JP5225843B2 - Steel produced by powder metallurgy, tool including the steel, and method for producing the tool - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tip removal tool, preferably a cutting tool, tap and end with a shaving separator, which has improved grindability and requires good hardness, particularly high temperature hardness and high toughness. The present invention relates to a new steel suitable for a coated tool such as a cutter, preferably a high-speed steel produced by powder metallurgy. Yet another field of application is tools whose use requires high toughness with the hardness and strength appropriate for the application. Among these applications are advanced machine elements such as hot working tools, eg aluminum profile extrusion dies and hot rolling rollers, and press rollers, ie stamps of patterns or profiles such as metal Tools. Yet another application area may be cold working tools where good grindability and good hardness are important properties.

  For example, one of the most important properties for steel used in aluminum profile extrusion tools is that the steel has a high tempering resistance, which is imparted to the steel by hardening and tempering. It means that the steel can be exposed to high temperature for a long time without losing its hardness. On the other hand, this hardness need not be extremely high and is suitably on the scale of 50-55 HRC.

  Instead, when steel is used for advanced mechanical elements, the main properties are high hardness and strength with high toughness, and there are stringent requirements for homogeneity. In this case, the hardness after tempering may generally be in the range of 55-60 HRC.

  However, for steel for stamping tools with patterns or profiles such as metal, and steel for chip removal with shaving separators such as hobbing tools, taps, and end cutters, higher hardness and 60-70 HRC are required. Is done. The tap should have a hardness in the range of 60-67 HRC and the end cutter should have a hardness in the range of 62-70 HRC. When steel is used in a cold work tool, the steel must have similar hardness.

  The invention also relates to a tool for hot working or chip removal or cold work made from said steel, or an advanced machine element, and a method for its production.

Prior Art One type of steel used for cutting operations is a high speed steel marketed under the trade name ASP® 2052, which is characterized by the following nominal composition. 1.6% by weight C, 4.8 Cr, 2.0 Mo, 10.5 W, 8.0 Co, 5.0 V, balance iron, and inevitable impurities. Another high speed steel has a nominal composition of 1.28 C, 4.2 Cr, 5.0 Mo, 6.4 W, 3.1 V, 8.5 Co, balance iron, And ASP® 2030 with inevitable impurities. Yet another high speed steel has a nominal composition of 2.3 C, 4.2 Cr, 7.0 Mo, 6.5 W, 6.5 V, 10.5 Co, the balance ASP (R) 2060 with iron and inevitable impurities. All contents are weight%.

BRIEF DESCRIPTION OF THE INVENTION Since grinding is a time consuming operation in the manufacture of a tool for chip removal, it is desirable that the steel used in such a tool improve grindability. Accordingly, it is an object of the present invention to provide a new steel, preferably a high speed steel, which has the same beneficial properties as the prior art steels described above except that the grindability of the material is improved. . More specifically, the steel should have the following properties:

-Good grindability in quenched and tempered conditions,
Good toughness in quenched and tempered conditions,
Good hardness in quenched and tempered conditions,
High yield point,
・ High fatigue strength,
・ High bending strength, and ・ Good wear resistance.

  These and other requirements are manufactured by powder metallurgy and are 1.1 to 2.3 C + N by weight%, 0.1 to 2.0 Si, 0.1 to 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 in equilibrium with respect to the ratio (Nb / V) between the niobium content and the vanadium content, As a result, the contents of these elements and the ratios between them are shown in coordinates A, B, C (A: [4.0; 0.55], B: [4.0; 4.0] in FIG. , C: [7.0; 0.55]) and from the manufacture of a total of 1% or less of Cu, Ni, Sn, Pb, Ti, Zr and Al, the balance iron, and steel It can be realized by a steel characterized by having a chemical composition containing unavoidable impurities.

BRIEF DESCRIPTION OF THE FIGURES The present invention will be described in more detail by the following description of an implementation test with reference to the accompanying drawings.

  FIG. 1 shows, for a steel according to the invention, in the form of a coordinate system between the total content of one Nb and V (Nb + V) and the relationship between the other Nb content and the V content (Nb / V). Show the relationship.

  FIG. 2 shows a graph of MX carbide size as a function of the volume fraction of MX carbide.

Figure 3 shows a graph of the size of M ₆ X type carbides as a function of the volume portion of the M ₆ X type carbides.

  FIG. 4 shows a graph of carbide size distribution for various heat treatments and Nb / V ratios.

