JP2004216413A - Sleeve for die-casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sleeve for die-casting which has both the merits of conventional steel materials and ceramic materials and is excellent in wear resistance, erosion resistance, and toughness. <P>SOLUTION: The sleeve for the die-casting is characterized in as follows. A covering layer excellent in the wear resistance is formed at least on the inner face of a part contacting molten metal of an outer cylinder made of a hollow cylindrical steel material. The covering layer is made of an Fe based alloy containing, by wt.%, 1.0-3.0% C, 0.1-2.0% Si, 0.1-2.0% Mn, Ni≤4.5%, 3.0-10.0% Cr, 0.1-9.0% Mo, W≤10.0%, and 1.0-10.0% V. Further, it contains one or more kinds of either Co≤10.0% and Nb≤10.0%. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sleeve used for die casting for non-ferrous metal products such as aluminum alloys, zinc alloys, and magnesium alloys, and relates to a member excellent in wear resistance, erosion resistance, and toughness for molten alloys thereof.
[0002]
[Prior art]
The die casting method is a method capable of casting a metal product made of aluminum, zinc, or the like at high speed and with high accuracy, and is widely used for manufacturing various components such as automobile products and home electric appliances. The die casting sleeve constitutes a molten metal injection device of a die casting machine, and is required to have abrasion resistance against sliding of a plunger tip, erosion resistance against molten metal, and the like.
[0003]
Conventional die casting sleeves are generally made of alloy steel for hot dies represented by SKD61. However, in recent years, from the viewpoint of improving productivity and quality, further wear resistance and erosion resistance have been improved. Sex is being demanded. In view of this, many die-casting sleeves have been proposed in which a portion in contact with a molten metal is formed of a material having excellent wear resistance and erosion resistance.
[0004]
For example, Patent Document 1 discloses a sleeve having a configuration in which a sleeve inner cylinder made of a ceramic material is shrink-fitted into a sleeve outer sleeve made of a metal material. By interposing a friction reducing material between the cylinder and the sleeve inner cylinder, the friction resistance between the sleeve outer cylinder and the sleeve inner cylinder can be reduced, and the residual stress of the sleeve outer cylinder and the sleeve inner cylinder after shrink fitting. This discloses a die-casting sleeve capable of preventing collapse due to protrusion of the distal end of the sleeve inner cylinder during use of the sleeve and achieving a longer life of the sleeve inner cylinder.
[0005]
Patent Document 2 discloses an injection sleeve for a die-casting machine having a composite structure including two layers, an inner cylinder and an outer cylinder, wherein the outer cylinder of the injection sleeve is formed of carbon steel S48C for mechanical structure, and the inner cylinder is an inner cylinder. The first part other than the vicinity of the tip and the second part of the inner cylinder tip part, the first part is made of a nickel alloy excellent in erosion resistance, and the second part is made of a nickel alloy excellent in toughness. An injection sleeve for a die casting machine is disclosed in which a cylinder and an outer cylinder are metallized to each other by using a HIP method.
[0006]
Further, Patent Literature 3 discloses that a portion corresponding to a molten metal dropping portion on the inner peripheral side of a sleeve has excellent corrosion resistance and heat retention to a molten metal such as an aluminum alloy, and has sufficient strength against thermal shock. A die casting sleeve is described in which an inner cylinder in which a lining layer made of ceramic or cermet is formed on an inner peripheral surface of a base material is exchangeably fitted to a main body of the sleeve.
[0007]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 9-10881 [Patent Document 2]
Japanese Patent No. 308258 [Patent Document 3]
JP-A-2000-61604 [0008]
[Problems to be solved by the invention]
The steel die-casting sleeve represented by the conventional SKD61 has good toughness and excellent durability against impact when injecting a light alloy melt. However, since the wear resistance and the erosion resistance are not sufficient, there is a problem that the damage is advanced in a short period of time and a large number of steps, cost and time are required for maintenance.
