JPS5834160A - Wear resistant cast iron cast in metallic mold - Google Patents

Abstract

PURPOSE:To obtain wear resistant cast iron cast in a metallic mold and showing superior properties as cast even under severe conditions of high speed and high surface pressure applied to a sliding part, etc. by restricting the precentage of each of C, Si, Mn, P, S, Cr, and Ti in a composition and carrying out casting in the mold. CONSTITUTION:This cast iron consists of, by weight, 2.2-2.4% C, 3.6-4.4% Si, 0.3-0.5% Mn, <=0.1% p, <=0.1% S, 0.3-1.0% Cr, 0.05-0.20% Ti and the balance Fe. The matrix of the cast iron is a pearlite structure as cast, the cast iron has a phase contg. precipitated eutectic graphite, and it shows high hardness, high strength and superior wear resistance. By hardening the cast iron at a low temp. such as <= about 1,000 deg.C, the pearlite matrix is easily converted into a perfect martensite structure to further enhance the properties. Said cast iron is obtd. by blending mild steel with prescribed amounts of a recarburizer and an alloying material such as ferrosilicon, melting the blend, and pouring the melt in a metallic mold having about 3-10 mold ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wear-resistant cast iron made by die casting, and more specifically, it has excellent wear resistance even under severe wear conditions such as sliding parts under high speed and high surface pressure loads. This article relates to wear-resistant cast iron produced by die casting that exhibits toughness.

Wear-resistant cast iron is widely used as a base material for various mechanical parts that are used under excessively dynamic wear conditions, such as the cylinder parts of internal combustion engines and the low-Y @ sliding mechanical parts of p-tally air conditioners. These sliding parts usually slide at high speed and under high surface pressure loads, so Part II! There are some disadvantages such as mechanical breakage due to a decrease in the strength of minute parts on the surface, resulting in abnormal wear, or seizing of the lubricant due to the generated heat.

Therefore, such sliding parts have high hardness and high 5!1L.
In addition to having excellent wear resistance at If, it is preferable that the part surface has as few irregularities as possible and does not cause problems such as destruction of minute parts.

Japanese Patent Publication No. Sho 53-6929 discloses a cast iron with good wear resistance that has been prepared with the component: 1III in order to eliminate such inconveniences such as abnormal wear. This cast iron suppresses the precipitation of the soft 7-elite phase during the identification of foreshadowing of the as-cast iron, and mainly due to the effect of addition of panasium, coarsens the precipitated black ships and causes the fracture of such coarse black I& during initial wear. The fine graphite produced by the process increases the lubricity.

However, if such coarse graphite exists on the sliding surface of a component O that slides at high speed under high surface pressure loads, and the roughness of the wrinkling sliding motion O * S = large, the above-mentioned There is a drawback that problems such as abnormal wear of the parts are likely to occur.

The inventors of the present invention have conducted intensive research to develop a wear-resistant cast iron that is free from abnormal wear caused by the destruction of such microscopic parts, and has found that such cast iron generally has a soft 7-enite phase in its matrix structure. [It is preferable that the precipitated graphite does not have coarsening and that the precipitated graphite does not become coarse.
In addition, graphite has a fine and dispersed structure, such as the D-shape (non-directional array) of graphite-shaped layers, as established by the American Foundry Association-American Society for Testing and Materials (Ar1-ASTM). It was concluded that a material having a precipitated phase of crystalline graphite is preferable.

Conventionally, in order to obtain cast iron having such eutectic graphite and having a pearlite structure as a base by sand casting, the carbon content of the cast iron should be t-3.0 weight or less, and the sulfur content should be 0.05 weight. - or less, with trace amounts of OTi, Mo, and Ni.

Products containing Cr and Cu as alloying elements were manufactured. However, even in such a composition, the graphite is not entirely eutectic, or because of the sand mold, the graphite shape and texture I are non-uniform on the surface and inside.

In general, the solidification rate of some metal castings is faster than that of sand casting, so crystallization of cementite (FesC) and disproportionation of the lead structure O occur, or crystalline graphite There is a danger that there will be problems such as crystallization and precipitation of ferrite phase.

