JPH05214497A - High performance low carbon ferrous sintered material and its manufacture - Google Patents

Abstract

PURPOSE:To provide a high performance low carbon ferrous sintered material improved in the deterioration in corrosion resistance and to provide its manufacturing method. CONSTITUTION:This is a high performance low carbon ferrous sintered material in which, in a sintered material having the compsn. of stainless steel having, by weight, 10 to 30% Cr content, the average C content in the whole of the sintered material is regulated to <=0.06% as well as the average O content expressed by weight % exceeds 4/3 of the said average C content and the C content in the depth of at least 10mum from the surface of the sintered material is regulated to <=0.06% as well as the O content is regulated to one less the average O content of the sintered material, and this is its manufacturing method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-performance low-carbon iron-based sintered material containing a non-reducing element and having excellent corrosion resistance, and a method for producing the same.

[0002]

2. Description of the Related Art As a method for producing a sintered material, a method of using a metal powder having a small average particle diameter to obtain a high-density and high-performance material by sintering shrinkage is being developed. Above all,
The method of utilizing injection molding of metal powder (hereinafter referred to as metal powder injection molding method) is a promising technology because it is advantageous for mass production of small and three-dimensionally complex metal parts.

In order to obtain high performance, iron-based sintered materials produced by these methods are generally required to reduce oxides contained as impurities as much as possible. When the metal element contained in the iron-based sintered material is limited to an element that produces only an easily-reducible oxide, a low-oxygen sintered material can be produced by using a hydrogen-containing gas or the like.

However, with regard to the iron-based sintered material containing an element such as Cr, which produces a hard-to-reduce oxide, the amount of the hard-to-reduce metal oxide that can be reduced per unit hydrogen is very small, so that a low-oxygen sintering is performed. To obtain a binder, an excessively large amount of hydrogen having a low dew point is required, and thus a method using hydrogen is difficult to be industrially established.

Therefore, the present inventors have employed a method of directly reacting oxides and carbon contained in a molded body with each other by using heating under reduced pressure to remove as CO gas, thereby sintering low oxygen. A material was obtained (see JP-A-2-138435). However, when a direct reaction between oxide and carbon is used, it is difficult to reduce both oxide and carbon because the reaction rate is proportional to the product of oxide concentration and carbon concentration. If both the oxide concentration and the carbon concentration decrease in the final stage, the reaction rate proportional to the product thereof becomes extremely small.) Therefore, it is necessary to slightly leave either the oxide or the carbon.

[0006]

When reduction of carbon is prioritized over reduction of oxide (low oxygen sintered metal material) from the viewpoint of corrosion resistance, such as stainless steel, some oxide remains. I had to tolerate. As a result, the obtained sintered material contains higher oxygen than the ingot,
There was a problem that the performance was somewhat inferior. Particularly, in stainless steel, the performance such as corrosion resistance of the sintered material was lower than that of the ingot material.

The present invention has a Cr content of 10 to 30 wt%.
It is an object of the present invention to provide a high-performance low-carbon iron-based sintered material having improved corrosion resistance deterioration of the sintered material due to residual oxide, and a manufacturing method thereof.

[0008]

In order to achieve the above object, according to the present invention, in a sintered material having a stainless steel composition with a Cr content of 10 to 30 wt%, the average C content of the entire sintered material is C. Content is 0.06 wt% or less, and the average O content expressed in weight% exceeds 4/3 of the average C content, and the C content is 0 at a depth of at least 10 μm from the surface of the sintered material. 0.06 wt% or less and O content
Provided is a high-performance low-carbon iron-based sintered material, characterized in that the amount is less than the average O content of the sintered material (hereinafter,
In order to clarify which part of the sintered material or molded body the content of impurities is, the content of the sintered material or the whole molded body should be specified as "average" and the content of the surface portion List separately).

Here, the average O content in the entire sintered material is 0.1 wt% or more, and the O content in the depth of at least 10 μm from the surface of the sintered material is 0.05 w.
It is preferably t% or less.

