SE500134C2 - End mill with a core of quick or tool steel and a casing of hard material - Google Patents

Abstract

An end mill which both drills and mills has main cutting edges (4) and end cutting edges (5) as well as reinforcing chamfers (6) between these. The end mill consists of a core of high speed steel or tool steel and an over-lying layer made of a hard material with 30-70 % by volume of sub-micron hard constituents in the form of carbides, nitrides and/or carbonitrides of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and/or W in a metallic matrix based on Fe, Co and/or Ni, whereby the external surface of the overlying layer at least partly is coated with a thin layer of TiN, Ti(C,N) and/or (Ti,Al)N. The tool's pitch angle is 40 +/- 5 DEG and its rake angle is 12 +/- 5 DEG .

Description

~~ C = 0 10 15 20 25 30 ”lšll 2 the edges, a positive cutting geometry that provides smooth machining, as well as safety during machining so that cutting breaks are prevented.

The end mills that exist today are often high-speed steel or cemented carbide tools. Although these work satisfactorily in several applications, they do have several disadvantages. Thus, high-speed steel often causes so-called loose egg formation (chips get stuck on the edge) and they have a relatively short service life. Carbide is known to be a more brittle material and therefore has poorer safety.

Swedish patent SE 392 482 discloses a material containing 30-70% by volume of submicron hard substances in a metallic binder phase. This material has superior wear resistance compared to qualified high-speed steels and can therefore be placed in the property gap between cemented carbide and high-speed steels. Furthermore, Swedish patent SE 440 753 has shown how superior compound tools could be manufactured with, among other things, the above materials placed in the areas that have been exposed to high cutting speeds and with high-speed steel in the center for drilling applications.

The purpose of this latter invention was partly to obtain a tool with better macro toughness with the help of a tougher core, and partly to achieve better grinding economy since hard material-rich material is perceived as much more difficult to grind than, for example, high-speed steel. Furthermore, the zero-velocity problem and loose egg formation areas were perceived as problematic for the submicron hard material with 30-70% by volume of hard substances.

From US-A-5,026,227 a pin milling is previously known which in its entirety consists of a, solid so-called cermet material, U 15 CD CD ... Ä 04 4> 3 consisting essentially of an NbC-Tic-TiN-based composition. This tool is relatively brittle and is used in principle only for finishing. It is unsuitable to use for coarser pin milling where great demands are placed on the tool's toughness.

It has now been found possible to achieve end mills with high productivity, very fine surfaces, high service life and good machining economy in modern machining machines. This has been achieved by manufacturing a end mill of a compound material and with a geometry according to claim 1. In addition, loose edge formation has been avoided over a very wide cutting speed range. This leads to low wear and a maintained sharp cutting edge which generates good shape accuracy and very good surfaces of the workpiece.

This also applies to workpiece materials that are traditionally considered very difficult to machine.

The tools are used in a coated design and it is then so-called PVD procedure that is most relevant.

The coating is mainly done with titanium-based hard materials such as TiN, Ti (C, N), (Ti, Al) N, etc. Particularly excellent properties have been obtained with 2-4 μm Ti (C, N).

According to the invention, there are now long, slender, solid end milling tools with a casing of a hard material with 30-70% by volume of submicron hard materials in the form of carbides, nitrides and / or carbonitrides of Ti, Zr, Hf, V, Nb, Ta, Cr , Mo and / or W in a metallic matrix based on Fe, Co and / or Ni.

Preferably, the hard material consists of 30-70% by volume of hard materials of mainly TiN in a fast steel type matrix where the enriched hard blanks have a (N 10 15 20 25 30 grain size of <1 μm, preferably <0.5 μm. By a well-balanced combination of tool materials and tool geometry have been able to obtain unique tools with superior performance.The material also exhibits, due to its fineness and good dispersion between hard blanks and binder phase, a uniquely good adhesion to applied, clean hard blanks applied by PVD method. compared with the more metallurgical bonding that occurs in so-called CVD process.The reason is mainly that CVD takes place at higher temperature.The layers applied are mainly titanium-based and especially good properties have been obtained with Ti (C, N) but also (Ti , Al) N has great advantages.

Tools according to the invention work very well in addition to normal steels also in hard metal piece materials, 250-500 HB, such as tool steel, lubricating materials such as stainless steel, aluminum alloys or titanium alloys.

