JPS6029445A - Composite cylinder liner having excellent resistance to corrosion - Google Patents

Abstract

PURPOSE:To provide a strong and tough composite cylinder liner having excellent resistance to corrosion by using a spheroidal graphite cast iron contg. a specific amt. of Cu as an outside layer and a special cast iron material having excellent resistance to wear and seizure as an inside layer and joining both layers by welding. CONSTITUTION:Cu is incorporated at 0.3-4.0wt% into a spheroidal graphite cast iron and said iron is used an outside layer. A special cast iron material having excellent resistance to wear and seizure is used as an inside layer. Both layers are joined by welding to form a composite cylinder liner. The outside layer consists, by wt%, of 2.8-4.0% C, 1.5-3.5% Si, 0.2-1.0% Mn, <=0.3% P, <=0.04% S, <=2.5% Ni, <=0.8% Cr, <=0.6% Mo, 0.03-0.1% Mg and the balance Fe with impurities, in addition to Cu. A pseudo-spheroidal graphite cast iron and graphite steel having a specific compsn. contg. 0.3-4.0wt% Cu are usable in place of the spheroidal graphite cast iron.

Description

[Detailed description of the invention] The present invention relates to the provision of a tough composite cylinder liner.

Since it must slide simultaneously with the piston ring and maintain airtightness, wear resistance and seizure resistance are basically required. For this purpose, conventional cylinder liner applications include type A graphite, Or', B, P, V, Mo, N
Special cast iron castings containing wear resistance improving elements such as b.

However, with the recent increase in the size of internal combustion engines and the demand for lighter weight and lower fuel consumption, the above-mentioned conventional materials are insufficient in terms of strength, and improvements in strength are desired.

For the purpose of improving strength, it is possible to select a liner material with high strength, but this may impair the wear resistance and seizure resistance, which are the essential characteristics of cylinder liners, so there is a practical limit. There is. It is also effective to increase the thickness of the liner, but this goes against the goal of reducing weight.

By the way, when analyzing the usage conditions and causes of damage to cylinder liners, we find that: (1) The only part that requires wear resistance and seizure resistance is the part that contacts the piston ring, that is, the inner surface of the liner.

(2) Damage to the cylinder liner starts from its outer surface.

(3) There are three causes of damage: thermal stress, internal pressure, and corrosion due to external cooling water.

The present invention focuses on this point, applies unprecedented composite technology to the cylinder liner, and aims to achieve the stated purpose. 1. The applicant has filed a patent application No. 57-134049 for a new cylinder liner to which the composite technology is applied.
It has already been proposed as 57-134050 and 57-146649. In other words, these inventions are
The inner layer (near the inner surface) is made of a special cast iron material with excellent wear resistance and seizure resistance, as in the past, while the outer layer (near the outer surface) is made of special spheroidal graphite cast iron, pseudospheroidal graphite cast iron, and other materials with excellent toughness. It is made of graphite steel and is welded and bonded to each other, making it possible to improve the desired strength without sacrificing the wear resistance and seizure resistance required as a whole. It is something. The present invention improves corrosion resistance by adding 0.3 to 4.0% by weight of Cu to the specific outer layer materials proposed above, such as spheroidal graphite cast iron, pseudospheroidal graphite cast iron, and graphite steel. In other words, by improving the corrosion resistance of the outer layer material that comes into contact with cooling water, we can contribute to preventing cracks from the outer surface and provide a cylinder liner that is even better than the previously proposed cylinder liner. was completed.

The present invention will be explained in detail below.

The composite cylinder liner of the present invention has a structure as shown in FIG. That is, the outer layer ←) is made of spheroidal graphite cast iron, pseudospheroidal graphite cast iron, which has excellent toughness, which will be detailed later.
It is made of graphite steel material, while its inner layer +M+ is anti-seizure,
It is made of a conventional special cast iron material with excellent wear resistance, and is metallurgically welded together.