FIG. 5 shows a graph of lattice spacing in the plane d _(hkl) of d ₍₁₁₁₎ MX type carbide and d _{(331) -0.5Å} M ₆ X type carbide as a function of Nb / V ratio. Show.

  FIG. 6 shows a photograph of the microstructure of steel F of the present invention after heat treatment of number 6.

  FIG. 7 shows a graph of grindability G ratio as a function of MX carbide size.

  FIG. 8 shows a graph of energy consumption during grinding with respect to the excavation rate of the chip.

DETAILED DESCRIPTION OF THE INVENTION The importance of various alloy materials as well as various structural elements in achieving a desired property profile will be described in more detail without being bound by any theory. Unless otherwise stated, in the case of alloy content, the percentage always means weight percent, and in the case of structural elements, the percentage always means volume percent.

When carbon, together with nitrogen, is dissolved in martensite, it should be at least 1.1%, up to 2.3%, preferably at least 1.1%, so as to give the material a suitable hardness for that purpose under quenched and tempered conditions. It should be present at a content between 1.4%, max 2.0%, even more preferably between 1.60 and 1.90%. In addition, carbon and nitrogen, together with niobium and vanadium, should contribute to the appropriate amount of (Nb, V) X type primary precipitated MX type-carbides, nitrides, carbonitrides, tungsten, Together with molybdenum and chromium, it should contribute to the realization of the proper amount of primary precipitated M ₆ X-type carbides, nitrides, carbonitrides in the matrix. For simplicity, such hard phase particles are referred to as carbides in the following description, but the term carbide relates to nitrides and / or carbonitrides when the steel contains nitrogen. I want you to understand. The purpose of such carbides is to impart the desired wear resistance to the material. In addition, since carbides can serve to limit grain growth, they contribute to imparting a fine grained structure to the steel. In one preferred embodiment, the steel contains between 1.65 and 1.80% carbon and nitrogen, which are other alloyed elements of the balanced amount, in particular silicon, chromium, vanadium, and niobium. At the same time, it will give the steel a property profile that is well suited for its purpose, which is achieved by a standard manufacturing process, i.e. by a process in which the manufacturing proceeds according to standard methods without any special effort. Can do.

  Normally, the nitrogen content is 0.1% or less, but higher powders of nitrogen can be dissolved in the steel by powder metallurgy manufacturing techniques. Thus, one embodiment of the steel features a steel containing as much nitrogen as up to 2.3%, which can be obtained by solid phase nitration of the produced powder. Here, the carbon in the hard material that becomes part of the steel of the final tool can be replaced by nitrogen. Replacing carbon with nitrogen provides the advantage of reduced adhesion wear resistance, particularly when the tool operates on sticky materials such as aluminum and certain stainless steels. The steel is also easy to temper, which means that the tempering temperature can be lowered, which is advantageous. If the carbon + nitrogen content is less than 1.1%, adequate hardness and wear resistance cannot be obtained, but if the content exceeds 2.3%, brittleness problems may occur.

Silicon is added to the steel in a content of at least 0.1% in order to improve the fluidity of the steel, which is important in the melt metallurgy process. As the silicon addition to the steel increases, the steel melt becomes more fluid, which is important to avoid clogging associated with granulation. In order to avoid clogging during granulation, the silicon content should be at least 0.2%, even more preferably at least 0.4%. Silicon also contributes to increased carbon activity in silicon alloy embodiments and can be present in amounts up to about 2%. Problems with brittleness occur at contents greater than about 2%, and therefore the steel should suitably not contain more than 1.2% Si. This is because the content exceeding that increases the risk of formation of large M ₆ X-type carbides and reduced hardness under quenched conditions, which limits the silicon content to 1.0% or less. Means even more preferable. In a preferred embodiment, the silicon content is between 0.55% and 0.70%, which, in addition to the advantages mentioned above, provides a steel that is easy to heat-treat in combination with the preferred carbon content for the steel. There was found. That means that the steel can be heat-treated within a wide temperature range while maintaining its characteristic profile, which provides manufacturing advantages.

  Manganese can exist mainly as a byproduct derived from the metallurgical melting process, in which manganese has the known effect of inactivating sulfurous impurities by forming manganese sulfide. For this purpose, manganese should be present in the steel in a content of at least 0.1%. The maximum manganese content in the steel is 3.0%, but the manganese content is preferably limited to a maximum of 0.5%. In a preferred embodiment, the steel contains 0.2-0.4% Mn.

