apologize for a wee bit of a thread hijack
Brian,
re: your comments about science, religious/political fervor surrounding bans
This article on Freeman Dyson just recently
caught my attention. Seems germane somehow...
http://www.nytimes.com/2009/03/29/magazine/29Dyson-t.html?_r=1
At 07:40 AM 3/30/2009, Brian Ellis wrote:
>Titanium is a funny metal. Fabricated items, such as snob-value watch
>cases, are often sintered into a rough shape before machining, rather
>than cast, as would be gold. This is because casting is very expensive
>as it is done in a vacuum (hot Ti burns on O2 and N2 long before its
>melting point!!!). Ti is extremely difficult to machine, whether
>sintered or derived from a casting, but sintered is the worst. The tool
>must be really perfectly ground without wear and the Ti must be really
>well cooled (pumped cutting oil systems such as for steel or non-ferrous
>metals are often insufficient). This is because there is a phase change
>induced by pressure at temps above ambient, locally softening the metal
>crystal-by-crystal and this causes the metal to deform onto the tool and
>gall. This often 'snowballs' by minor galling inducing ever-increasing
>deformation. I don't know all the ins and outs of Ti galling but I have
>observed it as a severe problem in practice (in a former life, I
>designed a part for working in HCl that had to be turned from bar; the
>turner had hell's own job!).
>
>I mention this because your "squamous" surface may be due to galling,
>especially if the part is sintered, rather than cast.
>
>As for TCE, I knew one of the guys who was behind the ban in Sweden. At
>the time, I had long and heated discussions with him that he was making
>a BIG mistake. I never was a fan of halogenated solvents but I always
>admitted there were some applications for which they were indispensable.
>The idiocy started in E Germany where a factory's employees had an
>abnormal number of cancer cases ascribed to TCE. No epidemiological
>study was made or confounding factors determined. It later transpired
>that the TCE was stabilised with epichlorohydrin, a known carcinogen but
>it was too late, Germany had already decreed TCE was a known carcinogen
>in humans (MAK1) with a PEL of (I think) 1 ppm. For some reason, they
>never wanted to correct this error, despite serious studies to the
>contrary, and some other countries followed suit. FYI, perc, which is
>potentially more toxic than TCE, is classed as MAK3 in Germany with a
>PEL of 25 ppm. Carbon tetrachloride, which is KNOWN to be a lot more
>toxic than TCE, is also classed as MAK3 with a PEL of 10 ppm. It simply
>makes no sense whatsoever. I think you will find Germany's stupid
>classification of TCE will reach REACH, if it hasn't already done so. To
>get back to my Swedish colleague, he argued that all applications using
>TCE could be replaced by aqueous cleaning methods. Memories of these
>arguments still make me squirm; you simply could not have a scientific
>discussion based on fact, he had a political point to make. At one
>point, in a committee meeting with ~20 persons present, he was shot down
>in flames by the consensus and he simply stormed out of the room,
>slamming the door (this was c. 1989, when we were desperately trying to
>promote all known means of cleaning using relatively safe non-ozone
>depleting solvents, such as TCE, in preference to 1,1,1-TCA).
>
>Would it be possible to use TCE in a zero-emissions machine? (Virtually
>0 ppm in the workshop at all times, certainly less than 1 ppm.) Surely
>that cannot be forbidden? It would also ensure compliance with the EU
>VOC Directive.
>
>Brian
>
>
>
>Hernefjord Ingemar wrote:
> > I reckon that some mineral oils seem to be
> very bullheaded. We had let parts pass aceton
> and etanol and some other cleanings, and to our
> surprise, after electron beam vacuum welding
> the two (cleaned)parts together, small and
> yellowish fatty things appeared on the liquid
> surface when the finished part was recleaned
> after the welding. This was done by dipping the
> flasklike part in a degreasing tank. Evidently,
> mineral oil was still hidden in the titanium
> surface after machining, despite it looked
> clean and left no debris when you rubbed with a
> white cloth. In a high magnification
> microscope you can see a lot of microscopic
> damages, void or what to call the rude surface.
> Just unlike steel and other metals. Whatever
> machining parameters or tools, it seeems as
> titanium is "squamous" after the drilling, milling etc.
> >
> > TRI...hmm...was cast out here twenty years
> ago...chemo textile cleaning is allowed to be
> done with perchloroethylene, which I find
> remarkable. The later is not better in a environmental point of view.