Note that due to the welding and integration of the outer layer +61 and the inner layer (6), a welded layer (intermediate layer (g+6)) having a composition intermediate between the outer layer (81 and the inner layer (6)) is inevitably generated between the outer layer (81) and the inner layer (6). In other words, the inner layer φ) is welded to the outer layer el.
y b t If I+A/ AJ mmmm rtt
Country ZAlx M 4! AM melting is unavoidable.

At this time, if the welding layer (a-4-b) causes a problem depending on the purpose of use, prepare a separate intermediate layer material in advance as shown in Figure 2, and It is also possible to cope with this by interposing an intermediate layer +61 between (6) and (6). That is, if necessary, the liner structure can be formed to have three or more layers.

A composite cylinder liner having such a multilayer structure can be easily manufactured by centrifugal casting. That is, first, after the outer layer is cast, the inner layer material is cast at an appropriate timing, and both are welded and integrated. For products with three or more layers, each layer may be similarly cast in order from the outer layer at appropriate timing.

In addition, any of horizontal type, inclined type, and vertical type can be applied to the centrifugal force casting method.

Each material used as the outer layer material of the present invention will be described below. All chemical compositions are in percent by weight.

<(I) Spheroidal graphite cast iron> (1) Chemical component C: 2.8 to 4.0% The material of the outer layer of spheroidal graphite cast iron consists of spheroidal graphite and a matrix (
However, a small amount of cementite crystallization is not a problem), and toughness is particularly important. However, if the C content is less than 8%, the castability deteriorates and the amount of cementite crystallized increases, making the material brittle, while if it exceeds 4.0%, casting defects are likely to occur.

Si: 1.5-3.5% Sl has the effect of promoting graphitization, and in the case of this material in which Mg is added as a graphite nodularizing agent, if it is less than 1.5%, the amount of cementite crystallization increases, This is because it becomes brittle. However, if it exceeds 3.5%, the base becomes ferrite and the proof strength deteriorates, and the sl dissolved into the ferrite makes the ferrite brittle.

Mn: 0.2 to 1.0% Mn usually combines with S to eliminate the adverse effects of S, and also stabilizes the base pearlite and increases its strength. MnQ,g
If it is less than 1.0%, this effect cannot be expected, and on the other hand, if it exceeds 1.0%, it will become brittle.

P: 0.3% or less P increases the fluidity of the molten metal, but it also creates phosphorus in the material, making it brittle. This effect increases as the P content increases, but the upper limit is set at 0.3% as a range that does not cause any actual damage. The lower the P content, the more advantageous it is in terms of toughness, but in practice it is difficult to reduce the P content to less than 1% due to cost considerations.

S: 0.04% or less Like P, S is generally understood as an impurity element and deteriorates mechanical properties. Also, since it has the effect of inhibiting the spheroidization of graphite, it should be kept at 0.04% or less.

Ni: 2.5% or lessN1 acts effectively on graphitization and strengthening the base, but 2.5% or less
If it exceeds %, it will not only be disadvantageous in terms of economic efficiency, but also
This is because quenched structures (bainite, martensite) and untransformed structures are likely to occur, which does not meet the purpose of the outer layer material.

Or: 0.8% or less Cr not only strengthens the base but also has a large stabilizing effect on cementite. That is, when CrQ exceeds 8%, C, S
Don't let cementite crystallize even if you adjust i,
This is because the outer layer material no longer meets the purpose.

Mo: 0.6% or less MO is effective in strengthening the base, but even if the content is increased, the effect will become saturated and it will not be economical, and it will also harden the material.
Since it also has the effect of making it brittle, it should be kept at 0.6% or less.

Mg: 0.08 to 0.1 Mg is of course included to make graphite spheroidal, but if it is less than 0.03%, the effect is insufficient, while if it is less than 0.1%
This is because if it exceeds this, it is undesirable because the chilling effect of Mg and casting defects such as dross are likely to occur.

