Page 10 - machining_titanium_05_2019

MACHINABILITY OF TITANIUM
Machinability Rating

1.8
1.6
1.4
1.2

1
0.8
0.6
0.4
0.2
0
Pure α- and α- β β- and near-β-
near-α-
Fig. 2 Machinability of titanium groups (averaged data)

β-stabilizers, which contribute to higher strength, increase specific cutting force.
As a rule, the β-phase structure reduces machinability and machining β- titanium is more difficult.

Extensive use of titanium in industry, particularly in the aerospace sector, led to in-depth study of
machining titanium and caused serious changes in technology. As a result, manufacturers built
reliable metal cutting processes and took titanium machining productivity to a new level.
This reduced production costs and caused added momentum to a wide penetration of titanium in
new designs. Today, for example, machining Ti-6Al-4V, the most commonly used titanium grade,
is considered already as a closed chapter, although 15-20 years ago it was not a cakewalk.

Success has boosted interest in a wider application of other titanium grades featuring better
strength but with poorer machinability. These grades focused the attention of designers as a
good alternative to steel and stainless steel for weight saving but the low productivity presented
a barrier. Following new demands, industry faced a problem with productive machining titanium
alloys such as Ti-10V-2Fe-3Al and Ti-5Al-5Mo-5V-3Cr (VST 5553) that had a strong presence
as key elements in different structural components. On the one hand, machine tool builders
(MTB) achieve an impressive success in high-efficiency machine tools specifically dedicated
to cutting titanium. These latest-generation multi-axis machines are intended for high volume
production capability and feature high-torque main drive, advanced CNC software and adaptive
control units, and high-pressure coolant supply. On the other hand, far slower progress in the
cutting tools field has presented an obstacle in taking full advantage of the new machines.

Finding a way how to close the produced gap dictates strict requirements for cutting
tools intended for machining titanium. The cutting tool, which often seems to be a
minor link in a whole technological chain, actually plays a role of the prime factor,
which can boost productivity of titanium and firstly its difficult-to-cut grades.

There are few options for substantial improvement of cutting tools. The main directions for the
development of advanced tools relate to cutting tool materials and cutting tool design (geometry).

8 ISCAR