[0009]
For this reason, the inner surface of the sleeve is generally subjected to nitriding treatment, but is insufficient in abrasion resistance or erosion resistance. Then, in recent years, as shown in the above-mentioned known example, the application of the assembly type die casting sleeve in which silicon nitride or sialon ceramics is fitted to the inner surface of the sleeve is spreading.
[0010]
When the portion that comes into contact with the molten metal is made of ceramic, the wear resistance and erosion resistance to the molten metal are significantly improved, but a large mechanical impact is applied during use, so the brittleness inherent in ceramics Therefore, there is a problem that local damage occurs particularly near the tip on the side of the injection port where internal pressure is applied, resulting in a short life.
[0011]
An object of the present invention is to provide a die-casting sleeve having excellent wear resistance, erosion resistance and toughness, which has the advantages of a conventional steel material and a ceramic material in view of the above problems.
[0012]
[Means for Solving the Problems]
The die-casting sleeve used in the die-casting method, which can cast light metal products made of aluminum, magnesium, zinc, etc. at high speed and with high precision, does not wear due to the sliding of the plunger tip and melts in the light alloy melt. It is required to have a performance not to be damaged and not to be damaged by the impact during casting. Therefore, the present inventors have invented a die-casting sleeve that satisfies the above-mentioned required performance and has a long service life by using a composite structure instead of a single structure for the die-casting sleeve.
[0013]
That is, a coating layer having excellent wear resistance is formed on at least a part of the inner surface of the outer cylinder made of a hollow cylindrical steel material that comes into contact with the molten metal, and the coating layer has a weight ratio of:
C: 1.0 to 3.0% Si: 0.1 to 2.0%
Mn: 0.1 to 2.0% Ni ≦ 4.5%
Cr: 3.0 to 10.0% Mo: 0.1 to 9.0%
W ≦ 10.0% V: 1.0 to 10.0%
, And further contains at least one of Co ≦ 10.0% and Nb ≦ 10.0%.
[0014]
Further, the coating layer is made of an MC-based (M is a metal element) carbide, an M ₂ C-based carbide, an M ₆ C-based carbide, an M ₇ C _3- based carbide, an M ₄ C _3- based carbide and an M ₂₃ C _6- based carbide. It is characterized by containing any one or more of them, and the total of the area ratios of these carbides contained in the coating layer is 25% or less.
[0015]
Further, the coating layer is formed by a centrifugal casting method. In addition, a nitride film layer and a film layer made of Cr nitride or Cr carbonitride are formed on the surface of the coating layer.
[0016]
[Action]
The sleeve for die casting of the present invention has a composite structure in which a coating layer is formed on the inner surface of an outer cylinder made of a steel material and a coating layer, and the component of the coating layer is made of a higher alloy than conventional SKD61 steel to improve wear resistance. Secured. The reason for limiting the content range (% by weight) of each element of the coating layer formed on the inner surface of the sleeve for die casting of the present invention will be described.
[0017]
C: 1.0 to 3.0%
C is necessary for the formation of carbides for improving wear resistance and for improving the hardness of the matrix during quenching and tempering by solid solution in the matrix. C produces MC, M ₂ C, M ₆ C, M ₇ C ₃ , M ₄ C ₃ , and M ₂₃ C ₆ series carbides to be provided with wear resistance. When C is less than 1.0%, there is little crystallization of carbides effective for improving wear resistance, and furthermore, C dissolved in the matrix is insufficient, and sufficient matrix hardness can be obtained even by quenching. At the same time, high alloying becomes difficult. On the other hand, if it exceeds 3.0%, the carbides become coarse and the crystallization amount becomes excessive, and the toughness required for the coating layer deteriorates, so the upper limit was made 3.0%.
[0018]
Si: 0.1 to 2.0%
The content of Si is preferably 0.1 to 2.0%. Si acts as a deoxidizing agent, and is dissolved in M ₆ C carbide to be contained by replacing elements such as W and Mo. Therefore, in order to save expensive elements such as W and Mo, It is valid. If the content of Si is less than 0.1%, the deoxidizing effect is insufficient, and casting defects are likely to occur. If it exceeds 2.0%, embrittlement is likely to occur.