  Sulfur can be present in the steel as a by-product from the manufacture of the steel at a content of up to 800 ppm without affecting the mechanical properties of the steel. Sulfur can be intentionally added up to 1% as an alloy element, which can contribute to improvement of machinability and workability. In one embodiment of the present invention in which sulfur is intentionally added for this purpose, the sulfur content should be between 0.1 and 0.3%, when the manganese content is greater than that of the non-sulfur alloy embodiment. Preferably, it should be selected from 0.5% up to 1.0% so that it is somewhat higher.

  Phosphorus can also be present in the steel at a content of up to 800 ppm as a by-product derived from the production of the steel without affecting the mechanical properties of the steel.

Chromium, when dissolved in the steel matrix, has a steel content of at least 3%, preferably at least 3.5% to contribute to providing a steel that achieves adequate hardness and toughness after quenching and tempering. Should exist. Chromium can also contribute to the wear resistance of steel by being contained in primary precipitated hard phase particles, mainly M ₆ X-type carbides. Other primary precipitated carbides also contain chromium, but not to the same extent. However, too much chromium can lead to residual austenite which can be difficult to convert.

  By deep freezing the material, the residual austenite content can be eliminated or at least minimized. Thus, steel can have a chromium content of up to about 20%, but the chromium content is preferably limited to a maximum of 12%. The steel need not necessarily contain more than 6% chromium in order to achieve the desired property profile in the field of application intended for the steel. In a preferred embodiment, the steel contains between 3.5 and 4.5% Cr, most preferably between 3.8 and 4.2% Cr.

Molybdenum and tungsten, like chromium, contribute to the steel matrix obtaining the appropriate hardness and toughness after quenching and tempering. Molybdenum and tungsten can also be included in the primary precipitation carbides of M ₆ X-type carbides, and as such contribute to the wear resistance of the steel. Other primary precipitated carbides also contain molybdenum and tungsten, but not to the same extent. Limits are selected to obtain appropriate properties by adapting to other alloying elements. In principle, molybdenum and tungsten can be partially or completely replaced with each other, which means that half the amount of molybdenum can replace tungsten, or double the amount of tungsten can replace molybdenum. However, experience has shown that approximately equal amounts of molybdenum and tungsten are preferred. This is because this provides several advantages for manufacturing technology or more specifically for heat treatment technology. The total content of molybdenum + tungsten should be in the range of 5-20%, more preferably 15% or less. Properties suitable for this purpose will be realized with a content between 9 and 12% (Mo + W / 2) in combination with other alloying elements. Within such a range, the molybdenum content should be selected from a range of 4.0-5.1% in a preferred embodiment, and the tungsten content is suitably selected from a range of 5.0-7.0. It should be. The nominal content of molybdenum is 4.6% and for tungsten is 6.3%.

  The presence of optional cobalt in the steel depends on the intended use of the steel. For applications where steel is usually used at room temperature or not heated to high temperatures during normal use, cobalt reduces the toughness of steel and the risk of chipping when using tools. The steel should not intentionally contain added cobalt. Furthermore, the hardness under soft annealed conditions increases with increasing cobalt content, and at a content above about 14%, the tool is significantly machined, ie turning, rolling, drilling, sawing, etc. It becomes difficult. When steel is used in a chip cutting tool with outstanding high temperature hardness, the steel preferably contains a substantial amount of cobalt, in which case a maximum content of 20% is possible. Desirable high temperature hardness can be achieved with a cobalt content in the range of 7-14%. When used in a chip cutting tool, the steel of the present invention still more preferably contains between 8.0 and 10.0% Co, even more preferably between 8.8 and 9.3% Co. Should do.

  Niobium is an element that plays an important role in the steel of the present invention. It is already known that the addition of as little as 1% niobium can reduce the size of the carbide, which is particularly favorable for the toughness and hardness of the material. According to known arguments, niobium can be replaced with vanadium. However, this affects the wear resistance and also makes the material difficult to grind, especially if the steel contains niobium and / or vanadium in a content of about 4% or more.

