Stainless Steel

[Eric]

The problem is that if the quality of what we can see is poor then what is the metallurgical quality that we cant see going to be like?

Some of these bits could be used in safety critical applications.

[cbranni]

DWS........thats not good quality, not trying to teach my granny but have you tried a magnet on them just to be sure?, I had some stainless bolts and hex finish was good but the part off finish was awful with big part off tit, ended up having to face them all off myself. Looks like you need to take 10 thou off each face to clean up, the A/F will then be 20 thou under size, thats half a mill, just my opinion but I'd return them
Colin

[Don Madden]

Replacement stainless hardware probably has a lot of iron in it which makes it easier to machine but subject to some corrosion. Low iron stainless is very tough stuff & expensive to machine. Cheers, Don.

[Eric]

Don I am not quite sure what you mean when you say some Stainless has a lot of Iron in it.

All Steel including Stainless starts life as Iron Ore and is processed to produce Iron.

Further processing and conversion creates Steel.

Even more processing creates Steel Alloys and Stainless Steel is one of many thousands of variations of Steel Alloys .

The main difference to ordinary Steel is that it has a very high percentage of Chromium within the alloy to make it non-corrosive.

The amounts of Chromium will vary but will be at least around 12% usually much more, otherise the alloy can still corrode (rust) there will always be a large amount of Iron because thats what it was when it started life.
Edited by - Eric on 20 Dec 2010 11:41:44 PM

[Don Madden]

Seems pretty much what I said, without going into specifications of the many types of stainless steel. Types with lower iron content are more corrosion resistant, lower response to a magnet. They are tougher, thus harder to machine & more expensive. Types with higher iron the opposite. Cheers, Don.

[alanengineer]

Yes but!
The stainless steel that i purchase is specifically purchased for marine applications, so the quality should be on the higher side, but the finish can still look rough as in the above photos.
My local supplier tells me its the stuff made in India. i have not contacted my larger stockholder for their response.

[Stan Palmer]

We are usually sold stainless steel type 1.4305 (grade 303 stainless steel). Grade 303 is the most readily machineable of all the austenitic grades of stainless steel. The machineable nature of grade 303 is due to the presence of Sulphur in the steel composition. Whilst the Sulphur improves machining, it also causes a decrease in the corrosion resistance and a slight lowering of the toughness. The corrosion resistance of type 303 is lower than that for 304. The toughness is still excellent.

For marine service below 50 degrees C: Stainless steel types 1.4401 and 1.4404 (grades 316 and 316L) are the standard molybdenum-bearing grade, second in importance to 304 amongst the austenitic stainless steels. The molybdenum gives 316 better overall corrosion resistant properties than Grade 304, particularly higher resistance to pitting and crevice corrosion in chloride environments. Excellent forming and welding characteristics. Machining OK but cutting edges must be kept sharp. Dull edges cause excess work hardening. Cuts should be light but deep enough to prevent work hardening by riding on the surface of the material.
The finish they gave you is awful compared to the material from the Metal man at autojumbles and stuff I have had from e.g. Wye Valley stainless. But if India is selling at low prices that will become the only source until the Chinese come up with something worse and cheaper.
Stan

[Eric]

The metallurgical quality and appearance are of course two completely different things, but having just read up a little elsewhere on the Internet Marine Quality needs to avoid the pitting we have seen in both of DWS pictures, as this would give the seawater an advantageous starting point for corrosion.

For anything motorcycle wise I would have thought tensile strength should be one of the significant factors.

[DWS]

For anyone who has had an older BMW Boxer, Keith Shaw Engineering (now run by his son Chris) has always supplied very high quality stainless steel parts for these bikes. They are beautifully made with the surfaces always polished and flawless. I have used Keith's services for years. Sadly he only supplies metric items for BMWs. I find it frustrating that now I have returned to owning a Matchless I cannot get the same level of service for this motorcycle. It seems to me that some suppliers are of the belief that us Brits will put up with any old rubbish. Sadly, this is not the first time I have come across this since starting to rebuild the Matchless. I suppose it's a sign of the times and quality of finish isn't so important any more.Edited by - DWS on 21 Dec 2010 3:20:11 PM

[reabow gary]

I think that Eric is correct in his assessment of the sample as being of the hot drawn variety that has been left unfinished or polished after descaling.

Stainless steel or any other steel for that matter will oxidise and scale when heated to high temperatures. 304 316 etc will scale at a temperature of 898 deg C.

After hot drawing the bar is descaled by either mechanical and /or chemical means ie it is pickled in acid and then passivated in nitric acid or similar. Mechanical descaling leaves behind clear mechanical evidence in the form of striations, whereas pickling in acid leaves pit marks as shown in the two photographs.

After this the material will be treated by a variety of methods to improve its appearance to meet what ever finish was specifiedby the customer.

It is therefore up to the customer to specify what finish is required; for example these can range from a No. 0 scaled finish to a No. 7 or 8 which would be a mirror finish. A No. 2D finish would be a cold drawn finish; this is the most common finish usually ordered. No. 2BA is a bright annealed cold drawn (through polished dies / formers) finish.

The way I see it is that at the end of the day, it all comes down to stating what you want and being prepared to pay for it.

I hope this is of some help with future orders?