Machinability of Metals - Machine Work Study Topic

Machinability explanation
https://www.americanmachinist.com/cutting-tools/media-gallery/21895130/cutting-tool-applications-chapter-3-machinability-of-metals

Aluminum - Machinability

Aluminum alloys are also among the most machinable of the common metals. Cutting forces are generally low,  cutting temperatures are kept low because aluminum is a good heat conductor and most alloys melt at temperatures between 500°C and 600°C,  and therefore tool wear rates are also low.

 When cut under proper conditions with sharp tools, aluminum alloys acquire fine finishes through turning, boring, and milling, minimizing the necessity for grinding and polishing operations.

Tools Used: Aluminum is commonly machined with HSS, carbide, and PCD tooling.

Not used: Silicon nitride-based ceramic tools are not used with aluminum because of the high solubility of silicon in aluminum.


Two major classes of commonly machined aluminum alloys are cast alloys, used especially in
automotive powertrain and component manufacture, and wrought or cold worked alloys, used in
airframe manufacture and similar structural applications.


The most commonly machined cast aluminum alloys by volume are cast aluminum-silicon alloys,
which are used extensively in automotive applications. From a machining viewpoint it is common
to distinguish between eutectic alloys, containing 6%–12% silicon, and hypereutectic alloys containing generally 17%–23% silicon.

Some of the  eutectic alloys are  319, 356, 380, 383, and most piston alloys.   From a tool life viewpoint, most eutectic alloys, when properly tempered, present few difficulties, so that long tool life can be achieved at relatively high cutting speeds. Tool life approaching one million parts can be obtained in some mass production operations using PCD tooling.

Cutting Speeds: Speeds up to 450 m/min can be used when turning with carbide tools, and speeds as high as 4000 m/min can be achieved in some milling applications with PCD tooling. Of the common eutectic alloys, the most easily machined are 319 and 380.

https://blog.aluminiumwala.com/2019/10/ponits-consider-while-choosing-aluminium-grades.html

http://manufacturing-videos.blogspot.com/2013/04/machinability-aisi-rating.html


Aluminum Alloys - Machinability AISI No. 1112 steel = 100
aluminum, cold drawn - 360%
aluminum, cast - 450%
aluminum, die cast - 76%

Maruti All Aluminum Low Weight Engine KB Engine

Machining Aluminum Engine Blocks
https://www.enginebuildermag.com/2017/07/machining-aluminum-engine-blocks/  2017

https://auto.howstuffworks.com/10-improvements-in-engine-design5.htm

https://www.productionmachining.com/articles/how-metallurgical-structure-affects-the-machinability-of-aluminum

https://sct-usa.com/technical-data/pcd-tipped-insert-speed-and-feed-chart/

The Optimum Cutting Condition when High Speed Turning of Aluminum
Alloy using Uncoated Carbide
B. Umroh et al 2019 IOP Conf. Ser.: Mater. Sci. Eng. 505 012041
https://www.researchgate.net/publication/334242391_The_Optimum_Cutting_Condition_when_High_Speed_Turning_of_Aluminum_Alloy_using_Uncoated_Carbide

Cast Iron - Machinability

MACHINABILITY OF FCD 500 DUCTILE CAST IRON USING COATED CARBIDE TOOL IN DRY MACHINING CONDITION
Jaharah Abd. Ghani, Mohd Nor Azmi Mohd Rodzi, +2 authors Che Hassan Che Haron
Published 2009
Materials Science
In this study, ductile cast iron grade FCD 500 was machined using carbide cutting tool in dry end milling condition. The end milling parameters used were cutting speed of 180 m/min, 210 m/min dan 260 m/min. The feed rate of 0.10 mm/tooth, 0.25 mm/ tooth and 0.40 mm/ tooth, and the depth of cut of 0.30 mm, 0.60 mm dan 0.90 mm.

