EP1052305B1 - Metallic material with high hardness, high wear resistance and high toughness - Google Patents

Description

The invention relates to a method for alloying control of the solidification kinetics and the matrix composition of carbide-forming metallic melts and to a material preferably produced by the method with high hardness, high wear resistance and high. Toughness.

Such alloys are state of the art. For example, in the field of iron-base alloys, tool steels are known which include, among others, the elements carbon, vanadium, niobium and aluminum.

DE 31 44 475 A1 discloses a Schnellarbeits- and tool steel, in addition to other elements 0.3 to 3.0 wt.% Carbon, 0.5 to 3.0 wt.% Silicon, 0.5 to 3.0 wt. % Aluminum 0.5 to 6.0 wt.% Vanadium has. The steel in which the vanadium may be partially or completely replaced by zirconium, niobium, hafnium, titanium, tantalum or a mixture thereof preferably has a sum of the contents of silicon and aluminum of about 2% by weight. The elements silicon and aluminum in combination should completely or partially replace cobalt and reduce the content of tungsten, vanadium and molybdenum at about the same material quality.

From EP-0425471 B1 a cold work steel with high compressive strength has become known, which inter alia in wt .-% 0.6 to 1.5 C, 0.2 to 1.6 Si, 0.3 to 1.5 V. , 0.2 to 1.6 Al and up to 0.5 Nb. Silicon and aluminum are said to improve the tempering behavior and hinder grain growth during hardening or austenitizing by nitride formation, thereby reducing the compressive strength Increase hardness, toughness and wear resistance of the material.

Due to the particular concentration of certain alloying elements in interaction with the other constituents, at least one desired property of materials that stabilize ledeburitically can be particularly promoted. For example, a high level of wear resistance can be achieved by alloying by increasing the amount of carbide, but the toughness of the material deteriorates.

However, the quality and the usability of the material are characterized by the property profile, which should be formed in accordance with the modern technical requirements of these as possible from each high or advantageous individual properties. It is important for reasons of reliability that the fluctuation range of the property values is as low as possible.

As mentioned at the beginning, alloying with aluminum has attempted to substitute expensive elements or to influence the thermal tempering in such a way that the material properties are improved.

An increased aluminum content in ledeburitic steels has proven to be favorable only in some cases, because this usually caused no significant improvement in the property profile of the material and the possibly improved individual properties had large fluctuations. The reasons for this are justified by the opinion of the solidification morphology. The result is coarse, in the solidification of the melt primarily precipitated carbides, which are not to shatter at a hot deformation of the material substantially, but can form a disadvantageous line structure and the achievable hardness and toughness of the matrix are considered as alloying limits for improving the overall properties ,

Here, the invention seeks to remedy the situation and sets itself the goal of specifying a method with which the solidification kinetics of carbide-forming metallic Melting technology is controlled such that the microstructure is formed morphologically advantageous with improved matrix properties Furthermore, it is an object of the invention to provide generic metallic materials with high hardness, high wear resistance and high toughness. Specifically, this means the creation of high pressure resistant, especially cold working materials, simultaneously with significantly improved resistance to abrasive wear, increased plastic bending work and flexural strength, and a significantly increased 0.2% compression limit of the material.

wobei das Niobäquivalent entsprechend dem Zusammenhang: $$\mathrm{AN}=\mathrm{0,3}+\mathrm{0,1}\hspace{0.17em}\mathrm{Gew}.-\%\mathrm{V}+\mathrm{Gew}.-\%\mathrm{Nb}+\mathrm{1,12}\hspace{0.17em}\mathrm{Gew}.-\%\mathrm{Ta}$$

und der Wirkungsbereichsfaktor aus: $$\mathrm{F}=\mathrm{0,7}\hspace{0.17em}\mathrm{bis}\hspace{0.17em}\mathrm{1,3}$$