Cu: 0.3-4.0% The purpose of containing Cu is to improve corrosion resistance, and by improving the corrosion resistance of the outer layer material that comes into contact with cooling water,
Effective in preventing cracks from forming on the outside. If it is less than 0.3%, the above effects cannot be expected, while if it exceeds 4.0%,
This is not preferable because the material strength deteriorates.

The spheroidal graphite cast iron material that forms the outer layer of cylinder litchi is
It contains each of the above components, and the balance basically consists of Fe and normal impurities.

In order to further improve the material properties of the spheroidal graphite cast iron material of the outer layer, in place of Fe, the following rare earth element, Sn, can be added as necessary.

Rare earth element: 0.05% or less If a rare earth element is added in combination with Mg, the spheroidization of graphite becomes better. At this time, the upper limit of the amount added is 0.05% by weight, at which the effect is saturated.

Sn: Q, 3% or less Depending on the casting conditions of the above-mentioned outer layer material, excessive ferrite may be present in the matrix, resulting in a decrease in yield strength and fatigue strength. In that case, S, which has a pearlite stabilizing effect,
It is effective to add n within a range of 0.3% by weight at which its effect is saturated.

(It) Inoculation of outer layer material Next, inoculation of outer layer material will be described. Generally, inoculation is effective for refining the casting structure and promoting graphitization. If the inoculation technique is also applied to the above-mentioned outer layer material, a material in which graphite is more finely and uniformly distributed can be obtained. At this time, the appropriate amount of inoculation is 0.05 to 1.0% assuming 81 minutes. That is, if it is less than 0.05%, no inoculation effect can be expected, and on the other hand, if it exceeds 1.0%, a corresponding effect cannot be obtained. CaSi and FeSi are suitable as the inoculant. Note that the S1 content after inoculation is also adjusted to the above range of 1.5 to 3.5%.

(g) Microscopic structure of outer layer material The microscopic structure of the above-mentioned spheroidal graphite cast iron material mainly consists of spheroidal graphite and a pearlite base. Although a small amount of cementite may be crystallized in the structure, since cementite is brittle, it is necessary to keep it as low as possible for the purpose of the present invention. The base is preferably pearlite from the viewpoint of yield strength and fatigue strength, and it is better to use as little ferrite as possible. Note that even if bainite or martensite partially precipitates, it may become somewhat brittle, but may actually have the advantage of increased strength. However, in order to precipitate bainite and martensite,
It is necessary to take measures such as high alloying or special heat treatment, which is disadvantageous in terms of cost.

<(■) Pseudo-spheroidal graphite cast iron material> (1) Chemical component C: 2.8-4.0% The pseudo-spheroidal graphite cast iron material of the outer layer consists of caterpillar graphite and a matrix (however, a small amount of cementite crystallizes No problem), the ingredients are adjusted with particular emphasis on toughness. However, C2,8
If it is less than %, the melting temperature increases and castability deteriorates, and the amount of cementite crystallized increases, making the material brittle.

On the other hand, if it exceeds 4.0%, casting defects are likely to occur.

Si: 1.0 to 3.0% Sl has the effect of promoting graphitization, but if it is less than 10%, the amount of cementite crystallized increases, making the material brittle. On the other hand 3. If Q% is exceeded, the base will become ferrite, the proof strength will deteriorate, and S will dissolve into the ferrite.
i makes ferrite brittle.

Mn: 0.2 to 10% Mn usually combines with S to remove the adverse effects of S, and also stabilizes the base pearlite to increase its strength. MnQ, 2
If it is less than 1.0%, this effect cannot be expected, while if it exceeds 1.0%, it will become brittle.

