ES2232809T3 - COLD STEEL MECHANIZED WITH HIGH WEAR RESISTANCE. - Google Patents

Abstract

Cold machined steel with high wear resistance for parts and tools manufactured powder metallurgically with high toughness and hardness, containing the alloy elements in% by weight as follows: ** (Table-table) ** as well as the supplementary elements: ** (Table-Table) ** impurities: ** (Table-Table) ** and the base element: ** (Table-Table) **.

Description

Cold machined steel with high resistance to wear.

The invention concerns a machined steel in cold with high wear resistance for parts and tools Powder metallurgically manufactured with high tenacity and high resistance.

According to the future developments of the technology parts and tools for machining applications cold exposed to increasingly high efforts and at the same time  Universal To be able to reach independently of the development orientations high qualities of material can be Choose your powder metallurgical manufacturing. In this case a composition  Alloy chemistry adjusted to this type of manufacturing with minimum solidification times of the grains allows another Increased quality of the steel part.

Cold machined steels with high strength wear has a high hardness in its structure incorporated into a matrix, especially carbides, that justify High abrasion resistance. Regarding a high toughness and hardness of the material however the carbide formation and matrix quality, especially its high strength

Austrian Patent No. 587/2001 describes a cold machined alloy steel for manufacturing powder metallurgical parts, and especially useful with high toughness and hardness, as well as high wear and fatigue resistance of the material. A material so chemically composed under all point of view can have high mechanical characteristics quality. However many times and in the case of hardening total large parts, especially with low temperatures of hardening a concentration of carbide mixtures is observed with chromium contents in the grain boundaries, so it is not it can exhaust without reserve the potential of toughness of the alloy. Many times a greater tenacity of the material of the product and a simpler heat treatment technology for East.

Starting from this state of the art, the invention aims to manufacture a cold machined steel With high wear resistance for parts and tools Powder metallurgically manufactured with high toughness and strength, which achieves the desired high quality also with a treatment thermally bonded and / or at a lower temperature of hardening.

This goal is achieved with a steel that It contains the following alloy elements in% by weight:

carbon (C) 2.21 to 2.64 silicon (yes) 0.08 a 1.1 manganese (Mn) 0.05 a 1.1 chrome (Cr) 3.71 a 4.69 molybdenum (Mo) 3.1 to 4.4 nickel (Ni) 0.14 a 0.3 vanadium (V) 8.45 a 9.5 tungsten (W) 0.5 to 1.5 Cobalt (Co) 1.1 to 4.9

as well as the elements Supplementary:

sulfur (S) until 0.3 niobium (Nb) until 0.1 nitrogen (N) until 0.1 aluminum (To the) until 0.06 titanium (You) until 0.01

the impurities:

match (P) 0.029 max oxygen (OR) 0.03 max

and the element base:

iron (Faith) as rest

The advantages of the invention consist above all in the fact that by means of alloy techniques and by a taking advantage of the interaction of the elements that direct the transformation of the structure and those that form the carbides has achieved on the one hand increase the total hardening of the material and on the other hand get a hardening of the mixed crystal, also reducing with low hardening temperatures a segregation of pretectic carbide, especially in the limits of grain.

In the sense of high wear resistance and at the same time with an improvement in tenacity and especially superior flexural strength, the elements must be considered carbide formants of group 5 of the periodic table in interaction with those of group 6. It has been proven that with niobium contents of 0.1% by weight and lower in contents of vanadium of the invention globulitic monocarbons are formed and mixed carbides with tungsten and molybdenum in the ranges of concentration indicated in the indicated concentration ranges of these elements, ensuring more or less spherical monocarbons especially vanadium, high wear resistance of material. Conditioned by the activity cannot occur highly stable tungsten or molybdenum monocarbons, without however, mixed carbides with vanadium content can be formed Rich in tungsten and molybdenum. These mixed carbides in the thermal bonus serve to harden the matrix, they have the advantage of a low segregation temperature and in the moment of austenitation can be more easily integrated into a solid solution These carbide configurations essentially niobium free are in chemical kinetics closely related to a low concentration of chromium, being able to guarantee a very high resistance to rupture by bending and bending by beating in the bonus material thanks to a solution lighter of mixed carbides.

