JPS59215459A - Compacted vermicular graphite cast iron having resistant to scuffing and wear - Google Patents

Abstract

PURPOSE:To provide a titled compacted vermicular graphite cast iron having excellent strength and toughness by consisting the same of specifically composed C, Si, Mn, P, S, Cr, V, Ni, Cu and Fe and distributing uniformly double carbide in the pearlite base. CONSTITUTION:A compacted vermicular graphite cast iron consists of 3.2- 4.0wt% C, 1.0-1.8% Si, <=0.5% Mn, <=0.1% P, <=0.015% S, 0.1-0.9% Cr, 0.1- 0.3% V, 1.5-2.5% Ni, 0.5-1.5% Cu, and the balance substantially Fe and has the structure distributed uniformly with 3-15% area ratio of double carbide contg. compacted vermicular graphite and Cr, V in the pearlite base. Said cast iron has high mechanical strength and excellent toughness as well as improved resistance to scuffing and wear. The cast iron is adequately used as a material for sliding parts such as piston rings or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to compacted vermicular graphite cast iron with improved scuff resistance and wear resistance.

Gray cast iron has graphite in its base that acts as a lubricant, so it has excellent wear resistance and has been widely used as a material for sliding parts such as piston rings and cylinder liners. It has a disadvantage of poor toughness because it has a crystallized structure. On the other hand, spheroidal graphite cast iron has a Mi weave in which graphite crystallizes in spherical shapes, so the internal notch effect caused by graphite is extremely small, and it has the highest toughness among cast irons, but it is not used as a material for sliding parts. This has the disadvantage of poor scuff resistance.

Recently, compacted vermicular graphite (Compact; cdVer.
Compacted vermicular graphite cast iron (hereinafter referred to as Cv graphite cast iron) has been attracting attention because its toughness is inferior to spheroidal graphite cast iron but considerably superior to gray cast iron. ing.

In view of the above-mentioned circumstances, the present invention has been developed to provide a carbon steel which is superior in toughness and has further improved scuff resistance and wear resistance than gray cast iron.
It was made for the purpose of providing V-graphite cast iron, and has a weight ratio of 3.2 to 4.0% C11.0 to 1.8
%Si, 0.5% or less M mouth, 0.1%% or less, 0.01
5%% or less, 0.1-0.9%Cr, 0.1-0.3
%V, 1,5-2, 5%Ni, 0.5-1.5%
Concerning CV black button@iron, which has a structure consisting of Cu, the remainder being substantially Fe, and having a structure in which double carbides with an area ratio of 3 to 15% including compacted vermicular graphite and Cr, (2) are uniformly distributed in a pearlite base. .

The CV graphite cast iron of the present invention has a matrix structure that does not contain free ferrite, and double carbides containing Cr and ■ are uniformly crystallized and distributed in the matrix in an area ratio of 3 to 15%, resulting in scuff resistance. It has improved wear resistance. If the amount of the double carbide is less than 3% in terms of area ratio, the effect of improving scuff resistance and wear resistance will be insufficient, and if it exceeds 15% in area ratio, it will become brittle and impair toughness.

In order to obtain such a structure, the chemical composition of the CV graphite cast iron of the present invention is as follows.

When the weight ratio of C is less than 3.2%, chilling tends to occur, and when the weight ratio exceeds 4.0%, the amount of graphite crystallized becomes too large, impairing toughness, and the crystallization of double carbides occurs. If the amount is insufficient, wear resistance will decrease, so 3.2
-4.0% by weight.

Hereinafter, when expressed simply in %, it will be expressed in % by weight.

If Sl is less than 1.0%, it tends to chill, and if it exceeds 1.8%, the amount of double carbide crystallization decreases, and free ferrite is generated in the matrix, impairing wear resistance. Since graphite tends to become flaky and impairs toughness, the content is set in the range of 1.0 to 1.8%.

Mn is an element that is unavoidably present in general steel materials, and has the effect of stabilizing pearlite in the matrix and suppressing the formation of free ferrite, but it also has the effect of impairing toughness, so it is In inventions, the less the better, 0.
5% or less.