Further, the amount of Cr contained at a depth of at least 10 μm from the surface of the sintered material is 80% of the average amount of Cr contained in the whole sintered material, and the density of the sintered material is relative to the true density. The ratio is preferably 92% or more.

Further, according to the present invention, in the metal powder compact, the average O content expressed in% by weight is the average C content.
After adjusting the amount of O contained in the vicinity of the surface, which is represented by weight% of the molded body, to be 4/3 or less of the amount of C contained in the surface, the amount of 1000 to
Provided is a method for producing a high-performance low-carbon iron-based sintered material, which comprises sintering in a sintering step including a step of heating at 1350 ° C.

Further, according to the present invention, there is provided a method for producing a high-performance low-carbon iron-based sintered material, which comprises heating in a non-oxidizing atmosphere after the heating under vacuum exhaust. To be done.

Here, the heating under vacuum exhaust is performed for 30T.
Orr or less, and heating in a non-oxidizing atmosphere is 12
It is preferable to carry out at 50 to 1400 ° C.

The present invention will be described in more detail below. In order to achieve the above-mentioned object, regarding the components of the surface portion having a depth of at least 10 μm from the surface of the sintered material (hereinafter, simply referred to as “surface portion” unless otherwise specified), the C content is 0.06 wt. %, It is necessary that the O content is lower than the average O content of the entire sintered material.

When the amount of C contained in the surface exceeds 0.06 wt%, the corrosion resistance is inferior to that of the ingot material and it cannot be used. Therefore, the C content in the surface portion needs to be 0.06 wt% or less. Further, if the content of O in the surface portion is equal to or more than the average content of O in the entire sintered material, the corrosion resistance becomes lower than that of the conventional simple sintered material. Therefore, it is necessary that the O content in the surface portion is lower than the O content in the entire sintered material. Further, usually, since any defects such as pores and scales are present on the surface of the sintered body, it is necessary to polish the depth direction to at least several μm or more.
When the depth of the surface portion is less than 10 μm, the thickness of the surface portion after polishing is not sufficient, and the effect of improving the corrosion resistance of the surface portion cannot be expected sufficiently. Therefore, the thickness of the surface part is 10
It must be at least μm. However, the thickness of the surface portion is preferably thicker, and is preferably 300 μm or more in order to perform grinding or the like.

Next, for the entire sintered material, it is necessary that the average C content is 0.06 wt% or less and the average O content exceeds 4/3 of the average C content.

The average C content of the sintered material is 0.06 wt%
When it exceeds, the carbon diffuses from the inside of the sintered body to the low C region of the surface portion when the heat treatment or the like is performed in a later step, and the C content of the surface portion exceeds 0.06 wt%. Therefore,
The average C content of the entire sintered material needs to be 0.06 wt% or less. On the other hand, the average content O of the sintered materials as a whole
4/3 of the average C content of the sintered material
If it is below, the reaction rate in the final stage of the direct reaction of C and O becomes small, and therefore it takes a long time to set the average content of C in the entire sintered material to 0.06 wt% or less. Therefore, it is necessary that the average O content exceeds 4/3 of the average C content.

Further, the Cr content in the surface portion of the sintered material is 80% or more of the average Cr content of the entire sintered material, and the ratio of the density of the sintered material to the true density is 92% or more. Is preferred.

In the case of a Cr-containing alloy such as stainless steel,
When heated under reduced pressure, Cr evaporates from the surface of the sintered body, and as a result, the Cr concentration near the surface becomes lower than that in the inside of the sintered body. In the case of stainless steel, a decrease in the Cr concentration on the surface causes deterioration of corrosion resistance. Therefore, it is preferable that the content of Cr in the surface portion having a depth of at least 10 μm from the surface of the sintered material is 80% or more of the content of Cr in the entire sintered material. The characteristics of the sintered material are better as the density is higher. Especially, the ratio to the true density is 9
It is preferable that it is 2% or more because the pores in the sintered body become closed pores.

