KR20190124547A - Iron based powders for powder metallurgy and its manufacturing method - Google Patents

Abstract

The present invention relates to an iron-based powder for a powder metallurgy for high-strength and high-toughness and a manufacturing method thereof. More specifically, the present invention relates to the iron-based powder for the powder metallurgy for high-strength and high-toughness and the manufacturing method thereof capable of reducing an amount of addition of an element affected by a sintering atmosphere at the same time while adding the elements which are less affected by the sintering atmosphere while having little influence on formability on an iron base, and the materials manufactured by a powder metallurgy process are capable of having a physical property of high-strength and high-toughness. The present invention relates to the iron-based powder for powder metallurgy comprising: 0.2-2.5 wt% of Mo; 0.1-0.6 wt% of P; 0.1-0.5 wt% of Mn; 0.1-0.8 wt% of Si; 0.1-1.0 wt% of Sn; and the remaining balance consisting of Fe and inevitable impurities.

Description

Iron-based powder for powder metallurgy for high strength and toughness and its manufacturing method {Iron based powders for powder metallurgy and its manufacturing method}

The present invention relates to an iron powder for powder metallurgy for high strength and high toughness, and a method of manufacturing the same. More specifically, the iron base is added to the iron base while the element is less affected by the sintering atmosphere while the moldability is less adversely affected. The present invention relates to an iron-based powder for powder metallurgy for high strength and high toughness which can make the materials produced by the powder metallurgy process have high strength and high toughness physical properties by reducing the amount of the elements to be affected, and a method of manufacturing the same.

In general, the powder metallurgy method refers to a method of manufacturing a component having rigidity by combining metal powder by compression molding and heat treatment, that is, sintering.

The most common processes in the powder metallurgy process for manufacturing parts are compression molding and sintering, which compress the powder by shortening it from a closed die to a punch to produce the product, and then diffusion bonding can occur between the compressed metal particles. The sintering process is performed at a sufficient temperature so that

The powder metallurgy process as described above has less mechanical processing than the casting or forging process and has an economical advantage because the amount of material loss is small. However, the powder metallurgy has a disadvantage that strength may be reduced due to internal pores generated during the production process. To compensate for these disadvantages and to be made of a high strength material, excessive alloying elements are used in comparison with casting materials and forging materials.

When a large amount of alloying elements are added in the process of manufacturing powder metallurgy powder by compression molding and sintering, physical properties such as strength and hardness are increased, but moldability is lowered, resulting in lower molding density and thus economical efficiency. It has a disadvantage.

In addition, when more kinds of alloying elements are added to compensate for these disadvantages, not only the moldability is lowered but also the economic cost increases.

In order to solve this problem, a process of pre-sintering at low temperature after compression molding and recompressing, followed by second sintering, or sintering after compression molding using a sinter forging method, and forging by taking out at high temperature Although this has been developed, such a prior art has a problem that the process is complicated and economical and the alloying elements cannot be reduced much.

In recent years, research has been actively conducted to develop lean alloys, which are low alloy steels in which a small amount of various elements are added instead of reducing the amount of expensive alloying elements added.

A lean alloy is a low alloy steel that minimizes the content of alloying elements while maintaining physical properties, and is economical instead of expensive elements such as nickel (Ni) and molybdenum (Mo) to improve properties. , Manganese (Mn), such as added, in the case of powder metallurgy steel lean alloys have the advantage of increasing the economic efficiency, but not only the moldability is deteriorated, chromium (Cr), silicon ( Additional elements such as Si) and manganese (Mn) have a difficulty in maintaining a difficult atmosphere during the sintering process due to an increase in affinity for oxygen.

1. Republic of Korea Patent Publication No. 10-2017-0080668 (published Jul. 10, 2017) 2. Republic of Korea Patent Publication No. 10-0978901 (August 31, 2010)

The present invention has been made to solve the problems of the prior art as described above, the object of the present invention is to add less elements to the sintering atmosphere and less affected by the sintering atmosphere while less adversely affect the formability to the iron base The present invention provides a powder metallurgical powder for high strength and high toughness, and a method for manufacturing the same, which enable the production of materials having high strength and high toughness physical properties by powder metallurgy.