[0019]
Mn: 0.1-2.0%
The content of Mn is preferably from 0.1 to 2.0%. Mn has a deoxidizing effect similarly to Si. Further, it has an effect of fixing S as an impurity as MnS. If Mn is less than 0.1%, deacidification is poor. On the other hand, when the content exceeds 2.0%, retained austenite is liable to be generated, so that sufficient hardness cannot be stably maintained.
[0020]
Ni ≦ 4.5%
Ni has the effect of improving hardenability and increasing hardness. The lower limit of Ni is 0%. If it exceeds 4.5%, the amount of retained austenite becomes excessive and high hardness cannot be obtained, so the upper limit was made 4.5%. A more preferred Ni content is 2.0% or less.
[0021]
Cr: 3.0 to 10.0%
Cr combines with C to form carbides by crystallization, and forms a solid solution in the matrix to increase the hardness of the matrix, thereby improving wear resistance. If the Cr content is less than 3.0%, the effect is small. On the other hand, if it exceeds 10.0%, the amount of retained austenite at room temperature increases, so that the number of tempering increases, which is uneconomical. Further, Cr forms a relatively low hardness M ₇ C ₃ and M ₂₃ C ₆ type carbides, the quantity of added wear resistance becomes these carbides excessive deteriorates. However, if the addition amount is small, the effect cannot be sufficiently secured, and if it is too large, carbides are coarsened and toughness is reduced. Therefore, the optimum range is set to 3.0% to 10.0%.
[0022]
Mo: 0.1 to 9.0%
Mo is an element capable of obtaining a hard carbide like Cr, and strongly contributing to the secondary hardening when tempering at a high temperature. Mo combines with C to form hard M ₂ C, M ₆ C-based carbides. If Mo is less than 0.1%, the effect is small. On the other hand, if the content exceeds 9.0%, M ₂ C and M ₆ C-based carbides are excessively crystallized in the balance of C, V and Mo, and the toughness is lowered. 0.0%. A more preferred Mo content is 1.0 to 8.0%.
[0023]
W ≦ 10.0%
W is necessary for improving the hardenability and obtaining the high-temperature hardness of the matrix similarly to Mo. Further, since W forms hard carbides like Cr and Mo, it is effective to substitute W for these elements and add them. Further, the hardenability of the matrix is improved, and the hardened M ₂ C and M ₆ C-based carbides are formed by combining with C. The lower limit of W is 0%. If the content exceeds 10.0%, the M ₆ C-based carbide coarsens and the brittleness deteriorates. Therefore, the appropriate range is set to 10.0% or less.
[0024]
V: 1.0 to 10.0%
V forms MC and M ₄ C ₃ which are hard carbides most contributing to the improvement of wear resistance. If V is less than 1.0%, the generation of carbides is small, and the wear resistance deteriorates. When V exceeds 10.0%, austenite or MC or M ₄ C ₃ -based carbide crystallizes as primary crystals depending on the balance with the C content. If austenite is crystallized as primary crystals, the hardness becomes insufficient. When MC and M ₄ C ₃ are crystallized as primary crystals, they coagulate during solidification, and when used as a die-casting sleeve, cohesion and segregation of MC and M ₄ C ₃ which are hard carbides cause brittle deterioration. Not preferred. A more preferred V content is 2.0 to 8.0%.
[0025]
Co ≦ 10.0%
Co forms a solid solution in the matrix irrespective of the formation of carbides, and has the effect of increasing toughness and improving high-temperature hardness and wear resistance. The lower limit of Co is 0%. If Co exceeds 10.0%, the effect is saturated and the cost increases, so the upper limit is set to 10.0% or less.
