HUE030403T2

HUE030403T2 - Corrosion and wear resistant cold work tool steel

Info

Publication number: HUE030403T2
Application number: HUE14187555A
Authority: HU
Inventors: Sebastian Ejnermark; Thomas Hillskog; Lars Ekman; Rikard Robertsson; Victoria Bergqvist; Jenny Karlsson; Petter Damm; Ulrika Mossfeldt; Roland Edvinsson; Svensson Annika Engstroem; Berne Hoegman
Original assignee: Uddeholms Ab
Priority date: 2013-10-02
Filing date: 2014-10-02
Publication date: 2017-05-29
Also published as: AU2014330080A1; EP2857126A2; EP2857126A3; RU2675308C2; CA2924877A1; RU2016109549A; AU2014330080B2; US20160214177A1; BR112016007332B1; BR112016007332A2; PL2857126T3; DK2857126T3; EP2857126B1; WO2015050496A1; CN105705667B; TW201522664A; JP6488287B2; TWI638054B; CN105705667A; CA2924877C

Abstract

The invention relates to a corrosion and wear resistance cold work tool steel. The steel comprises the following main components (in wt. %):
C
0.3 - 0.8
N
1.0-2.2
(C+N)
1.3 - 2.2
C/N
0.17 - 0.50
Si
≤ 1.0
Mn
0.2 - 2.0
Cr
13-30
Mo
0.5 - 3.0
V
2.0 - 5.0

balance optional elements, iron and impurities.

Description

TECHNICAL FIELD

[0001] The invention relates to corrosion and wear resistant cold work tool steel and a method of making the cold work steel and use of the cold work tool steel.

BACKGROUND OF THE INVENTION

[0002] Nitrogen alloyed martensitic tool steels have recently been introduced on the market and attained a considerable interest, because they combine a high wear resistance with an excellent corrosion resistance. These steels have a wide rang of applications such as for moulding of aggressive plastics, for knives and other components in food processing and for reducing corrosion induced contamination in the medical industry.

[0003] The steels are generally produced by powder metallurgy. The basic steel composition is firstly atomized and subsequently subjected to a nitrogenation treatment in order to introduce the desired amount of nitrogen into the powder. Thereafter the powder is filled into a capsule and subjected to hot isostatic pressing (HIP) in order to produce an isotropic steel.

[0004] The amount of carbon is generally reduced to a very low level as compared to conventional tool steels. By substituting most of the carbon with nitrogen it is possible to substitute the chromium rich carbides of the type M7C3 and M23C6 with very stable hard particles of the type MN-nitrides.

[0005] Two important effects are achieved. Firstly, the relative soft and anisotropic phase of M7C3-carbide («1700HV) is replaced by the very hard and stable phase of small and evenly distributed hard phase of the type MN («2800HV). Thereby, the wear resistance is improved at the same volume fraction of hard phase. Secondly, the amount of Cr, Mo and N in solid solution at the hardening temperature is very much increased, because less chromium is bound in the hard phase and because the carbides of the type M23C6 and M7C3 do not have any solubility for nitrogen. Thereby, more chromium is left in solid solution and the thin passive chromium rich surface film is strengthened, which leads to an increased resistance to general corrosion and pitting corrosion.

[0006] Hence, in order to obtain good corrosion properties the carbon content has been limited to less than 0.3 %C, preferably less than 0.1 %C in DE 42 31 695 A1 and to < 0.12 % C in WO 2005/054531 A1.

DISCLOSURE OF THE INVENTION

[0007] The general object of the present invention is to provide a powder metallurgy (PM) produced nitrogen alloyed cold work tools steel alloy having improved properties, in particular a good corrosion resistance in combination with a high hardness.

[0008] A particular object is to provide a nitrogen alloyed martensitic cold work tools steel alloy having improved corrosion resistance at a fixed chromium content.

[0009] A further object is to provide a method of producing said material.

[0010] The foregoing objects, as well as additional advantages are achieved to a significant measure by providing a cold work tool steel having a composition as set out in the alloy claims.

[0011] The invention is defined in the claims.

DETAILED DESCRIPTION

[0012] The importance of the separate elements and their interaction with each other as well as the limitations of the chemical ingredients of the claimed alloy are briefly explained in the following. All percentages for the chemical composition of the steel are given in weight % (wt. %) throughout the description.

Carbon (0.3 - 0.8 %) [0013] is to be present in a minimum content of 0.3%, preferably at least 0.35%. At high carbon contents carbides of the type M23C6 and M7C3 will be formed in the steel. The carbon content shall therefore not exceed 0.8%. The upper limit for carbon may be set to 0.7% or 0.6%. Preferably, the carbon content is limited to 0.5%. Preferred ranges are 0.32 - 0.48%, 0.35 - 0.45%, 0.37 - 0.44% and 0.38 - 0.42%. In any case, the amount of carbon should be controlled such that the amount of carbides of the type M23C6 and M7C3 in the steel is limited to 10 vol. %, preferably the steel is free from said carbides.

