EP2566640A2

EP2566640A2 - Powder-metallurgical steel

Info

Publication number: EP2566640A2
Application number: EP11719228A
Authority: EP
Inventors: Roland Alber
Original assignee: Guehring KG
Current assignee: Guehring KG
Priority date: 2010-05-05
Filing date: 2011-05-05
Publication date: 2013-03-13
Also published as: WO2011138422A2; WO2011138422A3; DE102010019599A1; JP2013528705A; JP5940058B2; KR20130124152A; US20130136647A1

Abstract

The invention relates to a method for producing powder-metallurgical steel. Said method consists of the following steps: a steel powder, preferably having a predetermined structure, is produced; the steel powder is mixed with a binding agent to form a plastically deformable raw material; the raw material is initially shaped to form a blank having a predefined spatial form; and the blank is sintered.

Description

Powder metallurgical steel

FIELD OF THE INVENTION

The present invention relates to a process for producing a

powder metallurgical steel, a raw material for producing a steel

powder metallurgical steel for making a tool and a steel.

BACKGROUND OF THE INVENTION

In the prior art cylindrical rods of HSS or HSS-E for the production of cutting tools are produced by rolling or drawing.

SUMMARY OF THE INVENTION

The production of blanks for the production of tools made of HSS or HSS-E has hitherto been carried out by rolling or drawing the steel in repeated machining cycles. These processing operations are both time-consuming and cost-intensive, since complex systems and processes are required for this purpose.

In contrast, the production of carbide or cermet blanks can be carried out with much less complex equipment and processes. A production of blanks made of hard metal or cermets can be achieved by extrusion with subsequent sintering. Relevant production methods are described, for example, in the documents US Pat. No. 2,422,994, DE 36 01 385 A1, EP 465 946 A1, EP 1 017 527 B1, EP-A-0 340 495, EP-A-0 458 774, WO-A-92/22390 or US-A-4,779,440.

It is advantageous in an extrusion process that in this way continuous rods can be produced, which are advantageous in the production of drilling, milling, friction, or Senkwerkzeugen, as this, the raw material (green / green form) are already brought into the desired cylindrical shape which can be an ideal starting point for the production of drilling, milling, reaming or countersinking tools. It is also advantageous in extruding that, for example, internal channels can be arranged in the extruded rods by simple extensions of the extrusion nozzle already during the extrusion process. These internal channels can be used in the finished tool to be able to lead coolant and / or lubricant through the interior of the tool to the cutting active parts of the tool.

One object, therefore, is to provide a way to obtain rods for manufacturing tools from HSS or HSS-E easier. Another object is to provide a raw material with which such tools can be produced economically.

This object is solved by the method according to claim 1, by the raw material according to claim 12 and by a steel producible with such a raw material according to claim 13 or 14.

According to the invention, it is possible in a very economical manner components or

To produce semi-finished products with very complex shapes from tool steel. The

A method according to the invention for the production of a powder-metallurgical steel, in particular tool steel, such as HSS or HSS-E steel, is characterized in that first of all steel powder having a predetermined microstructure is produced. By mixing the steel powder with a binder, e.g. Wax or paraffin, a plastically deformable raw material is prepared, which - can be subjected directly to a primary molding process, preferably due to the appropriate selection of the particle size and / or particle size distribution of the steel powder. It can do that without it

Interrupting a blank for a steel component are manufactured, which has an arbitrarily complex spatial shape.

During sintering of the blank, which may be preceded by a separate step of expulsion of the binder, the actual structure formation takes place, that is, the steel particles, which preferably have as close as possible a spherical shape to the

To promote extrusion process, merge with each other and grow together closely, creating a high-density and high-strength steel component. The structure in the interior of the steel powder particles is essentially retained, so that predictable Material properties are present. It has been found that the pressure which occurs when extruding through a nozzle is already sufficient to produce a blank made of a steel / binder raw material, which after an under approximate

Atmospheric pressure performed sintering process has sufficient density and strength. Of course, by overlaying or subsequently applying a HIP (Hot Isostatic Pressing) process, further microstructural improvement can be achieved.

In order to better prepare the raw material for the primary molding process, it is advantageous if the steel powder is subjected to homogenization of the geometry of the powder particles during mixing with the binder and / or before mixing.

With the development of claim 4, according to which the steel powder is subjected to a screening process before mixing, so that it is subjected to the mixing process in a predetermined particle size and / or particle size distribution, it is possible to exert further positive influence on the strength of the steel structure.

When the steel powder is obtained by grinding or grinding steel particles, the starting structure of the steel powder can be optimally selected freely from the manufacturing process of the powder.

If the steel powder is additionally treated with a binder metal, e.g. Cobalt is mixed, the material properties of the steel produced can be additionally influenced within wide limits.

To provide particularly high-density materials, it is advantageous if the blank is subjected to HIP (hot isostatic pressing) treatment before, during or after sintering.

It is particularly advantageous if the blank is subjected during the sintering process for controlling the steel structure to a temperature treatment, such as a hardening process. This is done by going through a suitable temperature / Time program, which can be selected according to material specifications as required.