Next, a method for producing the high-performance low carbon iron-based sintered material of the present invention will be described. As a method for producing the sintered material of the present invention, it is necessary to control C and O, which are impurities contained in the metal powder compact, prior to sintering.
For the average impurities of the whole compact, the average O content exceeds 4/3 of the average C content in weight%, and for the impurities of the surface portion of the sintered material, the O content is 4 / of the C content.
It is necessary to adjust it so that it is 3 or less.

When the average content of O is 4/3 of the average content of C in weight%, O and C react in a molar ratio of 1: 1 to produce CO gas. In this case, in the final stage of the CO gas generation reaction, both O and C in the sintered material decrease, and as a result, the reaction rate that can be expressed by the product of the O content and the C content decreases. Therefore, the molar ratio of O and C is 1: 1.
By further shifting, it is necessary to secure a reaction rate above a certain level even in the final stage of the CO gas generation reaction. Further, when the molar ratio of the content of O and the content of C is made O-rich, a sintered body having an extremely low C containing a certain amount of O remains as O and C.
When the molar ratio of C and C is set to be C-rich, an extremely low-O sintered body in which C remains to some extent can be obtained in a short time.

That is, it is necessary to adjust the amount of O contained in the surface portion of the sintered material so as to be less than 4/3 of the amount of C contained in the surface of the sintered body as a result of the CO generation reaction in a short time. This is to obtain an extremely low O sintered body in which C remains to some extent. Regarding the average impurities of the entire compact, it is necessary to adjust the average O content to exceed 4/3 of the average C content as a result of a short-time CO formation reaction, as a result of excluding the surface of the sintered body. This is because the inside of the sintered body is an extremely low C, in which O remains to some extent.

The surface of the sintered material became an extremely low O sintered body in which a certain amount of C remained, and the inside of the sintered body became an extremely low C sintered body in which a certain amount of O remained (hereinafter, in this state. The reaction until the reaction is called the first stage reaction), and then CO
When the production reaction is continued, the residual C on the surface of the sintered body rapidly diffuses inside the sintered body and reacts with O of the oxide remaining inside the sintered body (hereinafter, the reaction until this state is reached). Is called the second stage reaction). At this time, residual C on the surface
Is a small amount compared to the residual O in the interior, so that a reaction rate above a certain level can be secured, and after a short time, the O inside the sintered body is slightly reduced and the surface of the sintered body becomes extremely low C. The sintered material of the present invention has an extremely low C throughout the sintered body, an extremely low O on the surface of the sintered body, and a small amount of O remaining inside the sintered body.

The thickness of the surface portion of extremely low C and extremely low O is the first
It can be controlled by the thickness and the C concentration of the C-rich portion of the surface portion before the reaction of the step, and the thicker the C-rich portion is and the higher the C concentration is, the thicker it can be. However, it should be noted that an extremely low C sintered body cannot be obtained unless the average O content of the entire compact is in the range of 4/3 of the average C content in terms of weight%. Further, the position of the C-rich portion of the surface portion before the reaction in the first step may be in the vicinity of the surface of the molded body, and may be in the range where C of the C-rich portion can contribute to the reaction in the second step.

As described above, in order to make the vicinity of the surface of the metal powder compact C rich before the reaction of the first step, once the entire compact is made O rich, and then the C of the surface of the compact is increased. Easy to apply. However, it does not control this method. The method of controlling C and O will be described later.

In the sintering method of the present invention, at least a part of the sintering needs to be heated while evacuating, and the heating and holding temperature is 1000 to 1350 ° C.
Is preferred.

The contained O and the contained C are converted into CO by heating.
Produces gas. The equilibrium pressure of the produced CO gas depends on the temperature, but the reaction proceeds until the equilibrium pressure of CO is reached. That is, in order to continue the reaction, it is necessary to keep the produced CO gas pressure lower than the equilibrium pressure until the reaction is completed. As a method therefor, there is a method in which an inert gas is used as a carrier and CO gas is carried out of the reaction system. However, when a hardly-reducing metal oxide is contained, the CO equilibrium gas pressure is low, and therefore a large amount of CO gas is generated. It requires carrier gas and is not realistic. Therefore, as the only method, evacuation is required to carry the CO gas out of the reaction system.