In addition, the present invention is to maintain the ferrite phase at the time of sintering to increase the sintering properties, high-density molding and high-temperature sintering powder metallurgy for high strength high toughness to ensure the desired strength and toughness by a simple process through a simple process Another object is to provide a powder and a method of manufacturing the same.

The present invention for achieving the above objects,

Iron-based powder for powder metallurgy, containing 0.2 to 2.5% by weight of Mo, 0.1 to 0.6% by weight, 0.1 to 0.5% by weight of Mn, 0.1 to 0.8% by weight of Si, and 0.1 to 1.0% by weight of Sn, the balance being Fe and It is characterized by consisting of inevitable impurities.

At this time, the content of Mo is characterized in that 0.2 to 0.85% by weight.

In addition, the content of P is characterized in that 0.2 to 0.5% by weight.

In addition, the content of Mn is characterized in that 0.1 to 0.35% by weight.

In addition, the content of Si is characterized in that 0.1 to 0.4% by weight.

In addition, the Sn content is characterized in that 0.1 to 0.5% by weight.

And, the iron-based powder is characterized in that it further comprises 0.1 to 0.55% by weight of C.

In addition, the iron-based powder is obtained through a process of compression molding and sintering, it characterized in that to maintain a molding density of 7.45g / cm 3 or more and maintain a density of 7.40g / cm 3 or more after sintering.

On the other hand, the iron metal powder manufacturing method for powder metallurgy according to the present invention is a compression molding step of compression molding at a high pressure of 700MPa or more by adding C 0.1 ~ 0.55% by weight to Mo, P, Mn, Si, Sn, Fe having the above content; , Sintering step of sintering the green compact formed in the compression molding step at a temperature of 1,200 ~ 1,350 ℃.

At this time, the molding pressure applied in the compression molding step is characterized in that 800 ~ 1,300MPa.

According to the present invention, it is possible to produce materials having physical properties of high strength and high toughness by the powder metallurgy method by adding elements to the iron base which are less adversely affectable to moldability but less affected by the sintering atmosphere.

In addition, according to the present invention by limiting the element and its content added to the iron base to maintain the ferrite phase during sintering to increase the sintering properties, secure the desired strength and toughness by a simple process through high density molding and high temperature sintering It has the effect of making it possible.

In addition, according to the present invention it is possible to sinter in the ferrite region while minimizing the addition of P which may cause brittleness by the combination of Mo, Si and Sn to be added as additives can greatly increase the sinterability, instead of Cr (chromium) The addition of a small amount of Mn together with Si further has the effect of achieving high strength by the interaction between Mn and Si.

1 is a view showing an example of a general Fe-P state diagram.

Hereinafter, with reference to the accompanying drawings it will be described in detail preferred embodiments of the powder metallurgy powder for high strength and high toughness according to the present invention and a manufacturing method thereof.

According to the present invention, materials produced by the powder metallurgical method have high strength and high toughness by adding elements to the iron base which are less adversely affected by sintering atmosphere while reducing moldability. The present invention relates to a powder metallurgy powder for high strength and high toughness and a method for manufacturing the same, which may have physical properties. First, a powder metallurgy powder for high strength and high toughness according to the present invention (hereinafter referred to as 'iron-based powder') Contains Mo (molybdenum), P (phosphorus), Mn (manganese), Si (silicon) and Sn (tin) and the balance comprises Fe (iron) and unavoidable impurities.

In more detail, the Mo (molybdenum) serves to improve the strength and hardness of the iron-based powder, because it harden the iron particles when alloyed with iron while greatly helping in high strength, high strength because It is widely used as a sintering material.

When Mo is added, such as Si, Cr, Mn, etc., the mechanical properties are increased by interaction, especially in the case of Si, ie Si added with Mo, even if a small amount of P is added to promote the formation of ferrite and It also serves to increase the hardenability after sintering.

