JPS61147844A - Wear resisting cast iron for cylinder block - Google Patents

Abstract

PURPOSE:To obtain the cast iron for cylinder blocks excelling both in machinability and in wear resistance by blending specific amounts of C, Si, Mn, P, S, Sn, and Co. CONSTITUTION:The cast iron for cylinder blocks consists of, by weight, 3.4-3.9% C, 1.5-2% Si, 0.5-0.9% Mn, 0.08-0.5% P, <0.2% S, 0.02-0.06% Sn, 1.2-6.5% Co, and the balance Fe. This cast iron facilitates the casting and machining of cylinder blocks, so that an integral casting of cylinder blocks is made possible without using any cylinder liner.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to wear-resistant cast iron for cylinder blocks of engines, and more specifically to cast iron with excellent wear resistance and machinability for use in cylinder blocks of automobile diesel engines. It is.

(Traditional technique @) Diesel engine cylinder block.

Due to its complex shape, it is required to be made of a material with excellent castability and machinability during manufacturing.Moreover, when used, carbon particles generated during combustion accelerate wear, so the cylinder bore must be made of a material with excellent castability and machinability. Therefore, cast iron 1, which has excellent castability and machinability, is required.
For example, a cylinder block is made of Fe12, etc., and then various alloying elements are added to give wear resistance to the cylinder pore to improve castability.

A complicated method is used in which a wear-resistant cylinder liner made of cast iron alloy with enhanced wear resistance is assembled into the cylinder block, even at the expense of machinability (see Japanese Patent Publication No. 47-3701). .

In addition, in order to manufacture the cylinder block integrally without the complicated method of assembling the cylinder liner as described above, chromium (Cr), IJ (P), boron (B),
Vanadium (V), tungsten (W).

Casting is performed by adding elements such as titanium (Ti) to improve wear resistance (for example, see Japanese Patent Application Laid-Open No. 73160/1983 for adding V).

(Problems to be Solved by the Invention) However, in the above-mentioned conventional method of manufacturing a cylinder liner using wear-resistant cast iron and assembling it onto the cylinder block on the wear-resistant liner, the cylinder block and cylinder liner are manufactured in separate processes. Since each component must be prepared separately and an assembly process is necessarily required, each work process is complicated and the manufacturing cost increases. In addition, in a method in which various elements are added to improve wear resistance because the cylinder block is integrally formed without assembling the cylinder liner, the above-mentioned Cr and P are added.

Elements such as B, V, W, and Ti crystallize carbides in cast iron,
As a result, casting defects such as shrinkage cavities, pinholes, gas holes, etc. increase, and machinability tends to deteriorate due to the influence of carbides. For example, in the case of cast iron containing 0.1 to 0.3% vanadium (v) as described in JP-A-57-73160, ■ is a high melting point element (melting point approximately 1700°C), so addition to the cast iron is prohibited. This method is not easy and tends to cause segregation, resulting in poor yield and productivity.

The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to provide a cast iron for a cylinder block that is excellent in both machinability and wear resistance. Furthermore, it is an object of the present invention to provide a wear-resistant cast iron for cylinder blocks that has a good yield by adding a low melting point element.

(Means for Solving the Problems) The features of the wear-resistant cast iron for cylinder blocks according to the present invention to achieve the above object are that carbon (C) is 14% by weight.
~199, silicon (Si) L5~20, mango y
(Mn) 0.5-0.9%, phosphorus (P) 0.0%
8-0.5%, (S) 0.2m or less.

α02~0.06% tin (Sn), cobalt (C
o) is L2~6.51 and the remainder is substantially iron (Fe).

(Function) According to the cast iron according to the present invention, it is easy to cast and cut a cylinder block, so a cylinder block for a diesel engine or the like can be integrally cast without using a cylinder liner. Moreover, conventional vanadium (V
Since it is cast with the addition of cobal (Co), which has a lower melting point than cobalt (Co), it is possible to cast cylinder blocks with fewer internal defects such as segregation and a high yield. Further, the cylinder block cast in this manner has excellent machinability, and the bore portion also has good wear resistance.

Next, the reasons for limiting the chemical components of cast iron according to the present invention will be explained.

