SK286758B6 - Cold work steel with high wear resistance - Google Patents

Abstract

Cold work steel with high wear resistance for producing parts using powder metallurgy comprises (in wt.%): 2.21-2.64 carbon (C); 0.08-1.1 silicon (Si); 0.05-1.1 manganese (Mn); 3.71-4.69 chromium (Cr); 3.1-4.4 molybdenum (Mo); 0.14-0.3 nickel (Ni); 8.45-9.5 vanadium (V); 0.5-1.5 tungsten (W); 1.1-4.9 cobalt (Co); and accessory elements, polluting elements and as a basic element iron (Fe) in a residual amount.

Description

The invention relates to cold-working steel with high abrasion resistance for powder-metallurgical workpieces and tools with high toughness and strength.

BACKGROUND OF THE INVENTION

Components and tools for cold-working applications are subject to increasingly high and, at the same time, universal silent stress as technology evolves. In order to be able to achieve high parameters with properties independent of direction, they can be made by powder metallurgy, while the chemical composition of the alloy aimed at the shortest possible solidification times in the production process allows a further increase in the quality of the steel article.

Cold-working steels with high abrasion resistance have a high fraction in the matrix of the deposited hard phase, especially carbide, which causes high abrasion resistance. In view of the high toughness and hardness of the material, the importance of how the carbide is built and the properties of the matrix, especially their increased strength, is important.

Alloyed cold-working steel for the production of powder metallurgy components, in particular tools with high toughness and hardness, as well as abrasion and fatigue resistance, is disclosed in Austrian patent application no. 587/2001. A material with this chemical composition can have high mechanical properties while providing quality, but it is often found that with full turbidity through to large tools, particularly at low quenching temperatures, a coating containing mixed carbides with chromium forms at the grain boundary, thereby the potential of the alloy's toughness cannot be exhausted indefinitely. Therefore, higher toughness of the product material and simpler heat treatment technology would often be desirable.

Based on this prior art, it is an object of the invention to provide a cold abrasion-resistant steel for powder metallurgy workpieces and tools with high toughness and strength, which achieves the desired level of performance even with simpler heat treatment or lower quenching temperatures.

SUMMARY OF THE INVENTION

This object is solved by cold-working steel with high abrasion resistance for powder-metallurgical workpieces and tools of high toughness and strength containing alloying elements in wt. %: carbon (C) 2.21 to 2.64, silicon (Si) 0.08 to 1.1, manganese (Mn) 0.05 to 1.1, chromium (Cr) 3.71 to 4.69, molybdenum (Mo) 3.1 to 4.4, nickel (Ni) 0.14 to 0.3, vanadium (V) 8.45 to 9.5, tungsten (W) 0.5 to 1.5, cobalt ( Co) 1.1 to 4.9, as well as the accompanying elements sulfur (S) to 0.3, niobium (Nb) to 0.1, nitrogen (N) to 0.1, aluminum (Al) to 0.06, titanium (Ti) up to 0.01, contaminants phosphorus (P) max. 0.029, oxygen (O) max. 0.03 and iron (Fe) as the base element in the remaining amount.

In particular, the advantages achieved by the invention should be seen in that the alloying technical measures have been achieved, in particular by using the alternating action of the construction control elements and the carbide-forming elements, on the one hand to increase the opacity of the material and even at lower quenching temperatures the pre-decoidal deposition of carbides at the grain boundaries is reduced.

In view of the high abrasion resistance and at the same time improved toughness and in particular better flexural strength, the carbide forming elements of the 5th group of the periodic system interact with the 6th group elements. It has been found that with a niobium content of 0.1 wt% or less, with a vanadium content according to the invention, globular monocarbides and mixed tungsten and molybdenum mixed carbides are formed in the said concentration regions of these elements, with roughly bead-like vanadium monocarbides providing high material resistance abrasion. Highly stable tungsten and molybdenum monocarbides cannot form due to activity, whereas tungsten and molybdenum rich vanadium-containing carbides can be formed. These mixed carbides serve in the heat treatment to cure the matrix. They have the advantage of a lower deposition temperature and are easier to transfer into a solid solution even when austenitized. These carbide arrangements, which are substantially free of niobium, while providing very high fracture strength and bending impact strength of the refined material, due to the easier dissolution of the mixed carbides, are closely related to the lower chromium concentration in reaction kinetics.

Chromium, on the one hand, considered in isolation, can form at least three carbide formations with different carbon concentrations and is easily manageable as a metal component of carbide substitution. On the other hand, the chromium content also significantly affects the quenching behavior, such as hardness increase, hardenability and secondary hardness formation of the material. In principle, increasing chromium contents delay the structure change during quenching or increase the depth of cure and thus act in particular in the same way as nickel and manganese. On the other hand, the cobalt fractions in the alloy increase the carbon diffusion coefficient, which, on the one hand, may lead to lower deposition depths, on the other hand, cobalt largely suppresses pre-ductoid carbide excretion, particularly at grain boundaries.

