KR20210038691A - Modified high speed steel particles, powder metallurgy method using the same, and sintered parts obtained therefrom - Google Patents

Abstract

The present invention relates to particles (MHSS) prepared from high speed steel (HSS) modified to contain dispersed precipitates of manganese sulfide, and a powder metallurgy (PM) method using the same. The invention also relates to parts produced by the PM process using modified HSS particles. By forming a melt of HSS and 1) Mn or Mn-containing compound and 2) S or S-containing compound and then performing a spraying process, modified HSS particles containing dispersed sulfide precipitates containing mainly manganese sulfide are obtained. It has been found that it can be obtained. The amount of Mn and S is the weight ratio of Mn to S (Mn/S) is a weight% of the total weight of the particles, 8.0 to 1.0, preferably 5.5 to 3.0, for example, 5.5 to 3.5 or 5.5 to 4.1. It is chosen to be a range. Articles obtained by the PM production method using particles have improved compared to articles made from 1) Mn or Mn-containing compounds and 2) corresponding non-modified HSSs to which no S or S-containing compounds are added. It has machinability. Surprisingly, the physical properties of articles obtained from modified HSS particles are not impaired or significantly impaired compared to articles made from corresponding non-modified HSS particles.

Description

Modified high speed steel particles, powder metallurgy method using the same, and sintered parts obtained therefrom

The present invention relates to particles (MHSS) prepared from high speed steel (HSS) modified to contain dispersed precipitation of manganese sulfide, and a powder metallurgy (PM) method using the same. The invention also relates to parts produced by the PM process using modified HSS particles.

High Speed Steel is a high alloy steel, and is generally used in various applications due to its high hardness, bending strength, and durability at high temperatures. Typical applications for HSS alloys include cutting equipment for machining equipment or valve seat inserts (VSI) for combustion engines.

Due to its high hardness, machining or cutting of the HSS itself is an expensive and wear-intensive operation. However, this operation is also typically required for articles made by powder metallurgy to obtain articles with exactly desired dimensions, such as VSI.

It is also known to add additives that improve machinability to alloys other than HSS. For example, WO 93/19875 discloses at least one metal selected from the group comprising manganese and alkaline earth-based metals; Preparing a mixture of iron-based powders comprising at least one sulfur donating material; Pressing the powder mixture; And sintering the pressurized mixture to form by reaction while sintering at least one stable metal sulfide in the sintered material. Materials and articles made by this method are also described.

Another method is described in LG Roy et al in "Prealloyed Mn/S powders for improved machinability in P/M parts", Progress in Powder Metallurgy A. 1987, vol. 43, pp. 489-499]. The authors describe the pre-alloyed Mn/S iron powder MP 37S, and its preceding MP 36S different with respect to the higher Mn/S ratio. In these materials, Mn and S were added to improve the machinability of iron powder to form manganese sulfide (MnS) inclusions. These inclusions deform in the shear plane in the flow zone adjacent to the tool surface, which contributes to higher cutting speeds, longer tool life, good surface finish of the machined part, and lower tool forces. However, the literature also emphasized that in the case of the powder used for the PM process, various additional requirements must be met, such as the mechanical properties of the sintered part as well as the growth characteristics of the powder during sintering. Accordingly, the author investigated the effect of increasing the Mn/S ratio on the machinability, dimensional change and strength of sintered parts. From the chemical analysis, it was also confirmed that the inclusions in MP 36S and MP37 contained not only MnS but also MnFeO, SiO2, S, and/or FeS.

For high speed steel, high hardness and strength must be maintained. Accordingly, _{it is believed that machinability can be improved by adding an additive that improves machinability such as MoS 2} or MnS, but at the same time, it is believed that other properties such as a decrease in hardness and strength will be impaired.

Object of the present invention

It is an object of the present invention to provide a means for improving the machinability of a high-speed steel material, and to provide a high-speed steel base material having improved machinability.

Another object of the present invention is to provide a means for improving the machinability of a high-speed steel material without significantly impairing the physical properties of the high-speed steel. Preferably, the physical properties of the high speed steel, in particular the strength, are not impaired at all compared to the high speed steel which does not include the means of the present invention.

Another object of the present invention is to provide a material suitable for a powder metallurgy (PM) manufacturing process, and a PM method using the same. Parts obtained from PM must be suitable for applications requiring final machining prior to use and must have the properties to withstand harsh conditions of use, such as those present in combustion engines.