As mentioned above, Co has a low melting point of 1492°C, with a melting point of approximately 1
It is a stable element with a casting yield of 95 or more compared to vanadium at 700°C, and can be easily added to cast iron. Since the hardness and viscosity are higher than those of wrought iron and steel, it has excellent wear resistance, but it was set to L2 to A5 so as not to significantly impede cutting workability.

To suppress internal shrinkage cavities caused by CO addition, the CE value of cast iron (
It is necessary to make the CE value as high as possible (C%+ist*), but if the CE value exceeds 48, the mechanical strength will decrease, so a value of around 4 is desirable. Therefore, in the present invention, since it is necessary to increase the CE value to 3L9~46-, the amount of either C or 8i added is increased, but in order to increase the heat cracking resistance, the weight ratio of C is increased to 14~&9%. , 8i was set to L5 to 2.0ch, making it comparable to that of normal Fe12.

In addition, Iori is added to improve the mechanical strength of cast iron whose CE value is arrogantly increased by 19 to 46 as mentioned above, but its weight ratio is 0.70 to α85e, which is normally used for Fe12.
It was set to 0.5 to 0.9 inches, which is about the same as s.

Further, P is preferable in that it improves the flowability during casting, but since it tends to promote the crystallization of steadite and the generation of internal shrinkage cavities, the upper limit is set at 0.5%.

The reason why the lower limit value is set to α08s is that if it is lower than that, a problem will occur in the flowability of the metal. Incidentally, the chemical composition target for P in Fe12 is 0.20% or less.

S is a component derived from coke, and its presence in large amounts is undesirable for the durability of cast iron, so it should be set at α21 or less, and 8n increases workability but has a strong tendency to increase shrinkage, so Q, 02 to α06 The weight ratio was set to be relatively small.

(Example) An example of the present invention will be described below in comparison with a comparative example. In addition, the target values of the chemical components of the cast iron of this example are listed in the table together with the components of comparative layers 1 and 2.

table The remainder of ill is iron (re).

See Tsuboi Special Publication No. 1984-3701.

EXAMPLE A cylinder block was cast by adding each element as a target component within the range of the constituent requirements of the present invention.

When the chemical components of this cast cylinder block were analyzed, the weight ratios were as shown in @. The structure of this cast iron is a mixed structure in which graphite 3 is dispersed in a base of pearlite 1 and 7-elite 2, as shown in FIGS. 1 and 2.

First, a machinability test was conducted using a cylinder block having the above weight ratio as an example. In the cutting test, a cylinder block cast with the above components was cut using a cutting tool, and the amount of wear of the cutting tool was expressed in the graph of the example shown in FIG.

Next, a 4-cylinder diesel engine with a displacement of 2,400 cc was fabricated using the above-mentioned cylinder block, and a wear resistance test was conducted using this diesel engine as a test object. Abrasion resistance test is 47
A continuous high-speed rotation durability test was conducted under the conditions of GO rpm and 300 hours, and the wear and haze of the cylinder bore portion thereafter were measured and expressed in the graph of the example shown in FIG.

Although the cylinder block used in the above-mentioned embodiments was an as-cast cylinder block, the present invention is not limited thereto. , heat treatment may be performed.

Comparative Example 1 J, which was conventionally used as a material for cylinder blocks
A cylinder block was cast using PC25 cast iron specified in the I8 standard as a comparison material. The chemical composition of FC25 cast iron, which is the material of this cylinder block, is described in the column of Comparative Example 1 above.

The above-mentioned cylinder block cast from FC25 cast iron was cut using a cutting tool, and the amount of wear of this tool was expressed in the graph of Fig. 3.

Next, a 2400C0 4-cylinder diesel engine was manufactured using the above cylinder block with a linerless cylinder block, and the engine speed was 470Orpm under the same conditions as in the example.
After 300 hours of continuous high speed rotation.

The amount of wear on the cylinder bore was calculated and shown in the graph of FIG.

11 A linerless cylinder block was cast using cast iron (see 49 Publication No. 47-3701 @), which was originally proposed as a manufacturing material for cylinder bores, as a comparison material. This comparative material is specified in the JIS standard and is qFc25y (P
) was added at a weight ratio of 0.3%, R (Cr) was added at α2-, and niobium (Nb) was added at α25%.The chemical components are shown in the column of Comparative Example 2 in the table above. Are listed.

