KR20080038130A - Powder metallurgically manufactured steel, a tool comprising the steel and a method of making the tool - Google Patents

Abstract

Powder metallurgically manufactured steel with a chemical composition by weight of 1.1-2.3 C + N, 0.1-2.0 Si, 0.1-3.0 Mn, up to 20 Cr, 5-20 (Mo + W / 2), 0- The total content of niobium and vanadium (Nb + V), including 20 Co, so that the content of niobium and vanadium and the ratio between them lies within the area defined by coordinates A, B, and C in the coordinate system of FIG. ) Is determined in terms of the ratio (Nb / V) between niobium content and vanadium content, the coordinates being A: [4.0; 0.55], B: [4.0; 4.0], C: [7.0; 0.55] and total amounts of 1% or less, including Cu, Ni, Sn, Pb, Ti, Zr, and Al, and unavoidable impurities from the rest of the iron and steel manufacturing process. The invention also relates to a hot working tool or a cold working tool or a chip removal tool or a highly mechanical tool steel made of said steel, and to a method of manufacturing such a tool.

Description

Powder metallurgically manufactured steel, a tool including the steel and a manufacturing method of the tool TECHNICAL TECHNICAL TECHNICAL TECHNICALLY MANUFACTURED STEEL, A TOOL COMPRISING THE STEEL AND A METHOD FOR MANUFACTURING THE TOOL

The present invention relates to new steels, preferably powder metallurgically manufactured high speed steels with improved grindingability and suitable for chip removal tools. There are, for example, tools with shaving serarators which require good toughness such as gear cutting tools, taps and end-cutters, especially high toughness in combination with high temperature hardness. . Other applications include tools used where high toughness combined with hardness and strength to suit the application are required. Applications that may be applied include advanced machines such as tools for stamping patterns or profiles on metals, hot-working tools such as rollers for hot-rolling and dies for extrusion of aluminum profiles, and the like. Elements and press rollers. In other applications, it may include cold-working tools, where good abrasiveness and good hardness are important properties.

In the case of steel used in tools for the extrusion of aluminum profiles, for example, one of the most important properties is that the steel has a high tempering resistance, which is what the steel has by hardening and tempering treatment. This means that it can be exposed to high temperatures for a long time without losing hardness. On the other hand, such hardness does not necessarily have to be very high and would be suitable if the size is 50-55 HRC.

If steel is used for high mechanical elements, the main properties will be strength and high hardness combined with high toughness, and there will also be a strict demand for uniform properties. In this case, the hardness after tempering will typically be in the range of 55-60 HRC.

However, in steel for tools for stamping patterns or profiles on metals and the like, and for cutting tools such as gear cutting tools, taps and end-cutters with shaving separators, combined with great toughness High hardness of 60-70 HRC may be required. The tabs should have a hardness of 60-67 HRC, while the end-cutter should have a hardness of 62-70 HRC. Even for use in cold-working tools, there will be a similar demand for steel.

The invention also relates to a tool for hot working or chip removal or cold working, or to a highly mechanical element made of steel, and to a method for manufacturing such a tool.

One type of steel for use in cutting operations is the high speed steel marketed under the trade name ASP®2052, the weight percent nominal composition of which is: 1.6 C, 4.8 Cr, 2.0 Mo, 10.5 W, 8.0 Co, 5.0 V, remaining iron and inevitable impurities. Other high speed steels include ASP®2030, whose nominal composition includes 1.28 C, 4.2 Cr, 5.0 Mo, 6.4 W, 3.1 V, 8.5 Co, the remaining iron and inevitable impurities. Another high speed steel is ASP®2060, whose nominal composition includes 2.3 C, 4.2 Cr, 7.0 Mo, 6.5 W, 6.5 V, 10.5 Co, the remaining iron and inevitable impurities. All contents are expressed in weight percent.

It is desirable to improve the abrasiveness of steel for use in chip removal tools because abrasiveness is a time-consuming operation during the manufacture of such tools. It is therefore an object of the present invention to provide novel steels, preferably high speed steels, which have the same desirable properties as conventional steels as described above, but with improved abrasiveness of the material. More specifically, the steel should have the following characteristics. In other words:

Good abrasiveness in the hardened and tempered state,

Good toughness in the hardened and tempered state,

Good hardness in the hardened and tempered state,

High yield point,

-High fatigue strength,

High flexural strength, and

Good wear resistance.