Manganese sulfide powder commonly used in powder metallurgy mixes for improving machinability has an average particle size D50=4-6 μm, for example MnS-E commercially produced by Hoeganaes AB. This makes it very easy to dust the powder and the mix containing it. MnS is known to cause serious eye irritation and skin irritation in exposed humans [https://echa.europa.eu/registration-dossier/-/registered-dossier/10223/2/1]. Accordingly, another object of the present invention is to provide a material that improves machinability with reduced health risks.

Summary of the invention

The inventors of the present invention have determined that the HSS and 1) the formation of a melt of the Mn or Mn-containing compound and 2) the S or S-containing compound, and then the spraying process to form particles, mainly contain the dispersed sulfide precipitate containing manganese sulfide. It has been discovered that the particles can be modified. The amount of Mn and S is 8.0 to 1.0, preferably 5.5 to 3.0, for example 5.5 to 3.5, or 5.5 to 4.1, in which the weight ratio of Mn to S (Mn/S) is weight percent of the total weight of the particles. Is chosen to be in the range of. Articles obtained by the PM manufacturing method using particles are improved mechanically compared to articles made from 1) Mn or Mn-containing compounds and 2) corresponding non-modified HSSs to which no S or S-containing compounds are added. It has workability. Surprisingly, the physical properties of articles obtained from modified HSS particles are not impaired or significantly impaired compared to articles made from corresponding non-modified HSS particles.

The material of the present invention does not contain free MnS particles, and thus Mn dusting and the above-described risks are greatly reduced.

The present invention includes the following aspects. Further aspects and features of the invention will become more apparent upon consideration of the following detailed description.

1.As high speed steel (HSS) particles modified to contain dispersed precipitates of manganese sulfide, the weight ratio of Mn to S (Mn/S) is a weight% of the total weight of the particles, from 8.0 to 1.0, preferably from 5.5 to 3.0, for example in the range of 5.5 to 3.5, or 5.5 to 4.1, high speed steel particles.

2. According to item 1, in% by weight,

C: 0.75 to 1.40

Mn: 0.41 to 2.00

Si: 0.10 to 0.45

Cr: 3.75 to 5.00

Ni: 0.20 max

Mo: 4.50 to 6.50

W: 5.50 to 7.50

V: 1.75 to 4.50

Cu: 0.20 max

S: 0.050 to 0.300

High speed steel particles modified to contain dispersed precipitates of manganese sulfide, having a composition consisting of the balance Fe and unavoidable impurities in an amount of up to 0.5% by weight, preferably 0.2% by weight.

3. According to item 1, when the longest axis of the manganese sulfide precipitate is measured by SEM image analysis, the dispersion of manganese sulfide is 1 to 10 µm, preferably 1 to 8 µm, and more preferably 1 to 5 µm. HSS particles modified to contain precipitates.

4. According to any one of items 1 to 3, the total amount of Mn and S (Mn+S) is 0.10 to 3.80% by weight, preferably 0.10 to 3.00% by weight, more preferably 0.20 to 2.50% by weight, eg HSS particles modified to contain dispersed precipitates of manganese sulfide, for example from 0.30 to 2.00% by weight.

5. The HSS particles according to any one of items 1 to 4, modified to contain dispersed precipitates of manganese sulfide, wherein the amount of Mn in the total particles is 3.00% by weight or less, preferably 2.00% by weight or less.

6. The modified according to any one of items 1 to 5, wherein the particles contain 4.00% by weight or more of a dispersed precipitate of manganese sulfide, containing at least one element selected from Mo, W, V and Cr. HSS particles.

7. The HSS particles modified to contain dispersed precipitates of manganese sulfide according to any one of items 1 to 6, wherein the amount of S is 0.10% by weight or more, and the amount of Mn is 0.45% by weight or more.

8. A number of HSS particles modified to contain dispersed precipitates of manganese sulfide according to any one of items 1 to 7, as measured by sieve analysis according to ISO4497:1983, of which 98% by weight or more of the particles are It has a particle size of 0 to 300 μm, and the amount of particles larger than 300 μm is 2% by weight or less; Preferably 98% by weight or more of the particles have a particle size of 0 to 200 μm, and the amount of particles larger than 200 μm is 2% by weight or less.