[0026]
Nb ≦ 10.0%
Like V, Nb forms MC and M ₄ C ₃ which are hard carbides most contributing to the improvement of wear resistance. The lower limit of Nb is 0%. If Nb exceeds 10.0%, austenite or MC or M ₄ C ₃ -based carbides are crystallized as primary crystals due to the balance between the toughness and the C content. If austenite is crystallized as primary crystals, the hardness becomes insufficient. When MC and M ₄ C ₃ are crystallized as primary crystals, they coagulate during solidification, and when used as a die-casting sleeve, cohesion and segregation of MC and M ₄ C ₃ which are hard carbides cause brittle deterioration. Not preferred. Nb can be replaced with V. Therefore, a more preferable content of Nb and V is (Nb + V) ≦ 2.0 to 8.0%.
[0027]
The sleeve for die casting of the present invention specifies the type of carbide constituting the inner surface of the sleeve in contact with the molten metal, and controls the area ratio of the total amount of the carbide to an optimal range. It is characterized by containing at least one of carbides, M ₂ C-based carbides, M ₆ C-based carbides, M ₇ C _3- based carbides, M ₄ C _3- based carbides and M ₂₃ C _6- based carbides.
[0028]
Further, by setting the total of the area ratio of carbide in the coating layer on the inner surface of the sleeve to 25% or less, the wear resistance can be remarkably improved. If the total carbide area exceeds 25%, the brittleness deteriorates. Furthermore, in order to secure hardness, the total sum of the area ratios of particularly hard MC-based carbide and M ₂ C-based carbide is preferably 10% or more. Also, if the amount of needle-like or network-like eutectic carbides is excessive, necessary mechanical properties, particularly toughness, cannot be secured. However, by appropriately crystallizing MC-based carbides, M ₂ C, M ₇ C ₃ The toughness can be secured by dividing the network of the carbide.
[0029]
Further, in the die casting sleeve of the present invention, a coating layer is metal-bonded to the inner surface of the outer cylinder by a centrifugal casting method. By performing the centrifugal casting method, the coating layer can be bonded to the inner surface of the outer cylinder with a fine uniform structure and a uniform thickness. In addition, by performing a nitriding treatment on the inner surface of the coating layer surface that comes into contact with the molten metal, a coating layer mainly composed of nitride is formed, whereby a die casting sleeve having more excellent erosion resistance can be obtained. Furthermore, by performing a dipping treatment in a molten salt containing a metal Cr powder and forming a coating layer made of Cr nitride or Cr carbonitride on the surface of the coating layer, a sleeve for die casting having even more excellent erosion resistance. Is obtained. In addition, the outer cylinder may be a single layer, or may have a multi-layer structure of two or more layers.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the sleeve for die casting of the present invention will be described below. FIG. 1 is a schematic sectional view of a die-casting sleeve of the present invention in which an Fe-based alloy coating layer is joined to the inner surface of a steel outer cylinder. In FIG. 1, a die-casting sleeve 1 is formed by welding a coating layer 3 made of an Fe-based alloy to an inner surface of a steel outer cylinder 2. A molten metal such as aluminum is supplied from a hot water supply port 4 opened through the outer cylinder 2 and the coating layer 3. Reference numeral 5 denotes an injection port side of the die casting sleeve 1, and reference numeral 6 denotes a rear end side.
[0031]
The outer cylinder 2 has a hollow cylindrical shape and is made of general structural steel. The outer cylinder 2 has an outer diameter of 130 mm, an inner diameter of 68 mm, and a length of 665 mm. An iron plate was welded to the rear end side 6 of the outer cylinder 2 to close it, and the outer cylinder 2 was set upright in the vertical direction with the rear end side 6 down, set in a heating furnace, and then heated to 1200 ° C.
[0032]
The coating layer has a weight ratio of C: 1.9%, Si: 0.8%, Mn: 0.4%, Cr: 4.7%, Mo: 5.7%, V: 6.5%. The ingot having the components was melted at 1600 ° C., and the molten metal was cast from the injection port side 5 of the outer cylinder 2 heated to 1200 ° C. described above. Then, a stopper was quickly driven into the hole on the injection port side 5 and moved to a centrifugal casting machine. The centrifugal casting machine was set so that the longitudinal direction was horizontal. The centrifugal casting machine was operated and rotated at 1000 rpm. When the outer surface temperature of the outer cylinder 2 reached 450 ° C., the rotation was stopped and the outer cylinder 2 was put into the lehr.
