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RELATIONSHIP BETWEEN MCF AND U10
U10 (m/min)
600
500
400
300
200
100
0
100
FIGURE 1
150 200 250 300 350
MCF
400 450 500 550
.
.
.
Hardness
Carbon content
Sulfur content
Ca/Al ratio
With these four parameters, it’s possible
to evaluate the microstructure and the
presence of carbides as well as the types
of inclusions.
Tests were carried out on seamless tubes
for mechanical applications in a range
of dimensions in carbon and micro
alloyed steel, completely killed and with
a minimum guaranteed aluminum content,
tested ‘as rolled’, normalized and
quenched and tempered.
In developing an index the cutting speed
was set as corresponding to a cutting
edge life of 10-minutes (U10). The conditions
adopted are summarized in the
table below. The objectives of the tests
carried out were to determine:
The material parameters (C, α) that link
tool life (L) with cutting speed (U), as
described in the Taylor equation mentioned
earlier.
A machinability index, also said the cutting
speed which corresponded to a tool
life of 10 minutes (U10).
Obtaining the chemical characteristics,
microinclusions and microstructure of
MAIN FEATURES
Reference standard UNI ISO 3685:1981
End of life criteria Maximum flank wear: VB=0.30 mm
Maximum crater wear KT=0.18 mm
Cutting operation dry turning
Cutting insert Coromant CNMG 120408-PM 4015
Rake angle k=75°
Cutting Depth 2.5 mm
Feed 0.4 mm/rev
100° corner, clearance angle: -6°
the steel enabled the MCF to be built.
The relationship between the MCF and
a cutting speed equal to a tool life of 10
minutes (U10) is illustrated in figure 1.
As it can be observed the MCF represents
a good machinability index.
Conclusions
With simple, easy to obtain measurements
it is possible to gain good tool life
prediction for the cutting conditions used
in the test and quantify the effects of the
factors analyzed here. Carbon content
and hardness can hardly be used to control
machinability because they are generally
fixed by customer specifications, but
understanding their effects can be important
when planning the production cycle
for a component, adding for example a
heat treatment to change the hardness.
On the other hand, sulfur content and the
Ca/Al ratio can contribute to up to a 60-
70 m/min improvement in the (U10) value
for a common steel for mechanical applications
like 20MV6, which means
improving the machinability index by as
much as 10-15%.
Based on experimental results conducted
to answer the need for a product with
superior characteristics in hydraulic cylinder,
roller, bushing, connector and gear
applications, Tenaris has developed special
seamless tubes with high machinability
(HL) and close tolerances for mechanical
applications: TAM ® plus.
Tenaris News 9