9. As a method of forming powder metallurgy products,

a. Providing a plurality of particles according to any one of items 1 to 8;

b. Compressing the composition comprising the particles to form a green part;

c. Sintering the green part; And

d. Optionally heat treating the part obtained from step c; And

e. Optionally machining the sintered part obtained from step c or from step d.

10. The method of item 9, wherein step a of providing the particles comprises

a.1-1 adding Mn or Mn-containing compound and S or S-containing compound to the HSS material, and melting the obtained mixture; or

a.1-2 adding Mn or Mn-containing compound and S or S-containing compound to the melt of HSS;

a.2. Forming particles from the melt, preferably by water spray or gas spray;

a.3. Optionally annealing the particles in a vacuum, inert or reducing atmosphere.

11. A sintered part obtainable from the particles according to any one of items 1 to 9 or from the process according to items 9 or 10.

12. The sintered part according to item 11, which is a component for a combustion engine, preferably a valve seat insert.

13. Use of a combination of Mn or Mn-containing compounds and S or S-containing compounds to improve the machinability of products made from HSS, preferably powder metallurgy products, for the formation of dispersed precipitates of manganese sulfide in HSS. Including, uses.

14. Use according to item 13, wherein the formation of a dispersed precipitate of manganese sulfide in HSS is achieved by forming a melt of HSS and Mn or Mn-containing compound and S or S-containing compound.

Justice

In the following detailed description, the following terms and definitions will be used and applied.

Any given range referred to as a lower limit and an upper limit, such as, for example, "2 to 5" or "between 2 and 5" is any value therebetween, including the lower limit and the upper limit. Values greater than the lower limit or lower than the upper limit are explicitly included. Accordingly, these terms are to be understood as an abbreviation for the expression "[lower limit] or more, but [upper limit] or less".

Whenever a range and a more preferred range are mentioned, the lower limit and the upper limit may be freely combined. As an example, the phrase “5 to 10, preferably 6 to 8” also includes a range of 5 to 8 and 6 to 10.

In the present invention, all physical parameters are measured at ^{room temperature (20° C.) and atmospheric pressure (10 5} Pa) unless otherwise indicated or otherwise specified according to standards such as ISO or ASTM. In the event of a discrepancy between the standard method and the method described in the following description or referred to in the following description, the present description takes precedence.

The singular form ("a") as used herein represents not only one but more than one, and does not necessarily limit its reference noun to the singular.

The term “about” means that the amount or value contemplated may be the specific value specified or may be some other value in the neighborhood that is generally within the range of ±5% of the specified value. Thus, for example, the phrase “about 100” represents a range of 100±5, and the phrase “about 60” represents a range of 60±3.

The term and/or (and/or) means that all or only one of the specified components is present. For example, "a and/or b" represents "only a", or "only b", or "a and b together". In the case of “only a”, this term also includes the possibility that b does not exist, ie “only a, but not b”.

As used herein, the term “comprising” is intended to be non-exclusive and open. Compositions comprising certain ingredients may thus contain ingredients other than those listed. However, this term also includes the more restrictive meanings “consisting of” and “consisting essentially of.” The term “consisting essentially of...” means Allows the presence of substances other than those listed for the individual composition, of up to 10% by weight (including threshold), preferably, up to 5% by weight (including threshold), where other substances may also be completely absent. In the latter case, the composition "consists of the listed ingredients."

In the present invention, the term high speed steel (HSS) is an alloy defined by the composition of Table 1 of ASTM 600-92a (2010), not including medium high speed steels M50 and M52, or an alloy having a composition as disclosed in WO2009/040369. And these documents are incorporated herein by reference in their entirety. These alloys can be in any form, for example, in the form of pre-alloyed water-sprayed iron-based powders, which are less than 10 to 18% by weight of Cr, 0.5 to 5% by weight of at least one of Mo, W, V, and Nb. , 0.5 to 2% by weight, preferably 0.7 to 2% by weight, more preferably 1 to 2% by weight of C, optionally 0 to 2% by weight of Si, the balance of Fe. The alloy according to this definition is not limited to the structure, but is not only less than 10% by weight of Cr, but also a large chromium carbide having an average size of 8 to 45 μm, preferably 8 to 30 μm, and an average size of less than 8 μm. Smaller, harder chromium carbide containing matrices may be included. The larger chromium carbide is more preferably present in an amount of 10 to 30% by volume, and the smaller harder chromium carbide is preferably present in an amount of 3 to 10% by volume.