In general, P has the effect of crystallizing Stedai 1~ in the structure of cast iron and improving wear resistance, but since it impairs toughness, in the present invention, it is preferable to use less P.
．． 1% or less.

S has the effect of making graphite flaky.

The lower the content, the more desirable it is, and in the present invention, it is set to 0.015% or less.

Cr and V form double carbides and improve scuff resistance and wear resistance, but if each of them is less than 0.1%, this effect is insufficient, and if Cr exceeds 0.9%, ■
If it exceeds 0.3%, the amount of double carbide crystallization becomes too large, making it brittle and impairing toughness, so Cr is 0.1-0.9% and ■ is 0.1-0.3 % range.

Both Ni and Cu suppress the formation of free ferrite, make the base structure 1 or higher, and improve toughness, but if Ni is less than 1.5% and Cu is less than 5%, the above effects will be lost. Even if Ni exceeds 2.5%,
Even if Cu exceeds 1.5%, the increase in the above effect is not remarkable, so Ni is 1.5 to 2.5% and Cu is 0.5 to 1%.
．． The range shall be 5%.

Examples will be described below.

Pig for spheroidal graphite cast iron, CV graphite cast iron return scrap, graphite layer, ferrosilicon, ferrochrome, ferrovanadium, electrolytic nickel, and electrolytic copper are mixed, melted and tapped in a high frequency induction furnace, and heated to 1510°C with 60% Si and 10% An inoculant of Ca, 5% Ce, and the balance Fe (Cv alloy manufactured by Osaka Special Alloy) was added at 0.6
% and late inoculation with 0.6% ferrosilicon, then cast into a green sand mold with a height of 230 m with a riser on the top.
The sample material had a width of 100 square meters and a thickness of 36 mm.

The analytical values of the sample materials are shown in Table 1.

For comparison, the same table includes cupola melted, Ca-3j, 0
．． Analytical values of gray cast iron obtained by inoculating with 55% ferrosilicon and 0.2% ferrosilicon and casting into a green sand mold are also shown.

Figure 1 is a micrograph at 100x magnification showing the structure of the CV graphite cast iron of the present invention thus obtained (no corrosion), Figure 2 is a micrograph at 100x magnification (picral rot M), and Figure 3 is a micrograph at 100x magnification (picral rot M). FIG. 4 is a microscopic photograph at a magnification of 100 times showing the structure of comparative gray cast iron (no corrosion), and FIG. 4 is a microscopic photograph at a magnification of 400 times (picral corrosion).

In the CV graphite cast iron of the present invention, graphite is crystallized as compacted vermicular graphite, as shown in Fig. 1, and as shown in Fig. 2, white double carbides are uniformly distributed in the barley base. I can see that you are doing it lol.

The amount of double carbide was measured by line integral method and was found to be 8% by area.

As shown in FIGS. 3 and 4, the comparative gray cast iron has a pearlite base structure with well-elongated flaky graphite (A-type black buttons), which is good for gray cast iron.

(1) Mechanical test From these test materials, an 8C test piece was taken as a tensile test piece, a No. C test piece was taken as a bending test piece, and a Charpy test piece (without grooves) was taken as an impact test piece. , bending test,
There are 41 impact tests and hardness tests. The hardness test piece was taken from the gripping force λ of the test piece after the tensile test. Note that each test was conducted three times.

The test results are shown in Table 2.

In comparison, it has greater mechanical strength and superior toughness, which explains b).

(2) Scuff test 5 + nm x 5 mm x 10 from the above sample material
A test piece of mm in diameter was taken, polished and subjected to a scuff test.

The test apparatus is schematically shown in FIGS. 5 and 6, and is mounted at the center of a polished disc 2 with a diameter of 80 IWl and a thickness of 10111 TI, which is removably attached to a stator holder 1. Lubricating oil is supplied from the back side through the oil filling hole 3. Stator 1 has a hydraulic system (not shown)
By this, a pressing force P is applied to the right with a predetermined pressure. A rotor 4 is provided opposite to the disk 2, and is configured to rotate at a predetermined speed by a drive device (not shown). A test piece holder 4a attached to the end face of the rotor 4 relative to the disc 2 has a square end face as a sliding surface, and four test pieces 5 can be removed concentrically at equal intervals, and It is slidably mounted.