[0014] US2008/233225 A1 discloses a powder metallurgically manufactured steel with a chemical composition containing, in % by weight: 0.01-2 C, 0.6-10 N, 0.01-3.0 Si, 0.01-10.0 Mn, 16-30 Cr, 0.01-5 Ni, 0.01-5.0 (Mo+W/2), 0.01-9

Co, max. 0.5 S and 0.5-14 (V+Nb/2), where the contents of N on the one hand and of (V+Nb/2) on the other hand are balanced in relation to each other such that the contents of these elements are within an area that is defined by the coordinates A’, B’, G, H, A’, where the coordinates of [N, (V+Nb/2)] are: A: [0.6,0.5]; B’: [1.6,0.5]; G: [9.8,14.0]; H: [2.6,14.0], and max. 7 of (Ti+Zr+AI), balance essentially only iron and impurities at normal amounts. The steel is intended to be used in the manufacturing of tools for injection moulding, compression moulding and extrusion of components of plastics, and for tools for cold working, which are exposed to corrosion.

Nitrogen (1.0-2.2%) [0015] Contrary to carbon, nitrogen cannot be included in M7C3. The nitrogen contentshould therefore be much higher than the carbon content in order to avoid the precipitation of M7C3-carbides. In order to get the desired type and amount of hard phases the nitrogen content is balanced against the contents of the strong carbide formers, in particular vanadium. The nitrogen content is limited to 1.0- 2.2%, preferably 1.1-1.8% or 1.3 - 1.7%. (C+N) (1.3 - 2.2%) [0016] The total amount of carbon and nitrogen is an essential feature of the present invention. The combined amount of (C + N) should be in the range of 1.3 - 2.2%, preferably 1.7 - 2.1 % or 1.8 - 2.0%. C/N (0.17-0.50) [0017] A proper balance of carbon and nitrogen is an essential feature of the present invention. By controlling the carbon and nitrogen contents the type and amounts of the hard phases can be controlled. In particular, the amount of the hexagonal phase M2Xwill be reduced after hardening. The C/N ratio should therefore be 0.17 - 0.50. The lower ratio may be 0.18, 0.19, 0.20, 0.21,0.22, 0.23, 0.24 or 0.25. The upper ratio may be 0.5, 0.48, 0.46, 0.45, 0.44, 0.42, 0.40, 0.38, 0.36 or 0.34. The upper limit may be freely combined with the lower limit. Preferred ranges are 0.20 - 0.46 and 0. 22 - 0.45.

Chromium (13 - 30%) [0018] When it is present in a dissolved amount of at least 11%, chromium results in the formation of a passive film on the steel surface. Chromium shall be present in the steel in an amount between 13 and 30 % in order to give the steel a good hardenability and oxidation and corrosion resistance. Preferably, Cr is present in an amount of more than 16% in order to safeguard a good pitting corrosion resistance. The lower limit is set in accordance to the intended application and may be 17%, 18%, 19%, 20%, 21% or 22%. However, Cr is a strong ferrite former and in order to avoid ferrite after hardening the amount need to be controlled. For practical reasons the upper limit may be reduced to 26%, 24% or even 22%. Preferred ranges include 16 - 26%, 18 - 24%, 19 - 21%, 20 - 22% and 21 - 23%.

Molybdenum (0.5 - 3.0%) [0019] Mo is known to have a very favourable effect on the hardenability. It is also known to improve the pitting corrosion resistance. The minimum content is 0.5%, and may be set to 0.6%, 0.7%, 0.8% or 1.0%. Molybdenum is a strong carbide forming element and also a strong ferrite former. The maximum content of molybdenum is therefore 3.0%. Preferably Mo is limited to 2.0 %, 1.7% or even 1.5%.

Tungsten (< 1%) [0020] In principle, molybdenum may be replaced by twice as much tungsten. However, tungsten is expensive and it also complicates the handling of scrap metal. The maximum amount is therefore limited to 1%, preferably 0.2% and most preferably no additions are made.

Vanadium (2.0 - 5.0%) [0021] Vanadium forms evenly distributed primary precipitated nitrocarbides of the type M(N,C) in the matrix of the steel. In the present steels M is mainly vanadium but significant amounts of Cr and Mo may be present. Vanadium shall therefore be present in an amount of 2-5. The upper limit may be set to 4.8%, 4.6%, 4.4%, 4.2% or 4.0%. The lower limit may be 2.2%, 2.4%, 2.5%, 2.6%, 2.7%, 2,8%, 2.8% and 2.9%. The upper and lower limits may be freely combined within the limits set out in claim 1. Preferred ranges includes 2 - 4%.

Niobium (<2.0%) [0022] Niobium is similar to vanadium in that it forms nitrocabides of the type M(N,C) and may in principle be used to replace vanadium but that requires the double amount of niobium as compared to vanadium. Hence, the maximum addition of Nb is 2.0%. The combined amount of (V + Nb/2) should be 2.0-5.0%. However, Nb results in a more angular shape of the M(N,C). The preferred maximum amount is therefore 0.5%. Preferably, no niobium is added.

Silicon (<1.0%) [0023] Silicon is used for deoxidation. Si is present in the steel in a dissolved form. Si is a strong ferrite former and should therefore be limited to <1.0%.