  What was not known, at least not known by the Applicant, is surprisingly related to the total content of one vanadium and niobium and the ratio between the other vanadium and niobium. Despite the high content of such carbide formers, the steel is still easy to grind. This relationship is the basis for the concept of the present invention and has become apparent to the applicant through extensive testing as described further below. According to the concept of the present invention, the total content of one niobium and vanadium is related to the ratio between the other niobium content and the vanadium content (Nb / V), the content of these elements as well as the ratio between them. It should be balanced so that it lies within the area defined by the coordinates A, B, C in the coordinate system of FIG. More preferably, the total content of these elements (Nb + V) and the ratio between them (Nb / V) is within the region defined by coordinates D, E, F, and even more preferably coordinates G, H, I Is balanced within the region defined by

[(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]
Despite the high alloy content of niobium and vanadium, it has been shown within the scope of the present invention that the size of the primary MX carbide can be limited, which contributes to improved grindability.

  Further, the steel of the present invention can further increase the Nb / V ratio of the steel and reduce MX carbide growth in various hot working operations that the steel undergoes during manufacturing, such as HIP sintering, forging, and rolling. Indicated.

In this study, it was also found that there was a relationship between the size of the formed carbides and their total content in the steel, and that the carbide content of the steel increased with increasing carbide size. This relationship is valid for both M ₆ X type carbides and MX type carbides. In addition, this study showed that at fixed volume and process parameters, M ₆ X-type carbides are larger than MX-type carbides. This means that if a steel with a given maximum size carbide is desired, the alloy composition is balanced to give the steel an MX type carbide content 1.5 to 2 times greater than the M ₆ X type carbide content. Is meant to be able to.

  More surprisingly, steels alloyed with niobium have been found to have a stronger relationship between the increase in MX carbide size and the content of MX carbide than steel without added niobium. It was done. This result shows that the addition of niobium is only advantageous up to a certain maximum content of MX-type carbides and not more.

The concept of the present invention provides a steel that meets high demands for high yield point, high fatigue strength, high bending strength, and relatively good wear resistance, as well as toughness and hardness, and improved grinding properties. be able to. This means that the steel is given the composition according to claim 1 of the present invention, which is balanced with respect to the combination of the total content of niobium and vanadium and a certain ratio between niobium and vanadium. Realized in the case. Therefore, the total content of niobium and vanadium should satisfy the condition 4.0 ≦ Nb + V ≦ 7.0, preferably 4.25 ≦ Nb + V ≦ 6.7, and more preferably 4.5 ≦ Nb + V ≦ 6.4. At the same time, the ratio between niobium and vanadium is 0.55 ≦ Nb / V ≦ 4.0, preferably 0.55 ≦ Nb / N ≦ 3.5, and even more preferably 0.55 ≦ Nb / The condition of V ≦ 3.0 should be satisfied. In the most preferred embodiment, the steel should contain 2.0-2.3% Nb and 3.1-3.4% V. Furthermore, the steel should have a MX type carbide content of 15% by volume or less, preferably 13% by volume or less, and even more preferably 11% by volume or less, and at least 80%, preferably at least 90% of MX type carbide. More preferably, at least 95% has a carbide size of 3 μm or less, preferably 2.2 μm or less, and even more preferably 1.8 μm or less, in the longest extension of the carbide. The composition of the steel is such that the M ₆ X-type carbide content in the steel is 15% by volume or less, preferably 13% by volume or less, even more preferably 12 with respect to chromium, molybdenum, and tungsten which are M ₆ X-type carbide forming elements. Volume% or less, and at least 80%, preferably 90%, even more preferably at least 95% of the M ₆ X-type carbides have a maximum carbide elongation of 4 μm or less, preferably 3 μm or less, and even more preferably 2.5 μm. Should be balanced to have the following carbide sizes:

Moreover, the steel of the present invention should not contain additional alloying elements that are intentionally added. The total content of copper, nickel, tin, and lead, and carbide formers such as titanium, zirconium, and aluminum can be less than 1%. In addition to these and the aforementioned elements, steel does not contain other elements other than inevitable impurities and other byproducts derived from the metallurgical melting process of steel.
Note that the M ₆ X-type carbide content under the quenched and tempered conditions is 15% by volume or less, preferably 13% by volume or less, and more preferably 12% by volume or less, and at least 80 % of the M ₆ X-type carbides. %, Preferably at least 90%, and even more preferably at least 95% have a carbide size with a maximum carbide length of 4 μm or less, preferably 3 μm or less, and even more preferably 2.5 μm or less.
It is also desirable for the steel to have a total carbon and nitrogen content of between 1.4 and 2.0%, preferably between 1.60 and 1.90%.
Further, steel containing 0.2 to 1.2% Si, preferably 0.4 to 0.8% Si is desirable.
Further, steel containing 0.1 to 0.5% Mn, preferably 0.2 to 0.4% Mn is desirable.
Further, steel containing 3 to 6% Cr, preferably 3.5 to 4.5% Cr is desirable.
Further, steel containing 5 to 15% (Mo + W / 2), preferably 9 to 12% (Mo + W / 2) is desirable.
Also desirable is steel containing 5.0-14.0% Co, preferably 8.0-10.0% Co, and even more preferably 8.8-9.3 Co.

