JPH0347952A - Wear-resistant ferrous sintered alloy and its production - Google Patents

Abstract

PURPOSE:To obtain the sintered alloy suitable for a valve gear mechanism member for internal combustion engine and excellent in wear resistance and heat resistance by providing a structure where respectively prescribed amounts of iron-base hard grains having higher Cr content than an iron matrix and copper (alloy) grains are dispersed in the iron matrix having the prescribed composition. CONSTITUTION:A wear-resistant ferrous sintered alloy which has a composition consisting of, by weight ratio, 1.8-4% Cr, 0.1-1% Mn, 0.07-1% Mo, 0.06-1.5% P, 1-10% Cu or Cu alloy, <=0.4% W or <=0.1% V, 0.03-0.9% S, 1.5-4% C, and the balance Fe and also has a structure in which 5-20% of iron-base hard grains having higher Cr content than an iron matrix and 1-10% of copper or copper alloy grains are dispersed in the iron matrix containing Cr, Mn, and Mo is provided. This ferrous sintered alloy has characteristics remarkably superior to those of conventional valve gear mechanism members and has characteristics sufficiently meeting the recent tendency of automobile engines.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sintered alloy having excellent wear resistance and heat resistance and suitable for a valve train member 1 of an internal combustion engine, such as a valve guide.

As valve guide materials for internal combustion engines, various sintered alloys with superior wear resistance, rigidity, and cost have been developed in place of molten materials such as ordinary cast iron and alloyed cast iron.
4-2%, Mn 0.1-1%.

A sintered alloy in which a steadite phase and free graphite are dispersed in an iron matrix containing 0.1 to 1% Mo (Japanese Patent Application Laid-Open No. 58177435
(see publication) and put it into practical use.

However, since the development of this material, the demand for wear resistance under high-temperature conditions has become even stricter with the recent trend toward high performance in automobile engines, and we have come to see cases in which conventional alloys cannot satisfy the requirements.

This invention was made in view of the above circumstances, and Or -
Iron-based hard particles having a higher Cr content than the base are dispersed in the iron base containing 1yln-1ylo to further strengthen wear resistance and heat resistance, and copper or copper alloy particles are not diffused. The main idea is to disperse it in the iron base to give it compatibility with the mating part, and if necessary, add sulfur to further improve the machinability of the part.

That is, this invention is an improvement based on the previous invention, and the improvement point is that the Or of the base is 1.8 to 1.8 compared to the previous invention.
Slightly more than 3.5%, and steadite phase with Cr4~10%
and a hard phase with higher Or than the base.

Free graphite is converted into copper (or Cu-8n, Cu-N+
) is replaced with a soft phase and strengthened. In this specification, the copper alloy is Cu-3% with a tin content of 8 to 11%.
and Cu-Ni alloys with a nickel content of 5 to 30%. This composition range is based on the standard range of commercially available alloy powders.

Further, since the alloy according to the present invention is a dispersion hardening type alloy, the base, hard phase and soft phase (copper or copper alloy) are blended in the form of alloy powders having respective compositions during production. That is, the gist of the manufacturing method is that the base is Cr1.8~
3.5%, Mn0.1-1%, Mo0.1-1% and iron balance: or as alloyed iron powder with 80.05-1% added to this, the hard phase is Cr4-10%, Mo0.05 ~
1%, Po, 2 to 0.7% and the balance of iron; or a hard alloy powder containing 2% or less of W or 0.5% or less of V is added, and the molded product is made to have the necessary strength and softness. The purpose is to sinter at a temperature (980 to 1130°C) at which the phase does not diffuse.

This invention will be described below with reference to its embodiments.

First, as raw material powders, copper powder, bronze powder (10%Sn>, Fe-20P alloy powder, and natural graphite powder with a particle size of 200 mesh or less), and base alloy powder with the following composition (42 pieces) were used.
and hard alloy powder (c, ii) were prepared. Further, the alloy of the prior application was used as a conventional material, and a base alloy powder (H) therefor was prepared.

A: Cr2%, Mn0.7%, Mo0.2% and Fe
The rest.

Mouth: Cr2%, Mn0.7%, Mo0.2%.

80, 2% and balance Fe.

H: 0.8% Cr, 0.7% Mn, 0.2% Mo and balance Fe.

C: 5% Cr, 0.45% MO, 0.45% P and l
“e remainder.

2: C "5%, Mo0.45%, Po, 45%.

Wl, 7%, Vo, 1% and balance Fe.

Next, regarding the preparation of samples, the conventional materials related to the above-mentioned prior application will be described first. 5% copper powder to base alloy powder (chi),
1.25% of Fe--P powder and 2% of graphite powder were blended, and 1% of zinc stearate was added thereto as a lubricant and mixed thoroughly. Next, this mixed powder was molded into a predetermined shape for a test piece at a molding pressure of 6t/cWi, and sintered for 30 minutes at 1060°C in a decomposed ammonia gas atmosphere furnace.
o, 18 was produced. The sintered density of this sample is 6.70
(J/cT/l.