Manganese (0.2 - 2.0%) [0024] Manganese contributes to improving the hardenability of the steel and together with sulphur manganese contributes to improving the machinability by forming manganese sulphides. Manganese shall therefore be present in a minimum content of 0.2%, preferably at least 0.3%. At higher sulphur contents, manganese prevents red brittleness in the steel. The steel shall contain max.2.0%, preferably max. 1.0 %Mn. Preferred ranges are 0.2 - 0.5%, 0.2 - 0.4%, 0.3 - 0.5% and 0.3 - 0.4%.

Nickel (< 5.0%) [0025] Nickel is optional and may be present in an amount of up to 5%. It gives the steel a good hardenability and toughness. Because of the expense, the nickel content of the steel should be limited as far as possible. Accordingly, the Ni content is limited to 1%, preferably 0.25%.

Copper (< 3.0%) [0026] Cu is an optional element, which may contribute to increasing the hardness and the corrosion resistance of the steel. If used, a preferred range is 0.02 - 2% and a most preferred range is 0.04 -1.6%. However, it is not possible to extract copper from the steel once it has been added. This drastically makes the scrap handling more difficult. For this reason, copper is normally not deliberately added.

Cobalt (< 10.0%) [0027] Co is an optional element. It contributes to increase the hardness of the martensite. The maximum amount is 10 % and, if added, an effective amount is about 4 to 6 %. However, for practical reasons such as scrap handling there is no deliberate addition of Co. A preferred maximum content is 0.2%.

Sulphur (< 0.5%) [0028] S contributes to improving the machinability of the steel. At higher sulphur contents there is a risk for red brittleness. Moreover, a high sulphur content may have a negative effect on the fatigue properties of the steel. The steel shall therefore contain < 0.5 %, preferably < 0.035%.

Be, Bi, Se, Mg and REM (Rare Earth Metals) [0029] These elements may be added to the steel in the claimed amounts in order to further improve the machinability, hot workability and/or weldability.

Boron (< 0.01%) [0030] B may be used in order to further increase the hardness of the steel. The amount is limited to 0.01%, preferably <0.004%.

Ti, Zr, AI and Ta [0031] These elements are carbide formers and may be present in the alloy in the claimed ranges for altering the composition of the hard phases. However, normally none of these elements are added.

Hard phases [0032] The total content of the hard phases MX, M2X, M23C6 and M7C3 shall not exceed 50 vol. %, wherein M is one or more of the above specified metals, in particular V, Mo and/or Cr and X is C, N and/or B and wherein the contents of said hard phases fulfil the following requirements (in vol. %): MX 3-25 preferably 5-20 M2X <10 preferably < 5 M23C6 + M7C3 <10 preferably <5 [0033] More preferably the content of MX is 5 -15 vol. %, the content of M2X is < vol. 3% and the content of M23C6 + M7C3 is < 3 vol. %. Most preferably the steel is free from the component M7C3.

PRE

[0034] The pitting resistance equivalent (PRE) is often used to quantify pitting corrosion resistance of stainless steels. A higher value indicates a higher resistance to pitting corrosion. For high nitrogen martensitic stainless steels the following expression may be used

PRE= %Cr +3.3 %Mo + 30 %N wherein %Cr, %Mo and %N are the calculated equilibrium contents dissolved in the matrix at the austenitising temperature (TA), wherein the chromium content dissolved in the austenite is at least 13 %.. The dissolved contents can be calculated with Thermo-Calc for the actual austenitising temperature (TA) and/or measured in the steel after quenching.

[0035] The austenitising temperature (TA) is in the range of 950 - 1200 °C, typically 1080-1150°C.

[0036] It follows from the above reasoning that the austenite composition at austenizing temperature may have a considerable effect on the pitting corrosion resistance of the steel. The lower limit for the calculated PRE-value may be 25, 26, 27, 28, 29, 30, 31, 32 or 33.

[0037] High nitrogen stainless steels are based on a replacement of carbon with nitrogen. By substituting most of the carbon with nitrogen it is possible to substitute the chromium rich carbides of the type M7C3 and M23C6 with very stable hard particles of the type MN-nitrides. The amount of Cr, Mo and N in solid solution at the hardening temperature is therefore very much increased, because less chromium is bound in the hard phase and because the carbides of the type M23C6 and M7C3 do not have any solubility for nitrogen. Thereby, more chromium is left in solid solution and the thin passive chromium rich surface film is strengthened, which leads to an increased resistance to general corrosion and pitting corrosion. Accordingly, it is to be expected that the pitting corrosion resistance would decrease if carbon replaces part of the nitrogen. High nitrogen stainless steels known in the art therefore have a low carbon content.

[0038] However, the present inventors have surprisingly found that it is possible to increase the corrosion resistance by increasing carbon content to above 0.3% as will be discussed in relation to the examples.

