JP3191156B2 - Method of manufacturing cylinder liner from hypereutectic aluminum-silicon alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The invention relates to a cylinder liner for an internal combustion engine from a hypereutectic aluminum-silicon alloy according to the preamble of claim 1, as is known, for example, from DE-A-195 23 484. To a method for producing

[0002] Cylinder liners for internal combustion engines are subjected to high frictional loads due to the piston rings and the locally generated high temperatures. Therefore, it is necessary that this surface be made of a wear-resistant and heat-resistant material.

[0003]

2. Description of the Related Art Hypereutectic AlSi alloys such as GK-Al-
The production of cast cylinder blocks from 17Cu4Mg is known, but for casting technical reasons the silicon content is limited to a maximum of 20% by weight. Another disadvantage of the casting method is that
During the solidification of the melt, silicon primary particles having relatively large dimensions of 30 to 80 μm are deposited. Such sharp-edged silicon particles cause wear of the piston ring. Therefore, the contact surface of the silicon particles with the piston ring is flattened by mechanical processing. An electrical process is then performed, which slightly retracts the aluminum substrate between the silicon particles, so that the silicon particles slightly project from the cylinder surface as a support framework. Disadvantages of the cylinder surface manufactured in this way are:
Cylinder liners and piston rings are used to prevent high production costs on the one hand, and imperfect distribution of silicon particles and strong abrasion of oxide inclusions, for example, causing pores, shrinkage holes and highly defective materials. , A relatively thick oil film must be formed. This results in increased pollutant emissions and increased oil consumption.

In order to be able to take advantage of the hypereutectic AlSi alloys as liner materials, these alloys must have as large a number of finely divided silicon particles as are homogeneously distributed. An Al alloy that cannot be realized by casting technology can be manufactured by a powder metallurgy method as is known. This type of method is followed by spray compression. International Application Publication W
From O87 / 03012, spray compression (also called spray compression) of hollow cylinders, so-called tube blanks, is known. To obtain the desired properties of the alloy, Al alloy melt is silicon and Kokingoka are atomization, about per second in a nitrogen jet in 1
It is cooled at a cooling rate of 000 ° C. The powder particles, which are still partially molten, are sprayed (sprayed) onto a carrier tube made of the same type of material or of a common aluminum material, which rotates horizontally about a longitudinal axis. The carrier tube is moved under the spray jet in the direction of its longitudinal axis during this process.
The superposition of both directions of movement of the carrier tube results in a cylindrical tube having the inner diameter of the carrier tube. The outline is obtained from the method parameters.

As an alternative to a tube rotating during spray compression, cooled, but still partially free, powder particles are sprayed onto a rotating dish, approximately symmetrical about the axis of rotation of the dish.
Circular powder particles gradually grow axially on the plate
You . During this process the dish is moved downward. The superposition of both movements usually results in a diameter of about 15-40 cm, about 1-2.
A cylindrical material having a length of m is produced. Due to the high cooling temperature of the molten AlSi alloy drops in the cooling gas jet,
Most of the material to be spray-compressed remains supersaturated. On the other hand, during the spray compression process, fine primary particles such as silicon primary crystals and intermetallic phases are formed according to the alloy phase of magnesium and silicon (Mg ₂ Si), iron aluminide and the like. Due to these hard particles, alloys produced by spray compression are suitable as liner materials.

However, depending on the initial thickness of the material, the wall thickness must be reduced to the required final dimensions by deformation via various methods. A solid cylinder must first be formed into a tube and processed into a liner material. High molding speeds and high molding pressures are required to make the liner final dimensions inexpensively by extrusion. However, it has been found that in such an alloy which is difficult to be extruded, a high molding speed may cause a cross-section to cleave when deformed to a target small wall thickness.

[0007] DE-A-195 23 484, mentioned at the outset, relates to the deformation of solid cylindrical blanks into tubular semi-finished products in addition to extrusion and rotary upsetting as well as shaking. Also states. In any case, the first type of method first produces a tube whose cross section is equal to the liner blank. However, from these tubes individual sections are cut which are equal in length to the desired liner blank. The known method is complicated and expensive because of the intermediate stage from spray-compressed material to liner material ready for casting.

[0008]

An object underlying the present invention is to provide a low-cost method for producing a thin material for a cylinder liner.

According to the invention, this object is solved by the features of claim 1. Subsequent processing of the spray-compressed starting material in a die-casting process results in inexpensive production of the liner material in a single processing step. Furthermore, the risk of tearing of the formed liner wall can be avoided, despite the high deformation rate, by die-casting in the laminar flow in the fluctuating temperature range. Thereby, the proportion of rejects can be reduced, which also has an advantageous effect on the production costs of the liner material.

During the deformation in the thixotropic temperature range, the secondary particles, especially S
Additional Si crystals are formed from the i supersaturated alloy, and the primary particles formed during the spray compression, especially the Si primary crystals, perform an advantageous growth and aging process.

