JPS61202767A - Production of sleeveless cylinder block - Google Patents

Abstract

PURPOSE:To improve castability and wear resistance and to reduce cost by disposing a heat insulating material on the surface of a core mold, coating alloy powder contg. P on the surface via a binder and pouring a molten metal into the mold to diffuse and crystallize steadite. CONSTITUTION:The heat insulating material 4 consisting of ceramic fibers, etc. is first provided and held on the surface of the core mold 2. An alcohol soln. as the binder is added to the P alloy powder or the powder mixture composed of said powder and carbide forming powder and is stirred. Such powder mixture is coated in a prescribed amt. on the surface of the heat insulating material 4. The mold 2 is dried in a furnace and is set to the prescribed position of a master mold 1, then a cylinder block is cast by pouring the molten metal into the mold. The molten metal is maintained at a high temp. by the heat insulating material; at the same time the P alloy is melted and P crystallizes as steadite near the surface during the course of solidification. The liner part having the wear resistance is formed by the above-mentioned method and since there is no need for a separate liner, the cost of the product is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cylinder block, and more particularly to a so-called cast iron cylinder block for an internal combustion engine that does not include a separately manufactured sleeve or liner. Sleeveless cylinder block (below).

This relates to a method of manufacturing a sleeveless block.

(Prior art and problems) Cylinder blocks for internal combustion engines are broadly classified into liner type and integral type depending on the inner wall type of the cylinder. Liner types include dry sleeve type (dry type) and wet liner type (wet type).
On the other hand, a one-piece cylinder block is one in which the entire cylinder block is manufactured as one piece without a sleeve or liner, and is called a sleeveless cylinder block.

In any of these types of cylinder blocks,
Wear of the liner sliding parts is a fundamental problem that affects the durability of internal combustion engines, and a considerable amount of research and development has been carried out in manufacturing to improve wear resistance, but each has its advantages and disadvantages. However, it cannot be said that satisfactory results are necessarily obtained.

In other words, cylinder blocks for internal combustion engines have traditionally been made of cast iron such as ordinary cast iron or alloyed cast iron, but the liner sliding parts in particular are required to have excellent wear resistance. A liner or sleeve is made separately from cast iron containing 0.15% or more of carbon dioxide, and is installed in the block body as a dry sleeve or wet liner.

This liner type cylinder block has a liner made of cast iron containing 0.15% or more of Pf, especially P of 0°3 to 0.
．． It is an alloy cast iron containing 6% Hv700 on the liner sliding surface.
~900 is a crystallized hard steadite (ternary eutectic gold phase of iron phosphides, Fe, P, cementite, Fe, C, and ferrite), so it has excellent wear resistance and can be used under high loads. Used in engines that are used for long periods of time. However, in this type of cylinder block, since the liner portion is manufactured separately, there is a problem that the number of processing and assembly steps is large, and the manufacturing cost is high. Furthermore, it is necessary to ensure the minimum thickness of the liner or sleeve (approximately 2 mm for the dry slitting method, approximately 6 to 10 m+ for the wet liner method).
s) etc., it is structurally difficult to shorten the liner pitch of a multi-cylinder cylinder, and there is a limit to compactness due to rigidity.

Therefore, it is expected that the trend will be to use sleeveless blocks in the future.

However, although sleeveless blocks have actually been manufactured for some time, they have only been used for engines that are used for short periods of time under light loads.

In other words, the material of the current sleeveless block is Cu.
, Cr, Sn, Sb, Mo, etc., one or two alloying elements.
This is an alloyed cast iron in which a combination of more than one species is added, and it is an alloyed cast iron that does not substantially contain P (P<0.10%) and aims to improve wear resistance. Therefore, the structure of the liner sliding part obtained by this method consists of pearlite and graphite strengthened by the above-mentioned alloying elements, and since there is no crystallization of steadite, the wear resistance is much higher than that of the separate system of steadite crystallization. As described above, the uses of sleeveless blocks are limited because they are inferior and have a limit in terms of wear resistance.

On the other hand, even in an integrated sleeveless block, the material of the liner or sleeve of the liner type is Pt-0.
, 15 to 0.8% is added to crystallize hard steadite on the sliding surface of the liner to obtain high wear resistance.In other words, the entire block is made of cast iron containing 0.15 to 0.8% of P. I have an idea. However, in this case, in cast iron containing 0.1% or more of P, steadite crystallizes, and the crystallization of steadite causes resiliency, so there is a large variation in wall thickness, and the boss part,
When casting products with complex shapes such as cylinder blocks with thick walls, elongation cavities occur, which can cause pressure leaks during use, and have low strength (deflection, impact value, etc.), making it particularly difficult to cast. This makes it difficult to put it into practical use.