Steel production [0039] The tool steel having the claimed chemical composition can be produced by conventional gas atomizing followed by nitrogenation of the powder before HIP-ing. The nitrogen content in the steel after gas atomizing is normally less than 0.2%. The remaining nitrogen is thus added during the nitrogenation treatment of the powder. After consolidation the steel may be used in the as HIP-ed form or formed into a desired shape. Normally the steel is subjected to hardening and tempering before being used. Austenitising may be performed by annealing at an austenitising temperature (TA) in the range of 950 - 1200 °C, typically 1080- 1150 °C. A typical treatment is annealing at 1080 °C for 30 minutes. The steel may be hardened by quenching in a vacuum furnace by deep cooling in liquid nitrogen, and then tempered at 200 °C for 2 times at 2 hours (2x2h). EXAMPLE 1 [0040] In this example a steel according to the invention is compared to a steel having lower carbon content and a different balance between carbon and nitrogen. Both steels were produced by powder metallurgy.

[0041] The basic steel compositions were melted and subjected to gas atomization. Subsequently the obtained powders were subjected to a nitrogenation treatment in order to introduce the desired amount of nitrogen into the powders. The nitrogen content was increased from about 0.1 % to the respective content.

[0042] Thereafter the nitrogenated powders were transformed to isotropic solid steel bodies by conventional hot isostatic pressing (HIP) at 1100 °Cfor2 hours. The applied pressure was 100 MPa.

[0043] The steels thus obtained had the following compositions (in wt. %):

Inventive steel Comparative steel C 0.35 0.18 N 1.5 1.9 (C+N) 1.85 2.08 C/N 0.23 0.09

Si 0.3 0.3

Mn 0.3 0.3

Cr 18.2 19.8

Mo 1.04 2.5 V 3.47 2.75 balance iron and impurities.

[0044] The steels were austenitised at 1080 °C for 30 minutes and hardened by quenching by deep cooling in liquid nitrogen in a vacuum furnace followed by tempering at 200 °C for 2 times at 2 hours (2x2h). The inventive steel had a hardness of 60 HRC and the comparative steel a hardness of 58 HRC.

[0045] The alloy microstructure consisted of tempered martensite and hard phases. Two distinct hard phases were identified in the microstructure of both steels: MX and M2X.

[0046] In the comparative steel the hexagonal M2X was the majority phase and the face centred cubic MX-phase was the minority phase. However, in the inventive steel MX was the majority phase and M2X was the minority phase.

[0047] The materials susceptibility for pitting corrosion was experimentally examined by anodic polarisation sweep. An electrochemical cell with a saturated Ag/AgCI reference electrode and a carbon mesh counter electrode, were used for cyclic polarization measurements. The 500 mesh grounded sample was first open circuit potential (OCP) recorded with a 0.1 M NaCI solution to ensure a stable potential was reached. Next, the cyclic polarization measurements were performed with a scan rate of 10 mV/min. Start potential was -0.2 V vs. OCP, and the final potential was set to the OCP. By choosing a setting in the software, the upward potential scan was automatically reversed when the anodic current density reached 0.1 mA/cm2.

[0048] Fig. 1 discloses a schematic anodic polarization curve and the information that can be obtained from the curve. The forward scan gives information about the initiation of pitting and the reverse scan provides information about the alloys repassivation behavior. Eb is the value of the potential for pitting breakdown above which new pits will initiate and existing pits will propagate. As the potential is decreased on the reverse scan , there is a decrease in current density. The alloy is repassivated where the reverse scan crosses the forward scan. Ep is the repassivation potential, or protection potential i.e. the potential below which no pitting occur. The difference between Eb and Ep is related to the susceptibility to pitting and crevice corrosion. The greater the difference the greater the susceptibility.

Table 1. Result of the anodic polarisation.

[0049] Table 1 discloses that the inventive steel with the increased carbon content has the less tendency to suffer localised corrosion and also that the inventive steel also repassivate more easily than the comparative steel. Accordingly, the inventive steel is much less sensitive to pitting and crevice corrosion.

[0050] These results were totally unexpected because the inventive steel had lower contents of Cr, Mo and N than the comparative steel. The reasons therefore are presently not fully understood. However, the present inventors suspected that the differences may be related to the type and amount of hard phases remaining in the steel after austenizing and quenching. EXAMPLE 2 [0051] The influence of the relative amounts of carbon and nitrogen on the formation of the different hard phases in the steel was calculated in Thermo-Calc for a steel having variable C and N contents and the following basic composition in weight %: Cr: 19.8, Mo: 2.5, V: 2.75; Si: 0.3, Mn: 0.3, Fe balance.

Table 2. Results of Example 2 at 1080 °C. Elemental concentrations in wt. %. Hard phases in vol. %. Cr, Mo and N denotes the calculated dissolved contents of the elements in the matrix at 1080 °C. PRE is calculated from the dissolved contents.

[0052] Fig. 2 discloses the amount of hard phases as a function of the ratio C/N and it can be seen that amount of M2X decreases rapidly with increasing ratio C/N. However, M23C6 starts to form already at a C/N ratio of about 0.25.

[0053] Fig. 3 discloses calculated PRE-values as a function of the ratio C/N and it can be seen that the highest values are obtained for the steels according to the invention. EXAMPLE 3 [0054] The influence of the relative amounts of carbon and nitrogen on the formation of the different hard phases in the steel was calculated in Thermo-Calc for a steel having variable C and N contents and the following basic composition in weight %: Cr: 18.2, Mo: 1.04, V: 3.47; Si: 0.3, Mn: 0.3, Fe balance.

