JPS60100649A - Cast iron for diesel engine - Google Patents

Abstract

PURPOSE:To obtain cast iron for a diesel engine with high tensile strength by adding specified percentages of C, Si, Mn, P, S, Ni, Cu, Mo, Cr, co and Sn to Fe. CONSTITUTION:Cast iron consisting of, by weight, 3.00-3.50% C, 1.30-2.00% Si, 0.60-1.00% Mn, <=0.07% P, 0.09-0.13% S, 0.50-1.50% Ni, 0.60-1.50% Cu, 0.20-0.50% Mo, 0.05-0.20% Cr, 0.01-0.03% Co, <=0.01% Sn and the balance Fe with inevitable impurities is prepd. The cast iron for a Diesel engine has high tensile strength while maintaining characteristics as cast iron.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the creation of cast iron for diesel engines, which provides cast iron for diesel engines that has high tensile strength while maintaining the characteristics of cast iron, and that can be used in applications such as cylinder heads with high tensile strength. This will contribute to the development of fuel-efficient engines.

It is well known that flake graphite cast iron is widely used in diesel engine cylinder heads because of its good thermal conductivity, low coefficient of thermal expansion, and excellent damping ability (vibration absorption ability). This is due to the fact that it can be obtained appropriately even in complex shapes. However, the recent development of fuel-efficient engines has led to an increase in the maximum pressure within the cylinder, and this increase in maximum pressure within the cylinder requires a higher tensile strength beyond the range of the conventionally required standard FC-30. That is, the tensile strength of FC cast iron is 20~
Since a tensile strength higher than 35 Kr/- is required, ductile cast iron (T, 5 = 40 to 80 Kf/-U) and vermikiller cast iron (T, 5 = 30 to 40 Kt/mj) are used in some cases. These ductile cast iron (FCD)
The thermal conductivity, coefficient of thermal expansion, and damping capacity of vermikiller cast iron (hereinafter referred to as CV) are inferior to those of flake graphite cast iron (hereinafter referred to as FC), as shown in Table 1 below. It is clear that even if it is excellent in tensile strength, it is not desirable as a diesel engine cast iron.

Table 1 Therefore, it goes without saying that there is a need for a material that is equivalent to FC in terms of mechanical properties necessary for an engine cylinder head as shown in Table 1, and also has high tensile strength.

The present invention was devised after repeated studies in view of the above-mentioned circumstances, and is based on WTS (hereinafter simply referred to as CH).
:3. OO~3.50%, St: 1.30~2. ．．
00%, Mn: 0.60-1.00%, P: 0.07%
Below, S: 0.09~0.13chi, Nl: 0.50~1
．． 50%.

Cu: 0.60-1.50%, Mo: 0.2
0-0.50To, Cr: 0.05-0.20%,
We propose a cast iron for engines consisting of Co: 0.01 to 0.03%, Sn: 0.01% or less, and the balance is Fe and unavoidable impurities.

That is, the cast iron of the present invention contains Ni, Cu, Mo, Cr,
It is obtained by adding appropriate amounts of each alloying element such as Co and Sn, and controlling other chemical components such as C, St, Mn, P, and S. The alloying elements mentioned above include graphitization promoting elements such as Ni and Cu. By combining graphitization-inhibiting elements such as , Cr, and Mo, and other property-imparting elements such as Co and Sn within an appropriate range, taking into consideration their respective effects, the tensile strength is 40 o/- or more, and the heat The conductivity is 0.125. x1
1/I: nl・d・(8)・℃ or less, the coefficient of thermal expansion is 9°51/°C or more, and the damping capacity (specific damping rate) is 15 cm or more. , the maximum pressure is 16 kg/d, whereas the conventional model has a maximum pressure of 135 kg/d or less.
Appropriately around 0 Kf/d is obtained, and the engine fuel efficiency is 130 tr/P compared to conventional models! 1. This effectively provides a reduction of about 120 fr/ps, h.

Regarding the composition range of each component as described above, c.
si is the same or lower than the conventional one, Mn is selected higher than the conventional one, and S is also higher than the conventional one. In addition, the fall of Cu is less than 0.6 inch for conventional products, but it is more than that, and Cr is also higher than that for conventional CV and FCD, which is about 0.04%. It can be said that it belongs to. Nl and Co are unique alloying elements in the present invention, whereas Sn is around 0.05 inch in conventional FC and C
Compared to the fact that v is around 0.055%, it is in a much reduced range. That is, it can be said that the composition range according to the present invention has sufficient characteristics as a cast iron for this type of engine.