The lower limit of the heating temperature is set to 1000 ° C. so that the CO equilibrium gas pressure is sufficiently high and the reaction rate is sufficiently high so that the reaction can be carried out effectively in a short time. When the heating temperature is lower than 1000 ° C., the CO equilibrium gas pressure of the reaction of the hardly reducing metal oxide and C is low and the reaction rate is not sufficient, so that it is difficult to complete the reaction in a short time. Become. Therefore, the lower limit temperature for heating needs to be 1000 ° C.

On the other hand, if the temperature is too high, the sintering of the powders will be remarkably fast and the sintered body will become dense and the pores will not be open pores (pores connected to the surface of the sintered body). As a result, the passage for the CO gas of the reaction product to escape from the sintered body is blocked, and it becomes difficult to complete the reaction in a short time. When the heating temperature exceeds 1350 ° C., the metal element having a higher vapor pressure than that of the sintered body is vaporized and composition distortion occurs. In particular, in the case of stainless steel containing Cr, the Cr concentration in the surface portion decreases, the surface portion has no stainless composition, and the corrosion resistance is significantly impaired. Therefore,
The upper limit temperature of heating in vacuum is preferably 1350 ° C.

Preferably, it is true up to 0.01 Torr or less.
Increase vacancy or H at the same time as evacuation ₂Gas or inert gas
The reaction can be completed efficiently and in a short time by introducing
It H₂When introducing gas or inert gas, pop capacity
The pressure within the range that does not deteriorate is preferable.
It is preferably set to Torr or less. Inactivity introduced here
From the viewpoint of availability, argon or nitrogen is preferable as the oxidative gas.

Further, for improving the density of the sintered body, and for Cr-containing alloys such as stainless steel, Cr is diffused from the inside of the sintered body to the low Cr portion of the surface of the sintered body which is inevitably generated during vacuum heating. In order to obtain the Cr concentration equal to that of the inside, after evacuation, in a specific oxidizing atmosphere, 1250
It is preferable to heat at ˜1400 ° C. As the non-oxidizing atmosphere that can be used at this time, an inert gas such as argon or nitrogen, a reducing gas such as hydrogen, or the like can be used.

The preferred embodiments of the present invention will be described in detail below. The raw material powder used in the present invention is water atomized powder,
Gas atomized powder, oil atomized powder, carbonyl powder, reduced powder, crushed powder and the like can be used alone or as a mixed powder. These powders are used by adjusting the average particle size and particle size distribution by classification or the like, if necessary. Further, the alloy component may be added as a mixed powder such as a metal oxide. The average particle size of the raw material powder is preferably 3 to 30 μm so that the final sintered body density ratio is preferably 92%.

The raw material powder of the present invention is molded by adding a molding aid, if necessary. As the molding, a general powder metallurgy press, injection molding or the like can be applied.

When a powder metallurgical press is applied, metal soap such as zinc stearate and organic compounds such as fats and oils are used as a molding aid, as is well known. The molding aid used is about 0.5 to 5 wt% with respect to the raw material powder. The molding pressure is usually about 0.3 to 10 t / cm ² .

When injection molding is applied, as is well known, an organic binder mainly containing a thermoplastic resin, waxes, a plasticizer or a mixture thereof is used as a molding aid. The mixing ratio of the organic binder and the raw material powder is about 30:70 to 70:30 in terms of volume. Injection molding pressure is about 0.3 to 3 t / cm ² , cylinder temperature of the molding machine is 80 to
The mold temperature is about 300 ° C and the mold temperature is about 5 to 50 ° C. However, the above molding method is only an example, and any powder molding method can be applied as long as a molded body can be obtained.