Table 3. Results of Example 3 at 1080 °C. Elemental concentrations in wt. %. Hard phases in vol. %. Cr, Mo and N denotes the calculated dissolved contents of the elements in the matrix at 1080 °C. PRE is calculated from the dissolved contents.

[0055] Fig. 4 discloses the amount of hard phases as a function of the ratio C/N and it can be seen that amount of M2X decreases very rapidly with increasing ratio C/N. It can also be seen that M23C6 starts to form at a C/N ratio of about 0.3.

[0056] Fig. 5 discloses calculated PRE-values as a function of the ratio C/N and again it can be seen that the highest values are obtained for the steels according to the invention.

[0057] These results verify that a proper balance of carbon and nitrogen is an essential features of the present invention. A carefully controlled increase of the carbon content can be made without obtaining problems with carbides of the type M23C6 and M7C3 in the steel. These results also reveals that if the carbon and nitrogen contents are controlled as defined in the claims, then the amount of the hexagonal phase M2Xwill be reduced after hardening. This phase is mainly referred to as Cr2N but it may also include a substantial amount of Mo. The reduction of the amount of M2X is a result of dissolution during the austenizing. Although a part of these elements under certain circumstances may be found in the increased fraction of MX (Fig. 2) it would appear that the dissolution of M2X results in increased amounts of Cr, Mo and N dissolved in the matrix with a corresponding increase of the PRE-number until a certain limit. Thereafter the PRE-value will decrease as a result of the formation of M23C6, because said phase is rich in Cr and Mo.

[0058] Another mechanism, which may contribute to the improved corrosion resistance disclosed in Table 1 and Fig. 1, may be that the boundary regions surrounding the hard phase M2X may be depleted in Cr and Mo due to the formation of Cr and Mo rich M2X.

[0059] Another possibility mechanism that may influence the corrosion resistance is that the increased carbon content in the hard phase MX may result in a lower solubility of Cr in this phase. This would result in a reduced volume fraction of MX and more chromium is retained in solid solution, which helps to improve the corrosion resistance.

[0060] Accordingly, the present invention provides a to provide a powder metallurgy (PM) produced nitrogen alloyed cold work tools steel having an improved corrosion resistance in combination with a high hardness.

INDUSTRIAL APPLICABILITY

[0061] The cold work tool steel of the present invention is particular useful [0062] in applications requiring good wear resistance in combination with a high resistance to pitting corrosion. Claims 1. A powder metallurgy manufactured steel consisting of (in weight %): C 0.3-0.8 N 1.0-2.2 (C+N) 1.3-2.2 C/N 0.17-0.50

Si <1.0

Mn 0.2-2.0

Cr 13-30

Mo 0.5-3.0 W < 1 (Mo+W/2) 0.5 - 3.0 V 2.0-5.0

Nb <2.0 (V+Nb/2) 2.0 - 5.0 (Ti+Zr+AI) <7.0

Ta < 0.5

Co < 10.0

Ni < 5.0

Cu < 3.0

Sn < 0.3 B < 0.01

Be < 0.2

Bi < 0.3

Se < 0.3

Te < 0.3

Mg < 0.01 REM < 0.2

Ca < 0.05 S < 0.5 balance iron and impurities. 2. A powder metallurgy manufactured steel according to claim 1, wherein the upper content of V is limited to 4.8 %, 4.6 %, 4.4 %, 4.2 % or 4.0 %. 3. A powder metallurgy manufactured steel according to any of the preceding claims, wherein the steel fulfils at least one of the following requirements (in weight %):: C 0.3-0.6 N 1.1-1.8 (C+N) 1.7-2.1 C/N 0.20 - 0.46

Cr 15-30

Mo 0.7-2.5 V 2.5-4.5

Nb < 0.5 4. A powder metallurgy manufactured steel according to any of the preceding claims, wherein the steel fulfils at least one of the following requirements (in weight %):: C 0.35-0.45 N 1.3-1.7 (C+N) 1.8-2.0 C/N 0.22 - 0.45

Cr 16-28

Mo 0.8-2.0 V 2.5-3.8

Co 4.0-6.0

Nb < 0.1

Cu 0.02-2.0 5. A powder metallurgy manufactured steel according to any of claims 1-3, wherein the steel fulfils at least one of the following requirements (in weight %):

