Oil & Gas Trade Show in Singapore

MTA Singapore Exhibition

Hailed as a resounding success by all in attendance, over the course of its duration MTA2015 attracted over 12,000 attendees from 41 countries.

As the manufacturing industry undergoes a restructuring and gears itself towards high value-added and high-tech production, companies are confronted with a pressing need to rise above traditional boundaries, by embracing new technologies and acquiring new knowledge. At MTA 2015, Titan showcased our titanium metal & alloy materials in various forms. We explained the specifications as well as their properties to the visitors. As MTA events are considered as major sourcing ground for many industry visitors, we received many new enquiries for materials.

Thank you for your support to make MTA2015 a success!

Why Titanium metal turns blue after wire-cut process?

At Titan Engineering - Singapore, we do a fair amount of titanium metal plates by wire-cut machine and the appearance is important to all our customers. It is usual that the surface will become blue in color after wire-cut machining. The bluing does not go very deep into the material and can be mostly removed by polishing with a scrub pad. Polishing does cause the recast layer to go a little deeper but not deep enough to affect the material.

Wire-cut bluing of titanium is often mistaken for thermal damage, but the coloration you sometimes see at the edges of a wire-cut titanium surface is actually nothing but anodic oxidation created by the field of electrical current around the wire electrode during wire cutting. This ionized field produces a thin, and transparent oxide film on the top and bottom surfaces adjacent to the wire path. This oxide can be in the atomic range to several hundred nano meters thick. The colors produced in this manner have no pigments, dies or chemicals in them and are known as interference colors.

Interference colors are created when light strikes an oxidized surface. Part of the light is reflected and part of it passes through the oxide film to be reflected off the metal surface beneath it. As the light bounces back and passes through the oxide layer, it is slowed or interfered with, hence its name. This interference creates a color similar to the way a prism bends white light and breaks it into colors depending upon the angle. Every color in the rainbow can be achieved by this effect with the thickness of the oxide film (amount of interference) determining the color. Like anodizing, voltages, current density, water chemistry and pH can all affect the colors produced. The visible oxide colors that WEDM current typically generates are mostly in the blue and red spectrums, being a definite blue along the wire path and often fading to a tinge of red on the outer edges of the discoloration.

Being aware of all this may sound rather obscure, but we actually had to learn about this out of necessity. In a galaxy far, far away, in another lifetime when we had our shop (pre-AC generators and AE technology), we had to explain what the bluing was to many a freaked-out know all aerospace engineer, who upon seeing a WEDM'ed titanium part for the first time, would mistakenly think we had somehow "thermally damaged" the cut surfaces of his part to a depth of 2mm and it was now expensive scrap and started to jump up and down. <-- Engineer's reaction, Seriously.

This may sound amusing today, but if we weren't able to explain bluing to the at-that time to those EDM-paranoid engineers, we would have never received another titanium job from any of them. After this incident, we quickly learned to buff the top and bottom surfaces a bit to camouflage the bluing and eliminate any frantic questions or arguing for another titanium job. 

As a side note, this color proves that your material is real titanium, as no other material turns blue after wire-cut. Happy Wire-cutting Titanium, with blue. :)

Titanium Metal & Alloy Supplier - Singapore

Machining Tips for Titanium Metal & Alloys.

Machining Titanium:

Titan Engineering Pte Ltd Singapore offer the following technical information on the machinability of Titanium. This information is derived from the ASTM Technical guide to Titanium and should be used for reference knowledge only.

Introduction:

Titanium can be economically machined on a routine production basis if shop procedures are set up to allow for the physical characteristics common to the metal.  The factors which must be given consideration are not complex, but they are vital to successful handling of titanium.

Most important is that different grades of titanium, i.e., commercially pure titanium and various titanium alloys, will not all have identical machining characteristics, any more than all steels, or all aluminum grades have identical characteristics.  Like stainless steel, the low thermal conductivity of titanium inhibits dissipation of heat within the workplace itself, thus requiring proper application of coolants.

Generally, good tool life and work quality can be assured by rigid machine set-ups, use of a good coolant, sharp and proper tools, slower speeds, and heavier feeds.  Use of sharp tools is vital, because dull tools will accentuate heat build-up, to cause undue galling and seizing, leading to premature tool failure.

The machinability of commercially pure grades or titanium has been compared by veteran shop men to that of 18-8 stainless steel, with the alloy grades being somewhat harder to machine.  

Characteristics Influencing Machinability.

The fact that titanium sometimes is classified as difficult to machine by traditional methods in part can be explained by the physical, chemical, and mechanical properties of the metal. For example:

Titanium is a poor conductor of heat. Heat, generated by the cutting action, does not dissipate quickly.  Therefore, most of the heat is concentrated on the cutting edge and the tool face.

Titanium has a strong alloying tendency or chemical reactivity with materials in the cutting tools at tool operating temperatures. This causes galling, welding, and smearing along with rapid destruction of the cutting tool.

Titanium has a relatively low modulus of elasticity, thereby having more “springiness” than steel. Work has a tendency to move away from the cutting tool unless heavy cuts are maintained or proper backup is employed.  Slender parts tend to deflect under tool pressures, causing chatter, tool rubbing, and tolerance problems.  Rigidity of the entire system is consequently very important, as is the use of sharp, properly shaped cutting tools.

Titanium’s fatigue properties are strongly influenced by a tendency to surface damage if certain machining techniques are used. Care must be exercised to avoid the loss of surface integrity, especially during grinding.

Titanium’s work-hardening characteristics are such that titanium alloys demonstrate a complete absence of built-up edge. Because of the lack of a stationary mass of metal (built-up edge) ahead of the cutting tool, a high shearing angle is formed. This causes a thin chip to contact a relatively small area on the cutting tool face and results in high bearing loads per unit area. The high bearing force, combined with the friction developed by the chip as it rushes over the bearing area, results in a great increase in heat on a very localized portion of the cutting tool. Furthermore, the combination of high bearing forces and heat produces cratering action close to the cutting edge, resulting in rapid tool breakdown.

 With respect to titanium’s fatigue properties, briefly noted in the above list, the following details are of interest.

As stated, loss of surface integrity must be avoided. If this precaution is not observed, a dramatic loss of mechanical behavior (such as fatigue) can result. Even proper grinding practices using conventional parameters (wheel speed, downfeed, etc.) may result in appreciably lower fatigue strength due to surface damage.  The basic fatigue properties of many titanium alloys rely on a favorable compressive surface stress induced by tool action during machining. Electro-mechanical removal of material, producing a stress-free surface, can cause a debit from the customary design fatigue strength properties. (These results are similar when mechanical processes such as grinding are involved, although the reasons are different.) 

For further information, please contact Titan Engineering Pte Ltd, Singapore.