The reason for limiting the chemical composition range of the cast iron of the present invention as described above is as follows.

C is required to be 3.00% or more for the thermal conduction effect, vibration absorption, and thermal fatigue reduction of an appropriate amount of flaky graphite, and 3.00% or more is required.
．． If it exceeds 50%, it will cause a decrease in strength, so 3,00%
~3650 chi.

St has a relationship with other elements, but it is necessary to contain 1.30% or more in order to obtain a stable structure depending on the wall thickness. If it exceeds -1200%, it inhibits heat conduction and at the same time Since it reduces bending (deflection), etc., it is set at 1.30 to 2.00%.

Since MJ and S are relatively large, it is necessary to contain 0.60% or more to prevent the harmful factors of S.
If it exceeds 0.60, it will tend to chill.
-1.00%.

If P exceeds 0.07%, casting defects (microporosity) will significantly increase and the material will become brittle, so this is the upper limit.

Regarding S, it is necessary to contain 0.09% or more in order to appropriately obtain graphite nuclei as MnS, but since S deteriorates mechanical properties, a low content is preferable.
If it exceeds 0.13%, the mechanical properties will deteriorate, so this is set as the upper limit.

It is essential to contain Ni in an amount of 0.50% or more as an alloying element in order to obtain high strength due to the mutual effect of the combination with other alloying elements. However, if the content exceeds 1.5i, it will not have much effect on stabilizing the morphology and structure of graphite, but rather will cause instability of the structure, so this is set as the upper limit.

Regarding Cu, 0.60% or more is necessary to stabilize the structure and ensure high strength in balance with Ni, but if it exceeds 1.50%, it is disadvantageous because it cannot be completely dissolved. This is the upper limit of 0.60 to 1
．． It shall be 50%.

MO requires a content of 0.20% or more because it has high strength and a remarkable effect on thermal fatigue in high temperature ranges, but it also increases the cause of bainite and shrinkage cavities, so it is limited to 0.50%. .

Cr is necessary to obtain high strength at 0.05% or more, but on the other hand, if it exceeds 0.20%, the castability (microporosity) will be significantly inhibited due to the additive effect with Mo. limited to.

It is necessary to contain Co in an amount of 0.01% or more in order to reduce the coefficient of thermal expansion, but if it exceeds 0.03,000, the effect will be reduced, so this should be limited to 0.01 to 0.
．． 03%.

Although it is necessary to add an appropriate amount of Sn in order to stabilize the pearlite structure, it is economically disadvantageous to add more than 0.01%, so this is the upper limit.

A specific manufacturing example of the product according to the present invention will be described below.

That is, first, the typical compositions of cast iron for diesel engines specifically manufactured by the present inventors and various cast irons as comparative examples thereof are shown in Table 2 below.

Table 2, cast irons 1 to 3, are according to the present invention, FC, FCD,
CV is a comparative example using a conventional method.

However, the results of measuring the tensile strength, thermal conductivity, coefficient of thermal expansion, and damping capacity of each cast iron according to Table 2 above are summarized in Table 3 below.

That is, the cast irons 1 to 3 according to the present invention have a tensile strength (tensile strength) of 40 cm or more and a thermal conductivity of 0.125.
~0.135a+11/crn・d・sec・℃, which is equivalent to or higher than the highest comparative example, and the thermal expansion coefficient is 9.5 to 10.01/℃, which is higher than any of the comparative examples. It was confirmed that the specific attenuation rate was 15 cm, which was the highest.

According to the present invention as explained above, the characteristic values such as thermal conductivity, coefficient of thermal expansion, and damping capacity, which are preferable for this type of cast iron for diesel engines, are sufficiently maintained, and high tensile strength (tensile strength) is precisely maintained. It can be equipped with a material that is suitable for the recent low fuel consumption engines with increased maximum pressures such as 160y4/d or higher, and has an industrially effective material. It can be called a great invention.

Claims (1)

[Claims] C2 3.00 to 3.50 wt%, Si: 1
．． 30-2.00 wt%, Mn: 0.60-
1.00 wt%, P: O-07 wt% or less, S
: 0.09-0.13 wt%, Ni: 0-50
~1-50 wt%, Cu: 0.60-1.50
wt%, Mo: 0.20-0.50 wt%, Cr
: 0.05-0.20 wt%, Co: 0-0
1 to 0.03 wt%, Sn: 0.01 wt% or less, and the balance is Fe and unavoidable impurities.