Cr 18-26

Mo 0.8 -1

Se < 0.05

Cu 0.05-1.5

Co < 0.2 W < 0.2

Ti < 0.1

Nb < 0.05 REM < 0.05 B < 0.004 6. A powder metallurgy manufactured steel according to any of the preceding claims, wherein the microstructure comprises tempered martensite and hard phases consisting of one or more of MX, M2X, M23C6 and M7C3 and wherein the steel has a hardness of 58 - 64 HRC, preferably 60 - 62 HRC and wherein M is one or more of V, Mo and Cr and X is one or more of C, N or B. 7. A powder metallurgy manufactured steel according to any of the preceding claims, wherein the content of the hard phases MX, M2X, M23C6 and M7C3 fulfil the following requirements (in volume %): MX 5-25 preferably 5-20 more preferably 5-15 M2X <10 preferably <5 more preferably <1 M23c6 + M7C3 <10 preferably <5 more preferably <1 wherein M is one or more of V, Mo and Cr and X is one or more of C, N or B. 8. A method of producing a steel having a composition as defined in any of the preceding claims comprising the steps of atomizing a steel alloy having a chemical composition as defined in any of the preceding claims apart from the nitrogen content, subjecting powder to a nitrogenation treatment in order to adjust the nitrogen content of the alloy to the content defined in any of the preceding claims, filling the powder into a capsule and subjecting the capsule to a HIP-treatment, forming the obtained steel and subjecting it to hardening and tempering. 9. A method of producing a steel according to claim 8 comprising hardening at 950 - 1200 °C, preferably at 1080 -1150 °Cfor30 min, deep cooling the hardened steel in liquid nitrogen and tempering twice at 180-250 °C, preferably at 200 ± 10 °C, for 2 hours. 10. A method of producing a steel according to claim 8 comprising hardening at 950 - 1200 °C, preferably at 1080 -1150 °Cfor30 min, deep cooling the hardened steel in liquid nitrogen and tempering twice at 450- 550 °C, preferably at 500 ± 10 °C, for 2 hours.

Patentansprüche 1. Ein pulvermetallurgisch hergestellter Stahl bestehend aus (in Gew.%): C 0,3-0,8 N 1,0-2,2 (C+N) 1,3-2,2 C/N 0,17-0,50

Si <1,0

Mn 0,2-2,0

Cr 13-30

Mo 0,5-3,0 W < 1 (Mo + W/2) 0,5 - 3,0 V 2,0-5,0

Nb < 2,0 (V + Nb/2) 2,0 - 5,0 (Ti + Zr + AI) < 7,0

Ta < 0,5

Co < 10,0

Ni < 5,0

Cu < 3,0

Sn < 0,3 B < 0,01

Be < 0,2

Bi < 0,3

Se < 0,3

Te < 0,3

Mg < 0,01

Seltene Erdmetalle < 0,2

Ca < 0,05 S < 0,5

Rest Eisen und Verunreinigungen. 2. Ein pulvermetallurgisch hergestellter Stahl gemäß Anspruch 1, wobei der obere Grenzwert von V auf 4,8%, 4,6%, 4,4%, 4,2% oder 4,0% beschränkt ist. 3. Ein pulvermetallurgisch hergestellter Stahl gemäß einem der vorhergehenden Ansprüche, wobei der Stahl mindestens eine der folgenden Anforderungen (in Gew.%) erfüllt: C 0,3-0,6 N 1,1-1,8 (C+N) 1,7-2,1 C/N 0,20 - 0,46

Cr 15-30

Mo 0,7-2,5 V 2,5-4,5

Nb < 0,5 4. Ein pulvermetallurgisch hergestellter Stahl gemäß einem der vorherigen Ansprüche, wobei der Stahl mindestens eine der folgenden Anforderungen (in Gew.%) erfüllt: C 0,35-0,45 N 1,3-1,7 (C+N) 1,8-2,0 C/N 0,22 - 0,45

Cr 16-28

Mo 0,8-2,0 V 2,5-3,8

Co 4,0-6,0

Nb < 0,1

Cu 0,02-2,0 5. Ein pulvermetallurgisch hergestellter Stahl gemäß einem der Ansprüche 1-3, wobei der Stahl zumindest eine der folgenden Anforderungen (in Gew.%) erfüllt:

Cr 18-26

Mo 0,8-1

Se < 0,05

Cu 0,05-1,5

Co < 0,2 W < 0,2

Ti < 0,1

Nb < 0,05

Seltene Erdmetalle < 0,05 B < 0,004 6. Ein pulvermetallurgisch hergestellter Stahl gemäß einem der vorhergehenden Ansprüche, wobei die Mikrostruktur getempertes Martensit und harte Phasen bestehend aus einem oder mehreren MX, M2X, M23C6 und M7C3 umfasst, und wobei der Stahl eine Härte von 58 - 64 HRC, vorzugsweise 60 - 62 HRC, aufweist, und wobei M eines oder mehrere von V, Mo und Cr ist und X eines oder mehrere von C, N oder B ist. 7. Ein pulvermetallurgisch hergestellter Stahl gemäß einem der vorhergehenden Ansprüche, wobei der Gehalt an harte Phasen MX, M2X, M23C6 und M7C3 die folgenden Anforderungen (in Gew.%) erfüllt: MX 5-25, bevorzugt 5-20, besonders bevorzugt 5-15 M2X < 10,vorzugsweise<5,besondersbevorzugt<1 M23C6+M7C3 < 10,vorzugsweise<5,besondersbevorzugt<1 wobei M eines oder mehrere von V, Mo und Cr ist und X eines oder mehrere von C, N oder B ist. 8. Ein Verfahren zur Herstellung eines Stahl mit einer Zusammensetzung wie in einem der vorherigen Ansprüche definiert, umfassend die Schritte des Atomisierens einer Stahllegierung mit einer chemischen Zusammensetzung wie in einem der vorherigen Ansprüche offenbart, abgesehen vom Stickstoffgehalt, des Untenwerfens des Pulvers einer Stickstoffbehandlung, um den Stickstoffgehalt der Legierung an den Gehalt, der einem der vorherigen Ansprüche definiert ist, anzupassen, des Einfüllens des Pulvers in eine Kapsel und des Unterwerfens der Kapsel einer HIP-Behandlung, des Formens des erhaltenen Stahls und seines Unterwerfens zum Härten und Vergüten. 9. Ein Verfahren zur Herstellung eines Stahl gemäß Anspruch 8, umfassend das Härten bei 950° bis 1.200°C, vorzugsweise bei 1.080° bis 1.150°C für 30 Minuten, Tiefkühlen des gehärteten Stahls in flüssigem Stickstoff und zweimaligem Vergüten bei 180° bis 250°C, vorzugsweise bei 200° ± 10°C, für zwei Stunden. 10. Ein Verfahren zur Herstellung eines Stahl gemäß Anspruch 8, umfassend das Härten bei 950° bis 1.200°C, vorzugsweise bei 1.080° bis 1.150°C für 30 Minuten, Tiefkühlen des gehärteten Stahls in flüssigem Stickstoff und zweimaliges Vergüten bei 450° bis 550°C, vorzugsweise bei 500° ± 10°C, für zwei Stunden.

