Stress Cracks in Steel Bar Products.

March 14, 2017

“Stress cracks are defined as transverse or near transverse open crevices created when concentration of residual stresses exceed the local yield strength at the temperature of crack formation. These stresses can be mechanically induced or can be attributable to extreme temperature differences and /or phase transformations. They can originate at almost any point in the manufacture of the steel.”AISI Manual Detection, Classification, and Elimination of Rod and Bar Surface Defects

Stress cracks are often found visually  at locations that experience bending or straightening. They are also referred to as “Cross Cracks” or “Transverse Cracks.” Originally they were identified in mill billet and bloom products, prior to rolling.

Micro examination can help determine crack origin by noting:

  • Orientation
  • Intergranular nature
  • Presence of scale
  • Presence of subscale

Additional microstructural characteristics can reveal the thermal history of heating and cooling at the crack location.

This photo shows stress cracks on a conditioned billet.

Causes and Corrective Action

  • Excessive load during straightening can exceed the local yield strength of the material causing it to crack; reduce load applied by machine, or consider tempering or stress relieving material prior to straightening or further cold work.
  • Cooling too quickly can also induce stress cracks. Critical cooling rates are highly dependent on steel chemistry. Crack sensitive chemistries (Medium carbon and high carbon steels; also medium and high carbon steels with straight chromium or straight manganese additions.) These steels should be slowly cooled through transformation temperatures to minimize the occurrence.
  • Design faults such as
    • Heavy sections adjacent to light sections and sharp corners 
    • Failure to fillet sharp corners
    • Use of fillets rather than tapers
    • Undercuts
    • Overloading the material during fabrication, processing, or application.

Detection of stress cracks  is problematic as their transverse orientation makes them difficult to detect on equipment set up to detect longitudinal defects.

Final caveat: The term stress crack is arbitrarily defined based on industrial usage in the market. It does not necessarily imply anything about the specific metallurgical nature of the crack, I know that a number of people use the term “stress crack” to describe longitudinal cracks on steel bar products as well, which the AISI calls “Strain Cracks.”

 

 

Advertisements

December ISM PMI Positive Bellwether for 2017

January 5, 2017

The Institute for Supply Management announced on Tuesday that its Purchasing Manager’s Index (PMI) for Manufacturing index rose 1.5 percentage points to 54.7 in December, its highest level in two years and up from 53.2 in November.

This is great news- let’s look at some details to find out why:

  • New Orders component– new orders rose 7.2 percentage points to 60.2 – their highest level since November 2014
  • Strength in Employment component– employment rose 0.8 percentage point to 53.1 – the highest since June 2015
  • And strength in the Production component-production improved to 60.3- very unusual outcomes for Manufacturing in December.

This is an unexpectedly solid report showing Manufacturing industry performance stronger in December than in November.

Highest in 2 years and up 1.5 points over November 2016

Highest in 2 years and up 1.5 points over November 2016

Here is why we see this as a bellwether for a great 2017 for our precision machining companies.

  • U.S. Light Vehicle (Auto) Sales set annual sales record according to the Wall Street Journal and reports we heard from online videos from AUTO NEWS. “A total of 17.55 million vehicles were sold in 2016, roughly 60% of which were classified as light trucks” according to the Wall Street Journal.
  • 2016 sales volume was up ~ 700,000 light vehicles, according to reports from Auto News
  • The average age of the U.S. Light Vehicle Fleet in 2016 was a record 11.6 years, According to Statista online, 

There is still plenty of reason to expect demand for light cars and trucks to be sustained based on the average age of the U.S. Fleet and the current low unemployment rate reported by the Federal government. Knowing that Automotive is the precision machining industry’s most heavily served market convinces us that these numbers reported by ISM, WSJ, Auto News and Statista bode well for our precision machining shops in 2017. I hope that you are preparing for success, not for hunkering down in 2017.

Happy New Year, indeed!

Auspicious!

Auspicious!

 

Link to ISM December 2016 report

Statista Age of Light Vehicles in U.S.

Calculated Risk December ISM Post and Chart


Thread Rolling Thin Walls- CJ Winters

November 3, 2016

Guest post by Lib Pietrantoni, CJWinter

Flaking threads and thread damage can be avoided when thread rolling thin walled parts.

Distortion during the thread rolling process can cause

  • Flaking,
  • Non-uniform thread geometry
  • Tearing
  • Collapse of threaded portion of part

These are particularly troublesome issues on thin walled parts.

These can be avoided if you assure that a minimum wall thickness is maintained for the process.

 

Minimum Wall thickness is determined by Nominal Thread diameter and thread pitch

Minimum Wall Thickness is determined by Nominal Thread Diameter and Thread Pitch

Larger nominal thread diameters require thicker minimum wall thickness; so do coarser thread pitches.

The way that you roll the thread can also be a factor.