As a result of the selection of the steel powder according to the invention, the plastically deformable mass succeeds in a preferably continuous extrusion process

subject, and still very good structural densities of the steel material to

to guarantee. Here, the plastically deformable mass is preferably by a

Extruding die extruded with a nozzle to form a continuous rod, which is then cut to length to the required dimensions. The blanks can be produced very economically in this way.

Thus, according to the invention, a possibility is provided to obtain powder metallurgical steel more easily. For this purpose, powdered steel is processed analogously as in the production of carbide with the addition of a binder. The powdered steel with the binder is then extruded and sintered.

A further aspect of the invention is the provision of a raw material for producing a steel according to claim 12.

Advantageous developments of the invention are the subject of the other dependent claims.

According to an exemplary embodiment of the invention, a method is provided wherein cobalt is additionally used as the binder metal.

In a further embodiment of the invention, a method is provided wherein the pressing is performed by an extrusion die with a die, whereby the raw mass can be extruded into a continuous rod.

According to another embodiment of the present invention is a

Method provided, wherein at least during the extrusion an inner channel for guiding coolant and / or lubricant is arranged in sections in the rod.

According to an exemplary embodiment of the invention, a method for

Provided provided, wherein the inner channel is formed at least partially helical or rectilinear.

In a further embodiment of the invention, a steel is provided, wherein the steel can be produced from a raw material according to claim 6.

As a decisive advantage of the invention can therefore be considered that powder metallurgical steel can be made easier and cheaper. As a starting material, in addition to a tool steel, such as HSS-E, also a e.g. high-alloy steel serve. The powder can be ground by spraying the molten steel or else. The production according to the invention of a powder-metallurgical steel requires few production plants and is therefore more cost-effective to manufacture than the prior art. Further, by the process of the present invention in the production of powder metallurgical steel, higher productivity can be obtained as compared with the prior art production methods.

Of course, the individual features can also be combined with each other, which can also be partially beneficial effects that go beyond the sum of the individual effects.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details and advantages of the invention will become apparent from the embodiments illustrated in the drawings. Show it:

1 shows a diagram to illustrate the method steps according to the invention, and FIG. 2 shows a nozzle for the extrusion of a continuous powder metallurgical rod DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

It is known in the art to use powdered steel to make powder metallurgy steels therefrom. This steel is typically a high alloy steel which may contain, for example, 0.46% carbon and 13% chromium. Here, the powdered steel is compacted by repeated repeated rolling. From the blocks thus formed, then e.g. Tools are made. The arrangement of cooling channels can be effected by making holes in the already partially compacted steel between the first rolling operations. Overall, this method of manufacturing a powder metallurgical steel requires a high amount of production equipment. In addition, the prior art manufacturing method is time consuming.

FIG. 1 shows the method sequence according to the invention for producing a

powder metallurgical steel, in particular tool steel, such as HSS or HSS-E steel. In this case, first of all, steel powder is produced in a first process step, which preferably has a previously selected structure, such as e.g. the fabric of a

High-speed steel in the cast state or that of an already heavily formed high-speed steel.

Subsequently, admixing of a binder, such as e.g. Paraffin or wax, so that a plastically deformable raw mass is formed directly in one

Urformprozess weiterverarbeitbar is. Dashed lines indicate a variant according to which the steel powder is additionally coated with a binding metal, such as e.g. Cobalt is mixed.

During mixing with the binder and / or before mixing with the binder

Binder, the steel powder - for example, in a ball mill - a machining to homogenize the geometry of the powder particles are subjected. The edges of the powder particles are removed in this way and the particles become an im

Essentially given spherical shape, so that the subsequent prototyping process is facilitated. It is also possible and advantageous, the steel powder before mixing a

To undergo screening process, so that it is subjected to the mixing process in a predetermined particle size and / or particle size distribution

The raw mass thus produced is now formed into a blank having a predetermined spatial shape, preferably extruded by means of an extrusion press, so that

Blanks with any complex spatial structure arise.

During the subsequent sintering or in an upstream

Working step, the binder is expelled at selected temperatures. Then the actual sintering process takes place, in which the steel structure is finally created. The blank may be subjected to HIP (hot isostatic pressing) treatment before, during or after sintering. This optional method step is indicated by a dashed line in FIG. 1.

Also optional is the variant whereby, during the sintering process to control the steel structure, the blank is subjected to a temperature treatment, such as e.g. one

Hardening process is subjected. The sintering plant passes through a predetermined temporally controlled temperature profile, so that the steel finally has the desired structure quality.

The steel powder can also be obtained by grinding or grinding steel particles

be won.

It has been shown that high-quality steel components made of HSS or HSS-E can already be produced if the plastically deformable mass is one

Preferably continuous extrusion process is subjected, wherein the plastically deformable mass - with relatively little compression - by a

Extrusion die with a nozzle (102) is extruded into a continuous rod.