By metallurgically bonding the hard material to a tougher core material, a very favorable combination of wear resistance and toughness behavior of end mills has been obtained.

The invention is described in the accompanying drawings in which: Fig. 1 shows a three-cut end milling tool in a side view, Fig. 2 shows a section through the tool along the line AA in Fig. 1, Fig. 3 shows an end view of a three-cut tool, Figs. Fig. 4 shows a section through the tool along the line BB in Fig. 1, radially from the center axis, Fig. 5 shows a section along the line CC in Fig. 4.

The tool generally consists of an elongated cylindrical body 1 which consists of a compound material according to SE 440 753 and which is manufactured in the manner specified in this patent specification. Thus, the core of the tool consists of high-speed steel or tool steel and a surface casing, the thickness of which is usually 15% of the tool diameter (doc at least 0.5 mm), consisting of a hard material specified in more detail above. A number of bars 2, usually two or three, run helically along the center line of the tool. The booms 2 are delimited by grooves 3. According to the invention it has proved surprisingly advantageous to arrange the helical booms and grooves with an angle of inclination of approximately 40 degrees, more precisely 40 in 3 ', and preferably 40 in 2 °.

Each boom is along its entire leading edge, seen in the direction of rotation, provided with a main cutting edge 4 with positive cutting geometry. According to the invention, it has proved surprisingly advantageous to arrange this main cutting edge with approximately a positive rake angle of approximately 12 degrees, more specifically 12 1 3 ', and preferably 12 in 2'.

The clearance angle α of the main cutting edge 4 varies depending on the diameter of the tool. The following values illustrate this variation: (TI (I) CD 10 15 20 25 30 511 6 Cutting diameter of the tool clearing angle 25 mm ll '20 mm 12' 10 mm 14 '4 mm 17' The cutting edges of the tool have an edge rounding of 10-30 μm, preferably 10-20 pm.

Since the tool must also be able to drill in the axial direction, there are a number of end cutting edges 5, 5 'corresponding to the number of booms 2 in the tip of the tool. The end cutting edge denoted by 5 goes over the center, while the other end cutting edges 5 'have a shorter length which is limited by a ground chip space 7. radial plane, cf.

According to the present invention, a reinforcing phase 6 is arranged on the corner between each main cutting edge 4 and the associated end cutting edge 5, 5 '. This reinforcement phase is intended to reduce the stresses to which these corners are subjected when they are in contact with the workpiece.

They are suitably angled about 20 ° main line and about 0 'along the end of the end cutter along the end insert. Thanks to these reinforcement phases, a number of inconveniences have been overcome in a surprisingly simple manner, such as chipping and germination in these corner portions and vibrations. In order for the pin milling tools to maintain power tolerance even in the case of requirements for long service life and high cutting data, they have also been coated with a thin layer of TiN, Ti (C, N) and / or Ti (Al) N. Preferably TiCN is used in a thickness of between 2 and 4 μm; especially with regard to the very good adhesion achieved with this particular material. The coating of the hard material with a thin layer takes place through the so-called so-known to the person skilled in the art. The PVD procedure.

In order to facilitate all the functions of the tool (in particular side milling, groove milling, drilling), it has been provided with considerable chip space, above all in order to avoid any chip penetration. This can be seen from the size of the rails 3 in Figs. 1 and 2.

For illustrative but non-limiting purposes, some examples are presented below which further illustrate the distinguishing features of the end milling tool according to the invention.

Example 1 The following example shows how materials and the new geometry could be combined into products with superior properties.

A rod in compound material prepared in accordance with SE 440 753 Example 3, was extruded to dimensions 9.6 mm.

This rod was ground after heat treatment to 8 mm's 2- and 3-cut end mills with different geometries.

A comparative side milling test in stainless steel austenitic steel SS 2343 was then performed with tools according to the invention, other self-made tools and conventional high-speed steel tools. All 10 test tools were coated with a thin Ti (C, N) layer of PVD type.

Tool A: Tool B: Tool C: Tool D: Tool E: 3-cut end mill according to the invention with pitch angle 40 degrees, rake angle + 12 degrees and with reinforcement phase between main and end cutting edges.

Tools according to A but without reinforcement phase.

Tools according to A but with a pitch angle of 45 ”. 3-cut end mill with cutting material according to the invention but with a pitch angle of 30 degrees. Span angle +12 degrees and reinforcement phase between main and end cutting edge. 3-cut high-speed steel end mill with pitch angle 35 degrees, chip angle + 10 degrees, without reinforcement phase.