A total of nine test materials were produced in a laboratory-scale experiment. The chemical composition of these materials is shown in Table 1 below.

  Powder was produced from steel by gas atomizing. Each steel powder was consolidated by high speed hot isostatic pressing, so-called HIP / QIH, in small test capsules on large production capsules. Samples were removed from the test small capsules and the samples were heat treated in several ways to simulate general manufacturing conditions according to Table 2 below.

Carbide Content and Size The MX type carbide content and size of the steel tested varies depending on the heat treatment of Table 2 to which the steel is exposed. This is clear from Table 3 below.

  FIG. 1 shows a graph of MX type carbide size for heat treatment number 6. In the figure, steel with niobium added is marked with black circles, and steel without niobium added is marked with white circles. In the figure, it can be seen that the MX type carbide of the Nb-containing steel is much smaller in size than that of the steel to which Nb was not added.

A corresponding study is shown in Table 4 below regarding the M ₆ X-type carbide content and size of the steels tested, depending on the heat treatment of Table 2 to which the steel is exposed.

  The maximum content at which niobium addition has a positive effect on the size of MX-type carbides is the dwell time and temperature during processes such as HIP, rolling, and forging, at temperatures common to high speed steels. It depends on you. One conclusion from this study is that the addition of niobium is advantageous for steels with MX type carbide content of 15% by volume or less, preferably 13% by volume or less, and even more preferably 11% by volume or less. For steels with more type carbides, the opposite is likely to result in large MX type carbides.

FIG. 3 shows a graph of heat treatment number 6 M ₆ X carbide size for the steels in Table 4. In the figure, steel with niobium added is marked with black circles, and steel without niobium added is marked with white circles. From the figure, it can be seen that the addition of Nb has no measurable effect on the size of the M ₆ X-type carbide.

  Further, as is apparent from FIG. 4, the steel of the present invention has an MX type carbide in various hot working operations that the steel undergoes during manufacture such as HIP, forging and rolling as the Nb / V ratio of the steel increases. It was found that the effect on the size of was reduced. FIG. 4 shows that the hot working operation has little effect on the MX type carbide size of the steel having an Nb / V ratio of about 0.6 or more.

FIG. 5 shows a graph of the lattice spacing in the plane d _(hkl) of MX type carbide and M ₆ X type carbide as a function of the Nb / V ratio. For the MX type carbide, the (111) plane spacing was measured, and for the M ₆ C type carbide, the (331) plane spacing was measured. Here, the addition of niobium does not seem to have any effect on the interstitial spacing of the M ₆ C type carbide, which has no effect on the composition of the M ₆ C type carbide. It is clear that it shows not giving. For MX type carbides, there appears to be a linear relationship between the lattice spacing and the increase in the Nb / V ratio, indicating that niobium dissolves in MX type carbides. However, steel G deviates from this, which is likely because large MX carbides (> 20 μm) are formed in the melt before granulation occurs, ie granulation. For MX carbides formed during or after granulation, this means that a small amount of Nb is available.

Microstructure The steel of the present invention has a microstructure composed of a tempered martensite structure containing MX type carbide and M ₆ X type carbide evenly distributed in martensite under the conditions of quenching and tempering. Is obtained by quenching the product from an austenitizing temperature between 950 and 1250 ° C., cooling to room temperature, and tempering at 480-650 ° C. The steel of the present invention should have an MX type carbide content of 15% by volume or less, preferably 13% by volume or less, and even more preferably 11% by volume or less, wherein at least 80%, preferably at least 80% of MX type carbides. 90%, even more preferably at least 95%, should have a carbide size with a maximum carbide elongation of 3 μm or less, preferably 2.2 μm or less, and even more preferably 1.8 μm or less. The composition of the steel is also such that the M ₆ X-type carbide content of the steel is not more than 15% by volume, preferably not more than 13% by volume, even more preferably not more than 12% by volume, preferably at least 80% of the M ₆ X-type carbide. Is an M ₆ X type carbide forming element such that 90%, even more preferably at least 95%, has a carbide size of 4 μm or less, preferably 3 μm or less, and even more preferably 2.5 μm or less at the maximum elongation of the carbide. Should be balanced with respect to some chromium, molybdenum, and tungsten.