The cylinder block was cut using a cutting tool, and the amount of wear of the tool is shown in the graph of FIG.

Next, use the above cylinder block for 2400 m.

A 4-cylinder linerless block diesel engine was manufactured, and a 470Orpm e300 under the same conditions as the above two examples was manufactured.
The cylinder bore was continuously rotated at high speed for several hours, and the wear amount of the cylinder bore was measured and shown in the graph of FIG.

The test results of cutting workability and wear resistance of the above Examples and Comparative Examples 1 and 2 will be explained using FIGS. 3 and 4.

First, the machinability test results are shown in FIG. The wear amount of the tool used to cut the cylinder block used in the example of the present invention was 0.09, which was the measured value of Comparative Example 1, which was cast (11 m+, made of Fe12, which has relatively good tensile properties).
The value is close to mK, which is 9.

In addition, in Comparative Example 2 using cast iron, which was proposed to improve wear resistance, the amount of tool wear was 0 during cutting.
．． It can be seen that the tool wear amount was 27 mm, which was about three times that of the above-mentioned Example and Comparative Example 1, and the cutting workability was low.

Next, to explain the wear amount of the cylinder bore part after continuous speed rotation after forming it as a diesel engine with reference to FIG. The amount of wear on the part is 6.2
5/a, this value is 5 pxntg of the diesel engine using the linerless cylinder block of Comparative Example 2, which is cast iron for the cylinder liner. It showed almost the same wear resistance as the bore part of the linerless cylinder block manufactured by . Similarly, in the case of Comparative Example 1 using Fe12, which is used with emphasis on machinability, it was cast as a linerless cylinder block, so the amount of wear on the cylinder bore was 13L75μ, which was λ2 times that of the example, and λ2 times that of Comparative Example 2. It can be seen that the bore portion is 275 times more worn.

As is clear from the above explanation, a cylinder block was formed from cast iron having a weight ratio within the range of the constituent requirements of the present invention, and machinability and wear resistance tests were conducted. The example recorded excellent cutting workability and wear resistance in one measurement.

(Effects of the Invention) As explained above, according to the wear-resistant cast iron for cylinder block according to the present invention, C is 3.4 to &9% at a weight ratio of 5.
, 8t-15~2.09k, Mn 15~(L9
%, Pwo 0.08~0.5%, 5t-0,
Less than 2%.

5nt-0.02~0.06%, Co 1.2~6.5
% and the remainder is substantially made of Fe, it exhibits excellent machinability when casting cylinder blocks such as diesel engines and machining them into linerless cylinder blocks, and even after the engine is completed, the cylinder bore part remains unchanged. Since the amount of wear can be reduced, it exhibits two excellent properties, cutting workability and wear resistance, which are contradictory to each other. Furthermore, it is possible to provide a wear-resistant @iron cylinder block with excellent O-C workability that does not require separate assembly of the cylinder bore section. Also, in order to improve wear resistance as a linerless cylinder block (unlike the case where sodium (V) is added, Co/<Co) has a low melting point, so adding it to cast iron and casting it is comparatively difficult. It is easy to carry out, and the yield can be increased by reducing defects such as segregation and shrinkage cavities, resulting in a highly productive wear-resistant cast iron for cylinder blocks.

[Brief explanation of drawings]

Fig. 1 is a micrograph at 100x magnification of the metal structure of an example of wear-resistant cast iron for cylinder blocks according to the present invention, Fig. 2 is a micrograph at 400x magnification, and Fig. 3 is a micrograph at 400x magnification. FIG. 4 is a characteristic diagram showing the machinability of a cylinder block cast from cast iron according to the present invention, and FIG. ...Pearlite, 2...Ferrite, 3.
··graphite. 4? Mischief applicant Toyota Motor Corporation Ramin 1 No. 2: Example 12

Claims (1)

[Claims] (1) Carbon (C) 3.4-3.9%, silicon (Si) L5-2.0%, manganese (Mn) 0.5% by weight
-0.9%, phosphorus (P) 0.08-0.5%, sulfur (S) 0.2% or less, tin (Sn) 0.02-0.
1.2 to 6.5% of cobalt (Co), and the remainder substantially of iron (Fe).