gebildet sind, worauf die Schmelze erstarren gelassen wird.The aim is achieved in a method of the type mentioned in that liquid metal consisting of the elements in wt .-%: 0.6 to 1.7 % carbon 0.6 to 1.1 % silicon 0.2 to 0.5 % manganese 7.0 to 11.0 % chrome 2.0 to 3.2 % molybdenum to 1.0 % tungsten to 0.8 % nickel 0.5 to 1.5 % vanadium 0.4 to 0.65 % Niobium, optionally tantalum,
optionally elements of group 4 of the periodic table to the extent of less than 0.24 wt .-%,
Remaining iron as well as production-related impurities
and, depending on the carbon content and the content of elements of group 5 of the periodic table, up to 4.6% by weight with aluminum in a concentration of 0.3 to 2.6% by weight of Al, with the proviso that the aluminum content equal to the carbon content multiplied by the niobium equivalent AN multiplied by the effective range factor F is: $$\mathrm{weight}\mathrm{,}-\%\mathrm{al}=\mathrm{weight}\mathrm{,}-\%\mathrm{C}\times \mathrm{AT}\times \mathrm{F}.$$

wherein the niobium equivalent according to the context: $$\mathrm{AT}=0.3+0.1\mathrm{weight},-\%\mathrm{V}+\mathrm{weight},-\%\mathrm{Nb}+1.12\mathrm{weight},-\%\mathrm{Ta}$$

and the effect area factor: $$\mathrm{F}=0.7\mathrm{to}1.3$$

are formed, whereupon the melt is allowed to solidify.

The advantages of the method according to the invention are essentially to be seen in that the solidification kinetics can be influenced by means of the effect-optimized aluminum content in such a way that a primary carbide release and carbide growth is largely suppressed for further cooling, ie that the carbides are eutectically substantially finely globulitic to form the melt. Furthermore, the composition of the matrix, in particular its carbon content, can be controlled by the respective aluminum concentration, and ultimately the matrix hardness and toughness can be determined. For the first time it was found that it was necessary for a Particularly advantageous high property profile of materials is important to adjust the aluminum content within limits depending on the carbon concentration and the niobium equivalent. Lower contents than 0.3% by weight or higher contents than 2.6% by weight aluminum no longer have a favorable effect, or may be effective overnight in a further distance from the upper limit owing to a deterioration in the matrix properties. Between these limits, in view of a substantially eutectic carbide formation during the initial aging and thus a morphologically desired structure of the solidification microstructure with improved matrix properties, the aluminum content must be set according to the abovementioned relationship in the alloy. The causes of the extensive suppression of a primary carbide excretion have not yet been completely clarified scientifically, but it can be assumed that aluminum in appropriate concentrations limits the crystallization nuclei in their effect and drowns a major related hypothermia.

A morphologically particularly favorable structure is achieved if the effective range factor F has a value between 0.9 and 1.2.

aufweist, wobei der Wert AN bzw. das Niobäquivalent gemäß: $$\mathrm{AN}=\mathrm{0,3}+\mathrm{0,1}\times \mathrm{Gew}.-\%\mathrm{V}+\mathrm{Gew}.-\%\mathrm{Nb}+\mathrm{1,12}\mathrm{Gew}.-\%\mathrm{Ta}$$

gebildet ist und der FaMör F: $$\mathrm{F}=\mathrm{0,7}\hspace{0.17em}\mathrm{bis}\hspace{0.17em}\mathrm{1,3}$$

den Wirkungsbereich angibt.The further object of the invention is achieved in the case of a metallic material, which is preferably produced according to the abovementioned method, in that the alloy of the elements in% by weight: 0.6 to 1.7 % carbon 0.6 to 1.1 % silicon 0.2 to 0.5 % manganese 7.0 to 11.0 % chrome 2.0 to 3.2 % molybdenum to 1.0 % tungsten to 0.8 % nickel 0.5 to 1.5 % vanadium 0.4 to 0.65 % niobium 0.3 to 2.6 % Aluminum, optionally further elements of group 5 of the periodic table up to a total of 4.6% by weight,
optionally elements of group 4 of the periodic table to the extent of less than 0.24 wt .-%,
Remaining iron as well as production-related impurities
and aluminum, depending on the carbon and the vanadium, niobium and tantalum content, a concentration according to the formula: $$\mathrm{weight},-\%\mathrm{al}=\mathrm{weight},-\%\mathrm{C}\times \mathrm{AT}\times \mathrm{F}$$

wherein the value AN or the niobium equivalent according to: $$\mathrm{AT}=0.3+0.1\times \mathrm{weight},-\%\mathrm{V}+\mathrm{weight},-\%\mathrm{Nb}+1.12\mathrm{weight},-\%\mathrm{Ta}$$

is formed and the FaMör F: $$\mathrm{F}=0.7\mathrm{to}1.3$$

indicates the range of effect.

The advantages of the material according to the invention essentially consist in the fact that all mechanical properties and also the resistance to abrasive wear thereof are substantially improved. However, an appropriate adjustment or maintenance of the aluminum content is important for this, because depending on the carbon content and the niobium equivalent depending on the formation of the cast structure and that of the structure of the deformed material. With a desired content of elements of group 5 of the periodic table, which together with the other constituents form the prerequisites for a desired property profile of the material, depending on the carbon content, that of aluminum is within the limits of 0.3 to 2.6% by weight. certainly.

A particular high level of the properties of the material in its entirety is achieved when the Wirkungselelchsfaktor F has a value between 0.9 and 1.2.

Cutting tools with improved service life and the same resistance to breakage are preferably produced when the base of the alloy is formed as a high-speed steel and alloyed with aluminum in the Erfindungsberelchn.

The advantages can be particularly pronounced in an alloyed cold work tool steel according to the invention. In particular, the high wear resistance and the high toughness and strength of the material give superior performance of tools made from them.

A resistance to abrasive wear to DIN 50320 greater than 12 1 / g in the SiC abrasive paper wear test P 120 (grinding pad diameter 300 mm, Schlelffteller speed: 150 mn ^-1 , sample diameter: 8mm: contact pressure: 13.33N). a flexural strength of at least 4500 N / mm ² and a plastic bending stress in the range of 3000 Nmm with a 0.2% compression limit of more than 2600 N / mm ^{2 of} the thermally tempered material can be achieved if the alloy is in% by weight: 1.0 to 1.4 % carbon 0.6 to 1.1 % silicon 0.2 to 0.5 % manganese 7.0 to 11.0 % chrome 2.0 to 3.2 % molybdenum to 1.0 % tungsten to 0.8 % nickel 1.0 to 1.5 % vanadium 0.4 to 0.65 % niobium Aluminum in the present invention dependent limits between 0.64 and 2.0, balance iron and manufacturing-related impurities.

The mechanical properties and the resistance to abrasive wear can be increased if the alloy has more than 0.5 wt .-% niobium.

Of particular importance for a morphologically favorable structure is a low concentration of the alloy on elements of Group 4 of the Periodic Table and optionally of nitrogen, because compounds of these elements can form effective nuclei for primary carbide precipitation. It is therefore advantageous if the content of elements of group 4 of the periodic table is below 0.24% by weight, preferably below 0.1% by weight, and the nitrogen content is less than 0.01% by weight.

In the following, the invention is explained in more detail by means of tables with the respective chemical composition and the test results of the experimental materials.

Table 1 shows the chemical composition of the trial alloy, with the remainder each consisting of iron and impurities caused by melting.

From Table 2 the respective test results and an evaluation number for the property profile of the alloy can be found.

The evaluation number in Table 2, which characterizes the properties of the material in its entirety, was formed by dividing the plastic bending work, the ultimate bending strength and the 0.2% compression limit by 1000, that for abrasive wear by 10, and so on have been multiplied together.

The alloys 1,2 and 10 are alloys according to the invention and have consistently superior individual properties. The plastic bending work of these materials is advantageous at values above 2900Nmm.

The same applies to the transverse rupture strength with respective characteristic numbers of more than 4500 N / mm ² and for the 0.2% compression limit with values above 2600 N / mm ² . With regard to the use and the service life of a tool formed from such alloys, often the wear resistance is of particular importance. The materials of the invention have, as shown in the table, a very high resistance to wear.

Although the materials used for comparison with the alloys composed according to the invention and possibly having similar element concentrations may often have outstanding individual properties, their property profile is often insufficiently developed for stresses in modern process engineering. In a comparative consideration of the material properties in their entirety representing evaluation index, the advantages of the alloys of the invention are particularly clear.

Claims (5)

1. A process for the control, by alloying technology, of the solidification kinetics and matrix composition of carbide-forming metal melts, characterised in that liquid metal, consisting of the following elements in wt.%: 0.6 to 1.7% carbon 0.6 to 1.1% silicon 0.2 to 0.5% manganese 7.0 to 11.0% chromium 2.0 to 3.2% molybdenum up to 1.0% tungsten up to 0.8% nickel 0.5 to 1.5% vanadium 0.4 to 0.65% niobium, optionally tantalum,
   optionally elements of group 4 of the periodic table in a quantity of less than 0.24 wt.%, remainder iron and impurities introduced during manufacture,
   is produced and alloyed with aluminium in a concentration of 0.3 to 2.6 wt.% Al as a function of the carbon content and of the content of elements of group 5 of the periodic table of up to 4.6 wt.%, with the proviso that the aluminium content is equal to the carbon content multiplied by the niobium equivalent AN multiplied by the effective range parameter F: $$\mathrm{wt}.\%\mathrm{Al}=\mathrm{wt}.\%\mathrm{C}\times \mathrm{AN}\times \mathrm{F},$$

   

   the niobium equivalent being formed according to the relation: $$\mathrm{AN}=0.3+0.1\mathrm{wt}.\%\mathrm{V}+\mathrm{wt}.\%\mathrm{Nb}+1.12\mathrm{wt}.\%\mathrm{Ta}$$

   

   and the effective range parameter from: $$\mathrm{F}=0.7\hspace{0.17em}\mathrm{to}\hspace{0.17em}1.3$$

   

   whereupon the melt is allowed to solidify.
2. A process according to claim 1, characterised in that the effective range parameter is: $$\mathrm{F}=0.9\hspace{0.17em}\mathrm{to}\hspace{0.17em}\mathrm{1.2.}$$

   
3. A metallic material, particularly produced by the process according to the foregoing claims, with high hardness, high wear resistance and high toughness, characterised in that the alloy consists of the following elements, in wt.%: 0.6 to 1.7% carbon 0.6 to 1.1% silicon 0.2 to 0.5% manganese 7.0 to 11.0% chromium 2.0 to 3.2% molybdenum up to 1.0% tungsten up to 0.8% nickel 0.5 to 1.5% vanadium 0.4 to 0.65% niobium, 0.3 to 2.6% aluminium, optionally other elements of group 5 of the periodic table up to a total of 4.6 wt.%,
   optionally elements of group 4 of the periodic table in a quantity of less than 0.24 wt.%,
   remainder iron and impurities introduced during manufacture,
   and aluminium exhibits a concentration, as a function of the carbon and the vanadium, niobium and tantalum content, according to the formula: $$\mathrm{wt}.\%\mathrm{Al}=\mathrm{wt}.\%\mathrm{C}\times \mathrm{AN}\times \mathrm{F}$$

   

   
   where the value AN or niobium equivalent is formed according to: $$\mathrm{AN}=0.3+0.1\times \mathrm{wt}.\%\mathrm{V}+\mathrm{wt}.\%\mathrm{Nb}+1.12\mathrm{wt}.\%\mathrm{Ta}$$

   

   and the parameter F: $$\mathrm{F}=0.7\hspace{0.17em}\mathrm{to}\hspace{0.17em}1.3$$

   

   gives the effective range.
4. A material according to claim 1, characterised in that the effective range parameter is: $$\mathrm{F}=0.9\hspace{0.17em}\mathrm{to}\hspace{0.17em}\mathrm{1.2.}$$

   
5. A material according to one of claims 3 or 4, characterised in that the content of elements of group 4 of the periodic table is less than 0.1 wt.%.