Modified high-speed steel (MHSS) is specified in Table 1 of ASTM 600-92a (2010), or WO2009/040369, excluding higher amounts of manganese (Mn) and sulfur (S) in the case of modified high-speed steel compared to the corresponding high-speed steel. Refers to an alloy that satisfies the composition as defined above with reference to.

1. Modified high speed steel particles

In one aspect, the present invention relates to high speed steel (HSS) particles modified to contain dispersed precipitates of manganese sulfide. These particles are also referred to as modified high speed steel (MHSS) particles. Such particles can be obtained by the method of the invention described below, and in general, a melt of an alloy as disclosed above with reference to HSS or WO2009/040369 as specified in ASTM 600-92a (2010) Mn or Mn-containing compound and S or S-containing compound are added to, or HSS is melted together with Mn or Mn-containing compound and S or S-containing compound, followed by atomization to form particles. Of course, Mn-containing compounds and S-containing compounds can be replaced by compounds containing both Mn and S, such as MnS. However, when MnS is added to HSS particles, it is not possible to form the structure of the particles of the present invention containing dispersed precipitates of manganese sulfide. It is necessary to form a homogeneous melt of the material(s) and HSS.

The HSS on which the MHSS is based is not particularly limited, but in one embodiment, it is preferably an M-type HSS, for example M2 (normal or high C), M3 (class 1 or class 2) or M35. Other HSSs that may be the basis of the MHSS include OB1, and T15, available from Hoeganaes AB (Sweden).

In one embodiment, MHSS is in weight percent,

C: 0.75 to 1.40, preferably 1.00 to 1.25

Mn: 0.41 to 2.00

Si: 0.10 to 0.45

Cr: 3.75 to 5.00

Ni: 0.20 max

Mo: 4.50 to 6.50, preferably 5.00 to 6.50

W: 5.50 to 7.50

V: 1.75 to 4.50, preferably 3.00 to 3.80

Cu: 0.20 max

S: 0.050 to 0.300

It consists entirely of Fe and inevitable impurities in an amount of 0.5% by weight or less, preferably 0.2% by weight or less. Herein, unavoidable impurities include any element not listed above, such as P or Si. The lower limit of Mn may also be 0.50 and/or the lower limit of S may also be 0.100.

The MHSS particles of the present invention are precipitates of manganese sulfide. However, this does not mean that elements other than Mn and S are not present in these precipitates at all. When the precipitate is analyzed (point analysis) by SEM/EDS mapping for, for example, 50 or more precipitates. In this SEM/EDS mapping, the amount of Mn is 40 atomic% or more, in a normalized connotation, where the elements Si, S, V, Cr, Mn, Fe, Mo and W (as long as they exist) The amount of forms 100 atomic percent. Here, Fe typically forms 15 to 25 atomic%, and S typically forms 25 to 35 atomic%.

The size of the precipitate is not particularly limited, but is usually not too large to provide a dispersed area that is believed to improve machinability without disturbing the structure of the HSS too much. When observed by SEM on the surface of the particles, the longest axis of all precipitates is usually 10 μm or less, for example 1 to 8 μm and usually 1 to 5, or 2 to 5 μm.

The total amount of Mn and S (Mn+S) is generally 0.10 to 3.80% by weight, preferably 0.10 to 3.00% by weight, more preferably 0.20 to 2.50% by weight, for example, based on the weight of the MHSS particles. 0.30 to 2.00% by weight. However, the lower limit in each of these ranges may also be 0.50, 0.60, 0.70, 0.80 or 0.90% by weight or more, for example 0.95% by weight or more.

It has been found that the weight ratio of Mn to S (i.e., in weight percent of the total weight of the MHSS particles, weight of Mn/weight of S) is relevant for at least two reasons:

The first reason is that these ratios are necessary to get the proper structure. If the relative amount of Mn (i.e., the weight ratio of Mn to S) is too high, excess Mn can cause distortion. If the ratio is too low, an excess of S can form a sulfide layer at the grain boundary, which can potentially lead to impairment of physical properties such as burst strength of articles obtained by the PM process using MHSS particles.

Secondly, the inventors have surprisingly found that adjusting the ratio of Mn and S can avoid a substantial loss of sulfur from the melt, as generally expected due to the relatively high vapor pressure of sulfur at elevated temperatures. While not wishing to be bound by theory, it is believed that sulfur reacts directly with (or binds to) manganese when there is a sufficient amount of manganese relative to sulfur. Thereby, the amount of elemental sulfur that can be lost due to the high vapor pressure is thus minimized. It also avoids or minimizes the need for maintenance work to remove sublimated sulfur, reduces the environmental burden, and also makes it cheaper and easier to produce MHSS.