If necessary, the molding aid obtained by the powder metallurgy press or the injection molding is removed from the molding aid prior to sintering. As is well known, heat treatment is usually used to remove the molding aid, and an atmosphere such as an inert gas such as nitrogen or argon, a reducing gas such as a hydrogen-containing gas, a vacuum, a pressurized gas or the atmosphere is used. Applicable. The heating conditions need to be changed depending on the amount and type of the molding aid as is known, but the heating rate is about 10 ° C / hour to 100 ° C / minute, and the maximum temperature is about 400 to 800 ° C. Yes, keep at maximum temperature as needed. In the case of a press-molded body that does not use a large amount of molding aid, the risk of defects occurring at the time of removing the molding aid is low, so the temperature increase rate is 1 ° C / min to 100 ° C in consideration of economy. / Min. In the case of an injection-molded article containing a large amount of molding aid, the risk of occurrence of defects during removal of the molding aid is high.
Time is about 10 ° C / minute.

At this time, the degreased body obtained is once made to be O-rich. Therefore, the amounts of C and O contained in the raw material powder are controlled in advance. Alternatively, the oxygen potential of the heating atmosphere is controlled to be O-rich.

Subsequently, the surface of the degreased body which has become O-rich over the entire compact is made C-rich prior to vacuum heating. This C-rich process may be performed prior to the final vacuum heating in terms of the process, and C and O may be removed to some extent by vacuum heating for a short time while remaining O-rich.
The vicinity of the surface can be made C-rich by heating by creating a so-called carburizing atmosphere with a CO-containing gas such as RX gas or methane gas. This carburizing atmosphere is known as a general "carburizing method for metallic materials". This heating may be performed in the temperature range of 600 to 1150 ° C. for about 10 to 180 minutes in order to make only the vicinity of the surface C-rich. It is also possible to immerse the O-rich compact in a liquid containing a C source such as graphite, evaporate the liquid, and deposit only the C source on the surface of the compact.

The sintered material of the present invention is obtained by heating the thus obtained C-rich compact only in the vicinity of the surface in a vacuum exhaust tank as described above.

[0040]

EXAMPLES The present invention will be specifically described below based on examples.

Example 1 As a raw material powder, the average particle size was 8.5 μm, the C content was 0.05 wt%, and the O content was:
0.62 wt% SUS316 composition (Cr: 17.8w
t%, Ni: 13.8 wt%, Mo: 2.6 wt%, S
i: 0.82 wt%, Mn: 0.75 wt%, P: 0.
011 wt%, S: 0.007 wt%) water atomized powder was prepared. A raw material for injection molding was obtained by adding and kneading 9.5 g of an organic binder to 100 g of the raw material powder.
The organic binder is acrylic resin 25 wt%, polypropylene 10 wt%, EVA resin 25 wt%, DBP15w
t% and 25 wt% synthetic paraffin wax were used.

This injection molding raw material was injection molded at 150 ° C. into a rectangular parallelepiped test piece having a length of 45 × a width of 15 × a thickness of 4 mm. Each of the obtained injection-molded articles was heated to 250 ° C. in nitrogen over 2 days, further heated to 600 ° C. in 12 hours, held for 1 hour, and then cooled.

Then, this was heated in hydrogen at a dew point of + 5 ° C. to 450
By holding at ˜600 ° C. for 20 minutes (hereinafter referred to as hydrogen treatment), the amounts of C and O contained were adjusted to obtain a degreased body. Furthermore, a part of the degreased body is heated to 1050 ° C. at a rate of + 5 ° C./min under a vacuum of 0.001 Torr,
After holding for 1.5 hours, it was cooled (hereinafter referred to as temporary sintering) to prepare a temporary sintered body.

The degreased body and the pre-sintered body are 0.001
In a vacuum of Torr, the temperature was raised to 1030 ° C. at a rate of + 10 ° C./min, methane gas was introduced and held at 300 Torr for 5 minutes, then supply of methane gas was cut off, argon gas was introduced, and cooling was performed to 200 ° C. in 1 hour. (Hereinafter, described as methane gas treatment).

Table 1 shows the C content and the O content before sintering. The degreased body and the pre-sintered body are uniformly O-rich or C-rich over the entire test piece, and the methane gas treated body is C-rich near the surface of the test piece and O-rich in the remaining inside. ..