At this time, Mo is about 0.2 to 2.5% by weight of the total iron-based powder is added, when the content of Mo is less than 0.2% by weight, the effect of the above-described Mo is not shown well, when it exceeds 2.5% by weight at high pressure There is a fear that the moldability of the resin may deteriorate.

In addition, since Mo is expensive compared to other elements, the Mo content is preferably added in an amount of 0.2 to 0.85% by weight in consideration of economical efficiency.

Next, P (phosphorus) serves to lower the sintering temperature and promote sintering by inducing a liquid phase while stabilizing the ferrite phase.

That is, the P is a liquid phase is formed by a process reaction at a relatively low temperature during sintering, and acts as a ferrite structure stabilizing element to promote the formation of ferrite has a high iron diffusion degree of several hundred times higher than austenite structure at high temperature Therefore, the effect of increasing the self-diffusion rate can be shown.

In addition, the P exhibits a solid solution effect even with a small amount of addition, which not only has the advantage of contributing to the high strength of the sintered product, that is, the iron powder, but also increases the sintering density and makes the pores inside the material to be spherical in strength, hardness and ductility. It can have the effect of improving everyone.

In this case, the content of P is different depending on the type and the amount of the added element, the region where the ferrite region appears and the region where the complete ferrite appears, it is preferred that about 0.1 to 0.6% by weight of the total iron powder is added.

In other words, when the P content is less than 0.1% by weight, the above-described effect of P is hardly exhibited. When the P content is more than 0.6% by weight, the sinterability is increased, but the risk of brittleness between particles is also increased. This is because the strength of the powder is lowered.

In addition, the content of the elements constituting the iron-based powder may be influenced by the content of other elements to be added, which is the gamma loop region that appears depending on the added element, that is, the region where the ferrite phase appears and the gamma loop completely becomes a ferrite region. This is because the area is different.

In the case of the iron-based powder according to the present invention, as a result of examining the influence between the elements to be added, in order to prevent intergranular brittleness and the above-described effect of P, the ferrite region may be formed with an amount of P as small as possible. It is better to make it appear. Therefore, if the content of P in the general Fe-P state diagram is more than 0.6% by weight, it is preferable to limit the content of P to 0.6% by weight or less by adjusting the amount of remaining ferrite-forming elements even if the ferrite region appears. desirable.

In this regard, Figure 1 shows the maximum value of the gamma loop in the Fe-P state diagram where the x-axis is the content of P and the y-axis is the temperature, respectively (Table 1) below by the ThermoCalc program. The maximum value of gammaloop, X1, X2, or P, calculated according to the calculated added elements and content, is shown in comparison with the pure Fe-P state (% in Table means weight%).

Furtherance X1 X2 Remarks Fe-P 0.30 0.60 Fe-0.5% Mo-P 0.27 0.53 -Mo, P ferrite forming element Fe-1.0% Mo-P 0.20 0.45 Fe-0.5% Mo-0.3% Si-P 0.20 0.43  -Si ferrite forming element Fe-0.5% Mo-0.5% Si-P 0.16 0.36 Fe-0.5% Mo-0.75% Si-P 0.12 0.29 Fe-0.5% Mo-0.2% Mn-0.2% Si-P 0.29 0.60 -Mn ferrite blocking element Fe-0.5% Mo-0.2% Mn-0.8% Si-P 0.18 0.42 Fe-0.5% Mo-0.5% Sn-0.2% Si-P 0.18 0.42  -Sn ferrite forming element Fe-0.5% Mo-0.5% Sn-0.6% Si-P 0.09 0.28 Fe-0.5% Mo-0.25% Sn-0.5% Si-P 0.17 0.37 Fe-0.5% Mo-0.75% Sn-0.5% Si-P 0.05 0.25

As can be seen in Table 1, in the case of pure Fe-P state, the maximum value of gammaloop X2, that is, the content of P is 0.6% by weight, as in the present invention, Mo, Si, Mn, It can be seen that when the Sn is used, the content of P can be reduced because the maximum value of gamma loop X2 can be lowered.