The present invention will be described below based on various embodiments.

[0012]

According to a first embodiment, an alloy I having the following composition by weight is used. Silicon 15 to 40%, preferably about 27% Magnesium 0.25 to 2.5%, preferably about 1.5% Zinc 4 to 15%, preferably about 9% Iron 0 to 1%, preferably about 0.5% Manganese 0 0.1-1%, preferably about 0.6% The balance is aluminum.

The Al alloy I is atomized in an oxygen-free atmosphere at a temperature of the molten metal of about 830 °, and about 4 m ³ /
Cooling is performed at a gas / metal ratio of kg metal, with a cooling rate of about 1000 ° C. per second being obtained. About 80% of the particles solidify during the flight phase, and the remaining droplets, which are still flowable when hitting the substrate surface, are used for the production of the particle composite. The powder particles or droplets are sprayed onto a rotating dish, on which a coarse mass having a diameter of 250 mm grows. During spraying, the melt is finely atomized and formed with a particle size distribution in the range of 3 to 50 μm in which the alloy droplets or particles are fairly narrowly divided. The primary silicon crystal formed in a coarse lump grown from the molten metal typically has a size of 0.1 to 10 μm.
Intermetallic layers such as g ₂ Si have a slightly smaller grain size. This fineness results in a finely dispersed distribution of the hard particles in the alloy being spray-compressed and a homogeneous material for subsequent processing.

Extrusion of blanks into tubes and forming cylinder liners from these tubes is known per se to those skilled in the art. According to the invention, the method is applied in a temperature range in which the material to be extruded is in a thixotropic state. 500-60
The operating temperature of 0 ° C. is related to the respective composition of the AISi alloy. At this operating temperature, the alloy is between the solidus and liquidus. The partially flowable lump or tube section is mechanically stable and is still handled. Under these conditions, the deformation force is small and a high molding speed can be obtained. During this process, a complete change in primary silicon formation takes place. 0.1-10
The general coarsening of primary particles that grows from a particle size distribution of μm to a particle size of 1 to 100 μm takes place, but a ratio of 2 to 10 μm is predominantly dominant. The formation of larger Si crystals occurs mainly in the grain boundary range.

By thixotropic extrusion of the spray compacted coarse mass, the wall thickness is reduced, if necessary, to the wall thickness required for the liner material. For this reason, the hollow front extrusion or the hollow rear extrusion can process a pipe portion having a slightly larger volume than the thin-walled pipe to be manufactured. When a particularly small wall thickness is required, the pipe portion can be set to a desired rework size even by cutting. The extruded tube is cut as needed to produce the cylinder liner material. In this case, for example, a sector is cut off.

The jet with the hard particles loose in the air stream creates a surface condition outside the liner that improves the melting process and thus the metallurgical bond between the liner and the surrounding casting during casting.

Another embodiment of making liner blanks is the known wobbled casting of components. In this case, however, according to the invention, the hypereutectic material, which is previously spray-compressed, is used in the form of a bar made of a special alloy, as described below. Each of these bars is one "shot" on the die casting machine.
Are divided into equal pieces of the same mass as required depending on the desired cast part weight, including the required circulating material. From this spray-compressed and separated starting material, in a process analogous to die-casting, a cylinder liner blank is cast directly in a fluctuating temperature range, with a plurality of liner blanks being economically simultaneously produced in one "shot". Can be cast. The thixotropic material is usually forced into the mold in a laminar flow condition, whereby the mold is filled without gas. The advantages of this method are as follows. The use of a die casting tool that can produce four or six liners simultaneously in one cycle of operation makes it possible to economically produce multiple cylinder liners simultaneously. In this case, only slight deformation forces occur. The method is cheap. A liner without porosity and shrinkage holes results. Since the liner material is manufactured by casting in a forming tool, the outside of the liner material can be structured by grooves, fine folds, waffle structure, and the like at the same time as casting. Such structuring outside the liner blank is advantageous for the metallic bonding of the liner when casting the crankcase casting material around the liner later. That is, the many points of the surface structure provide a favorable location for the onset of melting. In addition, such a structure forms an entanglement between the outside of the liner blank and the surrounding casting material.
In the rocking casting process, the intermetallic phase Al ₂ Cu or Mg ₂
The position of the primary crystal of Si and silicon is changed. These intermetallic phases and crystals are mainly provided in the grain boundary range,
Following particle size growth from an initial particle size of ３０30 μm to a final state with a particle size spectrum of up to 100 μm, most particles are in the range of about 30 μm.

[0018] In particular, as described above, casting for the crankcase
For additional entanglement during pouring of the building material around the cylinder liner (die-casting method ) , the outer contour has a surface with raised and recessed structures that are structured in relief. Can be formed.