(Object of the Invention) The present invention completely eliminates the drawbacks of the prior art described above, has good castability equivalent to the conventional sleeveless block or liner type block body, and has a separate sleeve or liner type block body. The object of the present invention is to provide a new method for inexpensively producing a sleeveless block having excellent wear resistance equivalent to that of the present invention.

(Structure of the Invention) In order to achieve the above object, the present inventors have created a sleeveless block material that contains P only on the sliding surface of the liner and its vicinity to crystallize hard steadite, thereby achieving high wear resistance. However, the block body, excluding the liner portion, was made of ordinary cast iron or alloy cast iron, and intensive research was conducted to find a method that would allow the entire sleeveless block to be cast simultaneously.

To this end, we first analyzed the applicability and drawbacks of conventional integral casting techniques.

Conventional methods for forming an alloy layer on the surface of cast iron or cast steel castings include metal coating casting methods (e.g., Japanese Patent Publication No. 48-209
68 Publication), these methods involve coating the surface of the mold with a thick layer of alloy powder and melting it with the heat of the molten metal to form an alloy layer on the surface, but the amount of heat escaping from the mold is large. It has been found that it is difficult to obtain the desired alloy layer, and is therefore limited to cases where the thickness is thick and the molten metal temperature is high.

In this regard, the castings used in today's sleeveless blocks are thin-walled and generate less heat, and the inner surface is machined, so the above method cannot achieve sufficient diffusion of alloying elements even if an alloy layer is created. There are no drawbacks. Incidentally, there is no report that a cast iron sleeveless block for an internal combustion engine could be manufactured using the above conventional method, and even less that steadite could be crystallized from cast iron containing P in the liner portion.

In addition, P is 0.1 on the casting surface of the cylinder block body.
A method of casting using a molten cast iron or alloy cast iron containing 5% or more is also considered, but such a method is practically impossible because the above molten metal has poor castability and the liner part is thin. It is no exaggeration to say that.

Therefore, based on the result of investigating the cause of the drawback of the conventional method described above, which was caused by insufficient heat during pouring, the present inventors proposed a method for ensuring sufficient heat of the molten metal by adding insulation such as ceramic fibers to the surface of the mold. The present invention was made based on the knowledge that this is possible by using a method of significantly reducing the amount of heat escaping from the mold using a material and extending the solidification time.

That is, in the method for manufacturing a sleeveless cylinder block according to the present invention, a heat insulating material such as ceramic fiber is provided on the surface of the core mold to significantly reduce the amount of heat escaping from the mold during pouring. The main idea is to diffuse steadite or carbide-forming elements to crystallize steadite or plate-shaped steadite only in the liner portion.

In this way, a mixed powder of alloy containing P (hereinafter referred to as P-based alloy) powder or alloy containing carbide-forming elements (hereinafter referred to as carbide-forming alloy) powder is applied to the surface of the core mold, such as cellulose-based, phenolic resin, etc. By providing a heat insulating material prior to applying the alcohol solution as a binder, it is possible to substantially block the escape of heat from the core mold and ensure sufficient heat from the molten metal. It is possible to diffuse P, carbide-forming elements, and other components of the above-mentioned P-based alloys and carbide-forming alloys into the liner portion without the need to raise the temperature of the molten metal, and the wear resistance is improved by crystallizing steadite or plate-like steadite containing carbides. A liner portion of tissue can be obtained. On the other hand, the block body excluding the liner part is made of ordinary cast iron or alloy cast iron, so it has excellent castability.
Mass production is possible.

The present invention will be explained in detail below with reference to the drawings.

As shown in Fig. 1, the mold used for casting the sleeveless block consists of a main mold 1 and a core mold 2.
is for forming a cavity in the cylinder block for piston reciprocation. In addition.

3 is the core of the water jacket section.

In the present invention, the surface of the core mold 2 is subjected to the special treatment shown below, and casting is performed using the core mold.

First, a heat insulating material 4 is placed on the surface of the core mold 2 as shown in the figure.
will be established. It is desirable to use fire-resistant fibers such as ceramic fibers for the heat insulating material 4.