https://www.semanticscholar.org/paper/MACHINABILITY-OF-FCD-500-DUCTILE-CAST-IRON-USING-IN-Ghani-Rodzi/be0483324ac6b1e6c91a9c22157f1dfd302a8d31

Stainless Steels

MATERIALS AND METHODS

The workpiece material used in the present work was austenitic stainless steel (grade SUS 304) with an approximate composition of 0.08% C, 2% Mn, 10% Ni and 19% Cr. The diameter and length of the workpiece were 200 and 500 mm, respectively. Titanium nitride coated cermet tool inserts (SNMG 120408-HM, grade 200) were used.  The cermet tools were mechanically clamped to the tool holder. Geometrical parameters of the inserts were as follows: relief angle-4°, rake angle-10°, principal cutting edge angle-85° and auxiliary cutting edge angle-5°.

The experiments were conducted on a lathe model Harrison M390. Cutting parameters were selected to cover roughing, finishing and fine finishing. Metal cutting was performed at cutting speeds of 300, 400, 500 and 700 m min-1. Feed rates were 0.05, 0.1, 0.2 and 0.4 mm rev-1. Depths of cut tried were 0.1, 0.2, 0.3 and 0.5 mm. A full factorial set of experiments (64 trials) was performed with 4 different cutting speeds, 4 levels of depth of cut and 4 levels of feed rates.  Each insert of the cutting tool had 8 edges (4 on each side). Thus each insert was capable of performing 8 trials.

Ahsan Ali Khan and Sami Salama Hajjaj , 2006. Capabilities of Cermets Tools for High Speed Machining of Austenitic Stainless Steel. Journal of Applied Sciences, 6: 779-784.
https://scialert.net/fulltext/?doi=jas.2006.779.784

Nickel-based Superalloys

PCBN Performance in High Speed Finishing Turning
of Inconel 718
José Díaz-Álvarez ID , Víctor Criado ID , Henar Miguélez and José Luis Cantero
Metals 2018, 8, 582; doi:10.3390/met8080582

Nickel-based superalloys with excellent mechanical properties at high temperature and corrosion
resistance find a wide range of applications such as aircraft engines power-generation turbines, nuclear power generation, and chemical processes.  Machining difficulties arise in cutting these alloys  due to strong work hardening, presence of hard carbides, and low thermal conductivity leading to high temperatures during machining.
Selection of proper tool material,   geometry,  coating; cooling strategy; and cutting parameters (cutting speed and feed) strongly determine tool wear evolution and surface integrity.

The candidate tool materials are cemented tungsten carbides, ceramics, and cubic boron nitride (CBN) used in rough machining of Ni superalloys. Carbide tools are restricted to cut in the range between 30 m/min to 70 m/min because of their poor thermochemical stability, however they can be used at high values of feed due to its toughness. Ceramic tools based on alumina (aluminum oxide, Al2O3) and silicon nitride (Si3N4), are suitable.  Alumina combined with TiC improve thermal properties of the insert allowing the increase of cutting speed about five times higher than the carbide tools (120–240 m/min), although thermal and mechanical shock resistance are not significantly improved compared to tungsten carbides. Whisker-reinforced alumina ceramics (Al2O3 + SiCw) can reach cutting speeds in the range between 200 and 750 m/min and feed between 0.18 and 0.375 mm/rev and present improved toughness. Silicon nitride, with low thermal expansion and elevated toughness, allows machining at higher speeds and feed than alumina. Finally, cubic boron nitride (CBN) can be used to machine nickel- or boron-based superalloys with hardnesses greater than 35 HRC at cutting speeds ranging from 200 to 350 m/min.

http://www.mdpi.com/2075-4701/8/8/582/pdf

NEW TOOLS AND STRATEGIES TAKE ON ISO S MATERIALS
https://www.secotools.com/article/21491?language=en

A detailed investigation of residual stresses after milling Inconel 718 using typical production parameters for assessment of affected depth
JonasHolmbergabAndersWretlandcJohanBerglundaTomasBeno
Materials Today Communications
Volume 24, September 2020, 100958
https://www.sciencedirect.com/science/article/pii/S2352492819309377