For the above at least two reasons, the weight ratio of Mn to S (Mn/S) is 8.0 to 1.0, more preferably 5.5 to 3.0, for example 5.5 to 3.5, or 5.5, in weight percent of the total weight of the particles. To 4.1.

The Mn content in HSS is mainly 0.15 to 0.40% by weight or less, according to the HSS type listed in Table 1 of ASTM A600-92a (2010). In the MHSS particles of the present invention, the Mn content is higher, and in one embodiment, 3.00% by weight or less, preferably 2.00% by weight or less, but 0.41% by weight or more, for example 0.45 % By weight or more, or even 0.50% by weight or more or 0.75% by weight or more.

In MHSS particles, the amount of S is also higher, as in the corresponding HSS, where it is limited to 0.03% by weight. In one embodiment of the invention, the amount of S is 0.05% by weight or more, for example 0.10% by weight or more or 0.15% by weight or more. The upper limit is not particularly limited, but may be 0.50% by weight or less, for example, 0.30% by weight or less, or 0.25% by weight or less.

HSS alloys contain different amounts of more than one of Mo, W, V and Cr, depending on the type of HSS. In one embodiment of the present invention, the MHSS particles contain 4.00% by weight or more, at least one element selected from Mo, W, V and Cr, and in one embodiment, 4.00% by weight or more, such It contains two or more of the elements. For example, the MHSS particles may contain 4.00% by weight or more, respectively, of Mo, W and Cr.

The MHSS particles of the present invention can be used in a PM manufacturing process, and for this purpose, a plurality of MHSS particles are required. In one embodiment of the plurality of MHSS particles of the present invention, 98% by weight or more of the particles have a particle size of 0 to 300 μm, wherein the amount of particles greater than 300 μm is determined by sieve analysis according to ISO4497:1983. When measured, it is 2% by weight or less. The amount of particles larger than 300 μm may also be 1% by weight or less, or such particles may not be present at all.

In one embodiment, 98% by weight or more of the particles have a particle size of 0 to 200 μm, and the amount of particles larger than 200 μm is 2% by weight or less. The amount of particles greater than 200 μm may also be 1% by weight or less, or such particles may not be present at all.

The MHSS particles of the present invention are formed by providing a melt of the raw ingredients, typically commercially available HSS, S and Mn (or a compound comprising S and Mn) and then atomizing the melt by conventional techniques. I can. The raw material components may be HSS scraps, but may also include natural raw materials such as Fe, FeCr, FeV, and the like. Nebulization can be achieved, for example, by gas spraying or water spraying, with water spraying being preferred.

MHSS particles can be annealed in a vacuum or protective atmosphere to reduce hardness and improve compressibility. Such annealing may be carried out under generally known conditions such as at 900 to 1100° C. for 15 to 72 hours.

MHSS particles are suitable for use in the PM manufacturing process. These have suitable powder compactibility and can provide low dimensional change during sintering.

2. How to form powder metallurgy products

The method of forming the powder metallurgy product of the present invention comprises the following steps:

a. Providing a plurality of MHSS particles as described above;

b. Compressing the composition comprising the particles to form a green part;

c. Sintering the green part; And

d. Optionally, heat-treating the part obtained from step c; And

e. Optionally, machining the sintered part obtained from step c or from step d.

In addition to the MHSS particles described above, the steps are common in the field of PM fabrication methods. Any suitable general method can be used in the present invention.

The composition referred to in step b may consist of only MHSS particles, but also, optionally, other metals or alloying components such as graphite powder (up to 1%), iron powder, low alloyed iron powder. ), Cu powder, hard additives such as Tribaloy, and may also contain other additives such as, for example, a lubricant (eg, amide wax) in an amount of 1% by weight. The MHSS particles of the present invention typically form 90% by weight or more, for example 95% by weight or more or 99% by weight or more of the composition of step b.

The sintering step "c" may be selectively performed with the presence of a Cu-based alloy. In this case, the Cu-based alloy is placed in contact with the green component in the sintering furnace. At the sintering temperature, the infiltrating alloy melts. The liquid Cu alloy will penetrate the pores by capillary force and form an almost completely dense composite material. The infiltrating alloy typically contains at least 95% Cu and optionally additional elements to improve the infiltrating behavior as is well known in the art. Cu infiltration increases the hardness and strength of the final PM component and improves thermal conductivity.