Revendications 1. Acier fabriqué par métallurgie des poudres, se composant de (en % en poids) : C 0,3-0,8 N 1,0-2,2 (C+N) 1,3-2,2 C/N 0,17-0,50

Si < 1,0

Mn 0,2-2,0

Cr 13-30

Mo 0,5-3,0 W < 1 (Mo + W/2) 0,5 - 3,0 V 2,0-5,0

Nb < 2,0 (V + Nb/2) 2,0 - 5,0 (Ti + Zr + Al) < 7,0

Ta < 0,5

Co < 10,0

Ni < 5,0

Cu < 3,0

Sn < 0,3 B < 0,01

Be < 0,2

Bi < 0,3

Se < 0,3

Te < 0,3

Mg < 0,01 REM < 0,2 (suite)

Ca < 0,05 S < 0,5 le reste étant constitué de fer et d’impuretés. 2. Acier fabriqué par métallurgie des poudres selon la revendication 1, dans lequel la teneur supérieure en V est limitée à 4,8 %, 4,6 %, 4,4 %, 4,2 % ou 4,0 %. 3. Acierfabriqué par métallurgie des poudres selon l’une quelconque des revendications précédentes, l’acier répondant à au moins une des exigences suivantes (en % en poids) : C 0,3-0,6 N 1,1-1,8 (C+N) 17-2,1 C/N 0,20 - 0,46

Cr 15-30

Mo 0,7-2,5 V 2,5-4,5

Nb <0,5 4. Acierfabriqué par métallurgie des poudres selon l’une quelconque des revendications précédentes, l’acier répondant à au moins une des exigences suivantes (en % en poids) : C 0,35-0,45 N 1,3-1,7 (C+N) 1,8-2,0 C/N 0,22 - 0,45

Cr 16-28

Mo 0,8-2,0 V 2,5-3,8

Co 4,0 - 6,0

Nb <0,1

Cu 0,02 - 2,0 5. Acier fabriqué par métallurgie des poudres selon l’une quelconque des revendications 1 à 3, l’acier répondant à au moins une des exigences suivantes (en % en poids) :

Cr 18-26

Mo 0,8 - 1

Se < 0,05

Cu 0,05-1,5

Co < 0,2 W < 0,2

Ti < 0,1

Nb < 0,05 REM < 0,05 B < 0,004 6. Acier fabriqué par métallurgie des poudres selon l’une quelconque des revendications précédentes, dans lequel la microstructure comprend de la martensite revenue et des phases dures se corn posant d’un ou de plusieurs éléments parmi MX, M2X, M23C6 et M7C3, et l’acier possédant une dureté de 58 à 64 HRC, de préférence 60 à 62 HRC, et dans lequel M est un ou plusieurs éléments parmi V, Mo et Cr et X est un ou plusieurs éléments parmi C, N ou B. 7. Acier fabriqué par métallurgie des poudres selon l’une quelconque des revendications précédentes, dans lequel la teneur en phases dures MX, M2X, M23C6 et M7C3 répond aux exigences suivantes (en % en volume) : MX 5-25 de préférence 5- 20 plus préférentiellement 5-15 M2X <10 de préférence <5 plus préférentiellement <1 M23C6+M7C3 <10 de préférence <5 plus préférentiellement <1 dans lequel M est un ou plusieurs éléments parmi V, Mo et Cr et X est un ou plusieurs éléments parmi C, N ou B. 8. Procédé de production d’un acier ayant une composition telle que définie selon l’une quelconque des revendications précédentes, comprenant les étapes consistant à atomiser un alliage d’acier ayant une composition chimique telle que définie selon l’une quelconque des revendications précédentes mis à part la teneur en azote, à soumettre la poudre à un traitement de nitrogénation afin d’ajuster la teneur en azote de l’alliage à la teneur définie selon l’une quelconque des revendications précédentes, à remplir la poudre dans une capsule et à soumettre la capsule à un traitement HIP, à former l’acier obtenu et à le soumettre à un durcissement et à un revenu. 9. Procédé de production d’un acierselon la revendication 8, comprenant une étape de durcissement à une température de 950 - 1200°C, de préférence 1080 - 1150°C pendant 30 min, une étape de refroidissement poussé de l’acier durci dans de l’azote liquide et deux étapes de revenu à une température de 180 - 250°C, de préférence 200 ± 10°C, pendant 2 heures. 10. Procédé de production d’un acierselon la revendication 8, comprenant une étape de durcissement à une température de 950 - 1200°C, de préférence 1080 - 1150°C pendant 30 min, une étape de refroidissement poussé de l’acier durci dans de l’azote liquide et deux étapes de revenu à une température de 450 - 550°C, de préférence 500 ± 10°C, pendant 2 heures.

