JPH052430B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method of welding a cutter segment made of a sintered body containing and holding diamond or CBN superabrasive grains to a base metal.

[Background Art and Problems] FIG. 1 shows a conventional method of fixing a cutter segment made of a sintered diamond body to a base metal. The figure shows a rotary cutter, which is fixed to a power rotating shaft through its center hole, and can be used as a handy cutter for cutting bricks, roof tiles, processing tiles, removing edges of stone, iron plates, humid pipes, concrete, etc. Used for cutting blocks, grooving concrete roads, machining curved surfaces of stone, chamfering and angular machining of stone, etc.

In the figure, 2 is a steel base metal, and 1 is a mixed powder of diamond abrasive grains or CBN (cubic boron nitride) abrasive grains and bond powder such as Co (cobalt), which is molded and sintered (in many cases, Hot pressed) to form a mass with almost true density, and diamond abrasive grains and CBN abrasive grains are dispersed in the bond base material.
A plurality of cutter segments are held and fixed to the peripheral edge of the disc-shaped base metal 2 by silver brazing.

However, the rotary multi-blade cutter having the above-mentioned configuration has the following problems and drawbacks.

(b) If unreasonable usage is adopted, such as not using lubricating oil such as water (dry), under harsh conditions that generate heat, and where uneven loads are applied to the segments,
As a result of heat generation concentrated in one segment, the silver solder may soften and an accident may occur where the segment comes off.

(b) In the case of segment brazing, heating with high frequency or burner will damage not only the brazed part but also the base metal 2.
The adjacent parts of the base metal are heated over a fairly wide range, which causes a change in the metallographic structure of the base metal, resulting in distortion of the entire base metal. For this reason, as shown in Figure 1, by providing grooves 3, the strain is locally released and each segment is thermally cleaved, so that the thermal effect of brazing spreads to adjacent segments. However, due to the large number of grooves 3, the design disadvantage is that the structure is weak against static and dynamic loads.

(c) Heating during brazing causes a wide range of annealing in the base metal 2, reducing its resistance to bending.

In general, in all conventional welding methods, including the aforementioned brazing, the necessary conditions for obtaining strong adhesive strength are as shown in Figure 2. , when the base metal altered layer is Z, a weak structure must not be formed in any of the three layers X, Y, and Z. (A) in the above explanation relates to the X layer, (C) relates to the Z layer, and (A) and (C) are also essential in the method of melting silver solder by high frequency etc. , (b) are also essential factors that cannot be avoided with high frequency heating.

On the other hand, instead of silver brazing as described above, it is also possible to weld the blade to the base metal using an electron beam.
50-117087. This disclosure shows that a narrow heating zone can be generated at a welding location using an electron beam, and welding can be performed in a short time.

[Problems to be Solved by the Invention] The present invention performs welding by directly joining a cutter segment and a steel base using the electron beam or laser beam disclosed above. Depending on the material of the steel base metal, a metallographic change occurs at the joint boundary, and this metallographically changed part creates a weak part, making it unusable for actual use as a rotary cutter. It often becomes unbearable.

The present invention is designed to prevent the formation of structures that would impair the strength of the welded portion and the periphery of the welded portion when welding a cutter segment and a base metal using an electron beam or a laser beam, and to provide a segment that can withstand practical use. It's about getting a cutter.

[Disclosure of the Invention] The present invention uses a pure Co powder sintered body sintered to a density close to the true density as a segment containing diamond or CBN abrasive grains, and this segment is attached to a disc-shaped base made of low carbon steel. This is a method of welding cutter segments in which cutter segments are placed around the periphery of gold and the boundaries between these segments and the base metal are irradiated with an electron beam or laser beam to weld the segments to the base metal.

The welding method of the present invention will be explained below, including the welding method using conventional silver solder.

In carrying out the present invention, electron beam welding was mainly used as the welding method in the experiments carried out, but in a preliminary experiment using a small sample, Fe-(Co sintered body) was welded using a YAG laser. It has been confirmed that the brazing situation is extremely similar to the brazing situation using an electron beam.

The usage specifications of the electron beam welding of the present invention are the voltage
150kV, beam current 2.5mA, electron beam irradiation width 1mm,
The degree of vacuum is 10 ^-6 mmHg.