These prerequisites can be achieved by steel made from powder metallurgy and having the following chemical composition by weight: 1.1-2.3 C + N, 0.1-2.0 Si, 0.1-3.0 Mn , Up to 20 Cr, 5-20 (Mo + W / 2), 0-20 Co, where the total content of niobium and vanadium (Nb + V) is related to the content ratio of niobium and vanadium (Nb / V) The content of these elements (niobium and vanadium) and the ratio between the contents are determined by the coordinate A in the coordinate system of Fig. 1: [4.0; 0.55], B: [4.0; 4.0], C: [7.0; 0.55, Cu, Ni, Sn, Pb, Ti, Zr, and Al, which are located in the area defined by the above, and in total, are inevitable impurities from the rest of the iron and steel manufacturing process.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings and the tests conducted.

1 is a graph plotting the relationship between the total content of Nb and V (Nb + V) and the ratio of Nb and V (Nb / V) of steel according to the invention.

2 is a graph showing the size of MX-carbide as a function of the volume of MX-carbide.

Figure 3 is a graph showing the amount of M ₆ X- carbide on the volume of ₆ M X- carbides as a function.

Figure 4 is a graph showing the distribution of carbides for the case of various heat treatments and Nb / V ratio.

FIG. 5 is a _{graph depicting} lattice constants in the plane d _{( hkl )} for d ₍₁₁₁₎ MX- and d _{(331) -0.5 μs} M ₆ X-carbide as a function of Nb / V ratio. to be.

Figure 6 is a photograph showing the microstructure after the sixth heat treatment of the steel (F) according to the present invention.

7 is a graph showing the abrasiveness, ie, the G ratio, as a function of the size of MX-carbide.

8 is a graph showing the energy consumption during polishing in relation to the chip excavation rate.

Without wishing to be bound by a particular theory, the importance of various structural elements and various alloy materials in achieving the desired property profile in accordance with the present invention is described. Unless otherwise stated, percentages are always in weight percent for alloy content and percentages are always in volume percent for structural elements.

With nitrogen, carbon should be present in an amount of at least 1.1% up to 2.3%, preferably at least 1.4% up to 2.0%, most preferably at least 1.60% up to 1.90%, which when dissolved in martensite To impart hardness to the material under conditions that have been cured and tempered appropriately for the purpose. In addition, carbon and nitrogen, in combination with niobium and vanadium, should contribute to the appropriate amount of primary precipitation of MX-carbide, -nitride, -carbonitride of type (Nb, V) X, and tungsten, molybdenum and In combination with chromium, one must contribute to achieve an adequate amount of primary precipitation of M ₆ X-carbide, -nitride, -carbonitride in the matrix. In summary, such hard phase particles will be referred to hereinafter as carbides, but it should be understood that the term carbide is also associated with nitrides and / or carbonitrides if the steel contains nitrogen. The purpose of such carbides is to impart desirable wear resistance to the material. Also, as carbides function to limit particle growth, carbides contribute to the micro-particle structure in steel. In a preferred embodiment, the steel comprises from 1.65 to 1.80% carbon and nitrogen, which is combined with a balanced amount of other alloying elements, in particular silicon, chromium, vanadium and niobium, to produce a steel profile suitable for the purpose. This may be achieved by a standard manufacturing process, that is, the manufacturing process will not require any special effort other than the procedure according to the standard method.

Generally, the nitrogen content is 0.1% or less, but it is possible to dissolve more nitrogen in the steel by powder metallurgical manufacturing techniques. Thus, one embodiment of the steel is characterized by containing a large amount of nitrogen, ie up to 2.3% nitrogen, which may be achieved by solid phase nitriding operations of the powders produced. Thus, carbon may be substituted for the hard material that becomes part of the steel of the final tool. The advantages obtained by replacing carbon with nitrogen are as follows. That is, the resistance to adhesive wear is reduced, which is particularly advantageous when the tool acts on a tacky material such as aluminum and certain stainless steels. In addition, the steel may be easily tempered, which means that the tempering temperature can be lowered, which would also be advantageous. A content below 1.1% carbon + nitrogen will not provide sufficient hardness and wear resistance, and a content above 2.3% may cause brittleness problems.