In addition, in the case of using elements such as Sn (tin) which have a large influence on the closing of the gamma loop, the content of P is limited to 0.5% by weight or less, and in order for the above-described effect of P to be properly expressed, It is preferable to make content into 0.2 weight% or more.

Next, Mn (manganese) serves to promote the sintering and at the same time to improve the hardenability after sintering, it may show a more improved effect when added together Si, P and Sn than used alone.

At this time, the Mn is about 0.1 to 0.5% by weight of the total iron-based powder is added, when the Mn content is less than 0.1% by weight of the above-described effect of the action of Mn does not appear well, when the content of Mn increases the iron-based powder It is preferable that the content of Mn be limited to 0.5% by weight or less, more preferably 0.35% by weight or less, because there is a risk that the sinterability may be inhibited by affinity with oxygen as well as the moldability being lowered.

Ni (nickel) and Cr (chromium) may be used as elements capable of exhibiting a similar effect to Mn. However, when Ni and Cr are used, formability is lowered compared to Mn.

In addition, when Cr is used, not only the tendency of suppressing ferrite is higher than that of Mn, but also a lot of influence of the atmosphere during sintering, and a large amount of Mn must be used, thereby degrading moldability and economic efficiency.

Next, Si (silicon), like P, is an additive that promotes the formation of ferrite and serves to contribute to the high strength of the iron-based powder while reducing the content of P.

In more detail, the high strength due to Si is due to the increase in the strength of the ferrite due to the solid solution strengthening, and when the Mn and Mo are added at the same time than when used alone, the effect of improving the hardenability due to the synergy can be seen. have.

In addition, when Si is added, the tendency to harden up to the inside of the iron-based powder is increased, so that the impact strength is improved, and accordingly, the iron-based powder may be improved in performance.

In this case, about 0.1 to 0.8% by weight of the total iron-based powder is added to the Si, when the content of Si is less than 0.1% by weight, the amount is too small, the effect of the above-mentioned Si does not appear well, the content of Si is high In case of hardness, hardness, strength and impact energy increase, but it causes expansion during sintering, thereby decreasing density and degrading moldability.

In other general sintered materials, the strength increase and density decrease effects are canceled. However, in the case of high strength and high toughness materials such as Si, the strength may be offset by pore increase, but the weakness may be increased. It is preferable to limit the content of Si to 0.8% by weight or less, more preferably 0.4% by weight or less.

Next, Sn (tin) serves to change a part of the iron-based powder in the liquid phase during the sintering process, to promote the formation of ferrite to densify the sintered body and to increase the strength by solid solution strengthening, low melting point (about 232 ℃) This lowers the sintering temperature and promotes sintering by the formation of ferrite.

Accordingly, the sintering is greatly progressed to promote bonding and alloying between the particles, thereby improving mechanical properties, and when the changed liquid phase penetrates into the grain boundary due to flow, the tendency of expansion of the sintered body is reduced.

At this time, the Sn is added in about 0.1 to 1.0% by weight of the total iron-based powder, when the content of Sn is less than 0.1% by weight of the amount is too small so that the effect of the above-mentioned Sn is not shown well, the content of Sn is much When the quality of the liquid phase formed during the sintering process may be left as pores to form pores to form pores, so the content of Sn is preferably limited to 1.0% by weight or less, more preferably 0.5% by weight or less.

In addition, in order to improve the toughness, since the peak point of the added amount is present, it is necessary to adjust the added content according to the type of the added element. When Sn is added simultaneously with P, the ratio of Sn and P is 1: It is preferable to limit to 0.3-2.0.

On the other hand, the iron-based powder according to the invention may be configured to further comprise C (carbon), the C serves to improve the sintering hardness and strength of the iron-based powder, the content is about 0.1 ~ 0.55 of the total iron-based powder % By weight is added.