On the one hand, and in particular chromium can form at least three carbide formations with different carbon concentrations and can be easily introduced as metal component by substitution in mixed carbides, by On the other hand the chromium content essentially influences the hardness behavior as hardness increase, mild Complete, secondary tempered material. In principle contents higher chrome delay structure transformation at the time of tempering and increase the depth of tempering penetrated and react in the same way, especially with nickel and manganese. Instead, cobalt parts in the alloy increase the diffusion coefficient for carbon, which by a part can lead to lower depths of hardness, on the other cobalt part oppresses a high degree of carbide segregation preeutectic, especially at the grain boundaries, so it they can achieve considerable improvements in the toughness of the material  Bonus

Regarding the desired quality of steel cold machining, which also develops with low hardening temperatures and penetrates deep into the piece, the elements chrome, manganese, nickel and cobalt must be adjusted to the concentration limits according to the invention, originating the Preferred ranges of content an increase in mechanical values of the material and a guarantee of quality in the material.

As mentioned above, the formation of monocarbon and the functions of the elements vanadium, molybdenum and Tungsten are important regarding a presentation of mixed carbide and a hardening of the matrix to obtain optimum qualities of cold machined steel according to the invention. It has been shown that in the narrow concentration ranges of the elements with a proportion according to the formula:

\ frac {V} {Mo + W} = 1.5 \ up to \ 2.2

you can get qualities top mechanics of the steel part with a bonus to low hardening temperatures compared to for example 1030ºC to 1050ºC, having a greater depth of tempering with inner grain structure fine.

Both regarding an increase in resistance to wear as for the greatest increase in toughness and tempering of the cold machined steel of the invention is advantageous, when one or more elements have concentrations in% by weight as follow:

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carbon (C) 2.3 to 2.6, preferably 2.4 to 2.55 silicon (yes) 0.3 to 0.8 preferably 0.42 to 0.68 manganese (Mn) 0.15 to 0.8 preferably 0.3 to 0.55 chrome (Cr) 3.85 to 4.58 preferably 4.0 to 4.45 molybdenum (Mo) 3.31 to 4.18 preferably 3.55 a 3.98 nickel (Ni) 0.16 a 0.25 vanadium (V) 8.61 to 9.34 preferably 8.81 to 9.2 tungsten (W) 0.7 to 1.3 preferably 0.75 a 1.25 Cobalt (Co) 1.4 to 3.82 preferably 1.61 to 2.42

Especially to achieve greater tenacity of material is advantageous when one or more elements supplementary have the following concentration values in % in weigh:

sulfur (S) up to 0.03, preferably up to 0.025 niobium (Nb) up to 0.01, preferably up 0.006 nitrogen (N) up to 0.09, preferably up 0.08 aluminum (To the) up to 0.05, preferably up to 0.04

and / or more than one impurity presents the following concentration values in% in weight:

match (P) 0.025 max oxygen (OR) 0.009 max

For a piece of cold machined steel, powder-metallurgically manufactured with a chemical composition according to one of the above-mentioned materials, with respect to greater toughness and hardness of the material, also in the case of using standard tempering temperatures for the bonus, that is also in the case of simple heat treatment, a high degree of purity of the steel according to a KO value of less than / equal to 3.0 according to DIN 50602 is important. Higher KO values can lead to a considerable worsening of the properties when using the
piece.

Based on the results of comparative studies the Invention will be explained in more detail.

They show:

Tab. 1 a presentation of the chemical composition of the cold machined steel of the invention and of the alloys of comparison.

Tab. 2 resistance measurement values at bending by flexion, resistance to bending by shock and from wear resistance of subsidized steels.

Fig. 1 a measurement arrangement to find out the resistance to breakage by bending.

Fig. 2 a prototype to check the resistance to shock flexion.

Fig. 3 a diagram of the device for wear resistance measurement.

Fig. 4 a comparative diagram of resistance at breakage by bending of steel alloys.

Fig. 5 a comparative diagram of flexion by shock.

Fig. 6 a comparison of resistance to wear of cold machined steels.