With regard to the desired level of cold working properties of steel, which reaches deep into the workpiece at low quenching temperatures, chromium, manganese, nickel and cobalt need to be adjusted in the concentration ranges of the invention, with preferred content areas causing increased mechanical values of material and ensure the quality of the material.

As mentioned previously, the formation of monocarbide as well as the activity of the vanadium, molybdenum and tungsten elements with respect to mixed carbide formation and matrix hardening are important for the excellent performance properties of the cold working steel of the invention. It has been found that, within narrow limits, the concentration of the elements in the ratio according to the formula:

IN

Mo + W = 1.5 to 2.2, excellent mechanical properties of the steel article can be achieved in the treatment with comparatively low quenching temperatures, for example 1030 ° C to 1050 ° C, giving a greater degree of opacity in the internal fine-grained structure.

The cold working steel preferably has a chromium plus manganese plus nickel to cobalt ratio of 2.05 to 2.95 according to the following formula:

Cr + Mn + Ni

Co = 2.05 to 2.95.

In order to increase the abrasion resistance as well as to further increase the toughness and hardness of the cold working steel, it is preferable that one or more elements have the following concentrations in wt. %: carbon (C) = 2.3 to 2.6, preferably 2.4 to 2.55, silicon (Si) = 0.3 to 0.8, preferably 0.42 to 0.68, manganese (Mn) = 0.15 to 0.8, preferably 0.3 to 0.55, chromium (Cr) = 3.85 to 4.58, preferably 4.0 to 4.45, molybdenum (Mo) = 3.31 to 4 18, preferably 3.55 to 3.98, nickel (Ni) = 0.16 to 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 to 1.25, cobalt (Co) = 1.4 to 3.82, preferably 1.61 to 2.42.

Furthermore, it has been shown to be beneficial, in particular to achieve increased material toughness, when one or more of the accompanying elements has the following concentration values in wt. %: sulfur (S) to 0.03, preferably to 0.025, niobium (Nb) to 0.01, preferably to 0.006, nitrogen (N) to 0.09, preferably to 0.08, aluminum (Al) to 0, %, Preferably up to 0.04, or more than one contaminant has the following concentration values in wt. %: phosphorus (P) maximum 0,025, oxygen maximum 0,009.

For a powder-coated steel cold work piece having a chemical composition according to one of the above materials, it is important, in view of the highest toughness and strength of the material, even when using standard quench tempering temperatures, given a higher degree of steel purity corresponding to a K0 value of less than or equal to 3.0 according to DIN 50602. Higher KO values may lead to an enhanced deterioration in the performance of the article.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail on the basis of the results of the comparative experiments by means of tables and drawings, wherein:

Table 1 shows the chemical composition of the cold working steel according to the invention and the comparative alloys; Table 2 shows the measured values of the fracture strength, the flexural impact and the abrasion resistance of the treated steels; 1 shows a measurement arrangement for determining the fracture strength in bending, FIG. 2 shows the shape of the test specimen for the bending impact test; FIG. 3 shows a diagram of an abrasion resistance measuring device, FIG. 4 is a comparative bar graph of the fracture flexural strength of steel alloys; FIG. 5 is a comparative bar graph of steel alloy impact work; FIG. 6 is a comparative bar graph of cold wear resistance of steels.

DETAILED DESCRIPTION OF THE INVENTION

Table 1 shows the chemical composition of the cold working steel according to the invention, designated Al alloy K, and the chemical composition of the comparative alloys designated Al alloy A to Alloy J.

Table 2 shows the results of the tests for fracture strength, flexural impact and abrasion resistance under the same designation, and the shaped test specimens were each upgraded to the same hardness of 61 HRc.

The cold fracture strength of steel alloys was determined on round test pieces (R _D = 5.0 mm) on the apparatus of FIG. 1. The forward force F was 200 N, the speed to full forward force was 2 mm / min. and the test speed was 5 mm / min.

Examination of the bending impact of the material was performed on the test bodies with the shape shown in FIG. Second

In FIG. 3 schematically illustrates the abrasion resistance measuring device used.

Fig. 4 shows in the form of a bar graph the excellent fracture strength of the alloy K according to the invention, the prior art corresponding to the comparative materials A to J, which also have a high fracture strength value.

From the bending impact work of FIG. 5, also in the form of a bar graph, shows the excellent toughness of the material according to the invention.

When again, in the form of a bar graph, in FIG. 6 compared the abrasion resistance values of steels of different compositions for cold work, so the alloy according to the invention lies in the region among the best materials in terms of this type of stress.

The results of the investigation show that the cold working steel according to the invention has an excellent level of toughness and strength properties and has a comparable abrasion resistance as compared to the best alloys of the prior art.