That is, when the content of C is less than 0.1% by weight, the effect of improving the sintering hardness and strength is not properly exhibited. Thus, in order to obtain a high-strength iron powder, the content of C is preferably 0.25% by weight or more, and the content of C If this increases, the strength increases, but the toughness decreases with expansion during sintering, so the C content is preferably limited to less than 0.55% by weight, more preferably less than 0.45% by weight.

The above-mentioned additives constituting the iron-based powder according to the present invention, that is, except for the content of Mo, P, Mn, Si, Sn and C is made of inevitable impurities such as Fe and C, O, N, S It is desirable that the unavoidable impurities generated during the compression molding or sintering process do not exceed 1.0% by weight of the total content.

On the other hand, the manufacturing method of the powder metallurgy powder for high strength and high toughness according to the present invention relates to a method for producing the iron-based powder containing Fe and the aforementioned additives, comprising a compression molding step and a sintering step.

In more detail, the compression molding step relates to a step of forming a molded body by press molding by including the Mo, P, Mn, Si, Sn and C additives in Fe as described above, and is usually for a smoother molding A small amount of lubricant for powder metallurgy may be added.

In this case, in the compression molding step, a pressure of 700 MPa or more is required to achieve high density, and more preferably, compression molding is performed at a molding pressure of 800 to 1300 MPa to have a molding density of 7.45 g / cm 3 or more.

That is, by sufficiently increasing the molding density through the molding pressure of 800 ~ 1300MPa to increase the strength and toughness of the molded body, and to allow sufficient self diffusion.

Accordingly, even if some elements cause expansion in the sintering process to be described later, the sintering property is increased to reduce the sintering density drop, and finally the sintering density of 7.40 g / cm 3 or more can be maintained even after sintering, and the maximum is 7.60 g / s. It is possible to exhibit a sintered density of the cm 3 level.

Next, the sintering step relates to the step of sintering the molded body, that is, the green compact, formed in the compression molding step. As described above, since the content of the additives other than Fe is limited so that the ferrite region appears in the sintering process, the sintering temperature It is preferable to sinter at 1,150 ° C. or higher, more preferably 1,200 to 1,350 ° C. to sufficiently sinter the ferrite.

In other words, the higher the sintering temperature, the higher the sintering property, but if the temperature is too high, the particles may coarsen and the mechanical properties may deteriorate. If the sintering temperature is low, the diffusion does not sufficiently occur during the sintering process and thus the toughness does not increase. The sintering temperature in the sintering step is preferably limited to 1,200 ~ 1,350 ℃.

As described above, when the high-density molding in the compression molding step and the high temperature sintering in the sintering step are performed at the same time, the sintering promotion effect is increased.

In addition, in the present invention, it is possible to minimize the addition of P, which may cause brittleness by the combination of Mo, Si, and Sn added as additives, and by adding a small amount of Mn together with Si instead of Cr (chromium), Mn and Si The high strength can be achieved by the interaction between them.

(Example 1)

Based on Fe, powder of 0.5% by weight Mo, 0.35% by weight P, 0.25% by weight Mn, 0.4% by weight Si, and 0.25% by weight Sn was prepared and added and mixed with 0.35% by weight C, and molded at a molding pressure of 900 MPa. Specimen was prepared.

After the specimen was heated to 1,200 ° C. in a reducing atmosphere and sintered for 30 minutes, the bending test value (TRS) was measured. As a result, a value of 1,520 MPa was obtained and good toughness (bending value) was found.

(Example 2)

Based on Fe, 0.5% by weight of Mo, 0.30% by weight, 0.20% by weight of Mn, 0.35% by weight of Si, 0.30% by weight of Sn, 0.3% by weight of C was added and mixed, and molded at a molding pressure of 1,000 MPa. To prepare a specimen.

After the specimen was heated to 1,250 ° C. in a reducing atmosphere and sintered for 30 minutes, the bending test value (TRS) was measured. As a result, a value of 1,480 MPa was obtained and similarly good toughness was exhibited.