[0019] around the cylinder liner material is the desired reworked dimensioned Thus, the incorporated investment casting material crankcase consisting of well-castable Al alloy, therefore in addition to various other conventional die casting Similar casting methods, such as squeeze casting or die-casting in the fluctuating temperature range using the starting materials prepared for the die-casting process, are also suitable in principle. For casting the crankcase around the cylinder liner, open the die casting tool, shea Rindaraina is fitted onto the guide pin. The die casting tool is closed and the crankcase material is poured into the die casting tool.

The filling process takes less than one second. Due to the rapid cooling and the possibility of regulating or cooling the cylinder liner via the guide pins, it is possible to prevent the melt of die-cast material from having a detrimental effect on the cylinder liner.

In this temperature range, the resulting deformation force is kept small. At this operating temperature of the mold and the melt, an improved metallurgical bonding of the alloy takes place, i.e. the onset of melting takes place in almost the entire boundary region between the cylinder liner material and the casting material. This results in a bondless inclusion of the liner without residual porosity.

After the cylinder liner is cast into the crankcase, the surface where the cylinder liner is still needed, especially the cylinder surface, is cut. These machining processes, for example by pre-turning and precision turning of holes and one or two-stage honing, are known. However, with the cylinder liner material according to the invention,
Advantageously, there are no micro-shrinkage pores or pores that would cause surface damage.

Subsequent to this mechanical continuation, particles consisting of Si crystals and intermetallic phases are exposed in a chemical manner. This is performed in a known manner by etching with an aqueous solution of caustic soda. By treating with a 4-5% aqueous solution of caustic soda at about 50 ° C. for about 30 seconds to 1 minute, the Si crystals and intermetallic particles are exposed. The cylinder surface of the cylinder liner thus obtained has the following roughness parameters: Averaged peak-to-valley height Rz = 2-5 μm Individual maximum peak-to-valley height Rmax = 5 μm Core peak-to-valley height Rh = 0.5-2.5 μm Reduced peak height Rpk = 0 0.1 to 0.5 μm Reduced groove depth Rvk = 0.3 to 0.8 μm (Concepts Rz and Rmax are DIN4768 Blatt1
And also the concepts Rk, Rph and Rvk are DIN 47
76.

According to another embodiment, the following alloy II is melted and spray-compressed. Si 15 to 40% by weight, preferably 17% by weight Mg 0.5 to 2.5% by weight, preferably 1.5% by weight The balance is Al.

During the spray-compression process of the alloy, furthermore, oxide ceramic Al ₂ O ₃ particles, which improve the friction surface properties of the cylinder liner, are mixed with the exposed alloy droplets by means of a particle injector. The amount of Al ₂ O ₃ is 1 to 5% by weight as much as possible 3%. Since a large number of these particles with a particle size distribution of 2 to 400 μm are obtained commercially, their addition gives a great deal of control over the friction properties of the alloy surface. The further method steps for producing the cylinder liner according to the invention are largely the same as in the first embodiment, i.e. the starting material thus formed is subsequently used in a thixotropic extrusion process or a thixotropic laminar flow die casting process. Processed.

The method according to the invention has the advantage that the material for the cylinder liner can be shaped to size. The high costs involved in the usual hot extrusion of thin-walled layers and in the usual die-casting processes, both in terms of molding pressure and molding speed as well as in terms of product quality and economy, are avoided by the above-mentioned production process.

As a precautionary note, two further alloys III and IV are also described, which are likewise suitable for the production of cylinder liners.
Alloy III has the following composition by weight: Silicon 23.0-28.0%, preferably about 25% Magnesium 0.8-2.0%, preferably about 1.2% Copper 3.0-4.5%, preferably about 3.9% Iron max. 25% Manganese, nickel and zinc each at a maximum of 0.01% The balance is aluminum.

Alloy IV has the following composition by weight: Silicon 23.0-28.0%, preferably about 25% Magnesium 0.8-2.0%, preferably about 1.2% Copper 3.0-4.5%, preferably about 3.9% Iron 1.0 ~ 1.4% Nickel 1.0 ~ 5.0% Manganese and zinc up to 0.01% each The balance is aluminum.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI // C22C 21/02 C22C 21/02 (56) References JP-A-9-19757 (JP, A) JP-A-62-161464 (JP, A) Special table 63-501803 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 17/00 B22D 23/00

Claims (1)

(57) [Claims] 1. A method for producing a cylinder liner material from a hypereutectic aluminum-silicon alloy, wherein a molten alloy is first treated by a spray compression method so as to be a fine starting material, and then the alloy is shaken. In the method of manufacturing a cylinder liner material using the abnormal state, the starting material is divided into small pieces having the same mass suitable for each die casting process of the cylinder liner as necessary, and these small pieces are alloyed by a laminar flow die casting method. Primarily molded into a cylinder liner surface material in a rocking state, and at least four cylinder liner materials are joined together.
In, wherein the producing simultaneously in the course of the laminar flow die casting method for manufacturing a cylinder liner.