The tools were tested in medium coarse milling with axial cutting depth of 8 mm and radial cutting depth of 2 mm.

Lifetime criterion was achieved average phase wear 0.08 mm or chipping.

Cutting data was selected according to the manufacturer's recommendation.

Cutting data and results are shown in the table below. 10 15 20 25 30 9 Test tool Cutting speed Table feed Lifespan mmin _1mmmin (m) A 45 270 23 i 2 B 45 270 15 i 5 C 45 270 19 i 5 D 45 270 i 2 E 30 180 8 i 4 On tool B, C and E were obtained with large service life spreads due to sudden chipping on the corners of the tools.

The test showed that test tools according to the invention gave clearly the best results in terms of long service life and good reliability. Example 2 2-cut 8 mm diameter end mills according to the invention were prepared similar to Example 1 and tested in groove milling in stainless steel austenitic SS 2343 in comparison with other coated conventional end mills in high speed steel or cemented carbide.

Tool A: 2-cut end mill according to the invention with pitch angle of 40 degrees, rake angle +12 degrees and reinforcement phase between head and end cutting edge.

Tool B: 2-cut end mill in solid fine-grained cemented carbide with pitch angle 40 degrees, chip angle +12 degrees, without reinforcement phase.

CH CD CD 10 15 20 25 30 10 Tool C: 2-cut end mill in solid high-alloy high-speed steel with pitch angle 40 degrees chip angle +13 degrees and without reinforcement phase.

The tools were tested in groove milling with an axial cutting depth of 6 mm.

Lifetime criterion was achieved average phase wear 0.06 mm or interrupted test due to chipping, tool breakage or unacceptable grooves.

Cutting data according to the manufacturer's recommendations and results are shown in the table below.

Test tool Cutting speed Table feed Service life m / min (mm¿min lgl A 40 140 9.5 B 35 120 6.0 C 3O 90 0.5 Tools B and C showed a considerably greater spread in service life due to large proportions of chippings on the corners of the tool.

Tool A according to the invention gave clearly the best results in terms of high productivity, long service life and safety.

Claims (9)

10 15 20 25 30 ll Claims 1. Stick milling tool with main cutting edge and end cutting edge consisting of compound material that forms the core resp. housing of the tool, the core being made of high-speed steel or tool steel and the housing being made of a hard material with 30-70% by volume of submicron hard materials in the form of carbides, nitrides and / or carbonitrides of Ti, Zr, Hf, V, Nb, Ta, Cr , Mo and / or W in a metallic matrix based on Fe, Co and / or Ni, and wherein the outer surface of the casing is at least partially coated with a thin layer of TiN, Ti (C, N) and / or (Ti, Al) N, k characterized by the fact that the pitch angle of the tool is 12 in 3 °, and by the fact that it is provided with a reinforcing phase between the main cutting edge and the end cutting edge. 2. A tool according to claim 1, characterized in that there are two or more main grooves, preferably two or three. 3. A tool according to claim 1 or 2, characterized in that the reinforcing phase is angled approximately 20 ° along the center line of the pin milling tool and approximately 0 ° along the end insert. 4. A tool according to any one of claims 1-3, characterized in that the cutting edge has an edge rounding of 10-30 μm, preferably 10-20 μm. Tool according to one of Claims 1 to 4, characterized in that the cutting diameter of the tool is 3-50 mm, preferably 4-25 mm, the clearance angle at the periphery being 17 in 2 ° for U1 CD CD 10 15 20 25 .. .You $> 12 diameter 4 mm and decrease to 11 in 2 ° for the diameter 25 mm. 6. A tool according to any one of claims 1-5, characterized in that the end notch slopes approximately 1.5 ° towards the center line of the tool and approximately 6 ° tangentially backwards towards the direction of rotation. 7. A tool according to any one of claims 1-6, characterized in that the thickness of the casing is at least 0.5 mm. Tool according to one of Claims 1 to 7, characterized in that the hard material consists of 30-70 by volume hair blanks of mainly TiN in a fast-acting type matrix where the enriched hard blanks have a grain thickness of <1 μm, preferably <0, 5 pm. Tool according to any one of claims 1-8, characterized in that it is coated with a 2-4 μm thin layer of TiN, Ti (C, N) or (Ti, Al) N, preferably Ti (C, N).