Claims

Corrosion and abrasion-resistant honeycomb tool steel Patent claims i. Powdered moth with a pound of head «Clipped with the following Kompoae shoelace: C 0.3 - 0 KN 1.0-3: (Ct-N I 3 2.2 C / N 0 1? ~ 0.50 S 1 <0: 0 Μη 0.2 - 2.0 Cr 13 - 30 Mo 0 3 ~ 3.0 W <t (Mo'î-W / 2) 0.3 ·· 3.0 V 2.0 - 5.0 Mb <2.0 (VfNb / 2) 2.0 - 5.0 (TCZm Ai) <7.0 Ta <0 .5 Co <10.0 Ni <5.0 Cu <3.0 Sa 7 0.3 B <0.01 8e <0 2 Bi <0 3 Sc <0.3 Te <0.3 Mg <0.01 REM <0.2 Ca <0.05 S <0.5 and the remainder is pollution.

2. What: 1, i | envunkt sæerifttl; pÄsMs * attal eibáüiMi steel where the content of the ¥ content MsS is 4.8%. 4.4% f 4.2% or 4.0% more ·: k0Ätoxott. 31 The: elM> d rit rit # ati ati ati ati ati ati ati ati M M M M M M M M ahol ahol ahol ahol ahol ahol ahol ahol ahol ahol ahol ahol ahol where m m & the following phytochemicals are at least one product mbg & m 0% wt ~ haftk: C 0.3 ~ 0.6 M: 1, 1J-pyN} :: 1.2- 2.1 «0: 20-0.46 Cr11-Moi ~ 2, SV 2.5 - 4 5 Nb <0.5

4. Âz. the previous one is made of steel, where the steel is the following stone veins € 0 35 - 0.43 N 1.3- 1.7 (CAN) - - 2.0 C2N 0.22-0.43 Cr 16 ~ 28 Mo: #: 1-2.0 Y 2.5 - 31 Co 4: .0-Μ Nb 10.1 Cu 0.02 - .2.0

5. For the first time, we have to use the following techniques: at least one of the following, and at least 0% of the horse:} Cr: -26 Mo 0.8 -1 Se <0.05 Cö 0.05 -1.5 Co 50 2 W <Ö; 2 Ti <0. i Nb 5 0.05 REM <0.05 B <0.004

6. Previously produced products produced by any of the following types of powder coatings where the microstructure is thermostated with MX, M2X, M23C # and M7C3! one or more solid phases are melted, and where the steel hardness is 58 »-64 MRÇ, preferably 60 to 62MM and where M is V, Mo and Ck or more, and X is one of €, N or B more.

7. Previous i ^ »ypantok: | ^ ^! L ^ f :: ^ ót) i: | ^ leiy ^ ÍWi .. # Cited: ^ # $ ^ o! MX, M2X »M23I and M2 € 3 hard phases correspond to xm $ 0 $ o $ ßt%? bm): MX 5-25, preferably 5-20, more preferably 5-15 M2X <10. preferably <5, more preferably <1 M22C6 + M7C3 <10, preferably <5, more preferably <1, where M is V * Mo and € f is reported by one or more Is X is € N or 8 is a desire more. HE. ját á éve előző előző előző előző előző előző előző előző ö ö ö Ê Ê Ê Ê Ê Ê Ê Ê Ê Ê Ê Ê Ê Ê Ê Ê Ê áta során során során során során során során során során során során során során során során során során során során során során során során során során során során során során során során során itr itr során során során során itr során során során során során során során során során során során során során során során során során során során során során során során során során során során itr itr itr itr itr itr éve itr itr éve itr éve itr éve éve itr éve éve port port port port port port To regulate, the powder is filled into a capsule and the capsule underneath the lilB treatment, the resulting cells are infested and under training and tempering. f. The method of claim 8 for the preparation of a blade in which the training is preferably 050 to 1200 XI at a temperature of 1080 to 1150 "C is 30 petetg, the hardened steel jfcJyekoay nitrogen has a deep hole: and two thousand 180 - 250 ^ C, with a temperature of 200 ± 10 €. The method according to claim 1i is for the drinker of # 1, for which the training is carried out at a temperature of 950 to 1200 XI, preferably 1080 to 1150 "Cl, until M · is added to the steel, and two times in silicone nitrogen. 450-530 ° C, preferably 500 A at 10 ° C for 2 hours.