JPS5938355A - Iron-base sintered body - Google Patents

Abstract

PURPOSE:To obtain an iron-base sintered body with superior hardenability and machinability, by adding specified percentages of Cu, C and P to iron. CONSTITUTION:Iron powder is mixed with P-Fe alloy powder, copper powder and carbon powder so as to provide a composition consisting of, by weight, 1.5- 2.5% Cu, 0.6-0.9% C, 0.07-0.12% P and the balance Fe with inevitable impurities. The powdered mixture is molded by compression in a mold, heated at 5-12 deg.C/min heating acceleration rate from 840 deg.C-940 deg.C, sintered by holding at about 1,120 deg.C for 15-30min, and cooled at 5-15 deg.C/min cooling rate from 1,138 deg.C-880 deg.C. P-Fe alloy powder having 0.4-0.7% P content passed through a 100-mesh sieve is used as the P-Fe alloy powder. Atomized iron powder passed through a 42-mesh sieve is used as the iron powder. The average particle size of the copper powder is 25-35mum, and the average particle size of the graphite powder is 1-5mum. A lubricant is added to the powdered starting material by 0.5-1.5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an iron-based sintered body having excellent hardenability and machinability, high strength, and high toughness.

In general, iron-based sintered bodies for machine structures can be made into predetermined product shapes as sintered bodies, so cutting of the sintered bodies is rarely performed. However, in the case of complex shapes that are difficult to mold, the obtained iron-based sintered body may be cut. Furthermore, depending on the application, heat treatment such as hardening may be performed to improve wear resistance and the like.

Usually, for sintered bodies that require hardenability, sintered materials such as nickel-molybdenum sintered steel or chromium-manganese sintered steel are used. However, these sintered materials have problems such as high cost and difficulty in sintering with butane-modified reducing gas. Further, although these sintered materials have good hardenability, they also have problems such as poor machinability.

In addition, for ordinary iron-based sintered materials for machine structures, the tensile strength is limited to 50 kg/mm2 at a density of 6°80/cm3, and the elongation is 1°0 to 1.5%. , it is difficult to make an iron-based sintered body with elongation.

The present invention has been made to overcome the above-mentioned problems, and aims to provide an iron-based sintered body that exhibits less deterioration in rigidity, excellent hardenability, low cost, and high strength and toughness.

As a result of examining a large number of iron-based alloys, the inventor found that the resulting sintered body contained 0.07% to 0.12% phosphorus (hereinafter % indicates weight%) to increase rigidity. We have discovered that it is possible to obtain an iron-based sintered body with little deterioration, a hardness of about 800 on the C1 Vickers hardness in heat treatments such as induction hardening and tempering, and low heat treatment distortion, This completes the present invention.

That is, the iron-based sintered body of the present invention contains 1.5 to 2.5% by weight of copper, 0.6 to 0.9% by weight of carbon, and 0.07 to 0.1% of phosphorus.
2%, the balance being iron and other impurities.

In the iron-based sintered body of the present invention, the phosphorus range is 0.07 to 0.12.
% because if the proportion of phosphorus is less than 0.05%, the tensile strength and elongation will be too small. On the other hand, if phosphorus is present in an amount exceeding 0.12%, the stiffness will be extremely deteriorated. The amount of copper is 1.5-2
．． The reason why it is set at 5% is that if it is less than 1.5%, the tensile strength and elongation will not be sufficient, and if it is more than 2.5%, distortion will be large during quenching and tempering. This is because the tensile strength is also insufficient. The reason for setting the carbon content to 0.6 to 0.9% is that if the carbon content is less than 0.6%, the hardening effect will be small and sufficient hardness will not be obtained. If it exceeds the limit, the strain during quenching and tempering will be large and the elongation will be small.