(Example 3)

Based on Fe, a powder of 0.35% by weight Mo, 0.40% by weight P, 0.25% by weight Mn, 0.35% by weight Si, 0.25% by weight Sn, and 0.25% by weight were added and mixed with C 0.40% by weight, and molded at a molding pressure of 1,100 MPa. To prepare a specimen.

After the specimen was heated to 1,300 ° C. in a reducing atmosphere and sintered for 30 minutes, the bending test value (TRS) was measured, and as a result, a value of 1,500 MPa was obtained and similarly, it was confirmed that it exhibited good toughness (bending value).

Therefore, according to the iron metal powder for powder metallurgy for high strength and high toughness according to the present invention as described above and a method for manufacturing the same, the powder metallurgy method by adding elements to the iron base with little influence on the sintering atmosphere while having a low adverse effect on formability It is possible not only to produce materials having high strength and high toughness physical properties, but also to increase the sinterability by limiting the content of added elements so that the ferrite phase can be maintained during sintering, and through high density molding and high temperature sintering, It has various advantages such as securing strength and toughness.

Although the above embodiments have been described with respect to the most preferred examples of the present invention, it is not limited to the above embodiments, and it will be apparent to those skilled in the art that various modifications are possible without departing from the technical spirit of the present invention.

The present invention relates to an iron powder for powder metallurgy for high strength and high toughness, and a method of manufacturing the same. More specifically, the iron base is added to the iron base while the element is less affected by the sintering atmosphere while the moldability is less adversely affected. The present invention relates to an iron-based powder for powder metallurgy for high strength and high toughness which can make the materials produced by the powder metallurgy process have high strength and high toughness physical properties by reducing the amount of the elements to be affected, and a method of manufacturing the same.

Claims (10)

In iron powder for powder metallurgy,
Mo 0.2 to 2.5% by weight, P 0.1 to 0.6% by weight, Mn 0.1 to 0.5% by weight, Si 0.1 to 0.8% by weight and Sn 0.1 to 1.0% by weight, the balance is characterized by consisting of Fe and unavoidable impurities Powder metallurgy powder for high strength and high toughness.
The method of claim 1,
Iron metal powder for powder metallurgy for high strength and high toughness, characterized in that the content of Mo is 0.2 ~ 0.85% by weight.
The method of claim 1,
Iron metal powder for powder metallurgy for high strength and high toughness, characterized in that the content of P is 0.2 to 0.5% by weight.
The method of claim 1,
Iron-based powder for powder metallurgy for high strength and high toughness, characterized in that the content of Mn is 0.1 ~ 0.35% by weight.
The method of claim 1,
Iron-based powder for powder metallurgy for high strength and high toughness, characterized in that the content of Si is 0.1 to 0.4% by weight.
The method of claim 1,
Iron-based powder for powder metallurgy for high strength and high toughness, characterized in that the content of Sn is 0.1 to 0.5% by weight.
The method of claim 1,
The iron-based powder is a metallurgy powder for high strength and high toughness, characterized in that it further comprises C 0.1 ~ 0.55% by weight.
The method according to any one of claims 1 to 7,
The iron-based powder is obtained through a process of compression molding and sintering, the powder metallurgical powder for high strength and high toughness, characterized in that the molding density of 7.45g / ㎠ or more and maintains a density of 7.40g / ㎠ or more after sintering .
The present invention relates to a method for manufacturing powder metallurgy powder for high strength and high toughness according to any one of claims 1 to 6,
A compression molding step of adding 0.1 to 0.55% by weight of C to Mo, P, Mn, Si, Sn, Fe having the above content and compression molding at a high pressure of 700 MPa or more;
Method for producing powder metallurgy powder for high strength and high toughness, characterized in that it comprises a sintering step of sintering the green compact formed in the compression molding step at a temperature of 1,200 ~ 1,350 ℃.
The method of claim 9,
The molding pressure applied in the compression molding step is a powder metallurgical powder manufacturing method for high strength and high toughness, characterized in that 800 ~ 1,300MPa.

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