Silicon is added to the steel in an amount of at least 0.1% to improve the fluidity of the steel, which is important for melt metallurgical processes. The more silicon is added to the steel melt, the more fluid it will be, which is important in preventing clogging associated with granulation. In order to prevent clogging during granulation, the silicon content should be at least 0.2%, more preferably at least 0.4%. In addition, silicon contributes to increased carbon activity in silicon alloyed embodiments, and such carbon may be present in amounts up to about 2%. At contents exceeding 2%, problems with brittleness will arise, and it will be desirable for the steel not to exceed 1.2% Si, which would increase the risk of M ₆ X-carbide formation and harden. This is because state hardness may be lost, which means that it is desirable to limit the silicon content to 1.0% or less. In a preferred embodiment, the silicon content is between 0.55% and 0.70%, which has been demonstrated to give the following results in addition to the advantages described above. That is, it has been proved to facilitate heat treatment in combination with the desired carbon content in steel. Thus, the steel can be heat treated over a wide temperature range while still maintaining the characteristic profile, which would be an advantage in manufacturing.

Manganese may also be present primarily as a residual product from the metallurgical melting process, in which manganese is known to have the effect of deactivating sulfur impurities by forming manganese sulfide, for which purpose manganese is 0.1%. It should be present in the steel in the above content. The maximum content of manganese in steel is 3.0%, but it is desirable to limit the content of manganese to a maximum of 0.5%. In a preferred embodiment, the steel comprises 0.2 to 0.4% Mn.

Sulfur may be present in the steel as a residual product from the steel making process and may be present in amounts up to 800 ppm without affecting the mechanical properties of the steel. Sulfur can be added deliberately as an alloying element up to 1%, thus contributing to improving processability and workability. In one embodiment of the invention with sulfur intentionally added for this purpose, the content of sulfur should be 0.1 to 0.3%, so that the content of manganese is somewhat higher than in embodiments that do not alloy sulfur, preferably Preferably from 0.5% up to 1.0%.

In addition, phosphorus may be present as a residual product from the production of the steel, up to 800 ppm of content without affecting the mechanical properties of the steel.

Chromium is present in the steel in an amount of at least 3%, preferably at least 3.5%, in order to contribute to the steel achieving the appropriate hardness and toughness after hardening and tempering when dissolved in the matrix of the steel. In addition, chromium may be included in the primary precipitated hard phase particles, mainly in the M ₆ X-carbide, thereby contributing to the increase in wear resistance of the steel. Other primary precipitation carbides may also contain chromium, but not the same extent. However, too much chromium can lead to the risk of residual austenite, which is difficult to convert. By deep freeze of the material, the residual austenite content may be removed or at least minimized. For this reason, up to about 20% chromium content in steel may be acceptable, but preferably the chromium content is limited to a maximum of 12%. In the field of steel application, the steel need not be included in an amount greater than 6% to achieve the desired property profile. In a preferred embodiment, the steel comprises 3.5 to 4.5% Cr, most preferably 3.8 to 4.2% Cr.

Molybdenum and tungsten, similar to chromium, will contribute to impart proper hardness and toughness to the matrix of the steel after curing and tempering. Molybdenum and tungsten may also be included in the primary precipitation carbides of M ₆ X type carbides and in such cases may contribute to the wear resistance of the steel. In addition, other primary precipitated carbides may include molybdenum and tungsten, but not to the same extent. The limit is selected so that appropriate properties can be obtained by adapting to other alloying elements. In principle, molybdenum and tungsten can be partially or wholly replaced with each other, which means that tungsten can be replaced by half the amount of molybdenum or molybdenum can be replaced by twice the amount of tungsten. However, from experience, the same amounts of molybdenum and tungsten are known to be preferred because they offer particular advantages in production techniques, in particular in heat treatment techniques. The total content of molybdenum + tungsten is 5-20%, more preferably 15% or less. In combination with other alloying elements, suitable properties for the purpose may be achieved at a content of 9 to 12% (Mo + W / 2). Within this range, the content of molybdenum is, in the preferred embodiment, selected from 4.0 to 5.1%, and the tungsten content is suitably selected from the range of 5.0 to 7.0. The nominal content of molybdenum is 4.6% and tungsten is 6.3%.