Conventionally, the composition of wear-resistant cast iron produced by mold casting includes 1 to 3.5% by weight of C3, 1.6 to 2.6% by weight of 8i, and 0.05 to 0.5% by weight of Cu as other components. %
, 8n 0.01-0.1 weight stf! According to this composition, a small amount of 7-elite is precipitated around the eutectic graphite, and 10
Even by quenching from the 0G'C slope, it is difficult for the matrix structure to become entirely miltinsite. Therefore, for practical purposes, cast iron does not have sufficient wear resistance.

The purpose of this Qo is to solve the above-mentioned disadvantages of conventional wear-resistant cast iron, and to create a structure in which the as-cast part has a pearlite structure as a matrix and has a precipitated phase of eutectic graphite. The pearlite base formed by quenching at temperatures below 1000°C easily becomes an all-martensitic structure, and therefore, even under severe wear conditions such as sliding parts under high speed and high surface pressure loads, Demonstrates excellent wear resistance. Our objective is to provide wear-resistant cast iron made by die casting.

That is, wear-resistant cast iron by mold casting of the present invention, carbon (C
) 2.2-2.41t%, ke(jlE(St)
3.6 to -4.4 weight-・, w y f n (Mn)
'0.3 to 0.5 weight -, phosphorus (P) 0.1 weight or less, sulfur (S) 0.1 weight or less, chromium (Cr)
0.3-1.0wt- and titanium (Tum) 0.0
5 to 0.20% by weight, with the balance consisting of iron (Fe) osi*.

Below, reasons for limiting the composition of the wear-resistant cast iron produced by die casting of the present invention will be explained. The main reason why the cast iron of the present invention is limited to the above-mentioned composition is that all the matrix structure of the as-cast cast iron is pearlitized, and the precipitated graphite is made into fine eutectic graphite. Traveling through tempered heat-fu Il,
- This is to make all of the base group m martensite. To explain in more detail, the lower limit of carbon content t 2.211
(Weight -1 or less, simply written as "chi") is due to 2.
If it is less than 2%, dragon mentite (FalC) will crystallize, and the upper limit is t2.41! ,! LIO1-1,2,
This is because if it exceeds 4$t-, the precipitated graphite becomes coarse.

The silicon content was limited to t-3,6 to 4.4-.
．． This is because if it is less than 611, it will be chilled and cementite will precipitate, and if it is more than 4.411, a ferrite phase will precipitate.

The contents of manganese, sulfur, and sulfur are in the normal range, i.e., Bdn 0.3-0.51i, P 0.1
% or less, and 80.1- or less. Among these, manganese is perlite! 1 woven stabilizing element, 0.31
If it is less than 0.5%, this effect will not be fully realized, and if it is added in excess of 0.5%, cementite will crystallize.

ri4mu Okai quantity tPQ, 3 ~ 1.0 - closed is 0,
If it is less than -, the ferrite phase will precipitate, and if it exceeds 1.0, it will be chilled and cementite will crystallize.
ij 1c, fl:/content to, 05~0.201s
If Oi;

In casting the cast iron of the present invention, for example, a predetermined amount of each of mild steel material, recarburized material, 7
Mix and dissolve erosilicon (such as a commercially available product containing 75% Si), ferro-ongan (such as a commercially available product containing 75% Mn), and 7Etochromium (such as a commercially available product containing 65% Cr). Furthermore, in order to suppress the crystallization of cementite or Fi7 equito, 0.2 to 0.3 weight of the above-mentioned 7erosilicon t-81 is inoculated (1 noculation) as the amount of 7erosilicon t-81 before casting.
A molten metal having the above composition is prepared. Next, the obtained molten metal t-
Cast into desired mold. The molding ratio of the mold used [ratio between the maximum internal thickness of the mold and the (maximum wall thickness x 1) of the casting] is 3 to 3.
Preferably it is lO. If it is less than 3, the life of the metal product will be shortened and cracks will easily occur, and if it exceeds 10, the weight of the mold will become large. The thus obtained cast product can be further subjected to O heat treatment such as quenching and tempering, or can be used as it is in the O state.

According to the wear-resistant cast iron made of gold casting of the present invention, in the as-cast state, the matrix structure is completely transformed into Yara F, and the graphite-AX1 precipitated in the matrix becomes fine eutectic graphite. Even in the as-cast state, it has high hardness, high strength, and excellent wear resistance. tX, when this cast iron is further subjected to heat treatment such as quenching and tempering, ・4-light structure 2! I; Even higher hardness! As rutinsite, wear resistance is further improved, and the heating temperature for quenching is reduced to 900~900℃ compared to the case where 1 ferrite force exists in the base.
It has the advantage that it can be made at a relatively low temperature of 1000°C, and there is no need to increase the secondary cooling rate to reduce residual ferrite.