FIG. 6 is a photograph of the microstructure of the steel of the present invention, ie, alloy F in Table 2. This figure shows evenly distributed MX type carbides as black / dark gray, and slightly larger M ₆ X type carbides are white / light gray. This steel has an average size of 5.5 μm MX carbide with an average size of 0.5 μm (100 large MX type carbides in the region of about 20,000 μm have an average size of 1.1 μm) ), And 11.8% by volume of M ₆ X-type carbide having an average size of 1.2 μm (100 maximum M ₆ X-type carbides in an area of about 20,000 μm have an average size of 2.2 μm) contains. The bright areas surrounding the MX-type carbides are formed by etching and there is actually no equivalent in material.

Grindability According to one aspect of the invention, the steel should have good grindability. Above all, the size of the MX-type carbide affects the grindability of steel, and the grindability is impaired as the carbide of steel increases. The grindability of a steel can be expressed as its G ratio, which is a measurement of the difficulty of grinding the material. The G ratio of the steel was measured by surface grinding a 7 × 7 × 150 mm specimen to a size of 2 × 7 × 150 mm with a commercially available disc of alumina, a so-called white disc, under quenching and annealing conditions. The G ratio is usually expressed as the volume of ground steel material relative to the volume of grinding disk consumed. Materials that are easily ground have high G ratios, and materials that are difficult to grind are characterized by low G ratio values. FIG. 7 shows grindability as a function of MX carbide size. It is clear that steel with small size MX-type carbides has a significantly improved grindability compared to other steels with MX-type carbide content in the same volume range.

  The following composition, 1.69% (C + N), 0.65% Si, 0.3% Mn, 4.0% Cr, 4.6% Mo, 6.3% W, 9. A steel of the invention called PUD169 with 0% Co, 3.2% V, and 2.1 Nb, balance iron, and impurities, and the following composition, 1.6 C, 4.8 A reference steel called ASP2052 with a Cr of 2.0, Mo of 10.5, Co of 8.0, Co of 5.0, V of balance, balance iron, and inevitable impurities. By comparing the energy consumption, we were able to compare the maximum excavation rate of the chips. The results are shown in FIG. 8, and it is clear from the results that the steel of the present invention can be milled with a chip drilling rate about 60% higher than the reference material with the same energy consumption. This is a significant advantage from a surface.

  Several cutting tool inserts coated with TiAlN, a so-called Futura coating, were produced from the steel according to the invention and a reference material. In the test, steel plates were used, and the cutting speed corresponding to the life of 1 hour (1 h) was determined for the two materials. The following parameters were used in the test.

Radial cutting depth = 10mm
Axial cutting depth = 3mm
Feed rate = 0.1 mm / tooth, dry machining Processed material = Impax
In this test, a cutting speed of 83 m / min was measured for the steel of the present invention, and the cutting speed of the reference material was measured to be 77 m / min, which means that the steel of the present invention was significantly more than the reference material. It means having good performance.

Pilot Scale Experiment Hardness under Quenched and Tempered Conditions From the steel of the present invention, two variants of approximately 200 kg each were produced by gas atomizing and HIP. About 10 kg of pilot capsules were produced from this powder, and test pieces were taken out of the capsules and evaluated for hardness after quenching and tempering. These steel deformation molds of the present invention are intended for applications requiring high toughness and high hardness. For example, tools for stamping patterns or profiles on metal, etc., and end cutters with taps and shaving separators, etc. Also contemplated for steel for other chip removal tools. When steel is used in cold work tools, the same is required for that steel. Table 5 shows the chemical composition of these steels. The results are shown in Table 6.

  Depending on the field of application for which the steel is intended, the optimum hardness is selected from a hardness in the range of 50-70 HRC. In applications where low toughness of 50-55 HRC is desired but high toughness is preferred, the primary C and any N and at least some W, V, Nb, Mo and Co content present is steel The austenitizing temperature during quenching is selected to be less than 1100 ° C.