The optimal content of cobalt in the steel depends on the intended use of the steel. For applications where the steel is typically used at room temperature or for applications that are not heated to a particular high temperature in normal use, the steel does not include intentionally added cobalt, which can reduce the toughness of the steel. And the risk of chipping when using the tool. In addition, increasing the cobalt content will increase the hardness in the soft annealed state, and at contents in excess of about 14%, the tool will be significantly more difficult to machine, ie turning, It will be very difficult to mill, drill and saw. If steel is used in chip cutting tools where high temperature hardness is an important issue, it will be desirable to contain a significant amount of cobalt, in which case up to 20% may be acceptable, although preferred high temperature hardness is 7 to It may be achieved at a cobalt content of 14%. When used in chip cutting tools, the steel according to the invention will more preferably comprise 8.0 to 10.0% Co and even more preferably 8.8 to 9.3% Co.

Niobium is an element that plays an important role in the steel according to the invention. It is known that the addition of small amounts of niobium of less than 1% can reduce the size of carbides, which is particularly positive in terms of toughness and hardness of the material. According to known logic, niobium may replace vanadium. However, this will affect the wear resistance and will make polishing of the material difficult, especially if the steel contains about 4% or more niobium and / or vanadium.

The correlation between the total content and proportions of vanadium and niobium in which steel can be surprisingly easily polished despite the high content of carbide formers, ie the total content of vanadium and niobium on the one hand and between vanadium and niobium on the other hand The interrelationships of the ratios were previously unknown and at least not known to the applicant of the present invention. Such interrelationships are fundamental to the spirit of the present invention and have been clearly understood by the applicant through extensive testing as further described below. According to the spirit of the invention, the content of niobium and vanadium elements and their proportions lie within the area defined by the coordinates (A, B, C) in the coordinate system of FIG. 1, while the total content of niobium and vanadium is different On the one hand, there is a balance with respect to the content ratio (Nb / V) of niobium and vanadium. More preferably, in the region where the total content (Nb + V) of these elements and their ratio (Nb / V) is defined by the coordinates (D, E, F), more preferably the coordinates (G, H, Balanced within the area defined by I), where:

[(Nb + V); (Nb / V)]

A: [4.0; 0.55]

B: [4.0; 4.0] C: [7.0; 0.55]

D: [4.25; 0.55]

E: [4.25; 3.5]

F: [6.7; 0.55]

G: [4.5; 0.55 H: [4.5; 3.0]

I: [6.4; 0.55].

Within the scope of the present invention, it can be seen that, despite the high alloy content of niobium and vanadium, the size of the primary MX-carbide can be limited, which contributes to the improvement of abrasiveness.

The steel according to the invention has been found that the higher the Nb / V ratio of the steel, the less it grows the MX-carbide at various high temperature operations during the production of such steel, for example in HIP operations, forging, rolling.

There is a certain relationship between the carbide formed in the steel and the total content of the carbide, and the investigation revealed that the higher the carbide content in the steel, the larger the size of the carbide. This relationship is valid for both M ₆ X-carbide and MX-carbide. In addition, the investigation confirmed that at constant volumeion and process parameters, the M ₆ X-carbide was larger than the MX-carbide. This means that when the maximum size of carbide in the steel is specified, the alloy composition can be adjusted such that the steel has an MX-carbide of 1.5 to 2 times the content of M ₆ X-carbide.

It has also been found that there is a closer correlation between the increase in the size of MX-carbide and the content of MX-carbide in niobium-alloyed steels than steel without niobium. These results indicate that addition of niobium is desirable only within certain maximum contents of MX-carbide, and in more cases not.

