Cemented Carbide Cutting Tools Bue

Bue by the chip stacking a hard wedge near the cutting edge in front of the cemented carbide cutting tool, it is a region in the Cap II deformation zone (Section II deformation zone refers to the bottom of the chips in contact with the front of the cemented carbide cutting tool to produce plastic deformation) inside, is formed by the friction and deformation of the physical phenomena. In the production of medium carbon steel, mild steel, aluminum, plastic metal car, drilling, reaming, pull and thread processing may occur bue.

Bue

Bue and its dimensions

Bue causes:
Generally considered to be the chips in the tool on the front of the bonding (cold welding) caused in the stagnant layer near the cemented carbide cutting tool cutting edge at the temperature and pressure is very low, the chips underlying plastic deformation is small, the friction coefficient is small, the adhesive is difficult to produce , difficult to form bue; at high temperatures, softening of the chips base material, the shear yield strength σ0.2 decreased, so that the friction coefficient μ decreases, bue also easy to produce; when the pressure, the temperature reaches a certain level, chip bottom shear yield strength of the shear stress exceeds the material in the material, so that the zero velocity in the stagnant layer cutting layer the shear breaking bonded rake surface, the adhesive metal layer by severe plastic deformation hardness increase, it in place of the cemented carbide cutting tool cutting edge to continue to shear the relatively soft metal layer, followed by layers of accumulation, the height gradually blocking increases forming bue. Long high bue external force or vibration role may fall off or partial fracture, then proceeded to repeatedly generate and fall off.

Cemented carbide cutting tool Bue cutting effects are: due to its hardness is higher than the workpiece 2 to 3 times, and deposited on the cemented carbide cutting tool cutting edge is able to replace the cutting of the cutting edge, and to protect the cutting edge; angle before the actual work is increased, reducing the cutting deformation; piled into blunt the Carpenter arc edge caused by extrusion and undercutting reduce machining accuracy;The bue shed adhesion on the surface of the machined surface rough. The finishing should avoid bue produce.

Productions often take the following measures to suppress or eliminate bue:

1) low-speed or high-speed cutting. Cemented carbide cutting tool cutting speed cutting temperatures affect bue. For example, cutting 45 steel at low speed u c <3 m / min and a high speed ν c ≥ 60 m / min range, the friction coefficient is small, it is difficult to form bue. Generate the bue height reached the maximum cutting speed υc ≈ 20m/min about cutting temperature of about 300 ℃.

2) Reduce the amount of feed, to increase the cemented carbide cutting tool rake angle, and to improve the quality of tool sharpening and reasonable choice of cutting fluid, so that the friction and adhesive reduce can achieve inhibition bue role.

3) Reasonable adjustment of the cutting parameters value, in order to prevent the formation of medium-temperature region. If selected feed amount ? to = 0 1.2 mm / r, rake angle γo = 0 °, the erasure bue cutting speed of 22m/min; optional feed amount ? to 0.2rnm / R, the front corner γO = 10 °, the speed of bue disappear s 32m/min.

The main factors affecting the cutting deformation

1 Processing materials

The strength of the material, the higher the hardness, the knife - chip face being greater the pressure, the greater the average positive stress, reduced coefficient of friction of the shear angle is increased, therefore, the cutting deformation decreases.

2 Rake angle

Rake angle increases, the wedge angle decreases, and reduce the radius of the arc of cutting edge is blunt, chip flow resistance is small, so that the friction coefficient decreases, the shear angle is increased, and therefore cutting deformation decreases.

3. Cutting speed

Cemented carbide cutting tool Cutting speed through cutting temperature and dust accumulation in tumor affecting the cutting deformation. Knife - chip face difficult due to the low temperature of the low-speed cutting, bonding, a small coefficient of friction, the cutting of small deformation; as the speed increases, the temperature is increased, the adhesive gradually serious, the friction coefficient increases, the cutting deformation increases; cemented carbide cutting tool cutting speed further The improved, so that the processing temperature material shear yield strength decreased, the shear stress is small, the friction coefficient is small, therefore, the cutting of small deformation.

4. Feed rate ?

When the feed amount is increased, the increase in the cutting thickness and chip thickness, so that increased positive pressure on the front, so that the average positive stress increases, therefore, the coefficient of friction is reduced and the chip thickness compression ratio decreases.

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