the compaction method, shape, and dimensions, but the inner diameter is in the range of 5 to 20%. Here, it is desirable that the material A is finished by turning so that the circumferential surface can be uniformly joined. In addition, dirt such as oil and fat has a negative effect on bonding properties, so it is necessary to thoroughly degrease and clean the product in advance. The steel type of material A is not particularly limited, but it must be capable of joining with the hard alloy and have the mechanical strength necessary for the screw. (For example, JIS SS,
SC, SNC, SCr, SCM, SNCM, SUJ, SK,
SKH, SKS, SKD, SKT, SUS, SUH, etc. ) Sinter bonding is performed at 1100 to 1400°C for 5 to 90 minutes in a vacuum or in a non-oxidizing atmosphere. At temperatures below 1100°C, not only is a good bonded state not obtained, but the hard alloy is also in an unsintered state. On the other hand, at temperatures above 1400°C, the hard particles become coarse and the hard alloy itself loses its shape. Further, if the sintering time is less than 5 minutes, sufficient densification of the hard alloy will not proceed, and even if the sintering time exceeds 90 minutes, no improvement in strength commensurate with the passage of time will be observed. The sintered body obtained as described above is cut to a predetermined length, and both end faces are finished by turning or the like to produce the composite cylindrical material shown in FIG. 1. Next, the material for the screw is created by combining the composite cylindrical materials as shown in Figure 2 or Figure ₃ . Figure, 3rd
The hard alloy with excellent corrosion resistance (corresponding to part B in Figs. 2 and 3) is used for the part _L1 in the figure). Relatively light corrosion and wear load
₂ copies of X (equivalent to ₂ copies of L in Figures 2 and 3)
is a hard alloy with slightly low hardness but excellent strength and toughness (corresponding to section C in Figure 2), or SKD11 and SUS440C, which are more advantageous in terms of toughness.
An alloy tool steel specified by JIS such as JIS, or a steel material plated with hard chrome (corresponding to section C in Fig. 3) may be used. Furthermore, the X ₃ part (corresponding to the L ₃ part in Figures 2 and 3), where wear due to resin is a problem, is made of the hard alloy (corresponding to the D part in Figures 2 and 3). will be used. These methods take advantage of the fact that the hard alloys can be welded, soldered, or diffusion-bonded with other hard alloys or with steel materials. When joining using friction welding, the heating pressure is 3 to 15 Kg/ ^mm2 , and the upset pressure is 10 to 30 Kg/mm2.
mm ² is preferred. Also, the deviation during heating is 0.5 to 3.5 mm.
It is desirable to do so. The combination of materials in the longitudinal direction can be selected depending on the type and degree of damage that the screw receives during use. [Example] An example of the present invention will be described with reference to the drawings. Example 1 The _L1 part and _L2 part in FIG. 2 were made using the material combinations shown in Table 1. As a result of observing the cross-sectional structure of the weld, it was found that the steel material used for the _core material ( _SCM440 in this case) has approximately
Although there is a heat-affected zone due to heat generation during welding of 10 mm, it is thought that this will not cause any problems in use since a torsional strength of 320 kg・m was obtained. The properties of each material are shown in Table 1, and the friction welding conditions and torsional strength are shown in Table 2.

【table】

[Table] Example 2 L ₁ part and L ₂ part shown in FIG. 2 were prepared using the combination of materials shown in Table 3. Table 4 shows the friction welding conditions and torsional strength.

【table】

[Table] Example 3 The parts corresponding to the _L1 part and _L2 part in Fig. 3 were created in the combinations shown in Table 5. Table 6 shows the friction welding conditions and torsional strength.

【table】

〔Effect of the invention〕

The screw of the present invention applies the most suitable material to each part depending on the type and degree of damage received during use, and the performance of the screw can be further improved. Injection molding of significantly more expensive materials has become possible. Furthermore, we actively try to substitute steel materials for the hard alloys in parts that can withstand the use of inexpensive steel materials, thereby making it possible to keep the amount of expensive hard alloys used to the minimum necessary. We were able to reduce manufacturing costs.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of the composite structure cylindrical material used in the construction of the composite structure screw of the present invention, Figs. 2 and 3 are cross-sectional schematic views of the composite structure screw material, and Fig. 4 is the injection molding machine screw section. FIG. A, A ₁ to _{A 4} ; Core metal, B, C, D, E; Iron-based boride hard alloy, F, G; Round bar made of steel material, 1;
Screw, 2; Cylinder, 3; Material input port,
X ₁ ; Melting section; X ₂ ; Compression section; X ₃ ; Supply section.

Claims (1)

[Claims] 1 Composite structure cylindrical material (first
), and _L1 part in the length direction is made of material A,
B, L ₂ parts are materials A, C, L ₃ parts are materials A, D, L ₄
The part is composed of materials A, E, etc., L ₁ and L ₂ , L ₂ and L ₃ ,
Composite structure screws for injection molding machines (here _, 1 to ₄
(can be extended up to n points). 2 Composite structure cylindrical material (first
), when the center member is L ₁ part, A 1 is used, and when L ₂ part is the center member, A ₁ is used.
Composite cylindrical material with different composition depending on each part: A ₂ , L ₃ part is A ₃ , L ₄ part is A ₄ (Fig. 2)
A composite structure screw for an injection molding machine characterized by using. 3 Composite structure cylindrical material (first
), L ₁ part is material A and B, L ₂ part is material F,
L ₃ parts are materials A and D, L ₄ part is material G, and a composite cylindrical material (3rd part) with different composition depending on each part.
A composite structure screw for an injection molding machine characterized by using the screw shown in the figure).