3. Sintered parts

The sintered part of the present invention is a part obtainable by using a composition comprising or consisting of MHSS particles as described above in a PM production process, for example the process described above.

The sintered parts of the present invention obtainable by using a composition comprising or consisting of MHSS particles as described above have improved machinability compared to sintered parts made from the corresponding HSS under the same conditions. Surprisingly, the sintered part of the present invention still has very satisfactory properties. In particular, the sintered part can still have the same hardness and strength.

Because of these beneficial properties, the present invention is particularly suitable for providing sintered parts (parts produced by the PM manufacturing method) for use under harsh conditions. Accordingly, the sintered component of the present invention is, in one embodiment, a component for a combustion engine, such as a valve seat insert (VSI) or a valve guide.

Example

Examples 1 and 2

MHSS particles having the following composition were prepared (balance: Fe and unavoidable impurities):

Table 1:

Chemical composition of the MHSS particles of Examples 1 and 2

By adding Mn and S to a natural material including Fe and its alloys, for example ferrochrome, ferrovanadium, ferrotungsten and ferromolybdenum, melting the composition and subsequently atomizing and sieving using a -212 μm screen , To prepare a melt of the material. Reference materials, referred to below as Ref1 and Ref2, were prepared in the same manner except that Mn and S were not added. The powder was vacuum annealed. The particles have the following particle size distribution:

Table 2:

Particle size distribution of MHSS particles (% by weight)

The vacuum annealed powder was examined by SEM. It was observed that precipitates of manganese sulfide having the longest axis of 2 to 5 μm were formed.

Elemental mapping (point chemistry analysis) using EDS was performed on more than 200 precipitates. The following results were obtained:

Table 3:

Composition of precipitates in Examples 1 and 2 (atomic%, normalized)

25 kg of the powder of Examples 1 and 2 and the non-modified HSS powder were mixed with 1% amide wax as lubricant and used in the PM production process. The compressibility of the modified HSS particles and the non-modified HSS particles was the same, and the compressed parts showed similar porosity after compression at 800 MPa and 50°C.

The compacted parts (green parts) were then sintered for 20 minutes at 1120° C. in nitrogen containing _{10 vol% H 2.} Thereafter, in order to deform the contained austenite, the particles were subjected to dipping cooled to sub-zero in liquid nitrogen for 20 minutes. Thereafter, final tempering at 560° C. in _{N 2 was performed for 2 hours.}

The dimensional change and hardness of the sintered material obtained from the MHSS particles (Examples 1 and 2) and the corresponding HSS particles (Ref1 and Ref2) are shown in Table 4 below.

Table 4:

Characteristics of sintered parts

The hardness values provided in Table 4 overlap at their margin of error (±15). Accordingly, it was concluded that the modification of the present invention did not impair the important properties of the sintered part, including hardness. In addition, all the sintered parts obtained from MHSS of Examples 1 and 2 showed similar porosity compared to the sintered parts obtained from individual reference particles made from HSS to which Mn or S was not added.

The machinability of the sintered part was evaluated using a sample of 55×45×15 mm annular shape under the following cutting parameters:

Cutting tool:

Sandvik CNGA120404T010208B, material-CBN, radius of cutting tip: 0.4 mm

Cutting depth: 0.4 mm

Cutting speed: 120 m/min

Radial flow: 0.07 mm/revolution

Tool tip wear or wear at break (mm) was used as a criterion for machinability. The test was repeated twice for each material. Results are provided in Table 5.

Table 5:

Machinability evaluation result

The material of Ref2 achieved a cutting distance of 2834 m until the tool tip was destroyed. The MHSS material of Example 2 can be machined up to 6720 m. Tool tip wear was about 0.18 mm.

The material of Ref1 could not be machined because the tool tip broke immediately after the start of the test. Changing the cutting conditions to 400 m/min and reducing the radial feed rate could slightly improve the situation, but still the tip broke after 48 cuts (538 m, data shown in Table 5).