According to Lib Pietrantoni at CJWinter, specialized pneumatic radial-pinch-type thread rolling machine attachments can apply equalized rolling pressure across the workpiece, ensuring thread concentricity, eliminating side pressure on both the parts and the machine, and allowing precise control of the penetration rate — especially important for thin-walled parts.

You can download the Thread Rolling Reference Chart at CJWinter’s website: reference chart

As a steel mill Quality Metallurgist, I saw my share of complaints that “the steel was flaking- it must be the steel.”

But the lab results never found the flaking anywhere except where the thread had been rolled – it was never on the bars as shipped.

Pay attention to minimum wall thickness when thread rolling!

And  don’t forget to pass this handy chart along to the engineer at your customer that is designing the parts that you make.

Thanks to Lib Pietrantoni at PMPA member CJWinter for providing this reference information.


Ten Points Worth Sharing- Cleveland Area OSHA Director Howie Eberts

August 25, 2016

We attended a presentation at WIRE-Net by Cleveland OSHA Area Director Howie Eberts. Howie did a great job of giving attendees a thoughtful, human view of how and why OSHA does what it does in his district.

Informative slides were the foundation of his talk, but the takeaways revealed some interesting insights into our joint  (Companies and OSHA) efforts toward employee safety.

We all have shared responsibility for safety.

We all have shared responsibility for safety.

1)      Safety is important- not just for ourselves, but also for our families that are counting on us.

2)      On the job fatalities have declined substantially from 1974 to the present- but there are still too many.

3)      Most OSHA inspections are conducted without notice.

4)      In Cleveland region, 85% of inspections are a result of employee complaints.

5)      Be very careful posting photos on your websites or literature- If someone is obviously in the shop without wearing their required PPE…

6)      It‘s your company-

  • Why wouldn’t you want to have a prepared written plan for how your company will respond to a serious injury or fatality?
  • It’s not unreasonable to assert your rights
  • You DESERVE to be treated with respect
  • So do our Field Agents
  • How you treat our officers is on you

7)      OSHA does have the right to interview your employees privately

8)      To prove employee misconduct you need to prove all four:

  • You have a work rule
  • The rule is communicated to all employees
  • You monitor compliance
  • You issue discipline for noncompliance

9) If the agent tries to expand the scope and you don’t understand why, ask them to clarify why, if you still don’t understand, ask to speak with Howie

10) The facts show that the most dangerous thing that any of us do involves a motor vehicle; roadway incidents alone accounted for nearly one out of every four fatal work injuries.

We took a number of specific actionable tips and insights away from his presentation that we’ll be sharing exclusively with our PMPA members.

Photo credit: http://www.medinacountysafetycouncil.com/

Wire-Net: https://www.wire-net.org/

 

 


Attending IMTS-Think Differently!

August 19, 2016

About this time of year the  advice starts rolling out – have a plan so you don’t miss anything. Make a  checklist of key contacts.  Map your show. Make sure to stop at So and So’s booth for the free give-aways. Etc.  Etc. Etc.

This year, I’ll not exhort you to go to IMTS with a plan of exhibitors to visit.  I’ll not ask you to make a list of the key people that you need to connect with. And will you really have room in you bag for whatever it is that So and So  is giving away this time?

Instead, I’d like to issue you a challenge. I’m asking you to think up a theme for your visit, an idea that you would like to discover the means of achieving while at IMTS.

Several IMTS’s ago, I had just such a theme in mind. My theme was, “What can I find  here at IMTS that will help us keep manufacturing jobs here in the U.S.? That will help our talent operate at their ‘Highest and Best Use?’

At that show, I found the PAWS Workholding System, and relearned the importance of knowing my multiplication tables.

Why hold (and machine) just one part, when I can hold and machine say, 16 at once?

They never told me about this when I was learning my times tables...

They never told me about this when I was learning my times tables…

Why indeed?

  • 60% increase in parts per shift
  • 50% reduction in Operator Load and Unload Time
  • 50% reduction in Operator Tasks/ shift
  • Reduced impact on operator of repetitive motion operations (Seriously, 10 hours a day of hand clamping?)

By using an automatic clamping system and multiple part holding fixtures, the operator is able to work on higher value added tasks while the machine runs  multiple parts. And because the clamping and pressure is more consistent, so is your process.  This also frees up your higher skilled individuals  to work on other things,  allowing a lower skilled individual to load and unload the operation, while increasing consistency of workholding accuracy and force applied.

Now, you might not need a reminder about  how the times tables can work in your favor by loading 16 parts at once, I get that.

And maybe your equipment only does machine one piece at a time.

But, my challenge to you remains-

  • Don’t go to IMTS looking for what you already know.
  • Don’t go just to speak with the people that you already know.
  • Go to find something that will make a marked difference in your quality, productivity, or ability to use your talent more effectively.

