CH666288A5 - STEEL DIE, METHOD FOR THE PRODUCTION AND USE THEREOF. - Google Patents

Description

DESCRIPTION

The invention relates to a die made of steel with a plurality of parallel extrusion channels, the inner surface of which is covered with a wear-resistant, metal-containing layer, a process for its production and the use of the die.

Matrices with a variety of continuous extrusion channels are used in various fields of technology. They serve e.g. for the extrusion of plastics, especially i0 other masses. Steel dies are used in particular for the production of catalyst supports based on ceramic materials, some of which are guided through the die bodies under considerable pressure. The provisional shaping of the ceramic mass i5 by the die can then be followed by the fixation of this state by firing processes, etc. In this case or also afterwards, catalytically active substances can also be applied which intervene to promote chemical processes. In the course of the tightening pre-20 regulations on the protection of the environment and the compulsion to make better use of existing energies, there is an ever-increasing need for permeable, temperature-resistant ceramic molding compositions which are suitable for taking up catalysts or other active substances. Different structures are common, e.g. Honeycomb structures, tubular structures, etc.

Matrices of the type described above must be in operation, i.e. during the production of carrier masses, etc., meet a number of requirements. These result from the continuous passage of aggressive and abrasive masses, some of which are pressed under high pressure. In particular, high demands are placed on the stability, shape retention and surface properties of the often very thin extrusion channels. This applies in particular to the extrusion of ceramic materials which, in the presence of aluminum oxides, have an abrasive and corrosive effect at the extrusion pressures used due to the weakly acidic pH and high hardness of the individual components.

To increase the service life of corresponding matrices for the production of ceramic catalyst supports, e.g. Steel matrices have hitherto been used as furnace inserts or for exhaust gas detoxification, the interior of their extrusion channels being lined with a nickel layer with embedded silicon carbide. The wear-resistant layer was deposited by electroless means. Although good results could be achieved with matrices of this type, they are not yet able to meet the high requirements in practice with regard to the dimensional stability of the channels, the service life of the matrix, etc.

It is the object of the invention to create matrices of the type described at the outset which, with improved shape retention, even very thin mold channels have a long service life when ceramic, possibly acidic materials pass through, and to find processes for producing such matrices and their use.

In the context of the invention, extensive and lengthy tests were carried out, which included both a variation of the die material and the investigation of the possibilities for protecting the existing extrusion channels 60. It has been shown that a mere modification of the matrix base body by choosing suitable starting materials and corresponding treatment steps to improve the surface hardness and toughness did not lead to completely satisfactory tool life. Due to the large number of extrusion channels, some of which are very small in cross-section, and in some cases long, attempts at galvanic coating or sputtering of wear-resistant metal layers using so-called PVD processes have not been successful. It has

3rd

666 288

However, surprisingly, it was shown in the context of the invention that matrices made of steel of the type defined at the outset can be achieved with long service lives, which are characterized in that the layer of titanium carbide, titanium nitride, titanium carbonitride, titanium carboxynitride or a mixture thereof in a thickness of 8 to 25 μm is formed.

In the context of the invention, it is generally completely sufficient if the wear-resistant layer is applied directly to the steel on the inner surface of the extrusion channels without an intermediate layer. However, it is not excluded within the scope of the invention to apply an intermediate layer, should this be desired depending on the passage medium etc.

The coating of one or more of the aforementioned titanium compounds is advantageously applied by a so-called chemical vapor deposition process (hereinafter CVD process). The deposition takes place in coordination with the steel selected for the die in a temperature range of generally 650 to 950 ° C., preferably below 900 ° C. A particularly favorable range for the deposition of the CVD layers within the scope of the invention is between 680 to 900 ° C., preferably up to 850 ° C. In this temperature range, it is possible in a particularly advantageous manner to match the coating temperatures to the temperatures of the steel's heat treatment, which the steel can undergo anyway, without accepting its decarbonization, significant warping of the die or other disadvantages.

In particular when the CVD coating is deposited in the range from approximately 680 to 850 ° C., the wear-resistant layer can be formed predominantly or completely from needle crystals which protrude from the surface of the extrusion channels essentially perpendicularly or “brush-like”. Crystals of this type adhere particularly firmly to the steel surface of the internal extrusion channels and, surprisingly, can withstand the long-lasting average of aggressive and abrasive ceramic materials under high pressures without being sheared, even without an intermediate, usually more elastic, diffusion layer. Surprisingly, a uniform coating of the titanium compounds mentioned can also be applied inside the extrusion channels even if the extrusion channels have extremely small diameters in the range from 20 to 500 μm, preferably between 200 to 450 μm. Depending on the type of die, the extrusion channels may have different cross sections in their course. Thus, in a preferred die according to the present invention, the extrusion channels have an outlet channel with a diameter in the range from 0.1 to 1 mm, which extends into a bore which is several times wider, the bore having diameters in the range from 1 to 10 mm, for example can. As extensive tests within the scope of the invention have shown, special abrasive and other loads occur in particular at the points where the cross-section changes in the bore or channel, which is why it is preferred for the wear-resistant layer to have at least the same layer thickness in the area of such cross-sectional changes in the outlet channels compared to intermediate surface areas and has a thickness of at least 12 µm.