Iron phosphide (F) in the iron particles constituting the iron-based sintered body of the present invention
The particle size of e3P) is preferably about 1 to 5 microns, and is preferably uniformly dispersed within the crystal grains. When the particle size of iron phosphide is smaller than 1 micron, it has no effect on improving mechanical properties. On the other hand, if it is larger than 5 microns, machinability deteriorates. In addition, microscopically, a fine pearlite structure appears, and it is preferable that ferrite containing phosphorus as a solid solution is contained in an area ratio of 5 to 15% and is present in the grains away from the grain boundaries. If the ferrite does not meet this condition, its tensile strength will be low.

Furthermore, the porosity of the iron-based sintered body of the present invention is preferably within 5%. The density is preferably 6.8 or more, more preferably about 6.8 to 7.19/cm3.

This iron-based sintered body! ! 81, the overall composition is 1.5-2.5% by weight of copper, 0.6-0.9% by weight of carbon, 0.07-0.12% by weight of phosphorus, and the balance is iron and unavoidable impurities. The process of mixing phosphorus-iron alloy powder, iron powder, copper powder, and graphite powder to obtain raw material powder. The method is characterized in that it consists of a step of compressing the obtained raw material powder in a mold to obtain a compacted body, and a step of sintering the compacted body to produce an iron-based sintered body. In the step of obtaining this raw material powder, an alloy powder of phosphorus and iron is used as a phosphorus component raw material. As this phosphorus-iron alloy powder, it is preferable to use a phosphorus-iron alloy powder that has a phosphorus content close to that of the obtained iron-based sintered body.

However, it is also possible to use a mixture of a phosphorus-iron alloy powder with a high phosphorus content and an iron powder that does not contain phosphorus by adjusting the ratio of the mixed powder so that it falls within the composition range of phosphorus and iron. . As this phosphorus iron alloy powder, the phosphorus content ff1
An alloy powder consisting of 0.4 to 17% O, balance iron and unavoidable impurities, or a phosphorous iron alloy powder consisting of 14 to 23% phosphorus, balance iron and unavoidable impurities, can be used.

The particle size of these phosphorus-iron alloy powders is preferably fine. However, powder with a fine particle size is expensive, so powders with an average particle size of 35 microns or less or 10
Preferably, a powder that passes through a 0 mesh sieve is used.

As the copper component, it is preferable to use copper powder. It is also possible to use iron and steel alloy powder, but iron and copper alloy powder is hard and difficult to compress. As copper powder, the average particle size is 25~
It is economical to use a 35 micron powder.

Even as graphite powder, fine culm is preferable if it is fine G.
Taking into consideration the cost-effectiveness, it is best to use particles with an average particle size of about 1 to 5 microns. Although it is possible to use carbon powder other than graphite powder, it is difficult and expensive to alloy, and graphite is preferable.

As the iron powder, spray iron powder and other various iron powders can be used. Here, mainly sprayed iron powder was used. In the range of experiments conducted by the present inventor, it is sufficient that the oxygen in the oxide contained in the atomized iron powder has surface oxygen of 100 to 40,0 Oppn and internal oxygen of 5001) H or less. I was able to use it. However, 4000p
When iron powder having surface oxygen of pm or more or internal oxygen of 500 ppm or more was used, it was found that the mechanical properties of the obtained iron-based sintered body deteriorated.

During the sintering process, the heating rate from 840°C to 980°C was set at 5 to 12°C per minute because if the heating rate exceeds 12°C, there would be variations in the appearance of stellite. This is because the grain size of Fe3P becomes excessive and the machinability deteriorates.On the other hand, if the heating rate is less than 5°C, the heating rate is extremely slow and is not practical. If the holding time at the sintering temperature around 30°C is less than 15 minutes, sufficient sintering will not be achieved and both tensile strength and elongation will be low. It is not practical to expect much improvement in tensile strength, elongation, etc. by extension.Therefore, the heating and holding time was set to 15 to 30 minutes.

In the cooling process, if the cooling rate from the heating temperature to 880° C. is rapidly cooled at 15° C. or more per minute, dimensional variations will increase. Further, since a cooling temperature of 5° C. or lower is not practical, the cooling temperature was set at 5° C. to 15° C. per minute.

Examples will be explained below.

