Here are the top posts from 2013 that YOU found most interesting.
Skills DO Pay the Bills

You need skills, not just high pay, to properly hitch the cart to the horse.
You need skills, not just high pay, to properly hitch the cart to the horse.

We paid attention!
With over 20,000 views, we adjusted to your interest by creating a new blog focused solely on careers:
Second most popular  was Multiple Solutions about the lesson I learned at Paul Horn Company about optimizing for product output and quality rather than lowest cost- over 14,000 views:
Yep Two solutions! Which one is right?
Yep Two solutions! Which one is right?

Accuracy and Precision in your Machining Shop
Accuracy describes 'close to true value;' Precision describes 'repeatability.'
Accuracy describes ‘close to true value;’ Precision describes ‘repeatability.’

Our post explaining accuracy and precision has had over 10,000 views.
We had two posts in our top ten addressing Safety and Lift Trucks:
OSHA Emphasis Lift Trucks
Inspection Compliance ForkLifts
And the balance  at 5000 views or less each addressed Metallurgy and it’s impact on our processes and products:
Hardness vs Hardenability
5 Benefits of Cold Work 
Blue Brittleness
5 Reasons to Anneal Steel
Seams on Steel Products
We started this blog to provide knowledge retention of important concepts that impact our precision machining businesses.
But you keep this blog going with your interest,  forwards to colleagues, and comments on group discussion on LinkedIn where we share.
What will be 2014’s most important posts? We suspect regulatory topics to garner a lot of attention, but there is always the economy…
What would you like us to blog about in 2014?

 What a difference a temperature range can make! Some plain carbon steels, some martensitic (quenched)  carbon and alloy steels, and some high Chromium content steels can become embrittled if the wrong temper temperature is used.

This means premature failure in impact applications.
Blue Brittleness
Upon heating some plain carbon and alloy steels-not necessarily those that have been quenched to martensite or bainite-can exhibit both an increase in strength and a substantial decrease in ductility/ impact strength.
In this low temperature range, we call this effect blue brittleness. 
Blue Brittleness is a strain aging mechanism that occurs in this blue heat  temperature range.

Temper Embrittlement

 Martensitic (Quenched) steels can become embrittled if the wrong temper temperature is used.

Two Ductility troughs, this is in degrees C.

Link to graph.
In the range of 700 to 1070 degrees F ( 375 to 575 degress C) most common low alloy  steels show an increase in their ductile to brittle transition temperatures- regardless of whether they are heated into this range, or slowly cooled through it.
(Think large section parts/weldments).
Lower Manganese (below 0.30 wt %) containing plain carbon steel grades do not seem to be susceptible, although elevated levels of Tin or Phosphorus can make even these grades somewhat suceptible.
For these reasons, we would NOT use any tempering cycle below 1100 degrees F (~595 degrees C) for the common carbon and alloy constructional steels typically designated by AISI and SAE in North America.
This gets us past the ductility troughs seen on the above figure.
500 Degree F Embrittlement
500 degree F Embrittlement also occurs in quenched and tempered High Strength Low Alloy  (HSLA) steels  when they are subjected to a temperature range between 400- 700 degrees F (~ 200-370 degrees C). This differs from Blue Brittleness in that it is a phenomenon of tempered martensite, it is not related to strain aging. I was taught that it is rather a result of  precipitation along prior austenitic grain boundaries.
 Proper selection of steel chemistry is the best defense against this type of embrittlement, with Aluminum additions above 0.1 weight %  usually effective at preventing the problem. (Some steel producers lack the ability to add  Aluminum to their steel melt due to technology constraints on their casters…)
400 to 500 Degree C Embrittlement
If the steel is high Chromium content  (15% or more by weight) it can be subject to embrittlement when held in a 400-500 degree C  (~750 -930 Degrees F) range for a long enough time.
(Think heat affected zone in welding Stainless steels.)
This embrittlement can be eliminated by a proper soak at a higher temperature to redissolve the carbide (and possibly nitride?) precipitates.
These are the primary forms of embrittlement that I have encountered in my career. Other types of embrittlement  can include Liquid Metal Embrittlement, Sigma Phase Embrittlement and Embrittlement driven by neutron irradiation, or environmental factors such as hydrogen absorption, (often in plating) or Stress Corrosion Cracking where outside chemical attack and mechanical stress produce fine cracks in the steel.
Bottom line: Thermal treatments, and post quench temper treatments below 1100 degrees F are not recommended because of their possible embrittling effects on susceptible steel grades in common use in North America.



  With increasing temper temperature, the plasticity of a quenched martensitic structure increases up to around 400 degrees F; decreases to a minimum in the 450-700 degree F  (230-370 degrees C) range, and then continues to increase.