[0033]
After stopping the rotation, it was air-cooled to a predetermined temperature and quenched. Thereafter, the strain relief annealing and annealing were performed three times at 400 to 600 ° C. to obtain a sleeve material for die casting.
[0034]
When the sleeve material thus obtained was examined, the hardness of the coating layer 3 metal-bonded to the inner surface of the outer cylinder 2 was Hs83, and the carbide was mainly MC-based carbide in an area ratio of 13% and M _2. C-based carbide was 5%.
[0035]
Next, the outer peripheral surface, the end surface, the inner surface, and the hopper hole of the sleeve material were finished to predetermined dimensions.
[0036]
Thereafter, the sleeve material was placed in a furnace and heated and maintained at 500 ° C. in an ammonia stream to perform a nitriding treatment to form a nitride coating layer 8 on the surface of the coating layer. Furthermore, in order to improve the erosion resistance, the sleeve material subjected to the nitride treatment is immersed in a molten salt containing metallic Cr powder, and the surface of the nitride film layer 8 subjected to the nitridation treatment is coated with nitride Cr. A carbonitride film layer 7 of nitride or Cr was formed, and a sleeve 1 for die casting was obtained.
[0037]
The thus manufactured die-casting sleeve of the present invention was mounted on an actual die-casting machine and subjected to injection molding of molten aluminum. As a result, compared to the conventional SKD61 steel, the sleeve has superior wear resistance, erosion resistance, and ceramics. Compared with the sleeve, the toughness was good without any breakage, and it could be used stably for a long time.
[0038]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the sleeve for die-casting of this invention, the sleeve for die-casting excellent in wear resistance, erosion resistance, and toughness which has the advantage of the conventional steel material and ceramic material can be provided, and it can operate stably for a long time. As a result, the number of maintenance steps, cost and time can be reduced, and the production efficiency can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a die casting sleeve according to an embodiment of the present invention.
[Explanation of symbols]
1 die-casting sleeve, 2 outer cylinder, 3 coating layer, 4 hot water supply port,
5 Sleeve injection port side, 6 Sleeve rear end side,
7 Cr carbide or Cr carbonitride film layer, 8 Nitride film layer

Claims (7)

A die-casting sleeve formed with a coating layer having excellent wear resistance on at least a part of the inner surface of the outer cylinder made of a hollow cylindrical steel material that comes into contact with the molten metal, wherein the coating layer has a weight ratio of:
C: 1.0 to 3.0% Si: 0.1 to 2.0%
Mn: 0.1 to 2.0% Ni ≦ 4.5%
Cr: 3.0 to 10.0% Mo: 0.1 to 9.0%
W ≦ 10.0% V: 1.0 to 10.0%
A die-casting sleeve comprising an Fe-based alloy containing: 2. The die-casting sleeve according to claim 1, wherein the coating layer further contains at least one of Co ≦ 10.0% and Nb ≦ 10.0% by weight. 3. The coating layer is either MC system (M is a metal element) carbides, _{M 2} C carbides, _{M 6} C _carbides, M 7 _{C 3 carbides,} M 4 _{C 3} carbide and _M 23 _{C 6} type carbides The die-casting sleeve according to claim 1, wherein the sleeve comprises at least one kind. The die-casting sleeve according to any one of claims 1 to 3, wherein the total area ratio of carbides contained in the coating layer is 25% or less. The sleeve for die casting according to any one of claims 1 to 4, wherein the coating layer is formed by a centrifugal casting method. The die-casting sleeve according to any one of claims 1 to 5, wherein a coating layer made of a nitride is formed on a surface of the coating layer. 7. The die-casting sleeve according to claim 6, wherein a coating layer made of Cr nitride or Cr carbonitride is formed on the surface of the nitride coating layer.

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