Similarly, samples Nos. 011 to 17 were prepared according to the blending ratios of the raw material powders shown in Table 1. The symbols ■ and ■ written in the remarks column of the table correspond to the numbers 1.2 assigned to each invention in the claims column, for example, sample No.
No. 17 indicates that the production method for one alloy of the invention in item 2 corresponds to an embodiment of the invention in item 1.

The chemical components of samples N001 to 18 thus obtained were
Shown in the table. Note that samples whose compositions or conditions are outside the predetermined range are indicated as comparative examples in the remarks column of Table 8.

Next, each sample was tested for wear resistance and stiffness.

Wear resistance was measured using an Okoshi type friction and wear tester at a temperature of 4. O
A diameter of 30 m rotating at a circumferential speed of 3.6 m10 in the atmosphere at 0°C.
The sample was pressed against a rotor (material S U l-1-3) with a width of 3 mm and a load of 12.6 kg, and the distance was 40 without lubrication.
Determine the wear amount of each sample after sliding 0m, and apply that value to sample N.
It is expressed as an index with 18 (conventional material) as 100. Therefore, the smaller the index, the better the wear resistance.

Rigidity is a property that is essentially incompatible with wear resistance, but it is particularly important from the factory side because it affects work efficiency in the processing process after sintering the component and in the assembly process into the engine. The test method uses a length of 40n+m.
For a cylindrical sample with an inner diameter of 7.4 mm, the inner diameter is 81 mm.
The time required for reaming up to 11111 was determined and expressed as an index with Sample No. 18 as 100, as in the case of wear resistance. Therefore, the smaller the index, the shorter the processing time, ie, the better the stiffness.

The test results are shown in the right column of Table 1, with N063 and N096 having the best properties across the samples.

Below, we will discuss the results based on this table and also explain the individual requirements. First, conventional examples No. 18 and No. 1 have the same raw material composition except for the difference in the base alloy powder forming the iron matrix. However, N001
The reason why N081 shows slightly better properties is that the base alloy powder of N081 contains a lot of Or.

This is also because it contains sulfur. However, this level of abrasion resistance does not reach the recently required level.

Samples No. 1 to No. 004 are high Or
The effect of hard alloy powder is shown, and by adding 5% or more of it, the rigidity deteriorates slightly, but the wear resistance improves markedly, and wear is minimized at around 10%. However, if the amount is further increased, both machinability and wear resistance deteriorate, so the upper limit is set at 20%.

Sample No. 16 is an example using a base alloy powder that does not contain sulfur, and has almost the same wear resistance as sample No. 13, but is inferior in stiffness. This tendency is also the same in the case of samples No. 15 and No. 17, in which different types of hard alloy powders were mixed.

The effect of sulfur on the machinability of the base material is as small as 0.05
%, but a content of around 0.2% is preferable. However, if it is excessive, it will cause a decrease in the strength of the base material, so the upper limit is set at 1% in the base alloy.

Samples No. 5, No. 3, and No. 006 were used to examine the influence of copper dispersed in an undiffused state in the iron base, and the wear was reduced compared to No. 5, which had no additives. The effect is significant from a blending amount of 1%, and shows almost the same effect up to 10%. However, as the content of copper increases, the amount of expansion during sintering increases, so the upper limit is set at 10% from the viewpoint of dimensional stability of the product.

In addition, sample No. 37 had bronze powder (instead of copper powder in No. 093).
The abrasion resistance is almost the same in the example in which 10% tin is added. The slightly low machinability is thought to be due to the progress of copper diffusion due to the influence of tin. Under the same conditions, in the case of 15Ni-Cu, the amount of wear is slightly less than No. 3, and the stiffness is almost equal to No. 3. Thus 8-11% Sn-Cu, 5
The ~3ONi-Cu copper alloy can be considered equivalent to copper for the purposes of this invention. In this invention, it is important to leave copper in an undiffused state, and sintering is carried out at a temperature in the range of 980°C to 1130°C. If it is more than this, the soft phase will diffuse, while if it is less than this, sintering will be insufficient and the necessary strength will not be obtained.

Samples No. 8 to No. 11 were used to examine the effects of phosphorus blended in the form of Fe-P alloy powder, and commercially available Fe-
The phosphorus content of P alloy powder is usually 10% to 30%. When this alloy powder is blended, it becomes a Fe-P-C compound during the sintering process to generate a liquid phase, which promotes sintering and partially forms a steadite phase to strengthen the base. As a result, the stiffness decreases slightly, but the abrasion resistance clearly improves at a blending amount of 015% or more, reaches a maximum at 1 to 1.5%, and then decreases again. If it exceeds 5%, the base material becomes brittle, and as shown in sample No. 11, both machinability and wear resistance deteriorate. Therefore, the appropriate amount of Fe-P is 0.5 to 5%.

Samples No. 12 to No. 14 were used to examine the effects of carbon blended in the form of graphite powder. With a blend ffi of 0.3%, machinability was good, but the important wear resistance was insufficient. 3. At 3%1 〇-, the stiffness is slightly lower, but the wear resistance remains at a good level.