In such a device, a predetermined pressing force P is applied to the stator 1 so that the disc (mating material) 2 and the test piece 5 come into contact with a predetermined surface pressure, and the test piece 5 is slid from the oil filling hole 3. The rotor 4 is rotated while lubricating the surface at a predetermined lubricating speed. The pressure acting on the stator 1 is increased stepwise at regular intervals, and the torque generated on the stator 1 due to the friction between the test piece 5 and the mating disk 2 due to the rotation of the rotor 4 (torque generated by frictional force) T is applied to the rotor self via the spindle 6, and the change is read by the dynamic strain IT8 and recorded on the recorder 9. Assuming that scuffing occurs when the torque T suddenly increases, the contact surface pressure at that time is taken as the scuffing surface pressure, and the quality of the scuffing resistance is determined based on the magnitude of the scuffing surface pressure.

The test conditions are as follows. The speed is 8m/see,
Lubricating oil and oil supply conditions are motor oil #30 and temperature 80.
℃, 400 m Q, contact pressure is 20 kHz at 40 kHz/c
After running-in for 3 minutes, the load was increased at 50 kg/cm for 3 minutes, and then increased by 10 kg/cm every 3 minutes.The mating material was cast iron FC25 for marine cylinder liners.

In the scuff test, in addition to the above-mentioned gray cast iron, a similar test was conducted on Barley 1-based spheroidal graphite cast iron FCD70 as a comparative material.

The test results are shown in Table 3.

From Table 3, it can be seen that the Cv graphite cast iron of the present invention has improved scuff resistance not only compared to spheroidal graphite cast iron but also compared to gray cast iron.

(3) The wear test test device used was the one used in the scuff test, the friction speed was 3.5.8 m/sec + the contact pressure was 1.00 kg/cJ, and the lubricating oil was 400 mQ of diesel durable oil at 80°C. The wear amount of each was measured by sliding it under the supplied conditions.

The test results are shown in FIG. In the figure, 3.5.8
The number represents the friction velocity (m/5ee). The amount of wear on the test piece is indicated by the decrease in height, and that of the mating material is indicated by the cross-sectional area in the radial direction of the disk of the groove that occurs in the ring-shaped sliding area on which the test piece slides.

The figure shows that the CVV lead cast iron of the present invention has less wear at all friction speeds than the conventional gray cast iron, and exhibits excellent wear resistance.

As explained below, since the CV black rust cast iron graphite of the present invention is compacted vermicular graphite, it has excellent mechanical strength and toughness, and also contains an appropriate amount of double carbide in its structure. It has excellent scuff resistance and wear resistance, and is suitable as a material for sliding parts such as piston links and cylinder liners.

[Brief explanation of the drawing]

FIGS. 1 and 2 are microphotographs showing an example of the structure of Cv graphite cast iron of the present invention, and FIGS. 3 and 4 are microphotographs showing the structure of comparative gray cast iron. Figures 5 and 6 show an outline of the test equipment used for the scuff inspection and wear test, with Figure 5 being a partial vertical cross-sectional view, and Figure 6 being a partial longitudinal sectional view.
The figure is a side view taken along the line Vl-Vl shown in FIG. 1...Stator, 2...Mating material disc,
4... Rotor, 5... Test piece, 3...
...Oil fill hole Figure 7 is a graph without showing the results of the wear test. Figure 1 Figure 2 x 100 Figure 5 Figure G

Claims (1)

[Claims] 3.2 to 4.0% C11, 0 to 1.8% Si by weight ratio,
0.5% or less M n, 0.1% or less P. 0.015% or less S, 0.1-0.9% Cr, 0.1
~0°3%■, 1.5~2.5%Ni, 0.5~1.5
%Cu, the balance substantially consisting of Fe, and compacted vermicular graphite having a structure in which double carbides with an area ratio of 3 to 15% are uniformly distributed, including compacted vermicular graphite and Cr, and ■ in the matrix. cast iron.