JPH01119738A - Testing method of cemented carbide cutting tool by milling - Google Patents

Abstract

PURPOSE:To make it possible to test a boundary damage of a throw away tip made of cemented carbide, by juxtaposing and combining an ordinary cast iron material and a cast iron material of which only the top surface part is made highly hard, and by using the material thus prepared as a material to be cut. CONSTITUTION:While JIS.FC 25 is used as an ordinary material 2, FC 25 of the same quality, of which a part from the surface to the depth of 2mm is made to be of prescribed hardness by induction hardening and tempering, is used as a hard-facing material 1. The respective widths of the ordinary material 2 and the hard-facing material 1 are adjusted by cutting or milling so that they are in a prescribed ratio (about 3:1) and the total thereof is 60mm. A material 6 obtained in this way is fixed by a machine vise 5, 5' and cut by a cutter having a plurality of edges 4. By this method, a boundary damage of a throw away tip made of cemented carbide can be tested.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a cutting test method for determining the cutting characteristics of cemented carbide tools for cutting tools, and in particular to a test method for milling tools. I will provide a.

(b) Problems with conventional technology The conventional method for evaluating the cutting characteristics of various cutting tools was to use prototype tools to measure actual steel or cast iron steel materials (round bars, square bars).
This was done by setting cutting conditions and measuring and observing the degree of wear on the cutting edge of the tool. In addition, when particularly examining toughness, interrupted cutting is performed using a round bar with grooves formed as a workpiece. Essentially the same method was followed for milling. In milling cast iron,
Among the various types of damage and wear on cemented carbide indexable inserts, there was no specific test method for boundary damage.

FIG. 2 schematically shows the state of damage to the cutting edge of the indexable insert. The upper figure shows crater wear (K7) on the rake face of the cutting edge 4, and the lower figure shows damage to the flank face. VB
is the average wear amount of the cutting edge, and VN is the boundary damage. In milling, the above-mentioned boundary damage often leads to the end of service life, and it has not been possible to prevent this from occurring and evaluate it internally before using it at a customer's site.

There are generally two possible causes of this boundary damage:

■A part of the workpiece material has high hardness, and when the cutting blade of the cemented carbide cutting tool cuts that hard part, a part of the cutting blade breaks off. In this case, the cause of high hardness is usually due to chilling or work hardening, so it is often the case that only the surface of the workpiece material is high hardness, and therefore defects occur only at the boundary of the cutting edge ( Deficit theory).

■Compared to other parts of the cutting edge, the boundary area is in constant contact with air, so oxidation wear progresses more easily (oxidation stage). ,
Here, since boundary damage does not occur in conventional cutting tests using simple work materials, the above-mentioned oxidation stage cannot be applied to cast iron milling, and it can be considered that boundary damage occurs due to the defect theory.

Therefore, a work material with high hardness may be used, but for the above-mentioned reason, only the surface portion must be a work material with high hardness.

(c) Means to solve the problem In order to solve the above-mentioned opening point, the work materials are cast iron that has been tempered to have high hardness only on the upper surface, and normal cast iron that has low hardness both on the surface and inside. Use the juxtaposition and combination of .

FIG. 1 is a conceptual diagram showing the method of the present invention.
In this method, the hardened surface material 1 and the ordinary material 2 are combined and fixed in a machine vise 5.5', and then cut with a cutter 3 having a plurality of cutting blades 4.

FIG. 3 is a sectional view taken along the line AA of the workpiece 6 in FIG.
8 is a surface hardened portion and 8 is a non-heat treated portion. By one rotation of the cutter, the shaded area of the workpiece in FIG. 1 is cut. At this time, it is necessary to cut a part of the hardened surface material.
After several rotations, only a portion of the cutting edge that corresponds to the hard part, that is, a boundary portion, is damaged.

At this time, it is possible to cause boundary damage to the cutting edge even if only the hardened surface material is used as the work material, but in this case, only the boundary area is severely damaged, and there is a difference in the degree of damage from other areas. , which is large compared to the damage situation at the customer's site. Therefore, in order to approximate the damage situation at the customer's site as closely as possible, it is appropriate to set the ratio of surface hardening material to normal material at a ratio of 1:3.

Also, the ratio b/a of the width a of high hardness material to the width of normal material is 20
The following is preferable; anything greater than this is unsuitable because the difference between boundary wear and flank wear becomes almost negligible and no significant boundary damage occurs.

