DE3015709A1 - HARD MATERIAL ALLOY - Google Patents

Description

Hard alloy.

Sintered hard material alloys made of metal carbide and metallic Binder, in particular steel, is one of all nickel martensitic steels also known for hardenable hard materials, e.g. B. DE-PS 12 98 293, DE-PS 12 57 440, DE-PS 15 58 477, DE-PS 26 30 266.

Nickel martensitic steel ties are used to provide high strength can be achieved by simple artificial aging.

When the wear resistance of these machinable and hardenable hard alloys with nickel martensitic binder is not sufficient, the carbide content is usually increased, e.g. B. to 60% by weight compared to 30% for the machinable alloys. In order to hardness values of 74/78 HRC are achieved after aging.

Machining by turning, milling is due to the high carbide content and the associated high hardness of 60 to 65 HRC in the solution-annealed condition not possible.

A disadvantage of these known alloys is the high sintering temperature of over 14300C, which is about 2000C higher than that of other hard material alloys. This means that there is also no possibility of composite sintering with steels that at these temperatures already liquid or so coarsely crystalline that they for are unsuitable for further use.

For combinations between normal hard materials with a high carbide content with ferritic steel matrix and steels through high temperature soldering is the heat treatment, that is, hardening at temperatures above 10000C in oil or in inert gas a big risk, because these well-known hardening methods always lead to too high There is tension that often leads to the solder layer tearing off.

The object of the invention is to create a hard material alloy, the highest hardness not only due to a high carbide content but also higher Strength of the matrix is achieved and can be sintered at a temperature that so is low so that in the case of composite sintering with steel, it does not melt away or becomes coarsely crystalline and brittle. This is for large area wear plates as they are in forms for building blocks, e.g. B. made of pumice concrete, for refractory stone slabs, for blown baffles, for lining slides, for covering large areas that are subject to wear and tear are particularly important. To achieve a cheap In terms of price / performance ratio, simple hardening without distortion is also required.

A special characteristic of nickel martensitic steels is that exceptionally low carbon for which a content of less than 0> 1 % is required0 because the nickel martensitic alloys due to larger amounts of carbon show great tendency to fold over into the austenitic, i.e. soft state. An increase in the carbon content to lower the sintering temperature is not an option therefore from. Another solution had to be found to this very interesting one Nickel-artensitic steel alloys as binders for hard material alloys are economical to be able to use.

According to the invention, a hard material alloy with the Proposed composition characterized in claim.

Tests have shown that there is a lowering of the sintering temperature to the service temperature and ideal temperature to avoid crystal growth can be achieved in the steels to be used by adding copper and aluminum. It is surprising that both elements in addition to a lowering of the sintering temperature cause an additional hardening effect at approx. 13000C, so that an increase in hardness the matrix is achieved and thus a higher wear resistance of the itself not so ideal platelet-shaped nickel martensite compared to the usual carbon martensite ft.

A Ni content below 4.5% prevents the formation of nickel martensite absolutely. The low Ni contents are with the addition of larger amounts of chromium and / or Manganese required to prevent austenite formation. At higher Ni contents there is also the risk of austenite formation, which means that no more hardening is possible given is.

Molybdenum and cobalt have the same reasons for the above and lower levels. Here, too, there is coordination among each other, especially at Addition of chromium and manganese, necessary to prevent austenite formation, but Ensure precipitation hardening through the formation of intermetallic compounds.

Titanium is used as a carbide former in these high-carbide alloys often just as little necessary as niobium or niobium / tantalum. An addition can then be appropriate if so much free carbon is brought in with other elements, that there could be increased austenite formation, which is due to the binding of the carbon is prevented by carbide images.

Manganese is used to harden the steel matrix and lower the sintering temperature. An addition is not absolutely necessary, above 4.0% there is a risk of austenite formation.

Boron serves to deoxidize and expand the sintering area, but also to lower the sintering temperature. Contents above 1.4% lead to porosity, depending on the composition of the matrix, especially those with no Cr content. Chromium boride also bring higher hardness.

Chromium is important when corrosion resistance is required.

Up to 20.0% Cr there is sufficient passivity so that higher Cr contents would be uneconomical. On a coordination of the content of chromium, Particular care must be taken with nickel and carbon in order to avoid austenite formation.

Copper thus serves as a special feature of the invention for lowering the sintering temperature and additional precipitation hardening.

Below 2.0% Cu there are no effects, above 6.0% there is no increase a.

Aluminum behaves similarly, in the form of master alloys such as Iron-aluminum, nickel-aluminum or the like can be added. Under 2, 0%, the desired benefits are not clearly visible, above 6.0% there is no longer any improvement in the positive values.

The invention is explained in more detail using the following examples: example 1 An alloy of 60% by weight titanium carbide and 40% by weight of a steel matrix (in% by weight) 2.0% copper 2.0% aluminum 13.0% nickel 15.0% molybdenum 15> 0% cobalt, remainder iron ° could be sintered at 1320 C to a dense body with a Density of 5.93 g / cm3. The hardness after the solution heat treatment of 840 ° C with air resp. Gas cooling resulted in 66 HRC, after aging for 6 hours at ° 480 C the hardness became 72/74 HRC achieved.

Example 2 The alloy according to Example 1, but with 4.0% aluminum and 4.0% copper could be sintered at 13000C to a density of 5.88 g / cm3, the hardness after aging for 6 hours at 4800b rose to 74/76 HRC.