  For steels used in hot working tools such as aluminum profile extrusion, one of the most important properties is that the steel has high tempering resistance, which is obtained from quenching and tempering. This means that it should be able to be exposed to high temperatures for a long time without losing its hardness. On the other hand, this hardness does not need to be extremely high, and is preferably a scale of 50 to 55 HRC. Instead, when steel is used for advanced mechanical elements, the main properties are high hardness and strength with high toughness. In this case, the hardness after tempering may generally be in the range of 55-60 HRC. For these two fields of application, the steel is preferably heat treated at an austenitizing temperature of 1000-1250 ° C., typically 1150-1200 ° C., and tempered 3 × 1 h at a tempering temperature of 550-600 ° C.

  Steels for tools that stamp patterns or profiles on metal, etc., and steels for chip removal tools such as hobbing tools, taps, and end cutters with shaving separators, have a hardness of 60-70 HRC with high toughness. Even more strongly required. The tap should have a hardness in the range of 60-67 HRC and the end cutter should have a hardness in the range of 62-70 HRC. When steel is used in cold work tools, the same is required for that steel. For these two fields of application, the steel is preferably heat treated at an austenitizing temperature of 1000-1250 ° C., typically 1150-1200 ° C. for chip removal tools, and 1000-1200 ° C. for cold work tools. And tempered for 3 × 1 h at a tempering temperature of 480-580 ° C., typically 550-570 ° C., and has a hardness in the range of 50-55 HRC. When the steel contains nitrogen, the tempering temperature can be lowered according to the above reason.

  In a preferred embodiment, the steel has the following nominal composition: 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, balance iron, and impurities. Such steels are particularly well suited for cutting tools that are comparable in other properties to the materials described in the introduction, but have shown significant grindability improvements. The steel also showed improved machinability, mainly compared to ASP2052.

A graph showing the relationship between the total content of one Nb and V (Nb + V) and the relationship between the other Nb content and the V content (Nb / V) in the form of a coordinate system for the steel of the present invention. It is. 6 is a graph of MX carbide size as a function of the volume fraction of MX carbide. The size graph of M ₆ X type carbides as a function of the volume portion of the M ₆ X type carbides. 2 is a graph of carbide size distribution for various heat treatments and Nb / V ratios. FIG. 7 is a graph of lattice spacing in the plane d _(hkl) of d ₍₁₁₁₎ MX type carbide and d _{(331) -0.5Å} M ₆ X type carbide as a function of Nb / V ratio. It is a photograph of the microstructure of the steel F of the present invention after the heat treatment of No. 6. FIG. 5 is a graph of grindability G ratio as a function of MX carbide size. FIG. Figure 5 is a graph of energy consumption during grinding in relation to tip excavation rate.

Claims (29)