P: 0.3% or less P increases the fluidity of the molten metal, but it also generates phosphorus in the material, making the material brittle. This effect deteriorates significantly as the P content increases, but the upper limit is set at 0.3% as a range that does not cause any actual damage. Note that the lower the P content, the more advantageous it is in terms of toughness, but in practice it is difficult to reduce the P content to 0.01% or less due to cost considerations. , is generally understood as an impurity element, and since it deteriorates mechanical properties, it is set at 0.06% or less.

Ni: 2.6% or less Ni acts effectively on graphitization and strengthening the base, but 2.5%
If it exceeds this value, it is not only disadvantageous in terms of economic efficiency, but also tends to generate hardened structures (bainite, martensite) and untransformed structures, and may even become brittle.

Or: 0.8% or less Or acts to strengthen the base and stabilize cementite. In other words, if Cr exceeds 0.8%, 0%S
Even with the adjustment in step 1, cementite crystallizes and becomes brittle.
This is because the outer layer material no longer meets the purpose.

No: Q, 5% or less Mo is effective in strengthening bases, but even if the content is increased too much, the effect will become saturated and it will not be economical. -Fall? ÷Existence 1) House m J-1h Rokuma h should be 0.6% or less.

Mg: 0.01 to 0.05 Mg is contained to form caterpillar graphite, but 0.01 to 0.05.
If it is less than 0.01%, the graphite shape becomes flaky and the strength is poor.

However, it is not necessary to include Mg in excess of 0.05%, and if the content is too high, Mg will diffuse into the inner layer material and tend to change the properties of the inner layer material. Therefore, in the case of this pseudo-spheroidal graphite cast iron material, the upper limit of Mg is set to 0.
．． 05%.

Cu: 0.3 to 4.0% (same as spheroidal graphite cast iron) The pseudo-spheroidal graphite cast iron material that forms the outer layer of cylinder litchi contains each of the above components, with the balance basically consisting of Fe and normal impurities. .

In addition, in order to further improve the material properties of the pseudo-spheroidal graphite cast iron material of the outer layer, the following rare earth elements and Sn are added instead of Fe.
, Ti as needed! Can be added.

Rare earth element: 0.05% or less If a rare earth element is added in combination with Mg, the graphite sphericity is further improved and the strength is improved. The upper limit of the amount of addition is 0.05 double fire at which the effect is saturated.

Sn: 0.3% or less Depending on the casting conditions of the above-mentioned outer layer material, excessive ferrite may be present in the matrix, resulting in a decrease in yield strength and fatigue strength. In that case, S, which has a pearlite stabilizing effect,
It is effective to add n within a range of 0.3% by weight at which its effect is saturated.

Ti: 0.1% or less Regarding the outer layer material, the graphite may become spheroidized depending on the casting conditions. In this case, T which is a spheroidization inhibiting element
By adding 1, the desired caterpillar-like graphite can be reliably obtained.

However, if the T1 content is too large, the above effect becomes too strong and flake graphite is produced, so the upper limit of the amount added is 0.1% by weight.

(It) Inoculation of outer layer material Next, inoculation of outer layer material will be described. Generally, inoculation is effective for refining the casting structure and promoting graphitization. If the inoculation technique is applied to the outer layer material, a material in which graphite is more finely and evenly distributed can be obtained. At this time, the appropriate amount of inoculation is 0.05 to 1.0% as Si content. That is, if it is less than 0.05%, no inoculation effect can be expected, and on the other hand, if it exceeds 1.0%, a corresponding effect cannot be obtained. CaSi and FeSi are suitable as the inoculant. Note that the S1 content after inoculation is also adjusted to the above range of 1.0 to 3.0%.