Other commercially available insulation materials may also be used. This is held by appropriate means on the surface of the core mold corresponding to the liner part, and a recess is formed in the surface of the core mold as shown in FIG.

It is preferable to provide it so that it is filled therein. Insulation material 4
has the effect of preventing the heat of the molten metal from escaping in the direction of the core mold 2 during pouring, so its thickness can be determined as appropriate by taking into account the dimensions of the core mold 2, the type of molten metal, the casting temperature, etc. can.

Next, a dilute alcohol solution of cellulose, phenolic resin, etc. (cellulose is preferred for diffusion) is added to the mixed powder with P-based alloy powder or carbide-forming alloy powder at a weight ratio of about 5.
A predetermined amount of powder 5 containing ~30% and thoroughly stirred is applied to the surface of the heat insulating material 4.

Examples of P-based alloys include Fe-P containing about 5 to 40% P, N
1-P, Cu-P, 5n-P, or a multi-component alloy thereof can be used. Further, as the carbide-forming alloy, a ferroalloy containing carbide-forming elements such as B, Cr, Mo, V, etc. can be used.

The amount of powder 5 to be applied is as follows:
The amount of P required to add approximately 0.15 to 0.8% of P is
It can be calculated as appropriate based on the P content of the system alloy. When P is less than 0.15%, the amount of steadite or plate-like steadite decreases, and no improvement in wear resistance can be expected.On the other hand, when P exceeds 0.8%, steadite or plate-like steadite becomes coarse and the strength is reduced. In addition, there are concerns about compatibility with rings and peeling of steadite or plate-like steadite from the viewpoint of wear resistance. Preferably, it is a worn tissue.

In the case of a mixed powder of a P-based alloy and a carbide-forming alloy, the mixing ratio varies depending on the whitening state of the whitening element (carbide-forming element). For example, in the case of B, 0.03 to 0.1% In the case of additions, Cr and V, additions of 0.4 to 0.8% are required.

After applying the powder 5, the core mold 2 is dried in a furnace at 100 to 200°C for 20 minutes to 1 hour to vaporize and remove volatile substances such as alcohol, and to prevent gas generation due to heat during pouring of the molten metal. We aim to suppress this.

Next, the core mold 2 that has completed these steps is set in a predetermined position in the main mold 1, and begins the pouring step.

The molten metal used at this time may be ordinary cast iron or alloyed cast iron with small amounts of Cu, Cr, Sn, Sb-Mo, etc. added, as long as it maintains the strength of the engine, with special consideration given to wear resistance. do not have to.

Therefore, elements such as P that inhibit castability are not substantially contained, and the amount of other alloys to be added may be small. When dissolved, the corrosion resistance is improved, and when Cu, Cr, Mo, etc. are added, the strength is increased, or when Ca is added, an inoculating effect can be expected.

The molten metal is poured at a general pouring temperature such as 1340'C or higher, and the alloy powder 5 corresponding to the liner portion is heated and filled into the mold.

The P-based alloy or carbide-forming alloy heated in this manner reaches a high temperature of 1200° C. or more, melts, and P or carbide-forming elements are diffused into the molten metal. At this time, since the heat insulating material 4 is provided on the surface of the core mold, the molten metal is maintained at a high temperature, and the time until the AI solidification is completed is prolonged. Therefore, even in small sleeveless blocks where the liner part is thin.

P-based alloys are sufficiently heated and melted, and P diffuses. However, carbide-forming alloys have high melting points and do not have good diffusivity, so the crystallization range of plate-shaped steadite may vary depending on the molten metal temperature and wall thickness. May be limited.

During the solidification process, P crystallizes as steadite,
If a carbide-forming element is present, it crystallizes as plate-like steadite containing carbide, and a liner portion with a wear-resistant structure in which graphite and steadite or plate-like steadite are distributed in a pearlite base is obtained. The liner part is hard, and in the case of steadite crystallization, it shows a hardness of Hv 700 to 900, and in the case of plate-shaped steadite crystallization, it is even harder, and shows a hardness of Hv 900 to 12o0 (
(approximately 1.5 to 2.0 times that of the former), and has excellent wear resistance. Further, when Ni and Cu are used in the alloy powder 5 such as a P-based alloy, Ni and Ca are dissolved in the base structure to form a dense structure, resulting in a liner portion having excellent wear resistance and corrosion resistance.