The behavior of carbon mixed in alloys is quite complex, solid solution strengthening of the iron base and formation of carbides with added elements.

It exhibits many effects such as promotion of sintering through reaction with Fe-P and solid lubrication in the form of free graphite.

The minimum amount required for this is 5% soil, and as sample No. 3 shows, about 2% is judged to be optimal. Excessive blending may cause powder segregation and deterioration of moldability, so the content should be kept at 4% or less.

Sample No. 15 is an example using hard alloy powder that does not contain W and V, and its properties are at a practical level, but from comparison with sample No. 003, W and V in the hard alloy powder have good wear resistance. It can be seen that this further improves the This also applies to samples No. 17 and No. 16. This is because both W and (2) react with carbon to form hard carbides and increase the hardness of the hard alloy phase, but if their content is excessive, they tend to damage the mating member. Therefore, the content of W in the hard alloy powder should be kept at 2% or less, and the content of ■ should be kept at 0.5% or less.

This concludes the explanation of the experimental results including the examples,
Next, the compositions of the base alloy powder and hard alloy powder, which are the main raw materials, will be described.

Cr: A component common to base alloy powder and hard alloy powder,
Forms carbides to improve wear resistance and oxidation resistance. However, if the concentration is distributed throughout the alloy in a negative manner, the properties will be poor. The advantage of this invention is that the content of soil in the base material is low at 8 to 3.5% to provide toughness, and the hard alloy phase containing a large amount of Or at 4 to 10% is dispersed in this base. It has characteristics. If the content in the alloy powder is less than 1.8%, the effect is poor;
On the other hand, if it exceeds 10%, the powder becomes hard and moldability is inhibited. The reason why the upper limit in the base material is 3.5% and the lower limit in the hard powder is 4% is to maintain a sufficient difference in Cr concentration between the base and the hard phase.

MO = This element is also a component common to base alloy powder and hard alloy powder, and in addition to having similar effects to Cr, it improves strength and wear resistance, especially at high temperatures. The effect is significant from as low as 0.01% for base alloy powder with low Cr content, and as low as 0.05% for hard alloy powder with high Or content.On the other hand, even when added in excess of 1%, the effect is commensurate with the amount added. In addition to not being able to obtain
The moldability of the powder is inhibited.

Mn: A component added to base alloy powder with low Cr content to strengthen the iron base, but if it is less than 0.1%, it has no effect, and if it exceeds 1%, oxidation during sintering becomes a problem. .

It is added to hard alloy powder in order to further increase the hardness of the hard alloy phase dispersed in the phosphorus dibase. The effect is significant at 0.02% or more, but on the other hand, when added in excess of 0.7%, the alloy powder becomes brittle and the compressibility deteriorates.

W, ■, and S: These are as already described in the discussion regarding each sample.

The overall composition of invention (2) of the alloy in this application is derived from the content of invention (2) of the manufacturing method described above, that is, the composition and blending ratio of the base alloy powder, hard alloy powder, etc. Note that hard alloy powder may also contain a small amount of Mn, and when manufacturing alloy powder, a small amount of Mn is added to improve the flow of the molten metal.
Although i may be added, any of them can be regarded as an impurity for the present invention.

As described in detail above, the sintered alloy according to the present invention is significantly superior to conventional valve train members, and has characteristics that can fully meet recent trends in automobile engines. These four types of alloys each have advantages and disadvantages in terms of wear resistance, machinability, and cost, so they should be appropriately selected depending on the characteristics of the engine. Although the above description has been made using an example of application to a valve guide, this material can also be applied to other members 1 of a valve mechanism, such as a valve seat.

Claims (1)

[Claims] 1. Overall composition is Cr...1.8-4% Mn...0.1-1% Mo.
...0.07-1% P...0.06-1.5% Cu or Cu alloy...1-10% W...0.4% or less and V...0.1% or less At least one of S...0.03-0.9%C...1.5-4%Fe
...The remainder exhibits a structure in which 5 to 20% of iron-based hard particles, which have a higher Cr content than the base, and 1 to 10% of copper or copper alloy particles are dispersed in the iron base containing Cr, Mn, and Mo. A wear-resistant iron-based sintered alloy with good machinability. 2 An iron matrix containing Cr, Mn, and Mo, characterized by blending the following powders B, D, and H to a predetermined weight ratio, press-molding, and sintering at a temperature of 980 to 1130°C. A method for producing a wear-resistant iron-based sintered alloy having a structure in which iron-based hard particles having a higher Cr content than the matrix and copper or copper alloy particles are dispersed. B Cr1.8-3.5%, Mn0.1-1%, Mo0
．． Alloy powder of 1-1%, S0.05-1% and balance of Fe, Cr4-10%, Mo0.05-1%, at least one of W2% or less and V0.5% or less, P0.2-0
．． 7% and the remainder of Fe hard alloy powder: 5-20% E Copper powder or copper alloy powder; 1-10% F Fe-10-30% P alloy powder; 0.5-5% G graphite powder; 1.5 ~4%.