(III) Microscopic structure of outer layer material The microscopic structure of the above-mentioned spheroidal graphite cast iron material mainly consists of caterpillar graphite and pearlite base. Although a small amount of cementite may be crystallized in the structure, since cementite is brittle, it is necessary to keep it as low as possible for the purpose of the present invention. The base is preferably pearlite from the viewpoint of yield strength and fatigue strength, and it is better to use as little ferrite as possible. Incidentally, even if bainite or martensite partially precipitates, it may become somewhat brittle, but may actually have the advantage of increased strength. However, in order to precipitate bainite and martensite, it is necessary to take measures such as high alloying or special heat treatment, which is disadvantageous in terms of cost. Furthermore, if the amount of bainite or martensite is too large, it becomes too brittle, which also poses a problem.

(2) Graphite steel material〉 (+) Chemical composition C: 1.0 to 2.0% The graphite steel material of the outer layer consists of spherical graphite and a matrix (
However, there is no problem with the crystallization of a small amount of cementite), and toughness is of paramount importance.

However, if C is less than 1.0%, there are disadvantages such as high melting and casting temperatures and increased costs, while if it exceeds 2.0%, graphite tends to lose its spherical shape, resulting in a decrease in toughness.

SS: 0.6-3.0% Sl has a close relationship with the crystallization of graphite, and if it is less than 0.6%, it becomes difficult to crystallize graphite, leading to deterioration of toughness. However, when the ratio exceeds 3.0, the tendency of material embrittlement due to the solid solution of Sl in the matrix becomes remarkable. It is effective for Mn0.2% powder has no such effect, while 1.0% Mn
This is because exceeding this makes the material hard and brittle.

P: 0.1% or less P increases the fluidity of the molten metal, but in the case of this material it makes the material brittle, it should be 0.1% or less.

S: 0.1% or less Like P, S also makes the material brittle, so it should be 0.1% or less.

Ni: g, 5% or less Ni acts effectively on graphitization and strengthening the matrix, but if it exceeds 2.5%, it is economically disadvantageous and tends to generate bainite, martensite, and untransformed structures. This is because it may actually become brittle.

Or: 1.0% or less Or is an element that has a strengthening effect on the base and a stabilizing effect on cementite, but if it exceeds 1.0%, it becomes difficult to crystallize graphite and deteriorates the toughness. be.

Mo: 1.0 or less MO is effective in improving toughness like N1, but 1.0
This is because if it exceeds %, it will become hard and the toughness will deteriorate.

Cu: 0.3 to 4.0% (same as spheroidal graphite cast iron) The graphite steel material forming the outer layer of the cylinder litchi contains each of the above components, and basically consists of the remainder Fθ and normal impurities.

Note that, in place of Fe, one or more of the following elements may be added to the graphite steel material of the outer layer, as necessary, in order to further improve the casting structure.

Single or combined addition of T1, J, and zr: 0.1% or less in total By adding one or more of these elements, it is possible to reliably prevent the occurrence of casting cavities in graphite steel materials, A healthier material can be obtained. At this time, since all of these elements are strong deoxidizers, they should not be added in excess.

Depending on the species, it is known to bring about good results in promoting graphitization and refining the structure. Regarding this material,
By applying inoculation technology, Cadi and Foc are added immediately before casting.
Adding 0.1 to 1.0% of an inoculant such as i for 81 minutes is more effective in improving toughness. If the amount of inoculation of Sabb is less than 0.1%, it will not be effective, and it is not necessary to exceed 1.0%. Note that the 81 content after inoculation is still the same as the above 0.
It is adjusted to a range of 6 to S,0%.

(lit) Microscopic structure of the outer layer material What is the microscopic structure of this material? ! It is mainly composed of spherical graphite and matrix, and may also contain a small amount of eutectic cementite. Since cementite is brittle, from the purpose of the present invention, it is desirable to suppress crystallization of eutectic cementite as much as possible. The base is mainly pearlite, and some ferrite, bainite, martensite, and retained austenite may be observed. Ferrite has excellent toughness, and depending on the purpose, it may be desirable to precipitate it. Bainite, martensite, and retained austenite deteriorate the material, so efforts should be made to prevent their occurrence.