The sleeveless block thus obtained is subjected to a poling process on the liner part in a normal processing process, but since P and carbide-forming elements are diffused from the coated surface to the inside of the wall thickness, the machining allowance t in normal poling process is (Fig. 2) is processed at 1.5 to 5.01, the processed surface, that is, the liner sliding surface 6, contains approximately 0.15 to 0.8% P, and the steadite is sufficiently It has a wear-resistant structure that crystallizes.

That is, as shown in FIG. 3, the amount of P contained in the liner portion gradually decreases depending on the degree of P diffusion, and the amount of crystallized steadite or plate-like steadite also decreases.

The base structure shows a homogeneous structure in both the liner part and the other cylinder block body.

The liner sliding surface 6 and the machining allowance t are 9 normal separate sleeves (
or liner), it has the same structure and hardness as
Processability is no different from conventional separate sleeves.

In addition, when mixing a carbide-forming alloy with the powder 5, as mentioned above, the carbide-forming element is difficult to diffuse, so it is preferable to mix the thickness of the liner part rather than manufacturing a small sleeveless block with a thin wall and a small amount of heat. It is suitable for manufacturing relatively large, high-load diesel engines for ships and construction machinery with a liner diameter of 100 mm or more with a sufficient thickness. In this case, it is particularly effective against wear of the liner portion.

(Example) A main mold and a core mold (outer diameter 76 mm) for sleeveless block casting were molded using a conventional method.Next, ceramic fibers were attached to a thickness of 10 mm on the surface of the core mold, and cellulose was added to the surface of the core mold. After applying P-Fe alloy powder (224%) to which 20% alcohol diluted solution was added, it was dried in an oven. In addition, separately, the above P-Fe
A core mold was also produced by applying a mixed powder in which Fe-Cr and Fe-B alloy powders were added to the alloy powder.

Set the obtained core mold into the main mold, and press T and C.

3.3%, Si2.0%, Mn0.07%, Sn
A molten metal made of alloyed cast iron containing 0.07% was poured.

After casting, poling was performed with a machining allowance of 3 m111 to obtain a liner sliding surface. The liner sliding surface contains 4% PO, and the hardness is Hv222 (P-based alloy only) and I (ν238), respectively.
(P-based alloy and carbide-forming alloy), and no casting defects such as shrinkage cavities were observed in any of the sleeveless blocks.

(Effects of the Invention) As described in detail above, according to the present invention, when casting a sleeveless block, P-based alloy powder or carbide-forming alloy powder is applied to the surface of the core mold through a heat insulating material such as ceramic fiber. Apply a mixed powder containing
Because it is cast using a core mold, it is possible to effectively melt and diffuse P, etc., and to manufacture a sleeveless block whose liner part has a hard, wear-resistant structure in which steadite or plate-shaped steadite crystallizes. be able to. In addition, cast iron with good castability can be used as the molten metal for pouring, and it does not require multiple processing steps like the conventional separate sleeve and liner method, so it can be produced in large quantities at a very low cost. This will greatly contribute to the manufacture of cast iron sleeveless blocks for various internal combustion engines, which are becoming lighter and more compact.

[Brief explanation of drawings]

Figures 3 and 2 are partial sectional views illustrating the mold used for carrying out the present invention. Figure 1 is a partial cross-sectional view of the cylinder blocker, and Figure 2 is an enlarged view of section A in Figure 1. FIG. 3 is a diagram showing the relationship between the depth of the liner portion and the P content. 1... Main mold, 2... Core mold, 2...
Nakako of the water jacket club. 4...Insulating material, 5...Alloy powder, 6...
Liner sliding surface. Figure 1 2yA

Claims (1)

[Claims] 1. In the casting of a sleeveless cylinder block that integrally has a liner part without a liner or sleeve, a heat insulating material such as ceramic fiber is provided on the surface of the core mold for the liner part, and the surface A method for manufacturing a sleeveless cylinder block, characterized in that alloy powder containing P is applied as an alcohol solution as a binder, and then molten metal is poured to diffuse P and crystallize steadite only in the liner portion. 2. In the casting of a sleeveless cylinder block that integrally has a liner part without a liner or sleeve, a heat insulating material such as ceramic fiber is provided on the surface of the core mold of the liner part, and P is further added to the surface. It is characterized by applying an alloy powder containing an alloy powder and a carbide-forming element using an alcohol solution as a binder, and then pouring hot water to diffuse P and a carbide-forming element to crystallize plate-shaped steadite only in the liner part. Manufacturing method of sleeveless cylinder block.