Instead, ahead of time, ask yourself what would be a delightful thing to discover that could really move the needle in your shop operations and quality. While at IMTS keep your eyes open, and ask EVERYBODY if they have seen what it is that you are hoping to discover.

Yes, of course you need to see your stalwart suppliers.

But I ask you, are they the ones that will give you that unexpected new insight to reduce your operations time or tasks by 50-90%?

(I’m guessing that they have already given you their best advice and counsel.)

Or will it be something new, unexpected, and unanticipated?

By all means, make your plans of what booths to visit and who to talk to. 

That’s why most folks go to shows like IMTS.

But the REALLY BIG PAYOFF will come if you find that unanticipated, as yet undiscovered technology that will yield incredible benefits for your operations.

Success at a show like IMTS is not about making a plan- that’s a given. In my mind, it is about discovering your next surprising insight into doing what you do better- with fewer inputs and more consistently.

Think differently this trip. Discovery mode rather than checklist mode. Prepare by asking yourself “What can I find here that will…?”

And if you must have a checklist, well, try this checklist for checklists from  Projectcheck.org

You can see the PAWS workholding system at this year’s IMTS  at Booth W-2138

 


OSHA’s Top Ten Most Frequently Cited Standards- FY 2015

July 22, 2016

OSHA Penalties increased 78% August 1, 2016.

Think of your efforts here as an investment in "Penalty Prevention."

Think of your efforts here as an investment in “Penalty Prevention.”

The following is a list of the top 10 most frequently cited standards following inspections of worksites by federal OSHA for Fiscal Year 2015.

  1. 1926.501 – Fall Protection (C)
  2. 1910.1200 – Hazard Communication
  3. 1926.451 – Scaffolding (C)
  4. 1910.134 – Respiratory Protection
  5. 1910.147 – Lockout/Tagout
  6. 1910.178 – Powered Industrial Trucks
  7. 1926.1053 – Ladders (C)
  8. 1910.305 – Electrical, Wiring Methods
  9. 1910.212 – Machine Guarding
  10. 1910.303 – Electrical, General Requirements

Note,  the standards that are numbered 1926.XXX – Numbers 1. Fall protection, 3. Scaffolding, and 7. Ladders, are Construction industry, rather than General Industry. Nevertheless, Fall Protection and Ladders are relevant in our manufacturing shops as well. Source: Top Ten Standards 2015

In our work with shops involved in OSHA inspections, we have learned that failure to have documented training and evidence is the more likely to be the root cause of the citation. You must train and you must be able to provide documentary evidence of the training.

A savvy management will take steps in their shops to find and fix recognized hazards addressed in these and other standards before OSHA shows up.

 

Action Steps:

  1. Electrical-On your next walk around the shop, look for outlets and power boxes that are not in good condition and schedule their repair ASAP. If you can see wiring or damage- that is likely a violation.
  2. Machine GuardingThis is a particular area of OSHA emphasis. Are all provided guards in place, or are they being removed or defeated? Each instance would be a violation.
  3. Lockout/TagoutThis too is an OSHA emphasis and on their regulatory agenda for review. Now would be a good time to review that all affected employees have been trained. That evidence exists of that training. And that you have audited  to assure performance. (If I went into your shop and saw a machine undergoing a major changeover, would I find it locked out?)

Photocredit

 

 


Thinking Precision, Thinking Big- Keystone Threaded Products

June 9, 2016

The Team at Keystone Threaded Products shows us that “Precision” doesn’t necessarily mean “Tiny” as they thread the ends of some 20 foot long, 10 inch stainless steel bars for a Metalworking press. The thread is a 10-1/4″ : 4 UNJ RH applied to  each end of the  3 and a half ton bar.

@0 feet long two ends to thread, 3 and a half tons of precision.

20 feet long, two ends to thread, 3 and a half tons of precision.

At Keystone, they roll the thread form onto the material which makes for a stronger thread. Alignment and following the process is critical to assure a good thread.

Thread rolling dies create the thread form on the workpiece.

Thread rolls create the thread form on the work piece.

Multiple passes are needed to build the thread up to the proper dimensions.

HAldf a million pounds of pressure are imparted on the rolls to plastically move the steel of the bar into the thread form. Read the gage.

Half a million pounds of pressure are imparted on the rolls to plastically move the steel of the bar into the thread form. Read the gage.

Obviously it takes knowledge, skills, and experience to apply half  million pounds to produce precision work.

Rich says that he's rolled larger bars, but the confidence that skills and experience and a great team to work with make precision manufacturing a great career.

Rich says that he’s rolled larger bars, but  skills and experience and a great team to work with  create the can do spirit that makes precision manufacturing a great career.

Here’s another look at a finished bar. Precision does not necessarily mean tiny!

Just another point of view so you can see the size of the work.

Just another point of view so you can see the size of the work.

 

Thanks to Betsy Minnick and the Team at PMPA member Keystone Threaded Products for showing us that “Precision” is not a synonym for “Tiny.”