The degreased body, the pre-sintered body and the methane gas treated body were heated to 1160 ° C. at a rate of + 10 ° C./min under a vacuum of 0.001 Torr and held for 3 hours, and then in an argon gas atmosphere at + 10 ° C. The temperature was raised to 1350 ° C. at a rate of / min and held for 4 hours, then cooled to complete sintering. The density, C and O contents of the sintered body were measured, and the pitting corrosion potential was measured to evaluate the corrosion resistance. The characteristics are shown in Table 1.

As is clear from Table 1, when the overall analysis value before sintering is C-rich (ΔO is negative) (Comparative Example 1), the average C content is C even after sintering using vacuum. 0.
It cannot be made less than 06 wt%, and as a result, the pitting corrosion potential becomes extremely low, and corrosion resistance cannot be expected. In addition, the content of C in the vicinity of the surface of the sintered body due to carburization by methane gas treatment
When the amount was not increased and the surface portion was not made to be C-rich (where ΔO is negative) (Comparative Example 2), the surface of the final sintered body could not be made to have an extremely low O, so that the pitting potential was similar to that of the ingot material. Cannot be raised to.

On the other hand, the average C content in the entire sintered body is C.
The amount is less than 0.06 wt% and 1 from the surface of the sintered body.
In the range of 0 μm, all of the sintered materials of the present invention having a surface-containing O content much lower than the inside of the sintered body have SUS3 because the surface of the sintered body has extremely low O and extremely low C.
It showed a pitting potential comparable to that of 16 L ingot (Comparative Example 3) (Invention Examples 1 to 5). Further, in the production of the sintered material of the present invention, the entire compact is once made to be O-rich (ΔO is a positive number), and thereafter the amount of carbon in the vicinity of the surface of the compact is increased to make the surface C-rich (ΔO is negative). It can be efficiently manufactured by the method of (1). Further, it is not necessary to increase the carbon immediately after degreasing (Invention Examples 1 and 2) or to some extent after removing C and O (Invention Examples 3 to 5) and before heating in vacuum. I know it's good.

(Example 2) The methane gas treating material shown in Example 1 of the present invention of Example 1 was sintered by changing only the vacuum heating and holding temperature. The holding temperature is shown in Table 2 together with the evaluation results. As is clear from Table 2, the heating and holding temperature is 100.
When the temperature is lower than 0 ° C (Comparative Example 4), the reaction between C and O does not proceed sufficiently, and as a result, only a sintered material having a high average C content is obtained. Therefore, the pitting corrosion potential was extremely low, and corrosion resistance could not be expected at all. Moreover, when the heating and holding temperature exceeds 1350 ° C. (Comparative Example 5),
Due to the evaporation of Cr from the surface of the sintered body, the Cr concentration on the surface of the sintered body became low. As a result, a sintered material with a low pitting corrosion potential was obtained for which corrosion resistance cannot be expected. From the above, it can be understood that the heating and holding temperature for sintering needs to be 1000 to 1350 ° C.

(Example 3) In order to further confirm the effect of the present invention, as raw material powder, SU having an average particle size of 9.5 μm, C content: 0.02 wt% and O content: 0.15 wt% is used.
S316 composition (Cr: 17.3 wt%, Ni: 12.4)
wt%, Mo: 2.7 wt%, Si: 0.94 wt%,
Mn: 0.22 wt%, P: 0.020 wt%, S:
0.009 wt%) gas atomized powder was prepared. 6.5 g of the same organic binder as in Example 1 was added and kneaded with 100 g of the raw material powder to obtain a raw material for injection molding. Thereafter, injection molding was performed in the same manner as in Example 1. All the obtained injection-molded articles were heated to 250 ° C. in nitrogen over 2 days, further heated to 600 ° C. in 12 hours, held for 1 hour, and then cooled to complete degreasing and degreasing ( No hydrogen treatment was performed). Also, add 3 g of camphor and 0.5 g of zinc stearate to 100 g of the raw material powder,
A rectangular parallelepiped test piece having a length of 25 mm, a width of 25 mm and a thickness of 10 mm was press-molded at ² t / cm ² , heated in hydrogen at a rate of + 10 ° C./min to 650 ° C., held for 2 hours, and then cooled. Degreasing (dewaxing) was completed.

