Cutting fluids contribute 3 ways to our machining processes.
1) They provide lubrication. Lubrication reduces friction. Reduced friction means less heat. Less heat means better dimensional capability and faster cycle times are possible.
2) They help remove heat. Even though they provide lubrication, some frictional heat is produced. So the ability to capture, and remove heat is an important property of metalworking fluids.
3) They prevent the welding of workpiece material onto the tool.Pressure of the workpiece against the tool and the heat and temperatures involved contribute to the buildup of workpiece material on the tool. Cutting fluids provide an antiweld film to discourage this.
For a thorough tutorial on the subject of cutting fluids, check out Barbara Donohue’s article on this subject in Today’s Machining World click this link.
Photo credit.
Author: Miles Free
Here are 5 reasons to anneal steel.
To alter the grain structure;
To develop formability;
To improve machinability;
To modify mechanical properties;
To relieve residual stresses.
The annealing process is a combination of a heating cycle, a holding period or “soak” at temperature, and a controlled cooling cycle. Atmospheric controls are generally used to protect the steel from oxidation.
The temperatures used and the cooling rates are carefully selected to correspond with each steel grade’s chemical composition in order to produce the results desired.
For bar steels used in our precision machining shops, there are three kinds of annealing that may be encountered:
Subcritical Anneal
Solution Anneal
Spheroidize Anneal
Subcritical Anneal
A subcritical anneal is the metallurgical name for what is termed a process anneal or stress relief anneal in North American commercial practice. It consists of heating the steel to a temperature close, but below, the steel’s lower critical temperature or Ac1. This simple anneal reduces stress and hardness in the material and makes modest changes in its microstructure. Steel mills often employ this to improve cold shearing or cold forming. This is sometimes used between cold forming operations to reduce hardness.
Solution Anneal
Solution annealing is referred to in commercial practice as ‘LP Anneal’ or Lamellar Pearlite Anneal. Lamellar pearlite is the microstructure that predominates when doing this kind of anneal. The cycle for this anneal involves heating the material above the critical range (Ac3) and holding the steel (soaking) at that temperature for a length of time followed by slow cooling below the critical range (Ar1) temperature. This cycle reduces hardness and reprecipitates the carbide phase as lamellar pearlite. Controlling the time and temperature gives the metallurgist a means to alter the resulting lamellar pearlite structure, and refine the ferritic (as rolled) grain size.
LP anneals are usually applied to medium carbon (0.40-0.65 weight %) plain carbon and alloy steels for precision machining in order to reduce hardness and improve machinability.
Spheroidize Anneal
Spheroidize annealing is the term that describes a thermal process which results in a globular or spheroidal type of carbide after heating and cooling. There are several types of spheroidize cycles which we will write about in a future post.
Spheroidized microstructures are desireable for machinability and improved surface finish when machining higher carbon steels. Spheroidized microstructures are also preferred when the steel is to be severely cold worked: cold extruded, cold upsetting, or bent. Most bearing steels are first spheroidize annealed prior to machining.
Lamellar Pearlite photo
Spheroidized Photo
In one word: “demographics.”
Here are five reasons from Shirley A. Engelhardt, President and Founder of ORTHOWORLD Inc., a strategic services firm solely focused in orthopaedics, and Founder and Managing Member of Knowledge Ventures, LLC, an early stage musculoskeletal investment fund.
5 Reasons:
1) We’re getting older.
2) We’re becoming more demanding, both mentally and physically.
3) We’re not taking such good care of our bodies, even at a young age.
4) We’re continuing to believe, at 40 or 50, that we’re still 25.
5) We’re prone to falls, accidents and other foibles of daily living (and always will be).
Shirley Englehardt has plenty of facts and data to back that up, and if you are in (or thinking about entering) the medical orthopedic parts market, the article at the link below will be Gold for you.
Orthoworld article.
Photocredit:
Thanks to Jeff Remaley at Orthoworld for sharing the great article.
All of the crucial raw materials that we track are up double and triple digits compared to same month last year. Material cost component of our manufactured products is up, and holding in the short term, but subject to variability of global forces as well as local and market demands.
See the full report here.
Here are 5 benefits of cold working of steels that make a difference to your machining operations.
- Increased strength
- Improved surface finish
- Controlled dimensional tolerance and concentricity
- Improved straightness
- Improved machinability.