The tab 1 presents the chemical composition of a cold machined steel alloy according to the invention with the Leg.K designation and those of alloy comparisons with denominations Leg.A to Leg.J.

With the same denominations the tab. 2 presents the test results, and precisely the resistance to flexural breakage, shock flexion and resistance to wear, the pieces to be tested bonded to the same hardness of 61 HRC-.

The resistance to breakage by bending of the cold machined steel alloys were tested on specimens round (RD = 5.0 mm) in an installation represented in figural. The preliminary force Fr was 200 N, speed up to force Full preliminary was 2 mm / min and the test speed was 5 mm / min

Flexural strength tests by Material collision was performed with a tool according to figure 2.

Figure 3 shows schematically the installation to find out the wear resistance of materials.

Figure 1 shows in the diagram the optimum flexural strength of the Leg.K of the invention, having the materials d comparison A to J corresponding to current moment of the technique high resistance values to the breakage by flexion.

In a comparison of shock flexion according to the diagram in figure 5 shows the optimum toughness of the material of the invention.

In the diagram of figure 6 the comparison of the wear resistance values of the different steels of cold machining, it is shown that the alloy of the invention is within the range of the best materials of this kind of effort.

The test results show that the cold machined steel of the invention has excellent qualities with respect to toughness and hardness and that presents a resistance to wear comparable to the best alloys of the current moment of The technique.

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Claims (7)

1. Cold machined steel with high strength to wear for parts and tools manufactured powder metallurgically With high toughness and hardness, which contains the alloy elements in% by weight following: chrome (Cr) 3.71 to 4.69 molybdenum (Mo) 3.1 to 4.4 nickel (Ni) 0.14 a 0.3 vanadium (V) 8.45 a 9.5 tungsten (W) 0.5 to 1.5 Cobalt (Co) 1.1 to 4.9 as well as the elements Supplementary: sulfur (S) until 0.3 niobium (Nb) until 0.1 nitrogen (N) until 0.1 aluminum (To the) until 0.06 titanium (You) until 0.01 the impurities: match (P) 0.029 max oxygen (OR) 0.03 max and the element base: iron (Faith) as rest 2. Cold machined steel according to claim 1, with the reservation that the ratio vanadium to molybdenum plus tungsten be 1.5 to 2.2: \ frac {V} {Mo + W} = 1.5 \ up to \ 2.2 3. Cold machined steel according to claim 1 or 2, with the reservation that the proportion of chromium more manganese plus nickel to cobalt be 2.05 to 2.95: \ frac {Cr + Mn + Ni} {Co} = 2.05 \ a \ 2.95 4. Cold machined steel according to one of the claims, presenting one or more elements the following concentration values in% by weight:

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carbon (C) 2.3 to 2.6, preferably 2.4 to 2.55 silicon (yes) 0.3 to 0.8 preferably 0.42 to 0.68 manganese (Mn) 0.15 to 0.8 preferably 0.3 to 0.55 chrome (Cr) 3.85 to 4.58 preferably 4.0 to 4.45 molybdenum (Mo) 3.31 to 4.18 preferably 3.55 a 3.98 nickel (Ni) 0.16 a 0.25 vanadium (V) 8.61 to 9.34 preferably 8.81 to 9.2 tungsten (W) 0.7 to 1.3 preferably 0.75 a 1.25 Cobalt (Co) 1.4 to 3.82 preferably 1.61 to 2.42 5. Cold machined steel according to one of the claims 1 to 4, having one or more supplementary elements The following concentration values in% by weight: sulfur (S) up to 0.03, preferably up to 0.025 niobium (Nb) up to 0.01, preferably up 0.006 nitrogen (N) up to 0.09, preferably up 0.08 aluminum (To the) up to 0.05, preferably up to 0.04 6. Cold machined steel according to one of the claims 1 to 5, having one and / or more than one impurity the following concentration values in% by weight: match (P) 0.025 max oxygen (OR) 0.009 max 7. Cold machined steel part manufactured powder metallurgically with a chemical composition according to one of the claims before and with a corresponding degree of purity at a value 0 of less than / equal 3.0 according to DIN 50602.