Therefore, the wear-resistant cast iron produced by O mold casting of the present invention is
l@ cylinder part or rotary air conditioner o -
It is extremely useful as a base material for various machines used under severe wear conditions, such as sliding machine parts such as ').

As Example 夷mlF'llll~3 and Reference Examples 1 to 5, each molten metal (hot water temperature 1350°C) having the composition shown in the table was heated to 350~350°C.
The mixture was cast into a cast iron mold (wall thickness: 50 cm) preheated to 400°C, and a disc-shaped cast product with a diameter of 50-1 and a thickness of 15 cm was obtained under conditions of a mold ratio of 7. In KII, where the molten metal is cast into a mold, approximately 0.0% of Ni3Q-Aj20 alloy powder is applied to the surface of the mold. −
, and then acetylene soot was applied on top.

Thus, the microstructure AT in the as-cast O state of the wear-resistant cast irons obtained by O-gold casting of the present invention obtained as Examples 1 to 3 and the nine cast irons obtained as Reference Examples 1 to 5 in the as-cast O state, and the metallographic microscopy. Did you observe it using 9 and implement it? All of the cast iron rods of the present invention obtained as 1i1 to 1i3 had a /4-lite structure as a matrix, and the precipitated graphite was fine and eutectic. On the other hand, the surfaces of the cast irons obtained as Reference Examples 1 and 112 were both chilled and cementite crystallized. In addition, the cast iron obtained as Reference Example 3 and Reference Example 4 was
ftjlil! A ferrite phase precipitated in the i-weave, and some of the precipitated graphite also became coarse. Furthermore, the cast iron obtained as Reference Example 5 had a large amount of precipitated ferrite and coarse graphite compared to the reference percentage of 3.4.

Next, each of the as-cast cotton castings obtained as Examples 1 to 3 and Reference Examples 1 to 5 was further subjected to an oil quenching treatment at 950°C and then a Qts return treatment at 400°C. When the microstructures of the base metals of the nine cast irons subjected to such treatment were observed using a metallurgical microscope, the base metals of the cast irons of Examples 1 to 3 all had a martenside structure, but those of Reference Example 1 In the case of ~50 cast iron, the ferrite phase remains in the base.

As-cast O-state cast iron produced as Example 2 (
(hereinafter referred to as sample), Examples 1 to 3% and Comparative Example 3
15X12XIO- wear test pieces were cut out from each of the cast irons prepared as samples 5 to 5 and further subjected to the above-mentioned quenching and tempering treatment (hereinafter referred to as sample b-1). A wear test was conducted on a testing machine under the following conditions.

Test conditions> Mating material: 855C (JI8 leg steel for machine structures.

Straight 1140 m, thickness 1O-) Load: rokf Speed f: 2.5 to 2.7 wi/sec Lubricating oil:
Turn oil 9041 Amount of wear of the above sample is shown in the drawing.

The points B, C, D and the curve 1cmQ each show the relationship between the test distance and the amount of wear from sample farm to g.

As is clear from wAWJ, the wear-resistant cast iron produced by the gold casting of the present invention has excellent wear resistance in the as-cast state or in the state where it has been further quenched and tempered.

[Brief explanation of the drawing]

The drawings show the as-cast cast iron manufactured in "r@Example" or the wear-resistant cast iron produced by die casting of the present invention, which is a cast iron that has been quenched and tempered, and a reference example. This is a diagram showing a comparison of the wear resistance of the curve A1.
Points B, C, and D represent the wear resistance of the cast iron of the example of the present invention, and curves E%F and G represent the wear resistance of each cast iron of the comparative example.

Claims (1)

[Claims] Charcoal: IA 2.2-2.4% by weight, silicon 3.6-4.4
Weight -1! ngan 0.3 to 0.5 weight, phosphorus 0.1 weight or less, sulfur 0.1 weight or less, chromium 0.3 to 1
．． A wear-resistant cast iron made by die casting, characterized in that it contains 0 weight and titanium 0.05 to 0.20 weight set, and the balance is released from the composition of iron.