Comparative Example 1

In order to evaluate whether the addition of MnS to the HSS particles has the same effect, the HSS material of Ref2 was mixed with MnS powder (D50 = 5 μm) to prepare the powder of Comparative Example 1 (Comp. Ex. 1). . Thereafter, the sintered parts were produced in the same manner as described above. The following results were obtained:

Table 6:

Material properties after sintering and heat treatment

Machinability was evaluated in the same manner as in Examples 1 and 2. Machinability for Comparative Example 2 (Comp. Ex 2) was the same level as for Example 2. Example 2 and Comparative Example 1 provided a tool life of at least 3 times that of Ref 2. In addition, the mixing of MnS in Comparative Example 1 resulted in a significant decrease in material strength, which was not observed for the material of Example 2.

Claims (14)

As high speed steel (HSS) particles modified to contain dispersed precipitation of manganese sulfide, the weight ratio of Mn to S (Mn/S) is as a weight% of the total weight of the particles, from 8.0 to 1.0, preferably 5.5 to 3.0, for example 5.5 to 3.5, or in the range of 5.5 to 4.1, high speed steel particles. The method of claim 1, by weight percent,
C: 0.75 to 1.40
Mn: 0.41 to 2.00
Si: 0.10 to 0.45
Cr: 3.75 to 5.00
Ni: 0.20 max
Mo: 4.50 to 6.50
W: 5.50 to 7.50
V: 1.75 to 4.50
Cu: 0.20 max
S: 0.050 to 0.300,
High-speed steel particles modified to contain dispersed precipitates of manganese sulfide, having a composition consisting of the balance Fe and unavoidable impurities in an amount of up to 0.5% by weight, preferably 0.2% by weight. The dispersion precipitate of manganese sulfide according to claim 1, wherein the longest axis of the manganese sulfide precipitate is 1 to 10 µm, preferably 1 to 8 µm, more preferably 1 to 5 µm, as measured by SEM image analysis. HSS particles modified to contain. The method according to any one of claims 1 to 3, wherein the total amount of Mn and S (Mn+S) is 0.10 to 3.80% by weight, preferably 0.10 to 3.00% by weight, more preferably 0.20 to 2.50% by weight, HSS particles modified to contain dispersed precipitates of manganese sulfide, for example from 0.30 to 2.00% by weight. HSS particles according to any one of claims 1 to 4, modified to contain dispersed precipitates of manganese sulfide, wherein the amount of Mn in the total particles is 3.00% by weight or less, preferably 2.00% by weight or less. . The modification according to any one of claims 1 to 5, wherein the particles contain 4.00% by weight or more of a dispersed precipitate of manganese sulfide, containing at least one element selected from Mo, W, V and Cr. HSS particles. The modified HSS particles according to any one of claims 1 to 6, wherein the amount of S is 0.10% by weight or more, and the amount of Mn is 0.45% by weight or more. . As a plurality of HSS particles modified to contain the dispersed precipitate of manganese sulfide of any one of claims 1 to 7, as measured by sieve analysis according to ISO4497:1983, 98% by weight or more of the particles are It has a particle size of 0 to 300 μm, and the amount of particles larger than 300 μm is 2% by weight or less; Preferably, 98% by weight or more of the particles have a particle size of 0 to 200 μm, and the amount of particles larger than 200 μm is 2% by weight or less. As a method of forming powder metallurgy products,
a. Providing a plurality of particles according to any one of claims 1 to 8;
b. Compressing the composition comprising the particles to form a green part;
c. Sintering the green component; And
d. Optionally, heat-treating the part obtained from step c; And
e. Optionally, machining the sintered part obtained from step c or step d. The method of claim 9, wherein the step a of providing the particles is
a.1-1 adding Mn or Mn-containing compound and S or S-containing compound to the HSS material, and melting the obtained mixture; or
a.1-2 adding Mn or Mn-containing compound and S or S-containing compound to the melt of HSS;
a.2. Forming particles from the melt, preferably by water spray or gas spray;
a.3. Optionally, annealing the particles in a vacuum, inert or reducing atmosphere. A sintered part obtainable from the particles according to any one of claims 1 to 9 or by the method according to claim 9 or 10. The sintered component according to claim 11, which is a component for a combustion engine, preferably a valve seat insert. Use of a combination of Mn or Mn-containing compounds and S or S-containing compounds to improve the machinability of products made from HSS, preferably powder metallurgy products, comprising the formation of dispersed precipitates of manganese sulfide in HSS. , Usage. The use according to claim 13, wherein the formation of dispersed precipitates of manganese sulfide in HSS is achieved by forming a melt of Mn or Mn-containing compound and S or S-containing compound and HSS.