Table 1

alloy K *) Alloy A Alloy B alloy C Alloy D Alloy E Alloy F Alloy G Alloy H Alloy I Zliatina J C 2.46 2.44 2.55 2.49 2.42 2.61 2.63 2.52 2.44 2.49 2.30 Are you 0.56 0.98 1.05 0.95 1.12 0.97 1.13 0.87 0.94 0.63 0.32 Mn 0.40 0.52 0.53 0.49 0.55 0.66 0.71 0.55 0.50 0.32 0.31 Cr 4.25 6.22 6.93 6,12 6.27 6.08 6.21 6.28 5.66 4.19 12.31 W 1.01 1.41 0.95 2.74 1.30 1.06 1.50 2.22 0.05 3.68 0.35 Mo 3.73 3.98 3.95 3.78 4.00 3.60 3.98 5.05 1.31 3.21 1.17 IN 9.01 8.12 7.85 7.92 7.88 6.77 7.83 8.20 9.84 8.72 3.94

alloy K *) Alloy A Alloy B Alloy C Alloy D Alloy E Alloy F Alloy G Alloy H Alloy I Zliatina J nb 0,005 1.19 1.15 1.12 1.86 1.45 0.61 0.9 0.01 - - WITH 0,023 0,008 0,011 0.03 0,012 0,028 0,009 0,039 0.07 0.01 0,013 N 0,056 0,095 0.08 0,064 - - 0.09 0.06 0,075 0,038 0.13 What 1.98 0.4 <0.1 - - <0.1 0.13 0,038 - 0.04 Ni 0.20 0.7 0.43 0.17 0.28 0.89 0.51 0.76 - 0.36 - ABOUT 0.0059 0.0091 0,032 - - 0,041 0,068 0,044 - 0,054 0.0098

*) alloy according to the invention

Table 2

alloy Fracture bending strength [N / mm ² ] Four-point bending test Bending impact [J] sample without notch Abrasion resistance [1 / g] against SiC sandpaper The 5329 45 14.3 A 4843 43.5 14.7 B 4487 34 14.5 C 4524 35 14.3 D 4636 36.8 14,15 E 4720 39.9 13.1 F 4825 43 12.8 G 4585 35 14.35 H 4716 36 14.73 I 4845 44 13.80 J 4468 33 11.86

Always refined to a hardness of 61 HRc. Alloy K = alloy according to the invention

PATENT CLAIMS

Claims (7)

1. Cold-working steel with high abrasion resistance for powder metallurgy-produced workpieces and tools with high toughness and strength, characterized in that it contains alloying elements in wt. %: carbon (C) 2.21 to 2.64, silicon (Si) 0.08 to 1.1, manganese (Mn) 0.05 to 1.1, chromium (Cr) 3.71 to 4.69, molybdenum (Mo) 3.1 to 4.4, nickel (Ni) 0.14 to 0.3, vanadium (V) 8.45 to 9.5, tungsten (W) 0.5 to 1.5, cobalt ( Co) 1.1 to 4.9, as well as the accompanying elements sulfur (S) to 0.3, niobium (Nb) to 0.1, nitrogen (N) to 0.1, aluminum (Al) to 0.06, titanium (Ti) up to 0.01, contaminants phosphorus (P) max. 0.029, oxygen (O) max. 0.03 and iron (Fe) as the base element in the remaining amount. Cold work steel according to claim 1, characterized in that the ratio of vanadium to molybdenum plus tungsten is 1.5 to 2.2 according to the following formula: IN Mo + W = 1.5 to 2.2. Cold working steel according to claim 1 or 2, characterized in that the ratio of chromium plus manganese plus nickel to cobalt is 2.05 to 2.95 according to the following formula: Cr + Mn + Ni ''_'nc ---- 7; --------- = 2.05 to 2.95. What Cold work steel according to any one of claims 1 to 3, characterized in that one or more elements have the following concentration values in wt. %: carbon (C) = 2.3 to 2.6, preferably 2.4 to 2.55, silicon (Si) = 0.3 to 0.8, preferably 0.42 to 0.68, manganese (Mn) = 0.15 to 0.8, preferably 0.3 to 0.55, chromium (Cr) = 3.85 to 4.58, preferably 4.0 to 4.45, molybdenum (Mo) = 3.31 to 4 18, preferably 3.55 to 3.98, nickel (Ni) = 0.16 to 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 to 1.25, cobalt (Co) = 1.4 to 3.82, preferably 1.61 to 2.42. Cold working steel according to any one of claims 1 to 4, characterized in that one or more of the accompanying elements has the following concentration values in wt. %: sulfur (S) to 0.03, preferably to 0.025, niobium (Nb) to 0.01, preferably to 0.006, nitrogen (N) to 0.09, preferably to 0.08, aluminum (Al) to 0, 05, preferably up to 0.04. Cold work steel according to any one of claims 1 to 5, characterized in that one or more of the contaminants has the following concentration values in% by weight; phosphorus (P) not more than 0,025, oxygen not more than 0,009. Cold working steel according to one of Claims 1 to 6, characterized in that the 5 powder metallurgical article produced therefrom has a degree of purity corresponding to a K0 value of less than or equal to 3 according to DIN 50602.