According to the spirit of the present invention, high demands for toughness and hardness in combination with high yield point, high fatigue strength, high flexural strength and relatively good wear resistance can be satisfied and steel with improved polishing properties can also be provided. This can be achieved when the steel has a composition according to claim 1, wherein the composition is balanced with respect to the total content of niobium and vanadium with a specific ratio between niobium and vanadium. Accordingly, the total content of niobium and vanadium must satisfy the conditions of 4.0 ≦ Nb + V ≦ 7.0, preferably 4.25 ≦ Nb + V ≦ 6.7 and more preferably 4.5 ≦ Nb + V ≦ 6.4, while simultaneously between niobium and vanadium The ratio of must satisfy the conditions of 0.55 ≦ Nb / V ≦ 4.0, preferably 0.55 ≦ Nb / V ≦ 3.5 and more preferably 0.55 ≦ Nb / V ≦ 3.0. In the most preferred embodiment, the steel comprises 2.0 to 2.3% Nb and 3.1 to 3.4% V. In addition, the steel has an MX-carbide content of at most 15% by volume, preferably at most 13% by volume, more preferably at most 11% by volume, wherein at least 80% of the MX-carbide, preferably at least 90%, More preferably at least 95% has a carbide size with a longest extension of 3 μm or less, preferably 2.2 μm or less, more preferably 1.8 μm or less. Further, the content of M ₆ X-carbide in the steel is at most 15% by volume, preferably at most 13% by volume, and more preferably at most 12% by volume, and at least 80% of the M ₆ X-carbide, preferably M ₆ X-carbide forming elements such that the longest extension is at least 90%, more preferably at least 95%, and has a carbide size of 4 μm or less, preferably 3 μm or less, more preferably 2.5 μm or less. With respect to chromium, molybdenum and tungsten the composition of the steel must be balanced and adjusted.

In addition, the steel according to the invention does not contain additional alloying elements intentionally added. The total content of copper, nickel, tin and lead, and carbide-forming agents such as titanium, zirconium and aluminum should be less than 1%. In addition to these elements and the aforementioned elements, the steel does not contain any elements other than unavoidable impurities and other residual products from the metallurgical melting treatment of the steel.

Experiment at the laboratory scale

A total of nine test materials were prepared. The chemical compositions of these materials are listed in Table 1 below.

The powder was obtained from steel using a gas atomizing method. Each steel powder was consolidated by a rapid hot hydrostatic press called HIP / QIP in a small test capsule on a larger production capsule. Samples were taken from small test capsules and the samples were heat treated in several ways to simulate typical manufacturing conditions according to Table 2 below.

Carbide Content and Size

The size and content of MX-carbide in the experimental steels was dependent on the heat treatment in Table 2 where the steel was exposed. These results can be confirmed from Table 3.

1 shows a graph of the size of MX-carbide for the sixth heat treatment. In the figure, the niobium-added steel is indicated by black dots, and the niobium-free steel is indicated by a hollow circle. From the figure, it can be seen that the MX-carbide is significantly smaller in Nb-containing steel than in steel without the addition of Nb.

The results of investigations on the content and size of the M ₆ X-carbide of the experimental steel depending on the heat treatment according to Table 2 with the steel exposed are described in Table 4 below.

The maximum content that niobium addition can have a positive effect on the size of MX-carbide depends on the temperature and dwell time during processes such as HIP operation, rolling and forging at normal temperatures for high speed steel . As a result, the addition of niobium was advantageous for steels having an MX-carbide content of 15% by volume or less, preferably 13% by volume or less, more preferably 11% by volume or less, but having a higher proportion of MX-carbide. In the case of steel, the addition of niobium inversely resulted in larger MX-carbide.

FIG. 3 shows a graph of the size of M ₆ X-carbide for the sixth heat treatment for steels in Table 4. FIG. In the figure, the niobium-added steel is indicated by black dots, and the niobium-free steel is indicated by hollow circles. From the figure it can be seen that the addition of Nb did not have a measurable effect on the size of the M ₆ X-carbide.

As clearly shown in Fig. 4, in various hot-working operations in which steel is subjected to manufacturing during manufacturing such as HIP work, forging and rolling, the higher the Nb / V ratio of the steel, the steel according to the present invention is characterized by We can see that it is less affected by the size. It can be seen from FIG. 4 that the hot-machining operation has a small impact on the size of the MX-carbide in steels with an Nb / V ratio of about 0.6 or higher.

FIG. 5 is a graph showing lattice constants (lattice spacing) in the plane d _{( hkl )} for MX-carbide and M ₆ X-carbide as a function of Nb / V ratio. In the case of MX-carbide, the (111) -spacing was measured and in the case of M ₆ X-carbide, the (331) -spacing was measured. Here, the addition of niobium does not appear to affect the spacing between the lattice of M ₆ X-carbide, indicating that the addition of niobium does not affect the composition of M ₆ X-carbide. In the case of MX-carbide, a linear relationship seems to be established between the lattice constant and the increase in Nb / V ratio, indicating that niobium is dissolved in the MX-carbide. However, steel (G) deviates from this because it appears that large (> 20 μm) MX-carbide is formed in the melt before granulation occurs, which means that less Nb is formed during or during the granulation. It can be used in the MX-carbide formed later.