A low-carbon, martensitic, semi-martensitic and austenitic precipitation-hardenable, corrosion-resistant steel is preferably used for the die according to the invention. This steel regularly contains chromium, nickel and / or manganese as alloying additives in a higher proportion.

The matrices according to the invention can be produced by first making out a die body with a large number of parallel extrusion channels located therein

Steel manufactures, and then applies a wear-resistant, metal-containing layer inside the extrusion channels, the method being characterized in that the die is made from low-carbon, precipitation-hardenable steel, and then by chemical vapor deposition in the medium temperature range from 650 to 950 ° C, with a Titanium compound and at least one carbon source and / or nitrogen source coated the interior of the extrusion channels in a layer thickness of 8 to 25 microns. Depending on the desired titanium compound or a mixture thereof, the choice of the suitable carbon, nitrogen source, etc. will be determined. In the context of the invention it is preferred to use organic carbon compounds as the carbon and / or nitrogen source, which then,

if nitrogen-containing titanium compounds are desired in the layer, at the same time also contain nitrogen. Preferred organic carbon and / or nitrogen sources are amines, hydrazines and nitriles, of which nitriles are particularly preferred. Typical C-N sources that can be mentioned are, for example, aceto-nitriles, CEhCN, trimethylamine, dimethylhydrazine, hydrocyanic acid, etc. In addition, customary reactive and carrier gases are used.

In the context of the method according to the invention, it is further preferred to carry out the temperature of the CVD coating below the temperature at which the martensite / austenite phase transformation of the steel of the die takes place. Changes in the shape of the die during or after the CVD coating can thereby be minimized or avoided. An additional high-temperature heat treatment is not necessary.

The coating pressures can vary within a wide range and are preferably, for example, in the range from 1333.22 to 100,000 Pa. The choice of organic C-N sources can surprisingly ensure that the substrate is not decarburized on the coating surfaces. This is possible in particular when choosing nitriles and also those amines, triazines, etc. which convert to nitriles at higher temperatures.

The coating times are usually in the range of a few hours, with coating times of between 4 and 10 hours being used, depending on the type of steel selected and the coating gases.

As already mentioned above, the coating thicknesses of the applied CVD layer are in the range from 8 to 25 μm. The use of less thick CVD layers generally leads to a reduction in the steel time of the matrices, while layer thicknesses lying above 25 µm can tend to crack under certain operating conditions of the matrix, which is why the range mentioned is favorable and thicknesses above 12 µm are particularly preferred.

At the specified average temperatures in the range from approximately 680 to 900 ° C., fine needle crystals can be formed, which can have typical needle diameters in the range from 0.1 to 0.8 μm, the length of which can reach that of the layer thickness. If higher temperatures are used for the CVD coating in the context of the invention, more fine-grained or conical stem crystals result, i.e. the needle crystals change into cone crystals and a diffusion zone can occur. However, it is preferred according to the invention to produce predominantly or completely needle crystals up to a layer thickness of about 25 μm directly on the steel without a diffusion layer, since here the CVD layer optimally adheres to the die surface, sufficient thickness for the abrasive and corrosive stress and dimensional stability of the CVD layer can be reached without cracking even under heavy loads5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

666 288

4th

are cash.

Preferred hardnesses in the extrusion channels and preferably on the exit side of the die itself are in the range from 1,800 to 2,500 Vickers, at a load of 50 g, but preferably above 2,000 Vickers.

The for the manufacture of the die preferably in

Steels in question are relatively low in carbon, have good corrosion resistance and should preferably not form any carbon martensite. However, it should be precipitation hardenable steels, whereby the alloying components can act as martensite formers. Typical, well-suited steels are, for example, the following: A steel with the composition of: C 0.09%, Si 1%, Mn 1%, P 0.045%, S 0.03%, Cr 16 to 18%, Ni 6.5 to 7.5%, AI 1.5%, balance iron (all percentages based on weight).

A steel with the designation X 20 DU with the following composition: C = 0.07, Cr 20.00 Ni 9.00, Mo 2.50, Cu 1.50 (stainless steel that can be hardened against precipitation).