In this example, a total of 16 types of iron were used, including 8 types of samples No. 1 to 8 shown in Table 1 within the composition range of the present invention and 8 types of No. 101 to 108 outside the composition range of the present invention. A system sintered body was made. This iron-based sintered body of 16 rods is 8
It is a mixture of iron powder, phosphorus-iron alloy powder, copper powder, and graphite powder so as to have the chemical composition shown in Table 111. In addition to these composition materials, a mold lubricant consisting of 1% of the total amount of zinc stearate was blended. Incidentally, it was used here. As the phosphorus-iron alloy powder, various phosphorus-iron alloy powders containing 0.4% to 21% of phosphorus alloy as shown in Table 1 were used. In addition, phosphorus-iron alloy powder with a phosphorus content of less than 0.8% is 100%
It has passed through the mesh sieve. The phosphorus-iron alloy powders having a phosphorus content of 10% or more had an average particle size of 25 to 35 microns. The graphite powder used had an average particle size of 1 to 2 microns. Further, as the copper powder, a copper powder having an average particle size of 25 to 30 microns was used. Further, as the iron powder for adjusting the composition range of phosphorus and iron, a sprayed iron powder that had passed through a 42-mesh sieve was used. In addition, the surface oxygen amount of the atomized iron powder used was 1500 to 40
00 Dl)m oxygen and internal oxygen, 300-50
01) I) III contained oxygen. Furthermore, as a mixing method for adjusting the raw material powder, A shown in Table 1,
Eighty-two different mixing methods were employed. Mixing method A is to mix all the raw material powders in a predetermined ratio and then mix with a V-type mixer for 30 minutes.
It is mixed for □ minutes. Mixing method B involves first mixing two types of phosphorus-iron alloy powder and copper alloy powder in a V-type mixer for 30 minutes, and then adding atomized iron powder, graphite powder, and mold lubricant to this mixed powder. , and further 30 with a V-type mixer.
This is a mixing method that involves mixing for minutes.

The obtained 16 kinds of raw material mixed powders were put into compression molds, and 4,500 to 7,000 kl per 10,112
A load of ff was applied to obtain a consolidated body having an outer diameter of 50 mm, an inner diameter of 113 mm, a height of 28 RI11, and a JSPM standard. Then, this compacted body was sintered under the sintering conditions shown in Table 1. Note that a butane-modified reducing gas was used as the sintering gas atmosphere.

The properties of the sintered body thus obtained are shown in Table 2. In Table 2, as the characteristics of the sintered bodies, the density, the particle size of iron phosphate in the iron particles by microscopic observation, and the area ratio of ferrite were measured. In addition, the machinability, hardenability, and mechanical properties of the v1 sheet were investigated.

The machinability evaluation test was conducted using a lathe with an outer diameter of 5Q mm and an inner diameter of 18 mm.
Using the ring-shaped machinability evaluation test piece No. 1, the test piece was rotated at 1000 revolutions per minute and the feed rate was 0.05 mm per revolution.
, 5KH57 on the cutting tool under the condition of cutting depth 110n+m
The amount of wear on the cutting tool was measured by cutting without using cutting oil, and the results are shown in Table 2.

As for hardenability, the outer diameter of the obtained sintered body is 5Qnv.
Inner diameter 181! A ring-shaped test piece of lIn was made, and this test piece was heated and held at 900°C for 3 seconds using an induction heating coil, then cooled with water, and further tempered at 350°C for 10 seconds. After this heat treatment, the surface hardness was measured using a 1200g Vickers hardness tester. Incidentally, the quenching strain was measured by the change in the outer diameter roundness.

Mechanical properties were measured using an Instron type tester at room temperature of 20±5°C using JSPM standard 2 tensile test pieces and J15Z2241 metal material tensile test method.
A tensile test was conducted at a tensile rate of 11 NFFL per minute to determine the tensile strength and elongation to break. These results are shown in Table 2.