Microstructure

The steel according to the invention has a microstructure consisting of a structure of tempered martensite comprising MX-carbide and M ₆ X-carbide uniformly distributed in martensite in the hardened and tempered state, such tissue being between 950 and 1250 It may be obtained by curing the product from an austenitization temperature of ° C, cooling to room temperature and tempering at 480-650 ° C. The steel according to the invention has an MX-carbide content of up to 15% by volume, preferably up to 13% by volume, more preferably up to 11% by volume, wherein at least 80%, preferably at least 90% of the MX-carbide More preferably, at least 95% has a carbide size of 3 m or less in the longest length, preferably 2.2 m or less, more preferably 1.8 m or less. Further, the content of M ₆ X-carbide in the steel is at most 15% by volume, preferably at most 13% by volume, and more preferably at most 12% by volume, and at least 80% of the M ₆ X-carbide, preferably Is a M ₆ X-carbide forming element, chromium, molybdenum, so that it has a carbide size of at least 90%, more preferably at least 95% and its longest length is 4 μm or less, preferably 3 μm or less, more preferably 2.5 μm or less. And with respect to tungsten the composition of the steel should be balanced.

Figure 6 is a photograph showing the microstructure of the alloy (F), that is, according to the present invention. From such photographs we can see uniformly distributed black / dark gray MX-carbide and somewhat larger white / light gray M ₆ X-carbide. The steel is 5.5 volume% MX-carbide with an average size of 0.5 microns and the largest 100 MX-carbides in an area of about 20,000 μm, and an average size of 1.1 μm, and a largest 100 in an area of 1.2 μm with an average size of 1.2 μm the average size of the M ₆ X- carbide comprises a carbide of M ₆ X- 11.8% by volume of 2.2 ㎛. The bright areas surrounding the MX-carbide are due to etching and in practice there is no corresponding in the material.

Abrasiveness

According to one aspect of the invention, the steel has good abrasiveness. Above all, since the size of the MX-carbide affects the polishing property of the steel, the larger the carbide in the steel, the lower the polishing property. The abrasiveness of steel can be given as a G ratio, which is a measure of how hard the material is in polishing. The G ratio of the steel was measured in the hardened and annealed state by surface grinding the test piece from a size of 7x7x150 mm to 2x7x150 mm with a commercially available disk of alumina called a white disc. In general, the G ratio is given as the volume of the polished steel material to the volume of the abrasive disk consumed. Materials that are easily polished have high G ratio values, while materials that are difficult to polish are indicated by low G ratio values. 7 shows abrasiveness as a function of size of MX-carbide. It can be seen that the abrasiveness of steel with small size MX-carbide is significantly improved compared to other steels with MX-carbide content in the same volume range.

By comparing the energy consumption during polishing, referred to as PUD 169 and 1.69% (C + N), 0.65% Si, 0.3% Mn, 4.0% Cr, 4.6% Mo, 6.3% W, 9.0% Co, 3.2% V and 2.1 % Nb and the steel according to the invention having a composition consisting of the remaining iron and impurities and referred to as ASP 2052 and having a composition consisting of 1.6 C, 4.8 Cr, 2.0 Mo, 10.5 W, 8.0 Co, 5.0 V and the remaining iron and unavoidable impurities The highest chip excavation rate values were compared for the reference steel. The results are shown in FIG. 8, and from the results it can be seen that the steel according to the invention can be milled at a chip excavation rate of about 60% greater than the comparative material when the energy consumption is the same, which is significant from a manufacturing standpoint. This can be an advantage.

A number of cutting tool inserts were made from the steel and comparative material according to the invention, and such inserts were coated with TiAlN, so called Futura coating. Using a steel plate, a test was carried out on two materials to measure the cutting speed corresponding to the life of one hour. The test used the following parameters: In other words:

Radial cutting depth = 10 mm,

Axial cutting depth = 3 mm,

Feed = 0.1 mm / tooth, dry processing,

Working material = Impax.

In the test, a cutting speed of 83 m / min was measured in the steel according to the present invention, while a cutting speed for the comparative material was measured at 77 m / min, indicating that the steel according to the present invention had significantly better performance than the comparative material. It means to have.