Increased Strength
It is widely known that cold working strain changes the properties of most metals. When as rolled steel bars are cold worked by cold drawing through a die, a significant increase in yield and tensile strength is obtained. At the same time, The reduction in area and percent elongation are reduced.
The graph below shows the effect of cold drawing on the tensile properties of 1 inch round diameter steel bars.
There are two important lessons in this graph: 1) As strength properties increase, ductility measures decrease; 2) Up to about 15% cold reduction, yield strength increases at a much greater rate than tensile strength. The first 5% of cold work results in the greatest increase in strength.
Improved Surface Finish
Hot rolled steel bars are finished at high temperatures, and so the surface has a hard abrasive scale made up of various oxides of Iron. This scale is hard and abrasive ranging from 270 – 1030 DPH (Vickers) microhardness depending on the type of oxide (s) formed. In order to cold draw the bars, cold finshers typically remove the sacle by shot blasting or acid pickling. This results in the removal of the hard abrasive scale.
By pulling the bars though the die, the surface finish is also improved, with Cold Drawn bars typically running 50 microinches maximum and modern equipment typically working at 25-30 micro inches. Compare this to a roughness height of 250 or more for hot rolled bars.
Controlled Dimensions
Because the bars are cold reduced at room temperature by pulling through an oil lubricated die, the dimensional conformance of the steel is much more easily controlled. Typical tolerances for cold drawn 1 ” low carbon steel bars are +0.000″/ – 0.002″. this compares favorably to +/- 0.010 for hot rolled steel of the same chemistry and diameter. Concentricity is improved by the cold drawing operation.
Improved Straightness
The straightness of hot roll bars is generally 1/4″ max deviation in any 5 foot length. In cold drawn bars, depending on size and grade this deviation can be held to as little as 1/16″ in 10 feet.
Please see our post here for a more complete discussion of bar straightness.
Improved Machinability
Improved machinability is really the synergistic result of all of the above improvements made by cold work (cold drawing).
Higher yield to tensile ratio means the tool has less work to do to move the metal in the workpiece to its ultimate strength when it will separate as a chip. This translates into less force on the tool and greater tool life and productivity. Not putting hard abrasive scale and oxides into your cutting fluids nor on to your tool because the bar has been cleaned results in longer uptime and less maintenance for tools, workholding, and machines. More tightly controlled dimensions and concentricity means that the bars can be run at higher speeds without creating harmful vibrations and chatter. Finer tolerances can be held by your equipment when bars are sized properly going into the machine. Similarly, improved straightness results in less runout and permits higher speeds in production.
Bottom line: Hot roll bars may be cheaper by the pound, but machining them will cost your company a lot more because they lack the benefits of cold drawing:
Graph and data: AISI Cold Finished Steel Bar Handbook, 1968. (Out of print)
The new sheriff in town continues to make enforcement OSHA’s top priority.
Here are 12 good ideas from American Safety and Health Management Consultants,Inc. to help you and your team avoid the new sheriff’s thirst for fines and penalties.
- Make safety a key priority. Really.
- Be ready for an inspection. Do not be caught off guard. Even if you aren’t there- have a plan.
- Review all written programs and update where necessary.
- Ensure that all employees receive the OSHA required training, document the training and follow up to assure they “got it.”
- Inspect your facility, or have a safety professional do it for you.
- Correct any and all violations as soon as practical.
- Follow up on employee safety related concerns.
- Establish supervisor responsibilities and hold them accountable.
- Know what to do in case of an OSHA inspection. Have assigned personnel to handle this.
- Audit your safety programs at least annually and develop a safety action calendar for each new year.
- Enforce you company safety policies fairly and consistently.
- Recognize and reward employees for good safety performance.
Photo of eggs.
(Actually, they aren’t really eggs. And fining employers isn’t really about safety.)
The topic of heat treatment is one part science and often it seems, two parts smoke and one part black magic.
If the definition of heat treating that you have is close to the definition of steel that my neighbor has: “It’s dirty, it’s heavy, a magnet sticks to it and its made in fire,” then maybe you too could use an assist in figuring out how to communicate successfully with your heat treater.
We were pleased to see an article entitled ” How to Best Communicate Your Needs to the Heat Treater” co- written by PMPA Technical Member Nevada Heat Treating Vice President Patrick McKenna.
It was feature article in the April 2010 print edition of Industrial Heating magazine.
I predict that you will add it to your file of ‘articles you can use’ for sensemaking in this ever more complicated technical world that we harness for our customers.
You can read it at the link above.