As is clear from Table 2, within the composition range of the present invention,
The eight types of iron-based sintered bodies, samples No. 1 to No. 8, all exhibited a tensile strength of 60 kg or more and an elongation of 1.5%, and had good mechanical properties. In addition, the hardness after hardening is 660 to 880 on the Vickers scale, and has very good hardenability. Further, the amount of strain was relatively small, about 33 to 87 microns. The wear amount of the cutting tool, which indicates machinability, was about 34 to 95 microns.

The size of iron phosphide in the iron particles constituting the sintered body is 1 to 1.
3 microns, and the ferrite area ratio was 5 to 15%.

As shown in Comparative Samples No. 101 to No. 105, those containing 0.05% of phosphorus had a low tensile strength of 48.9.47 kq, and an elongation of 1.5%. It is as small as 0%. On the other hand, the amount of phosphorus added is 0.15%.
If there are many, sample No. 102, No.

As shown in No. 106, the wear amount of the cutting tool, which indicates machinability, is as large as 258 microns and 271 microns, and the machinability is extremely deteriorated.

When the amount of copper is as small as 1.0%, sample No. 103, No.
As shown in 107, the tensile strength is 42ko.

It weighs 41 kg and has poor mechanical properties with an elongation of 1.0%. On the other hand, when the copper content is as high as 3.5%, it is sample No.

As shown in No. 104, No. 108, the amount of strain indicating hardenability is very large, 153 microns and 137 microns. In addition, it shows mechanical properties and has a tensile strength of 53
The mechanical properties are also poor, with ka and elongation of 0.5%.

Regarding the carbon content, when the graphite blend m is as low as 0.5%, as seen in samples No. 103, No. 107, the tensile strength is 41:9 and the elongation is 1.0%, which is mechanically low. Bad nature. On the other hand, when the graphite content is as high as 1.2%, as seen in samples No. 104, No. 108, the strain during quenching and tempering is large and the elongation is poor.

Claims (9)

[Claims] (1) Quenching characterized by consisting of 1.5 to 2.5% by weight of copper, 0.6 to 0.9% by weight of carbon, 0.07 to 0.12% of phosphorus, and the balance iron and unavoidable impurities. Iron-based sintered body with excellent strength and machinability. (2) t9? The iron-based sintered body according to claim 1, wherein i is 6.8 to 7.1 (1/cm3), tensile strength is 60 kg/mm2 or more, and elongation is 1.0% or more. (3) The particle size of the iron phosphide in the particles constituting the sintered body is 1 to 5 microns, and the area ratio of ferrite is 5 to 15%. The iron-based sintered body according to scope 1. (4) The iron-based sintered body according to claim 3, wherein the iron phosphide is Fe3P. (5) The overall composition is 1.5-2.5% copper, 0.6-0.9% carbon, and 0.07-0°12% phosphorus.
, a step of mixing phosphorus-iron alloy powder, iron powder, copper powder, and carbon powder so that the remaining iron and unavoidable impurities are mixed to obtain a raw material powder, and compressing the obtained raw material powder in a mold to obtain a compacted body. ■ A method for producing an iron-based sintered body with excellent hardenability and machinability, which comprises the following steps: culm, and a step of sintering this compacted body to produce an iron-based sintered body. (6) Phosphorous iron alloy powder with phosphorus content of 0°4 to 0.
6. The manufacturing method according to claim 5, which uses powder passed through a 100-mesh sieve of 7% phosphorus-iron alloy. (7) Phosphorus content m14-23 as phosphorus iron alloy powder
% phosphorus-iron alloy powder having an average particle size of 25 to 35 microns. (8) Iron powder is atomized iron powder that has passed through a 42-mesh sieve, copper powder has an average particle size of 25 to 35 microns, graphite powder has an average particle size of 1 to 5 microns, and The manufacturing method according to claim 5, wherein the raw material powder contains 0.5 to 1.5% of type IIWi agent. (9) In the sintering process, the heating rate from 840°C to 940°C is 5 to 12°C per minute, and the sintering temperature is approximately 1120°C.
The holding time at the sintering temperature is 15-30 minutes, and the cooling rate from 1138℃ to 880℃ is 5 minutes per minute.
The manufacturing method according to claim 5, wherein the temperature is 15°C.