Pilot scale experiments

Hardened Tempered  Hardness in state

Two variants, each about 200 kg, were prepared from the steel according to the invention via gas atomization and HIP operations. About 10 kg of pilot capsules were made from this powder, and test pieces were taken from such capsules to measure hardness after curing and tempering treatment. These variants of the steel according to the invention are intended for applications with high toughness and high hardness, for example for tools for stamping patterns or profiles on metals, etc. and end-cutters with shaving separators. And for use in tool steels for removing chips, such as tabs. Similar properties will be required in steel for use in tools for cold-working. The compositions of these steels are listed in Table 5. The test results are listed in Table 6.

Depending on the intended use of the steel, an optimal hardness is selected in the 50-70 HRC hardness range. In applications where a high hardness is required while a low hardness of 50-55 HRC is desired, first the content of C, together with the content of N, and at least some of W, V, Nb, Mo and Co, are limited to The low limit for steel is approached approximately, and the austenitization temperature during cure is selected below 1100 ° C.

In the case of steel for use in hot-working tools, such as extrusion of aluminum profiles, one of the most important properties is that the steel must have a high tempering resistance, which means that the steel obtained from hardening and tempering even after prolonged exposure to high temperatures It means not to lose hardness. On the other hand, such hardness does not need to be extremely high, and sizes of 50-55 HRC would be suitable. Instead, if the steel is intended for use in advanced mechanical elements, the main property would be high hardness and strength combined with great toughness. In this case, it is common for the hardness after tempering to be in the range of 55-60 HRC. In these two applications, the steel is suitably heat treated at an austenitization temperature of 1000-1250 ° C., typically 1150-1200 ° C., and tempered for 3 × 1 h at a tempering temperature of 550-600 ° C.

However, in the case of steel for tool removal for stamping patterns or profiles on metals, etc. and for steel for chip removal, such as end-cutters, tabs, and gear cutting tools with shaving separators, 60-70 HRC High hardness is required.

The tabs should have a hardness of 60-67 HRC and the end-cutter should have a hardness in the range of 62-70 HRC. In these two applications, steel is used at austenitization temperatures of 1000-1250 ° C., typically 1150-1200 ° C. for tools for chip removal, and austenitization temperatures of 1000-1250 ° C. for cold working tools. Appropriately heat-treated at and tempered for 3 × 1 h at a tempering temperature of 480-580 ° C., typically 550-570 ° C., and has a hardness of 50-55 HRC. If the steel contains nitrogen, the tempering temperature may be lowered for the same reasons as described above.

In a preferred embodiment, the nominal composition of the steel is: 1.69% (C + N), 0.65% Si, 0.3% Mn, 4.0% Cr, 4.6% Mo, 6.3% W, 9.0% Co, 3.2% V and 2.1% Nb And the remaining iron and unavoidable impurities. Such steel is particularly suitable for cutting tools, since the abrasiveness is significantly improved over the materials mentioned in the introduction, while at the same time the other properties are similar. Such steels have also been found to have improved machinability, mainly compared to ASP 2052.

Claims (24)