The obtained degreased body was heated to 920 ° C. at a rate of + 10 ° C./min in a vacuum of 0.001 Torr,
A butane decomposition gas containing 0.20% of CO ₂ was flowed in and 10
After holding for a minute, the supply of the butane decomposition gas was stopped, the argon gas was introduced, and the mixture was cooled to 200 ° C. for 1 hour, whereby only the degreased body surface portion was made C-rich. The degreased body treated with butane decomposition gas and the degreased body not treated with butane decomposition gas were sintered and evaluated in the same manner as in Example 1 (see Table 3).

As is clear from Table 3, as long as the C and O of the molded body are adjusted and then heated in vacuum, the molding method may be injection molding (Invention Example 9) or press molding. (Invention Example 10) A sintered material having an excellent surface property in which the surface portion has extremely low C and extremely low O can be obtained. The properties showed excellent corrosion resistance as indicated by the high pitting potential.

The preferred examples of the present invention, particularly the stainless steel, have been described above. However, the present invention can be widely applied to the improvement of the surface properties of low-carbon iron-based sintered materials including a metal element that forms a non-reducible oxide.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

[Table 3]

[0057]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, regarding the sintered material having a stainless steel composition with a Cr content of 10 to 30 wt%, the average C content in the average impurities of the entire sintered material is Of 0.06 wt% or less and the content of O at a depth of at least 10 μm from the surface of the sintered material.
By making the amount lower than the average O content of the whole sintered material, the effect of improving the corrosion resistance of the sintered material is exhibited.
In addition, the amount of the component represented by weight% is included in advance for the average component of the entire compact, the average O content exceeds 4/3 times the average C content, and the surface component near the surface of the sintered material is included. After the O content is adjusted to be less than 4/3 times the C content, the sintered material can be efficiently produced by heating at 1000 to 1350 ° C. in vacuum at least in a part of the sintering step. Has the effect.

Claims (8)

[Claims] 1. In a sintered material having a stainless steel composition with a Cr content of 10 to 30 wt%, the average C content of the whole sintered material is 0.06 wt% or less, and the average O content expressed as a weight percentage. Content is more than 4/3 of the average C content, the C content is 0.06 wt% or less at a depth of at least 10 μm from the surface of the sintered material, and the O content is the average O content of the sintered material. High-performance low-carbon iron-based sintered material characterized by being less than the amount. 2. The average O content of the whole sintered material is 0.1.
The high-performance low-carbon iron-based sintered material according to claim 1, wherein the content of O is 0.05 wt% or less at a depth of at least 10 μm from the surface of the sintered material. 3. At least 10 μ from the surface of the sintered material.
The high-performance low-carbon iron-based sintered material according to claim 1 or 2, wherein the content of Cr in the depth of m is 80% or more of the average content of Cr in the entire sintered material. 4. The high-performance low-carbon iron-based sintered material according to claim 1, wherein the ratio of the density of the sintered material to the true density is 92% or more. 5. The metal powder compact has an average O content expressed in wt% exceeding 4/3 of the average C content, and the O content near the surface expressed in wt% of the compact. A high-performance low-carbon iron-based firing characterized by performing a sintering step including a step of heating at 1000 to 1350 ° C. while evacuation at least after adjusting the surface content C to 4/3 or less. A method of manufacturing a binding material. 6. The method for producing a high performance low carbon material according to claim 5, wherein the heating under vacuum exhaust is performed at 30 Torr or less. 7. A high-performance low-carbon iron-based calcination characterized by heating in a non-oxidizing atmosphere after the heating under vacuum exhaust by the method for producing a sintered material according to claim 5 or 6. A method of manufacturing a binding material. 8. The heating under vacuum evacuation is 30 Torr or less, and the heating in the non-oxidizing atmosphere is 1250 to 1400.
The method for producing a high-performance low-carbon iron-based sintered material according to claim 7, wherein the method is performed at ℃.