The material of the outer layer has been described in detail above, but as for the material of the inner layer of lychee, which requires -1 wear resistance and seizure resistance, it is sufficient to use a conventional special cast iron material and there is no special feature.

Next, examples will be given and explained.

<Example> Under the following casting conditions, A, B, 0. D, 1, II'
A composite cylinder was manufactured.

0 Casting mold inner diameter = 20φ 0 Thickness of layer casting: 75 pieces 0
Inner layer casting thickness: 40M11oChemical composition: As shown in the attached table () JP-A-60-29445 (7) Drawings 3 to 12 show microscopic photographs of the liner material of the present invention, and Fig. 3.4 is the outer layer material of AA, No. 5.6.7.8
The figure shows the outer and inner layer materials of &0, and Figures 9, 10, 11, and 12 show the outer and inner layer materials of AI (magnifications of 50 and 40
0).

The mechanical properties of the above outer layer material are shown below.

Black Tensile strength 0) Elongation (A) A 42.2 1. S2 B 45.6 2.00 0 60.3 2.30 D B5.2 1.80 1 [i 61.2 1.26 F 53.5 0.90 In addition, the general Mechanical properties are tensile strength 18-25Q7&d, elongation 0.2-0.8
It's within the range of regret.

Next, the following table shows that the present invention has superior corrosion resistance compared to the earlier inventions, Japanese Patent Applications No. 57-134049, No. 57-134050, and No. 1-146649.

Rotational bending for fatigue strength in seawater; 107 times) Outer layer material This invention: 15.0 times - Patent application 1982-1114049 12.5 1 This invention: AO° 2U, 3 1 Patent application 1982- 134050° 16.0 #Invention:
As described above, the composite cylinder lychee of the present invention has an outer layer made of specific spheroidal graphite cast iron, pseudospheroidal graphite cast iron, or graphite steel with zero Cu content. .3
The inner layer is made of a special cast iron material that has excellent wear resistance and seizure resistance as before, and the two are welded and bonded together, making the whole material resistant to wear. In addition to exhibiting properties such as durability and seizure resistance,
In particular, the Cu component in the outer layer greatly improved corrosion resistance, making it possible to provide an ideal cylinder lychee.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing structural examples of a composite cylinder litchi according to the present invention, and FIGS. 3 to 12 show micrographs of the structure of the liner material of the present invention using metallurgical micrographs. α...outer layer, δ...inner layer. Figure 1 Figure 2 γGa X'3θ0

Claims (1)

[Claims] 1. Spheroidal graphite cast iron, pseudospheroidal graphite cast iron, graphite steel, Cu
A composite cylinder liner with excellent corrosion resistance, characterized in that an outer layer containing 0.3 to 4.0% by weight of: and an inner layer made of a special cast iron material with excellent wear resistance and seizure resistance are welded together. 2. The outer layer is composed of weight% other than Cu: C2.8~4.0% N12.5% or less Si 1.5~
3.5% Or 0.8% or less Mn 0.2-1.0%
Mo □, 6% or less PO 13% or less MB O, C1
The composite cylinder liner having excellent corrosion resistance according to claim 1, characterized in that it is made of spheroidal graphite cast iron consisting of 0 to 0.1% SO, the balance 0.04% or less Fe, and impurities. 3. The outer layer is by weight except Cu, Si 1.0-3.0% cr Q, s % or less Mn
O, 2-1.0% MOo, 6% or less PO 13% or less
The composite cylinder liner with excellent corrosion resistance according to claim 1, characterized in that it is pseudo-spheroidal graphite cast iron consisting of Mg 0.01-0.05% S 0.06% or less, balance Fe and impurities. 4. The outer layer is - by weight except Cu, C1,0~2.01 ys 2.5 or less SiO,6
~3.0% Cr 1. Q% or less Mn 0.2-1. O
% Mo 1.0% or less P O, 1% or less 80.1% or less The balance is Fe and impurities.