In addition, the surface hardness of the high-hardness material is 35 on the Rockwell hardness scale.
~50 is appropriate. This is because if the HRc is less than 35, no significant boundary damage will occur even if the hardened surface material is used alone as a workpiece material, whereas if the hardened surface material exceeds 50, defects such as cracks will occur during the manufacturing stage of the hardened surface material, making it unstable as a workpiece material. It is difficult to obtain one with such characteristics. Various methods can be used to produce the above-mentioned hardened surface material, but after various studies, the method of induction hardening and then backfilling is currently the most stable method for achieving a given hardness and hardened layer depth. I found out that I can get it.

Next, an explanation will be given based on an example.

Example 1 JIS, Fe12 is a "normal material", and Fe12 of the same material
A "hardened surface material" was obtained by induction hardening and tempering to obtain a predetermined hardness from the surface to a depth of 2 mm. The width of each material was adjusted by cutting or milling so that the ratio of the widths of the "regular material" and the "hardened surface material" was a predetermined ratio and the total was 601.

A milling test was conducted under the conditions using the work material obtained as described above. At this time, the tested tool was JIS
There are two types of materials: 15 class cemented carbide and KIO class surface coated cemented carbide.

The test results are shown in Table 1.

m1 table, where VB is the average wear amount of the cutting edge and VN is the boundary damage ■Example 2 F C2530x 25X 300 A square piece of HRc20 or less was induction hardened and tempered to have a hardness of HRc40 from the surface to a depth of 2mm. Then 30X 3
2.5m by milling the 00 side and the back side.
A high hardness material having a cross-sectional hardness as shown in FIG. 3 was created by removing m increments. One piece of this high hardness material and a normal FC2525x 25x with HRc20 or less
Three pieces of 300 were placed in a vise on a milling machine as shown in Figure 1. This is the cemented carbide indexable tip S.
It was cut with a cutter equipped with PUN 120308. The cutting conditions were a cutting speed of 281 m/min, depth of cut of 3.5 mm, feed of 0.089 mm/tooth, and only one indexable insert was used. As a result, cemented carbide coated with hard material and cemented carbide without coating (J
I 5K10 types) 1.2mm each at the boundary
, 1.3mm boundary damage, and 0.10mm each on other cutting edges.

Flank wear of 0.15 mm occurred.

Example 3 A square piece of the same material and size as in Example 2 was subjected to HR in the same manner.
I created one with c30. When cutting with the same tool and cutting conditions, the hard material-coated cemented carbide had 0.5 mm of boundary damage at the boundary, and 0.5 mm at the other cutting edges.
Flank wear of 11 mm occurred.

Further, the cemented carbide KIO had boundary damage of 0.6 mm at the boundary and flank wear of 0.1 button m on the other cutting edges.

Example 4 A high hardness material of 5 x 25 x 300 was created in the same manner as in Example 1, and one of this and 19 normal Fe12 of 5 x 25 x 300 were sandwiched between a vise and the same tool as in Example 1, Cutting was performed under cutting conditions. As a result, the hard material-coated cemented carbide had boundary damage of 0.2 mm at the boundary and flank wear of 0.09 mm on the other cutting edges.

In addition, 0.3 mm of boundary damage occurred at the boundary of the cemented carbide KIO, and 0.14 mm of flank wear occurred on the other cutting edges.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the test method of the present invention; FIG. 2 is a schematic diagram showing the forms of damage and wear on the indexable tip;
FIG. 3 shows a cross-sectional view of the work material used in the test of the present invention. [Reference number] [Reference code] ■=Surface hardened material vS: Cutting edge retraction dimension 2: Normal material ■c: Cutting edge tip wear amount 3: Cutter ■,: Cutting edge average wear amount 4: Cutting edge
■, max: Maximum cutting edge wear amount 5.5':
Vise ■H: Boundary damage 6: Work material
KT : Crater depth 7 2 Surface hardened part 8 : Non-heat treated part

Claims (3)

[Claims] (1) Cast iron material and surface with high hardness tempered only on the upper surface,
This is a milling test method for cemented carbide cutting tools, which is characterized by cutting ordinary cast iron materials with low hardness inside as work materials. (2) In the test method described in claim (1), the hardness of the surface portion of the high-hardness cast iron material of the work material is 35 to 50 on the Rockwell hardness (HRc). Milling test method for hard metal cutting tools. (3) In the test method described in claim (1), the ratio b/a of the width a of the high hardness cast iron material and the width b of the normal cast iron material
A milling test method for a cemented carbide cutting tool, characterized in that: is 20 or less.