Example 3 An alloy of 60% by weight titanium carbide, the remainder steel as follows Composition (in% by weight) 14, 0% chromium 5, 0% molybdenum 5, 5% nickel 9, 0% cobalt 4.0% copper 4.0% aluminum 0.01 oIOBor the remainder iron let himself sinter at 1300 ° C to a dense body with 5.5 g / cm³ density. With a hardship from 70 HRC in the solution-annealed condition, this could be achieved by aging for 6 hours at 4900C bring it to 76/78 HRC.

Example 4 60% TiC / Cr3C2, consisting of 70% TiC and 30% Cr3C2, and a matrix of 4.0% copper 4.0% aluminum 13.0% nickel 15.0% molybdenum 15, 0% cobalt, 0, 01% boron, 1% carbon, remainder iron can form bodies at 1300 ° C be sintered with a density of 5.85 g / cm³. After that there is a hardness of 69/70 HRC, which increases to 78/80 HRC after 8 hours of aging at 4800C.

Example 5 Due to the low sintering temperature, there is composite sintering possible with steel parts.

A compact of 200 × 100 × 15 mm of the alloy according to the example was thus obtained 3, i.e. from (wt. -So) 60% titanium carbide 40% steel with 4.00% copper 4.00% aluminum made of Al / Fe 50: 50 5, 50% nickel 5 »00% molybdenum 9.00% cobalt 14.00% chromium 0, 01% boron, remainder iron on a planed steel plate with the material number 6511 (0> 36% C, 0.60% Mn, 1.00% Cr> 0.20% Mo, 1.00% Ni, remainder Fe) laid and sintered at 13000C in a vacuum of 10 Torr. A steel-hard material composite was created as a result of diffusion. Aging for 6 hours at 480.degree. C. resulted on the hard material side a hardness of 78 HRC and on the steel side a hardness of 34 HRC. From the steel side the network was able to use known methods such as milling, planing and turning without any problems and the like are processed to comply with tolerances.

The hard material side is only ground flat due to its high hardness, to save costs. The composite guarantees high strength against breakage and has high dimensional adaptability.

Example 6 A mixture according to Example 2, i.e. from (% by weight) 60% Titanium carbide 40% steel with 4.00% aluminum from Al / Fe 50:50 4.00% copper 13> 00% nickel 15, 00% molybdenum 15, 00% cobalt remainder iron was in a rectangular Stahlpreßform the size 100 mm high x 150 mm wide x 300 mm long filled, so that 1/3 of the shape, i.e. about 100 mm, was filled with it. A piece of cardboard or a split, separate stamp prevents the powder from running off. The second middle third is then the same with a mixture of normal hard material Matrix as indicated above, but only filled with 33% titanium carbide. One piece Cardboard or a raised lower punch that is divided twice prevent it from running off of the powder in the remaining third. This is then combined with a normal sintered steel mixture filled without additional carbide content. composition about 0.90% carbon 0.80% manganese 0, 20% silicon 3, 00% chromium 0, 50% molybdenum 0.40% vanadium, remainder iron.

The whole thing is then compressed with approx. 1,000 kg per cm2 and the like The resulting compact is sintered at 1320 ° C. in a vacuum of approx. 10 2 Torr.

Since all three alloys according to the invention at a sintering temperature were brought and all experience almost the same shrinkage during sintering, arises a composite body that has the highest wear resistance in the upper third, i.e. where the greatest abrasion occurs, for example on a mallet in hammer mills. The middle third of normal hard material is easy to machine in the annealed condition, while the lower third z. B. is very easy to drill and has the highest toughness. Wear does not occur in the lower third.

After aging for 8 hours at 490 ° C, the upper third has a hardness of 78/79 HRC, the middle piece a hardness of 68/69 HRC and the lower fastening part one of 35/40 HRC. The composite body is very stable and withstands extremely high levels Impact stress.

For a mallet made entirely from the hard material alloy with 60 TiC given the risk of rupture. The wear parts manufactured in this way for the highest Compared to those made of highly wear-resistant cast iron, impact stress brings a 10 to 20 times higher performance.

The advantages of the hard material alloy according to the invention over comparable ones known materials are: - highest hardness also of the steel matrix above 72 HRC, combined with high wear resistance, - lower sintering temperature of approx. 1300 ° C, easiest heat treatment by aging 4 - 8 h at 460 - 5000C, thereby Production of panels with a thickness of less than 5 mm, because there is no distortion, and inexpensive Price / performance ratio, possible combinations through composite sintering with steels without damaging crystal growth in steel, - exceptionally low density less than 6.0 g / cm3, i.e. lighter than steel and half the weight of hard metal.

Claims (2)

Claims 1. Sintered hard material alloy from 40 to 80 wt. -Qlo Metal carbide, primarily titanium carbide, with up to 70% by weight of the titanium carbide through replaced one or more of the carbides of tungsten, molybdenum, vanadium or chromium could be. Remainder of an alloy of (each wt .-%) 4, 5 to 19, 5% nickel 4, 5 to 16, 5% molybdenum 4, 5 to 16, 5% cobalt 2, 0 to 6, 0% copper 2, 0 to 6, 0% aluminum 0 to 0.1% carbon 0 to 4, 5% titanium 0 to 1.4% boron 0 to 4, 5% niobium 0 to 20, 0% chromium 0 to 4, 0% manganese balance iron, with the composition is coordinated in such a way that the alloy is nickel (soft) martensitic structure having. 2. Use of a hard material alloy of the composition according to claim 1 for composite sintering with steel parts.