Tool steels for hot working or tool steels for cold working or tool steels for chip cutting devices or steels for highly mechanical elements, which are manufactured from powder metallurgy and which have a chemical composition of% by weight: 1.1-2.3 C + N 0.1-2.0 Si 0.1-3.0 Mn Up to 20 Cr 5-20 (Mo + W / 2) 0-20 Co, The total content of niobium and vanadium (Nb + V) is the niobium content and vanadium so that the content of niobium and vanadium and the ratio between them lies within the area defined by coordinates A, B and C in the coordinate system of FIG. Determined in relation to the ratio between the contents (Nb / V), The coordinate is A: [4.0; 0.55], B: [4.0; 4.0], C: [7.0; 0.55], And inevitable impurities from Cu, Ni, Sn, Pb, Ti, Zr, and Al, the remaining iron and steel manufacturing, with a total amount of 1% or less. Tool steel. The method of claim 1, The content of niobium and vanadium and the ratio between the contents are coordinates D: [4.25; 0.55], E: [4.25; 3.5], F: [6.7; 0.55], the total content of niobium and vanadium (Nb + V) is determined in relation to the ratio between niobium content and vanadium content (Nb / V). Tool steel. The method of claim 2, The content of niobium and vanadium and the ratio between the contents are coordinates G: [4.5; 0.55], H: [4.5; 3.0], I: [6.4; 0.55], the total content of niobium and vanadium (Nb + V) is determined in relation to the ratio between niobium content and vanadium content (Nb / V). Tool steel. The method of claim 3, wherein The total content of carbon and nitrogen in the steel is 1.4 to 2.0%, preferably 1.60 to 1.90% Tool steel. The method of claim 4, wherein The total content of carbon and nitrogen in the steel is 1.65 to 1.80% Tool steel. The method of claim 1, The steel comprises 0.2-1.2% Si, preferably 0.4-0.8% Si Tool steel. The method of claim 6, The steel comprises 0.55-0.70% Si Tool steel. The method of claim 1, The steel comprises 0.1-0.5% Mn, preferably 0.2-0.4% Mn Tool steel. The method of claim 1, The steel comprises 3-6% Cr, preferably 3.5-4.5% Cr Tool steel. The method of claim 9, The steel comprises 3.8-4.2% Cr Tool steel. The method of claim 1, The steel comprises 5-15% (Mo + W / 2), preferably 9-12% (Mo + W / 2) Tool steel. The method of claim 11, The steel comprises 4.0-5.1% Mo and 5.0-7.0% W Tool steel. The method of claim 11, The steel comprises 4.4-4.9% Mo and 6.1-6.7% W Tool steel. The method of claim 1, The steel comprises 5.0-14.0% Co, preferably 8.0-10.0% Co, more preferably 8.8-9.3% Co Tool steel. The method of claim 1, The steel comprises 2.0-2.3% Nb and 3.1-3.4% V Tool steel. The method of claim 11, Cured at an austenitization temperature of 950-1250 ° C., tempered for 3 × 1 h at tempering temperature of 480-650 ° C., and having a hardness of 50-70 HRC Tool steel. The method of claim 16, Has a micro-structure consisting of tempered martensite having an MX-carbide content of up to 15% by volume and an M ₆ X-carbide content of up to 15% by volume, At least 80% of the MX-carbide has a carbide size of 3 μm or less in its longest length, and at least 80% of the M ₆ X-carbide has a carbide size of 4 μm or less in its longest length. Tool steel. The method of claim 17, The content of the MX-carbide is 13 vol% or less, more preferably 11 vol% or less, 90% or more, more preferably 95% or more of the MX-carbide has a longest length of 2.2 m or less, more preferably Has a carbide size of 1.8 μm or less, The M ₆ X-carbide content is 13% by volume or less, more preferably 12% by volume or less, 90% or more, more preferably 95% or more of the M ₆ X-carbide has a longest length of 3 μm, More preferably having a carbide size of 2.5 μm or less Tool steel. In tools for hot working or chip cutting machining or for cold working or highly mechanical elements, 19. A tool comprising the steel according to any one of the preceding claims. The method of claim 19, The steel is hardened at an austenitization temperature of 950-1050 ° C., tempered for 3 × 1 h at a tempering temperature of 550-600 ° C., and has a hardness of 50-55 HRC. The method of claim 19, The steel is hardened at an austenitization temperature of 1000-1250 ° C., tempered at 3 × 1 h at a tempering temperature of 480-580 ° C., and has a hardness of 60-70 HRC. A method for manufacturing tools for hot working or chip cutting machining or for cold working or highly mechanical elements, A method of manufacturing a steel melt and gas spraying the melt of the steel to form a steel powder, the steel powder is agglomerated by hot hydrostatic pressing called HIP to have a shape close to the final shape of the tool. Forming a tool blank or steel blank having a chemical composition according to any one of the preceding claims, and grinding the tool blank to a final dimension, The blank is cured at an austenitization temperature of 950-1250 ° C., tempered for 3 × 1 h at a tempering temperature of 480-650 ° C., has a hardness of 50-70 HRC, an MX-carbide content of 15% by volume or less and 15 Has a micro-structure consisting of tempered martensite having a M ₆ X-carbide content of up to volume percent, 80% or more of the MX-carbide has a carbide size of 3 μm or less in the longest length, and 80% or more of the M ₆ X-carbide has a carbide size of 4 μm or less in the longest length. The method of claim 22, Prior to said hardening and tempering, hot forming said steel blank and / or cold working said steel blank to form a tool blank. The method of claim 22, A tool manufacturing method, characterized in that the surface of the tool is coated by, for example, PVD or CVD.

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