Or contact Patrick at Nevada Heat Treating or Miles Free at PMPA and we’ll email you the article as a .pdf.
It will really be worth your time before you send that next batch of parts out to take a ride through the Fire…
The topic of heat treatment is one part science and often it seems, two parts smoke and one part black magic.
If the definition of heat treating that you have is close to the definition of steel that my neighbor has: “It’s dirty, it’s heavy, a magnet sticks to it and its made in fire,” then maybe you too could use an assist in figuring out how to communicate successfully with your heat treater.
We were pleased to see an article entitled ” How to Best Communicate Your Needs to the Heat Treater” co- written by PMPA Technical Member Nevada Heat Treating Vice President Patrick McKenna.
It was feature article in the April 2010 print edition of Industrial Heating magazine.
I predict that you will add it to your file of ‘articles you can use’ for sensemaking in this ever more complicated technical world that we harness for our customers.
You can read it at the link above.
Or contact Patrick at Nevada Heat Treating or Miles Free at PMPA and we’ll email you the article as a .pdf.
It will really be worth your time before you send that next batch of parts out to take a ride through the Fire…
The American Trucking Associations’ advance seasonally adjusted (SA) For-Hire Truck Tonnage Index increased for the sixth time in the last seven months, gaining another 0.9 percent in April. This followed a 0.4 percent increase in March.
The latest improvement put the SA index at 110.2 (2000=100), which is the highest level since September 2008.
Over the last seven months, the tonnage index grew a total of 6.5 percent.
We add this indicator to a growing list of indicators that show that this recovery has “legs” and we are now in what we have been calling “a new normal.”
Compared with April 2009, SA tonnage surged 9.4 percent, which was the fifth consecutive year-over-year gain and the largest increase since January 2005.
Year-to-date, tonnage is up 6 percent compared with the same period in 2009.
ATA Chief Economist Bob Costello said that the latest tonnage reading fits with a sustained economic recovery. “Truck tonnage volumes continue to improve at a solid, yet sustainable, rate. Tonnage is being boosted by robust manufacturing output and stronger retail sales.” (emphasis ours!)
Bottom Line: Trucking serves as a barometer of the U.S. economy, representing 68 percent of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods. The latest ATA numbers confirm our manufacturing markets continue their recovery.
The American Trucking Associations is the largest national trade association for the trucking industry.
Read the full article here.
And lets hope that precision manufacturing keeps on truckin’..
What do you think? Have your shipments increased as reflected in the ATA report?
R. Crumb Keep On Truckin sticker
What’s it gonna be? Feed or Speed?
For a given production rate of metal removal, better tool life is obtained by using heavy feed and low speed.
Sorry, Flash.
Less horsepower per cubic inch of metal removal is required for heavier feeds (see the diagonal lines on the chart below.)
This also means fewer revolutions of the work (or tool) to get the job done.
This reduces wear on the tool.
Slower speeds results in less friction, less heat.
Surface finish declines as feed rate increases, but it is usually acceptable until a critical rate is reached (see the numbers along the curves above- they are the values for surface finish in RMS).
In steels, grades that are rephosphorized and renitrogenized can take heavier feeds than steels that are not. (That’s why I’m showing C1213 at 0.07-0.012 phosphorous compared to C1215 at 0.04-0.09 Phos.)
Here is another graph to illustrate the effect of feed rate and surface finish.
As feed rate increases bottom (horizontal) axis so does surface roughness (vertical) axis measured in RMS.
The contract shop industry remains seduced by the siren song of speed to reduce cycle time.
Perhaps the proper use of the feed approach can make you some new friends among your customers…
These data are based on HSS tools. Obviously using carbide one needs to have sufficient speed to take advantage of the carbide.
Bottom Line: Increased feed rather than speed can result in longer tool life and less problems than increasing speed and dealing with the heat that results.
What is your approach? Speed for cycle time? Or feed for minimizing HP for removal and longer tool life and fewer problems?
Feed or speed? What’s it gonna be?
Photo credits:
The Flash: http://www.ramasscreen.com/wp-content/uploads/2009/07/Flash-Adam-Strange-Aquaman.JPG
The Incredible Hulk: http://keneller.typepad.com/photos/uncategorized/2008/06/14/lou_ferrigno_as_incredible_hulk.jpg
Playstations’ genius image of Finger of the Hulk beckoning link: http://www.sparehed.com/wp-content/uploads/2007/03/ad-hulk-playstation-2-2006.jpg