This irradiated the metal material in a 1 mm wide zone including the opposing boundary between the base metal and the segment so as to instantly melt and solidify it.

Dimensions of base metal. The shape is outer diameter 92mm, inner diameter 20mm, thickness
1.5mm, and there are 8 grooves of 3mm width on this disc-shaped base metal.
There are several places. Its material is SPCC (mild steel), which is a low carbon steel.

Segment dimensions. The shape is 32mm long and thick.
2.0mm, radius arc 46mmR, its material is a pure Co powder sintered body with diamond abrasive grains dispersed therein. As silver solder, Sil103 and Sil1023 manufactured by Nice Co., Ltd. were used.

The welding strength is measured by fixing the welded base metal, sandwiching the segment with a torque wrench, applying bending stress, and measuring the breaking force.

Data 1 (comparative example) As shown in Figure 3, segments brazed with Sil103 silver solder using the conventional method have a
110Kg. cm, but as the temperature increases from 250℃ to 350℃, the brazing strength decreases due to the softening of the silver solder. If measured at 350℃, the strength is 50Kg. It becomes less than cm.

Sil103 has a melting point of 620℃ and a chemical composition of Ag:
45.3%, Cu: 15.6%, Cd: 23.8%, Zn: remainder.

Data 2 (Example) A segment made of pure Co bond and a base metal made of low carbon steel SPCC, which were electron beam welded, weighed 60 kg. cm, the welded part did not break, but the base metal bent. The welding strength is greater than the base metal strength.

As mentioned above, cutter segments are made by molding and sintering (often hot pressing) a mixture of diamond abrasive grains or CBN abrasive grains and pure Co bond powder to form a solid with almost true density. Diamond and CBN abrasive grains are dispersed in the bond base material. It is a segment that is held, and the base metal is made of low carbon steel that is difficult to harden. A rotary cutter with such a combination can withstand use sufficiently in applications where large bending stress is not applied to the base metal during use.

In addition, if a pure Co powder sintered body containing diamond or CBN abrasive grains that is not sintered to a density close to the true density is used as a segment, when the boundary between the segment and the base metal is irradiated by the beam, the true density is low. The air contained in the gaps in the segments causes the diamonds contained in the periphery of the segments to
It reacts with CBN and causes changes in the metallographic structure of this periphery, thus forming a brittle layer in the area adjacent to the weld.

[Action. Effect] (a) Since the bond metal of the base metal and segment is once melted and alloyed, a complete molten layer is created (X-layer reinforcement), and low melting point metal is not used.
Unlike silver solder, which does not soften due to temperature, the adhesive force between the base metal and the segment is strong, and there is no risk of the segment coming off even when used dry.

(b) A Co powder bonded sintered body with diamond and CBN abrasive grains dispersed close to the true density does not cause any major changes in the metallographic structure even when heated near the melting point of Co (Y layer problem). No brittle layer is formed adjacent to the weld layer, Co and Fe are easily alloyed, and there is no fear of brittle structures forming from the alloy phase diagram (X layer problem). Since gold is a low carbon steel, a weak quenched structure will not form in adjacent areas (Z layer problem).

(e) Welding can be performed by applying heat locally and in a short period of time using an electron beam or laser beam, and as a result, there is no need for grooves in the base metal, compared to those with grooves. It has a strong shape,
A cutter that is not deformed by external force can be obtained.

[Brief explanation of drawings]

FIG. 1 shows a conventional method of fixing segments by brazing. FIG. 2 is an explanatory diagram of necessary conditions when welding segments to a base metal. Figure 3 shows the change in brazing strength depending on the temperature of the cutter in the brazing method. 1...Segment, 2...Alloy, 3...Groove.

Claims (1)

[Claims] 1. Pure diamond sintered to a density close to true density as a segment containing diamond or CBN abrasive grains.
Using a Co powder sintered body, the segments are arranged around the periphery of a disc-shaped base metal made of low carbon steel, and the boundaries between the segments and the base metal are irradiated with an electron beam or a laser beam to remove the segments. A method for welding a cutter segment, characterized by welding it to a base metal.