> >
> > Inge
> >
> > PS. VIGON 200 = 11-12 (pH)
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
> > Sent: måndag 30 mars 2009 13:04
> > To: [log in to unmask]
> > Subject: Re: [TN] Titanium
> >
> > I'm not sure that Vigon will be satisfactory
> for removing mineral oil residues and their
> additives, as these will not saponify in the amines.
> > You will need something with the pH exceeding
> 12-13 and with stronger tensio-active components.
> >
> > I'll shock you by suggesting a
> trichloroethylene blend in a zero-emissions
> cleaning machine with a vapour phase final. I
> don't care what people say, it is a damned good
> low-cost solvent, used sensibly it is perfectly
> safe, it is non-carcinogenic to humans (it is
> carcinogenic to rodents in high doses, but their metabolism of the substance is
> > different) AND IT WORKS!!! (If needed, I have
> details of epidemiological studies with cohorts
> of tens of thousands supporting my statements.)
> >
> > In the unlikely event that this alone would
> be insufficient for your needs, then consider
> an aqueous solution, depending on the residue analysis after TCE.
> >
> > Brian
> >
> > This alone would probably be sufficient and low-cost
> >
> > Hernefjord Ingemar wrote:
> >> The tests will show. If one or two
> steps can be left, of course very good. On the
> other hand, the cost for these units is so
> high, that some dollars saving is negligible.
> Unlike the normal production when cents are hunted for.
> >>
> >> The alcaline bath will possibly be
> superseded by our Vigon 200 tunnel cleaner.
> >> /Inge
> >>
> >> -----Original Message-----
> >> From: TechNet [mailto:[log in to unmask]] On Behalf Of R Sedlak
> >> Sent: måndag 30 mars 2009 11:28
> >> To: [log in to unmask]
> >> Subject: Re: [TN] Titanium
> >>
> >> Ingmar:
> >> The process you suggest probably will work,
> but I suspect it is overkill. I suspect that
> the alkaline cleaner will be enough on its own.
> >>
> >> Good luck.
> >> Rudy Sedlak
> >>
> >> --- On Sun, 3/29/09, Hernefjord Ingemar
> <[log in to unmask]> wrote:
> >>
> >> From: Hernefjord Ingemar <[log in to unmask]>
> >> Subject: Re: [TN] Titanium
> >> To: [log in to unmask]
> >> Date: Sunday, March 29, 2009, 11:58 PM
> >>
> >> Thank you, Rudy&Steve.
> >>
> >> It seems as a suitable treatment would be this one:
> >> a)Solvent degrease, followed by
> >> b)Alcaline bath, followed by
> >> c)DI ultrasonic bath, followed by
> >> d)Micropowder blast, followed by
> >> e)HNO3 dip, followed by
> >> f)DI ultrasonic bath.
> >>
> >> We will try this today already. We do not
> like HF, so that kind of process is skipped.
> Our problem is not primarily to remove the
> oxide, but to ascertain that all
> threading/cutting oil is gone, also that the
> numerous micro pores are emptied from their content.
> >>
> >> /Inge
> >>
> >>
> >>
> >>
> >> -----Original Message-----
> >> From: TechNet [mailto:[log in to unmask]] On Behalf Of R Sedlak
> >> Sent: lördag 28 mars 2009 20:19
> >> To: [log in to unmask]
> >> Subject: Re: [TN] Titanium
> >>
> >> Although Titanium lightly alloyed is used in
> some joint replacements, it may well be more
> commonly known for its use as Nitinol, a
> Nickel/Titanium alloy, which has weird "memory"
> properties. Nitinol is one of the more common stent materials.
> >>
> >> Cleaning Titanium is quite difficult,
> particularly if it is heavily oxidized, as the
> common "cleaning" agent, (Hydrofluoric Acid)
> attacks Titanium vigorously, and then to frost
> the cake, this causes Hydrogen embrittlement.
> >>
> >> Not everyone/everywhere is as "enlightened"
> as we like to think we are, and yes, there is
> still choro-ethanes still in use in cleaning (Think "dry cleaning" clothes).
> >>
> >> There are proprietary cleaners which purport
> to get around these issues. If interested, contact me off Technet.
> >>
> >> Rudy Sedlak
> >> RD Chemical Company
> >>
> >>
> >>
> >>
> >>
> >>
> >>
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