Produced by powder metallurgy tool steel for hot working or a tool steel for cold working, or a steel for chip cutting machining tool steel, 1.1 to 2 weight%. 3 C + N,
0.1-2.0 Si,
0.1 to 3.0 Mn,
Up to 20 Cr,
5 to 20 (Mo + W / 2), with a maximum of 7.0 W,
0-20 Co,
Here, the total content of niobium and vanadium (Nb + V) is related to the ratio between the niobium content and the vanadium content (Nb / V). The content of these elements and the ratio between them is expressed in the coordinate system of FIG. A, B, C
A: [4.0; 0.55]
B: [4.0; 4.0]
C: [7.0; 0.55]
Balanced to be within the area defined by
S of 1.0% or less,
P of 800 ppm or less,
1% or less total of Cu, Ni, Sn, Pb, Ti, Zr and Al, balance iron, and inevitable impurities
Having a chemical composition consisting of
And MX type carbide | carbonized_material content under the conditions hardened and tempered is 13 volume% or less,
Steel characterized in that at least 90% of MX type carbides have a carbide size of 1.8 μm or less at the maximum carbide length . The steel according to claim 1, wherein the W content is 5.0 to 7.0%. The steel according to claim 1 or 2, wherein the S content is 0.1 to 1.0%. The steel according to claim 1 or 2, wherein the S content is 800 ppm or less. The steel according to any one of claims 1 to 4, wherein the MX type carbide content is 11% by volume or less. The steel according to any one of claims 1 to 5 , characterized in that at least 95% of the MX-type carbide has a carbide size of 1.8 µm or less with the maximum length of the carbide. M _{6 X} type carbide content of conditions wherein is hardening and tempering is a below 15 vol%, at least 80% of the M _{6 X} type carbides, the carbide size of 4μm or less under the maximum length of the carbides The steel according to any one of claims 1 to 6 , characterized by comprising: The microstructure of the steel containing MX type carbide and M ₆ X type carbide is obtained by quenching at an austenitizing temperature of 950 to 1250 ° C. and three times of 1 h tempering at a tempering temperature of 480 to 650 ° C. The steel according to any one of claims 1 to 7 . 9. Steel according to any of claims 1 to 8 , characterized in that it has a hardness in the range of 50 to 70 HRC. The total content of niobium and vanadium (Nb + V) is related to the ratio between the niobium content and the vanadium content (Nb / V), and the content of these elements and the ratio between them are represented by coordinates D, E, F
D: [4.25; 0.55]
E: [4.25; 3.5]
F: [6.7; 0.55]
Steel according to any one of claims 1 to 9 , characterized in that it is balanced so that it lies in a region defined by. The total content of niobium and vanadium (Nb + V) is related to the ratio between the niobium content and the vanadium content (Nb / V), and the content of these elements and the ratio between them are represented by coordinates G, H, I
G: [4.5; 0.55]
H: [4.5; 3.0]
I: [6.4; 0.55]
Steel according to claim 10 , characterized in that it is balanced so that it is in the region defined by Total content of carbon and nitrogen in the steel, characterized in that is between 1.4 and 2.0%, the steel according to any one of claims 1 to 11. 13. Steel according to claim 12 , characterized in that the total carbon and nitrogen content of the steel is between 1.65 and 1.80%. Characterized in that it contains 0.2 to 1.2% of S i, steel according to any of claims 1 to 13. Steel according to claim 14 , characterized in that it contains 0.55 to 0.70% Si. Steel according to any of claims 1 to 15 , characterized in that it contains 0.1 to 0.5% Mn . Characterized in that it contains 3-6% of C r, the steel according to any of claims 1 to 16. 18. Steel according to claim 17 , characterized in that it contains 3.8-4.2% Cr. Steel according to any one of claims 1 to 18 , characterized in that it contains 5 to 15% (Mo + W / 2 ) . 20. Steel according to claim 19 , characterized in that it contains 4.0-5.1 Mo and 5.0-7.0% W. Steel according to claim 20 , characterized in that it contains 4.4 to 4.9 Mo and 6.1 to 6.7% W. Characterized in that it contains from 5.0 to 14.0% of C o, steel according to any of claims 1 21. The steel according to any one of claims 1 to 22 , characterized in that it contains 2.0 to 2.3% Nb and 3.1 to 3.4% V. 請 Motomeko characterized in that it comprises any steel according to one of 1 to 23, hot working or chip cutting machining or tool for cold working. The steel is hardened at an austenitizing temperature of 950 to 1050 ° C., is three times tempering 1h at tempering temperature of 550 to 600 ° C., and having a hardness in the range of 50～55HRC, claim 24 hot working for engineering tool according to. The steel is hardened at an austenitizing temperature of 1000 to 1250 ° C., is three times tempering 1h at tempering temperature of four hundred and eighty to five hundred eighty ° C., and having a hardness in the range of 60～70HRC, claim 24 The tool for chip cutting machining or cold working described in 1. A method of manufacturing a hot working or chip cutting machining or engineering tools for cold working,
A steel melt is produced, the steel melt is gas atomized to form a steel powder, and the steel powder is hardened by a hot isostatic press, so-called HIP, according to any of claims 1 to 23. Form a steel blank or tool blank with the stated chemical composition of the tool approximately in the final shape, quench it at an austenitizing temperature of 950-1250 ° C., and at a tempering temperature of 480-650 ° C. After tempering for 1 h three times , the steel has a hardness in the range of 50 to 70 HRC and an MX carbide content of 15% by volume or less, and at least 80% of the MX carbide has a maximum carbide length of 3 μm or less. of having a carbide size, M 6 _X type carbide content is not more than 15% by volume, have a following carbide size 4μm up to a length of at least 80% of the carbide M 6 _X type carbide That tempering gives a microstructure consisting of martensite, method characterized by comprising grinding said tool material to the final dimensions. 28. Hot working or chip cutting according to claim 27 , characterized in that the steel material is hot worked and / or cold worked before quenching and tempering to form a tool material. method for producing a machining or engineering tools for cold working. Tool, P by VD or CVD, characterized in that it is surface-coated, production method of hot working or chip cutting machining or engineering tools for cold working according to claim 27.

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