The resulting in the extrusion step blanks (green compacts / green forms) in the design as a steel / binder mixture can therefore analogously to the production of Cemented carbide or cermets are processed. The processing with an extrusion die, which may have a nozzle for extrusion, and the subsequent sintering process allow a simple, rapid and advantageous production of a powder metallurgy steel. The output form in the extrusion as continuous rods is advantageous because this can already be the rough geometric shape of a drilling, milling, sinking or reaming tool. Thus, in accordance with the invention, powdered steel is treated and processed, for example tungsten carbides as starting material for the production of hard metal (with the addition of a binder such as cobalt).

Further, because manufacturing using an extrusion process is possible in accordance with the present invention, internal channels can advantageously be easily formed in the extruded rod, which in particular have dimensions (diameter, circular or elliptical cross-section) through the further processing operations, e.g. sintering, can not change as much as compared to the processing of the prior art by rolling the case may be the case. It can therefore be ensured a higher dimensional accuracy in the production of the inner channels of powder metallurgy steels.

Fig. 1 shows an example of a nozzle for the extrusion of a continuous rod, wherein a raw material is injected into the nozzle through an inlet opening 103, 104, which may have the surface of a circular ring. According to the invention, the raw mass comprises powdered steel, wherein the steel may also be high-alloyed, and at least one further binding metal, such as e.g. Cobalt, may have. The raw mass is brought together in the region 105, whereby by e.g. continuously rotating rods 107 in the pressed raw mass wired inner channels 101 can be formed. From the nozzle 102 can then exit a continuous rod 106 with inner channels 101. If the bars 107 do not rotate but stand still, continuous bars 106 with straight inner channels can be formed.

Such extrusion nozzles or nozzles which can be used in a suitable manner are known per se and, for example, in the publications US Pat. No. 2,422,994, DE 36 01 385 A1, EP 465 946 A1, EP 1 017 527 B1, EP-A-0 340 495, EP-A-0 458 774, WO-A-92/22390 or US-A-4,779,440 whose disclosure content is expressly incorporated in the present application.

The invention thus provides a method for producing a powder metallurgical steel. The method comprises the steps of: producing steel powder, preferably with a predetermined structure; Mixing the steel powder with a binder to form a plastically deformable raw material; Original shapes of the raw mass to a blank with a given spatial shape; and sintering the blank.

It should be noted that the term "comprising" does not exclude other elements or method steps, just as the term "a" and "an" does not exclude multiple elements and steps.

The reference numerals used are for convenience of reference only and are not to be considered as limiting, the scope of the invention being indicated by the claims.

LIST OF REFERENCE SIGNS

101 inner channel

102 nozzle

103 entrance opening

104 inlet opening

105 mixing area

106 extruded rod

107 rod

Claims

1. A process for producing a powder metallurgical steel, in particular

Tool steel, such as HSS or HSS E-steel, with the following process steps:

Manufacture of steel powder with a predetermined structure;

Mixing the steel powder with a binder to form a plastically deformable raw material;

Original shapes of the raw mass to a blank with a given spatial shape; and sintering the blank.

2. The method according to claim 1, characterized in that the steel powder is subjected during mixing with the binder of a machining to homogenize the geometry of the powder particles.

3. The method according to claim 1, characterized in that the steel powder is subjected before being mixed with the binder of a machining to homogenize the geometry of the powder particles.

4. The method according to claim 3, characterized in that the steel powder is subjected to a screening process before mixing, so that it in a predetermined

Particle size and / or particle size distribution is subjected to the mixing process.

5. The method according to any one of claims 1 to 4, characterized in that the steel powder is obtained by grinding or grinding of steel particles.

A method according to any one of claims 1 to 5, characterized in that the steel powder is treated with a binding metal, e.g. Cobalt is mixed.

7. The method according to any one of claims 1 to 6, characterized in that the blank before, during or after the sintering of a HIP (hot isostatic press treatment is subjected

8. The method according to any one of claims 1 to 7, characterized in that the blank during the sintering process for controlling the steel structure of a

Temperature treatment, such as subjected to a hardening process.

9. The method according to any one of claims 1 to 8, characterized in that the plastically deformable mass is subjected to a preferably continuous extrusion process, wherein the plastically deformable mass is extruded by an extrusion die with a nozzle (102) to form a continuous rod.

10. The method of claim 9, wherein during the extrusion at least

an inner channel (101) is formed in sections for conducting coolant and / or lubricant into the rod (106).

1 1. The method of claim 10, wherein the inner channel (101) is formed at least partially helical or rectilinear.

12. Raw mass for producing a powder metallurgical steel, in particular

Tool steel, such as HSS or HSS E-steel, comprising:

Steel powder with a predetermined structure; and

such admixed binder that the raw material is suitable for extrusion and subsequent sintering.

13. powder metallurgical steel for the production of a tool, wherein the steel can be produced by a method according to any one of claims 1 to 1 1.

14. Steel according to claim 13, wherein the steel can be produced from a raw material according to claim 12.

15. Component or semifinished product, produced by the method according to any one of claims 1 to 1 1 or from a raw material according to claim 12 or a steel according to claim 13 or 14.