Martensitic hardening steels, such as (so-called nickel maraging steels):

X 2 NiCoMo 18 9 5 (18 Ni 300 grade),

X 2 NiCoMo 18 12 4 (18 Ni 350 grade),

X 2 NiCoMo 13 15 10 (13 Ni 400 grade) and X 1 CrNiCoMo 13 85.

Thyrodur 2709; X 3 NiCoMoTi 18 96: C 0.03 max, Mo 5.0, Ni 18.0, Co 10.0, Ti 1.0;

so-called maraging steels, e.g. :

Marval 18 with the following composition: C 0.02, Ni 18.00, Co 8.00, Mo 5.00, Ti 0.50;

Marval 18 H with the following composition: C 0.02, Ni 18.00, Co 9.00, Mo 5.00, Ti 0.60;

or according to the list below, in which Ni steels are listed:

25 Ni: C (b) 0.03, Mn (b) 0.10, Si (b) 0.10, S (b) 0.01, P (b) 0.01, Ni 25.0-26, 0, Ti 1.3-1.6, Al 0.15-0.30, Cb 0.30-0.50;

20 Ni: C (b) 0.03, Mn (b) 0.10, Si (b) 0.10, S (b) 0.01, P (b) 0.01, Ni 19.0-20, 0, Ti 1.3-1.6, Al 0.15-0.30, Cb 0.30-0.50;

18 Ni (280): C (b) 0.03, Mn (b) 0.10, Si (b) 0.10, S (b) 0.01, P (b) 0.01, Ni 18.0 - 19.0, Co 8.5 - 9.5, Mo 4.6 - 5.2,

Ti 0.5-0.8, Al 0.05-0.15;

18 Ni (250): C (b) 0.03, Mn (b) 0.10, Si (b) 0.10, S (b) 0.01, P (b) 0.01, Ni 17.0 - 19.0, Co 7.0 - 8.5, Mo 4.6 - 5.2, Ti 0.3 - 0.5 Al 0.05-0.15;

18 Ni (200): C (b) 0.03, Mn (b) 0.10, Si (b) 0.10, S (b) 0.01, P (b) 0.01, Ni 17.0 - 19.0, Co 8.0 - 9.0, Mo 3.0 - 3.5, Ti 0.15-0.25 Al 0.25-0.15;

Cast: C (b) 0.03, Mn (b) 0.10, Si (b) 0.10, S (b) 0.01, P (b) 0.01, Ni 16.0-17.5 , Co 9.5-11.0, Mo 4.4-4.8, Ti 0.15 0.15-0.45, Al 0.05-0.15;

1000F (c) Ni 15, Co 9, Mo 5, Ti 0, .7, Al 0.70;

Note: (b) = maximum, (c) nominal composition.

Or VEW N 700 with the following composition:

C 0.04, Cr 16, Ni 4.5, Cu 3.3, Nb 0.25;

or the following precipitation hardenable steels: PH 15-7 Mo (15 Cr, 7 Ni, 2.5 Mo, 1.15 Al);

17-4 PH (16.5 Cr, 4.25 Ni, 3.6 Cu, 0.25 Cb);

17-7 PH (17 Cr, 7 Ni, 1.15 Al);

AM-350 (16.5 Cr, 4.25 Ni, 2.75 Mo, 0.10 N);

AM-355 (15.5 Cr, 4.25 Ni, 2.75 Mo, 0.10 N);

The precipitation hardenable steels which can advantageously be used in the context of the invention preferably have a C content of less than 0.05% and Ni as an alloying constituent, optionally with further addition of Cr, Mo, Co and / or Mn or mixtures of these alloy metals.

In the context of the method according to the invention, it is also advantageous if the steel considered for the die has been previously annealed or solution-annealed to give it later dimensional stability. Furthermore, it is preferred to carry out an aging of the steel in the range of advantageously 450 to 650 ° C. after the CVD coating.

The die according to the invention surprisingly has a uniform, very adherent, corrosion-resistant coating in the extrusion channels, which considerably increases the dimensional stability and service life of the die compared to conventional solutions. As a result, the die is particularly suitable for the extrusion of ceramic materials and especially those containing aluminum oxide or other hard, abrasive components. The coatings based on the aforementioned titanium compounds also have good resistance to the ceramic compositions when they have an acidic pH. The use of the die according to the invention is therefore considered in particular for the production of 20 catalyst supports or temperature-resistant inserts on a ceramic basis.

A typical die according to the invention is shown in the attached FIGS. 1 to 2, extrusion channels of 25 diameters in the range from 30 to 500 μm lying at the intersections of the straight lines according to FIG. 1. As is illustrated in more detail in FIG. 2, the extrusion channels open into wider bores at the rear of the die, the exit channel, bore and exit surface of the die being coated with titanium compound. The production of the die according to the invention is illustrated below in examples, which, however, are not to be interpreted as restrictive.

■ Example I

35 A matrix of 17-4 PH (17% Cr, 4% Ni, 3.6% Cu, 0.25% Nb) is cleaned in an alkaline aqueous solution using ultrasound, rinsed with distilled water and subsequently cleaned with acetone.

The die is then placed in a CVD reactor 4o and stored on molybdenum sites. The reaction chamber is evacuated to 10-2 mbar.

The mixture is then heated to the coating temperature under an argon atmosphere. Thereafter, the matrix is heated for 5 hours at 875 ° C in a gas mixture of 45 1% titanium tetrachloride and 0.5% butyronitrile (C4H7N) in a carrier gas consisting of 60% H2 and 38.5% Ar at a pressure of 120 mbar coated. Total flow 25 1 / min. After cooling under Ar at atmospheric pressure, the die is stored for 3 hours at 482 ° C under Ar. The 50 die was uniformly coated within all the extrusion channels with a gray-brown layer of Ti (C, N) 12 μm thick with a microhardness of 2100 HV 0.05.

Example II

55 A matrix made of Aubert Duval steel X 20 DU 20% Cr, 9% Ni, 2.5% Mo, 1.5% Cu was cleaned, charged and heated as in Example I. Thereafter, coating was carried out for 8 hours at 750 ° C. in a gas mixture of 0.85% TiCk, 1.5% acetonitrile (C5H3N) and 97.65% H2 at a pressure of 100 mbar and a total gas flow of 40 1 / min. After cooling, the matrix was aged under Ar at 482 ° C. for 4 h. The die was uniformly coated in the extrusion channels with a gray layer of Ti (C, N) 16 μm thick with a microhardness of 2000 HV.

G

1 sheet of drawings

Claims (16)

666 288 1. Steel die with a plurality of parallel extension channels, the inner surface of which is coated with a wear-resistant, metal-containing layer, characterized in that the layer of titanium carbide, titanium nitride, titanium carbonitride, titanium carboxynitride or a mixture thereof in a thickness of 8 up to 25 µm. 2. Die according to claim 1, characterized in that that the wear-resistant layer is a chemical vapor deposition layer. 2nd PATENT CLAIMS . 3. Die according to claim 1 or 2, characterized in that the wear-resistant layer is applied directly to the steel without an intermediate layer. 4. Die according to claim 3, characterized in that the layer is applied in the range from 680 to 900 ° C. 5. Die according to claim 1, 3 or 4, characterized in that the layer is predominantly formed from needle crystals which protrude from the surface of the extrusion channels essentially perpendicularly or “brush-like”. 6. Die according to claim 1, characterized in that the layer is guided around the outlet opening of the extrusion channels. 7. Die according to claim 1, characterized in that the extrusion channels have a diameter in the range from 20 to 500 μm. 8. Die according to claim 1, characterized in that that the layer is present in the region of cross-sectional changes of the outlet channels in at least the same layer thickness in comparison to intermediate surface regions and has a thickness of at least 12 μm. 9. Die according to claim 1 or 2, characterized in that the steel is a low-carbon, precipitation hardened. represents nickel steel. 10. The method for producing a die according to claim 1, wherein a die body with a plurality of parallel extrusion channels made of steel is made therein, and then a wear-resistant, metal-containing layer is applied inside the extrusion channels, characterized in that the die is made of low-carbon, precipitation-hardenable Manufactures steel, and then by chemical vapor deposition in the medium temperature range of 650 to 950 ° C with a titanium compound and at least one carbon source and / or N2 source coated the interior of the extrusion channels in a layer thickness of 8 to 25 microns. 11. The method according to claim 10, characterized in that an organic compound, preferably a Nitrii, is used as the carbon source. 12. The method according to claim 10 or 11, characterized in that one sets the coating temperature below the temperature of the phase transition martensite-austenite of the steel of the die (so-called solution annealing temperature). 13. The method according to claim 10 or 12, characterized in that after the coating, the die in the range of 450 to 650 ° C is outsourced. 14. The method according to claims 10 to 13, characterized in that one uses a precipitation hardening, alloyed with Cr, Ni and / or Mn for the die body. 15. Use of the die according to claims 1 to 9 for the extrusion of ceramic materials. 16. Use according to claim 15 for the production of catalyst supports or temperature-resistant inserts.