Minimum yield strength of 1018CD 7

[tnteng]

Can anyone tell me what minimum yield strength should be used in design calculations when using 1018CD bar (1" dia. for this case) or tubing (2 1/2" OD for this case)? I have used 45 ksi in the past but I was wondering if that could be increased and if the tubing had a higher typical min. yield than the solid bar.

Thanks in advance for any help,



Tony Billeaud
Mechanical Engineer
Franks Casing Crew

 

[TVP]

Mandrel-drawn tubing (ASTM A 513) will have a minimum yield strength more like 55-60 ksi. Elongation is minimum 5% as-drawn, or 10% after stress-relieving. 55 ksi yield is a reasonable number for cold drawn bar as well.

 

[Cockroach]

For AISI 1018/1020 CD the yield strength is 48.0, 50.3 and 42.8 ksi for "as rolled", "normalized" and "annealed" condition(s) respectively. The corresponding tensile strengths are listed as 65.0, 64.0 and 57.3 ksi.

You can refer to AISI Specification Mt1015-1020 for additional properties for this and alternate mechanical steel round tubing, cold drawn.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[unclesyd]

Cockroach,
You and I must be using the same book by Bethlehem Steel.

 

[CoryPad]

Cockroach,

There is variation in mechanical properties of every material, so a single value with 0.1 ksi precision is unfounded. The American Iron and Steel Institute (AISI) does not publish a specification Mt1015-1020. Material or product property data would need to come from a consensus standards body (ASTM, ISO, etc.) or be agreed to by supplier and purchaser. A book from a steel producer no longer in business is not appropriate for design work.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Cockroach]

I realize the precision issue, however, I am merely submitting the numbers as published by CASTI, Metals Black Book Volume 1, Ferrous Metals, p.74. These cats are not "steel producers", infact they publish many engineering documents one of which is the above.


Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[CoryPad]

Cockroach,

Point taken, although these still are not sources that one could use if problems occurred (material defect, product liability, etc.). I should not have associated the last sentence of my previous post with your name, especially since unclesyd mentioned Bethlehem.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[unclesyd]

CoryPad,
I gather from your post we shouldn't use any information from any source where the company, author, organization, publisher doesn't exist or the material reference is out of print.
I have several textbooks that reference the Bethlehem Tables. Bethlehem had one of the largest materials testing facilities in the iron and steel for many, many years. Their date was considered impeccable at the time and I think still valid for the materials they produced and tested.
In fact most of my data is from companies/groups that no longer exist. I've found more discrepancies in some of the newer information that in the old Big Three’s handbooks.

Did CASTI generate the data or did they copy the data tables from a now defunct company. The only people that generated data for the different metals were producers/industries and a few universities. This is the same data used by most codes and standards after a review.

I agree that in design one should use a value published by the code or standard you are working to. Again this doesn't negate the value of the older data if it is needed and not addressed under the design conditions one is working to.

Case in point we used a lot of tool steels in pressure containing components where there was no data other that of the producers and that gleaned in house. If it hadn't been for Bethlehem and Vanadium Alloys we would have never gotten off the ground A2, D2, H-11, T-15 components.

 

[CoryPad]

unclesyd,

No, I don't think all of that data should be ignored. Rather, it should be placed in context. Maybe Bethlehem provided better properties than can be guaranteed by a newer minimill. Or any of a million other factors. I suppose my point is that anonymous Internet sources (i.e. Eng-Tips users) quoting data from bankrupt steel mills is no substitute for actual data generated by, agreed to, and correlated by user and supplier.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Sparweb]

This is a bit of a rant, but...

This is an interesting thread to read. The absence of a tested statistical basis for the materials you use casts a frightening shadow. This question wouldn't be posed - or would be firmly answered already - on the aircraft forum, with solid references.

I refer repeatedly to Mil-Handbook-5 when designing parts for aircraft, because no less will do. The statistically derived basis for the material properties virtually guarantees that 99% of the samples will meet or beat the number 95% of the time. Any number I quote is backed up by decades of testing by US government and university laboratories.

You guys are aware of these requirements, yet nobody is stepping up to the plate to provide this certainty to the properties of one of the most commonly-used types of steel. ASTM and AISI don't give the strength numbers; they're only concerned with the composition and heat-treatment. Any company that tests their lots can only be held responsible for the materials they produce.

Isn't the answer the ASME Boiler and Pressure Vessel Code? Section II give the properties of many types of steel, for all who can afford the 12,000$ price tag. I can't afford a copy - and have no reason to: most of these materials aren't used on aircraft.

Mil-Hdbk-5 is free, but there aren't any structural steels in it.
This economic barrier is preventing good engineers from obtaining the data they need to do their job properly
Responsibility for a huge number of military standards is also being transferred into private hands. Ultimately, all of them will have to be purchased, just like the BPVC. Eventually, I fear that Mil-Hdbk-5 will join them, for a price tag roughly equivalent.


Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout

 

[israelkk]

SparWeb:
You could get the ASME Boiler and Pressure Vessel Code section II - Materials from

http://www.knovel.com.

They allow free unlimited use of their site for 24 hours to see all their titles (in downloadable *.pdf files) or more time for selected titles.

 

[ccw]

Hi tnteng,

Mach. Hdbk 25ed:

Table 8 Page 432,
"Expected Minimum Mechanical Properties, Conventional Practice, of Cold Drawn Carbon Steel Rounds, Squares, and Hexagons"

Source: AISI Committee of Hot Rolled and Cold Finished Bar Producers as published in 1974 DATABOOK issue of the American Society for Metals' METAL PROGRESS magazine and used with its permission:

As Cold Drawn: (no stress relief after draw)
AISI 1018 and 1025 Steels
7/8-1 1/4 inch dia. bar range:

Tensile: 65Ksi
Yield: 55Ksi
Elongation in 2 in. 16%
Reduction in Area 40%
Hardness 131 Bhn

Editorial: An additional concern is that, with current trends, there will be no Cold Drawn Bar made in American anywhere soon. So, the source for the database used in the 1974 report will be extinct. Also, a few years back, ASTM was considering whether or not to replace their A36 spec with an A40 or A50 spec. It seems that due to increased quality control at the foundrys over the years, their A36 (36Ksi minimum yield spec) had become super conservative with the current 95/99 testing results number being more like 50Ksi, for the same chemical spec.

While I share the concerns raised by SparWeb, I would not use B&PV code Section II, allowable working stresses to design my airplane structure. Chances are it would not get off the ground.
;-)

 

[Sparweb]

ccw: neither would I!

(and I certainly didn't want to imply otherwise)

I've also experienced the disconnect between the mean values and the "A" values for materials. When pulling numbers of of Mil-Hdbk-5 S-n curves, one must be aware of the mean ultimate strength, which is often much higher than the "A" value.

I do feel silly that I didn't think of Machinery's Handbook. At 2-300$, it's much more accessible to the average engineer. Its average values are from reliable sources, too.



Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout