Month: November 2010

Leaded Steels-What You Should Know

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Lead is NOT banned by the European Union’s End of Life Vehicles Regulations for machining purposes in steel, aluminum and brass.
PDF HERE

Not banned in every application...

Lead is NOT banned by the European Unions Restriction of Hazardous Substances (RoHS) Directive.
The exemption for “Lead as an alloying element in Steel containing up to 0.35% lead by weight, aluminum containing up to 0.4% lead by weight, and as a copper alloy containing up to 4% by weight.” This exemption is located in article 4.2 and Annex, line 6.
UK link to RoHS exemptions
If even the European Union recognizes that additions of Lead in materials for machining is worthy of exemption, Lead must provide some significant benefits…

  • “Boosts machinability 25% at lower cost”- Pat Wannell, La Salle Steel April 1994, quoted in Modern Metals Magazine
  • “Cutting Speeds can normally be increased from 15-25% above those employed for the standard grade”- Monarch  Turning Manual
  • “Lead, found mainly enveloping manganese sulfide inclusions, promotes machinability in two ways, possibly three. By forming a layer of liquid lubricant at the tool chip interface, it reduces the stress required to overcome friction. By acting as an initiator of microcracks and, possibly, by causing some liquid metal embrittlement, it reduces the deformation stress.” American Machinist Special Report 790.
  • In our experience we have found leaded steels to  lower cutting temperatures and reduce wear rates on tools, resulting in greater up time. Surface finish on leaded materials  is superior to those on non leaded equivalents.

Increasing speeds and production, reducing power needed (and thus greenhouse gas emissions), and improving surface finish are some powerful advantages that are provided by the addition of lead to materials for precision machining.
What’s the down side?

In this photo lead is visible as tails (pointed out by arrows.)

1) Lead is not soluble in iron.  It is therefore a separate phase in the steel, usually visible enveloping the manganese sulfides as tails, though sometimes appearing as small particles.
2) Lead has a greater density than iron. This means that it will tend to segregate given enough time while the metal is liquid.
3) Lead has a relatively low melting point (liquidus) compared to steel. This can mean that at processing temperatures for heat treatment, leaded steel parts can ‘exude’ lead
These three factors mean that if you ABSOLUTELY MUST HAVE parts that are free from possible segregation, parts that will not have potential hollows or porosity after being exposed to high temperatures, and absolutely no visible indications of a separate phase in the steel (ie. what the shop guys call  “lead stringers,” you probably ought to forego the leaded grade.
And forego  the 25-30 % savings that it gives you on the piece part machining cost…
You want highest machinability or highest product integrity?

Take your pick.
Periodic
Photo of Lead on Manganese sulfides from L.E. Samuels Optical Microscopy of Steels.
Coin Flip
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Social Networking For Business- Its Not The Numbers

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The networking that matters is helping people achieve their goals.
Its not the number of superficial friends or followers.

Quality of connection, not quantity of "people who don't ignore you."

But inside, you already knew that.
Watch this short video.
Are you counting friends, or are you helping your friends?
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Manufacturing Picked Up Steam In October

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And Precision Machining is likely to show a similar pickup when we compile our numbers later this month.

Picking up steam!

Precision machined components are critical to many manufactured goods in many markets including automotive, off road, aerospace, medical, appliance and many, many,  more.
The Institute of Supply Management (ISM) said its survey of purchasing managers nationwide revealed strong gains in new orders and production; its index  rose to to 56.9%, from 54.5% in September. you can read their survey here.
Of the 18 manufacturing industries, 14 are reporting growth in October, in the following order: Apparel, Leather & Allied Products; Primary Metals; Petroleum & Coal Products; Machinery; Electrical Equipment, Appliances & Components; Miscellaneous Manufacturing; Fabricated Metal Products; Paper Products; Printing & Related Support Activities; Transportation Equipment; Computer & Electronic Products; Food, Beverage & Tobacco Products; Plastics & Rubber Products; and Chemical Products.
The two industries reporting contraction in October are: Nonmetallic Mineral Products; and Furniture & Related Products.
Manufacturing activity has expanded for 15 consecutive months but the rate of growth has been slowing since April. This latest strong showing provides hope for continued growth for the balance through the end of the year.
“This month’s report signals a continuation of the recovery that began 15 months ago, and its strength raises expectations for growth in the balance of the quarter,” said Norbert Ore, head of the ISM’s manufacturing business survey committee.
Photocredit.
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Predicting Size Change From Heat Treatment

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“By controlling the important variables, dimensional changes in heat treatment can be controlled.” Patrick McKenna
Variability is the enemy in our precision machining shops, and reducing variability is a key to sustaining our businesses and improving our capabilities.
When I talk about statistical process control with someone,  I listen closely to see if they are focused on the average (where the process is performing) or the standard deviation ( how the process is performing.)
If they are fixated on the average, I know I need to look at the data myself.  On the other hand if they are talking about standard deviations, I generally take their word on the data…
In the latest  issue of Production Machining Magazine, PMPA Technical Member Patrick McKenna from Nevada Heat Treating Inc., and Daniel Herring, the Herring Group Inc.  teach a nice class on how to reduce process variation in heat treat to minimize the post heat treat variability that all of us face.

Good advice here...

This is important if we are not to waste our production time trying to remove excess material because we left too much stock  for cleanup, or worse, finding the parts have shrunk in some critical dimension, rendering all of the parts ‘scrap.’
This article lists 9 variables NOT in control of the heat treater, and 14 that are under their control (furnace temperature uniformity, load configuration) or shared by the customer ( process selected, batch size, part size).
Not every order we produce is part of a long running job where we can control every input variable, but this piece does a great job of providing sensemaking on what can be a complicated and confusing subject.
I predict that you’ll keep this article in your “great to know” file.
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