Titanium 

Makino's New HMC for Titanium Machining

Purpose-built with rigidity, dynamic stiffness, vibration damping, and agility

MAY 25, 2011

https://www.americanmachinist.com/machining-cutting/article/21897803/makinos-new-hmc-for-titanium-machining

Gente and Hoffmeiste [2001] reported the chip formation of Ti–6Al-4V at very high cutting speed, ranging between 30 m/min and 6,000 m/min  According to experimental results, the structure of segmentation was changed at the cutting speed exceeding 2,000 m/min. Furthermore; no change in specific cutting energy coincides with this change in structure.

Gente A, Hoffmeister HW, Evans C (2001) Chip formation in machining Ti6Al4V at
extremely high cutting speeds. CIRP Ann Manuf Technol 50:49–52. doi:10.1016/
S0007-8506(07)62068-X

Open access peer-reviewed chapter
Machinability of Titanium Alloys in Drilling
By Safian Sharif, Erween Abd Rahim and Hiroyuki Sasahara
Submitted: May 17th 2011Reviewed: October 12th 2011Published: March 16th 2012
https://www.intechopen.com/books/titanium-alloys-towards-achieving-enhanced-properties-for-diversified-applications/drilling-of-titanium-alloys

Stainless Steel

2020 January

https://www.sme.org/technologies/articles/2019/december/taking-stainless-steel-machining-to-the-next-level/

Machinability of metals

Machinability of a material can be defined as the ease with which it can be machined.
Machinability depends on the physical properties.

Machinability can be expressed as a percentage or a normalized value. The American Iron and Steel Institute (AISI) has determined AISI No. 1112 carbon steel a machinability rating of 100%.

Machinability of some common materials in the scale: AISI No. 1112 = 100 are given below.  below:

Carbon Steels

1015 - 72%
1018 - 78%
1020 - 72%
1022 - 78%
1030 - 70%
1040 - 64%
1042 - 64%
1050 - 54%
1095 - 42%
1117 - 91%
1137 - 72%
1141 - 70%
1141 annealed - 81%
1144 - 76%
1144 annealed - 85%
1144 stress-proof - 83%
1212 - 100%
1213 - 136%
12L14 - 170%
1215 - 136%


Alloy Steels
2355 annealed - 70%
4130 annealed - 72%
4140 annealed - 66%
4142 annealed - 66%
41L42 annealed - 77%
4150 annealed - 60%
4340 annealed - 57%
4620 - 66%
4820 annealed - 49%
52100 annealed - 40%
6150 annealed - 60%
8620 - 66%
86L20 - 77%
9310 annealed - 51%


Stainless Steels and Super Alloys
302 annealed - 45%
303 annealed - 78%
304 annealed - 45%
316 annealed - 45%
321 annealed - 36%
347 annealed - 36%
410 annealed - 54%
416 annealed - 110%
420 annealed - 45%
430 annealed - 54%
431 annealed - 45%
440A - 45%
15-5PH condition A - 48%
17-4PH condition A - 48%
A286 aged - 33%
Hastelloy X - 19%


Tool Steels
A-2 - 42%
A-6 - 33%
D-2 - 27%
D-3 - 27%
M-2 - 39%
O-1 - 42%
O-2 - 42%


Gray Cast Iron
ASTM class 20 annealed - 73%
ASTM class 25 - 55%
ASTM class 30 - 48%
ASTM class 35 - 48%
ASTM class 40 - 48%
ASTM class 45 - 36%
ASTM class 50 - 36%
Nodular Ductile Iron
60-40-18 annealed - 61%
65-45-12 annealed - 61%
80-55-06 - 39%




Magnesium Alloys

magnesium, cold drawn - 480%
magnesium, cast - 480%

Updated on 17 Sep 2020

3 April 2020