In North America, the AISI/SAE steel grade nomenclature system is widely used.
In this system, 4 numeric digits (XXXX) describe the base grade. The first two digits tell you whether the steel is a carbon or alloy grade.
If the first digit is any number other than a “1”, that steel is an alloy steel. We’ll discuss alloy steels in a later post.
If the first digit is a ” 1 “, the steel is a carbon grade. 10XX is the template for the plain carbon steels. We’ll explain those last two digits at the end of our post. (Exception: if the second digit is a “3”- then its one of the alloy manganese 13XX grades- grades we don’t encounter very often these days.)
If the second digit is a “1”, the steel is a resulfurized carbon steel. 11XX. Guess how many “extra” elements were added to the grade? If you guessed 1- thats right. Sulfur is the one element added to promote machinability in the 11XX grades of steel.
If the second digit is a “2”, the steel is called a rephosphorized and resulfurized steel. Both sulfur and phosphorus,-2 elements- are added to make these free machining steels. 1215 and 12 L14 are the grades we mostly see today. (As many of you know, that “L” as an infix tells us that there is a lead addition in the 12L14 steel.)
If the second digit is a “5” the grade is a high manganese carbon steel. Grades 1524, and 1541 come to mind as the principal 15XX grades seen by our industry.
A “B” infix tells us that the steel has been treated with boron. This makes it especially adept at being heat treated. 15B21 is used to make fasteners that are heat treated.
So, now that you know what the first 2 digits mean in a US grade designation for steel, what about the last two?
The last 2 digits in the grade are the mean or average carbon content of the steel. In weight percent.
So grade 1018, is a plain carbon steel, 0.18% average carbon content.
1144 is a resulfurized 0.44% average carbon content steel for higher strength and machining.
And 1215, well- 1215 is a resulfurized, rephosphorized 0.09 max weight % carbon steel for machining. 0.09% max!
Don’t you just love exceptions?
Author: Miles Free
This 4 minute video was produced by a British high school in cooperation with a film-maker and local police authorities.
The fact that the cars are driving on the left helps it make more of an impression on those of us who drive on the right side of the road here in North America.
This is a graphic, but essential reminder to all of us to reconsider our choices of distractions while behind the wheel. Or operating machinery and equipment.
Choices have consequences.
Do we really need to answer that cellphone, right now?
Do we really need to send that text message? Really?
Please don’t answer these questions until after you watch the video.
Then, by all means, please share your opinion.
Actions always speak louder than words.
Here’s what GE’s CEO, Jeffrey Immelt, told the Detroit Press Club back in June:
“We would do much better to observe the example of China. they’ve been growing fast because they invest in technology and they make things. They have no intention of letting up in manufacturing in order to evolve into a service economy.”
This is the same GE that closed lighting manufacturing plants here in Ohio.
Who decided to close our manufacturing plants here in Ohio, Jeff?
Who decided not to reinvest money here in Ohio to “make things?”
Who decided that absorbing say, $500 000 000 in restructuring costs to close a small number of plants is better than spending, $40-45 000 000 in reinvestment to make new CFL technology light bulbs here in the USA?
Where do you suppose US workers might get those “green manufacturing jobs” if you’re not building the factories to make light bulbs here in the US?
So before you reach for that that “green” CFL lightbulb with the GE logo on it, remember the hypocrisy of Jeffrey Immelt, “20 % of US jobs should be manufacturing jobs,” while closing plants and failing to reinvest to make these “green products” here in the US.
When you see that ad on TV from GE to “Buy Green,” what they are really saying is “BUY FROM CHINA.”
Note to Jeff Immelt: US labor productivity is among the highest in the world. Our factories are subject to stringent regulations to assure that we protect the environment. Why would you not want to make this staple “green” product here?
Just wondering.
And how to minimize them.
Upon heating, steel parts change volume as they change crystal structure (I’ll spare you the technical terms and details). When these heated parts are quenched, their internal crystal structure changes again, and that volume change is not necessarily sufficient to offset the change upon heating. This change of volume can cause dimensional distortion. The rule of thumb that I have used for medium carbon alloy steels is to expect a change in linear dimensions of about 0.125% maximum. That is, one eighth of a percent of the linear dimensions could be the change encountered from heat treatment and quench. It generally is less, but 0.125% gives me a rule of thumb to evaluate capability to hold dimensions after heat treat. What rule of thumb do you use to estimate part growth as a result of heat treat?
Warpage or shape distortion as a result of heat treat is different because it is usually a result of process and design issues rather than the expected phase changes of the material.
Here are 8 reasons steel parts can warp upon quench and tempering:
- Rapid heating.
- Overheating.
- Non-uniform heating.
- Non-uniform cooling.
- Non-uniform agitation.
- Water contamination in oil.
- Large changes of mass and section.
- Asymmetric features.
Rapid heating can cause stresses to develop in parts due to excessive temperature gradients. Overheating similarly lowers mechanical properties, potentially leading to parts sagging or creeping depending on orientation in the furnace. Non-uniform heating also creates differences in properties within the parts as well as leading to incomplete transformation products or hybrid structures upon quenching. Non-uniform cooling allows unbalanced stresses to develop during the quench, as does non-uniform agitation of quench medium. Often non-uniform heating or cooling result from the way parts are stacked or piled in the basket or on the belt such that gradients of temperture are created. Water contamination in oil. This is difficult to figure out, but in addition to warped parts, inconsistent hardness readings between parts or on the same part are a sign of this. Parts with large section changes or that have asymmetric features are also more likely to warp than parts with balanced and uniformly distributed mass, regardless of process control.
Choosing steels with higher hardenability (alloys rather than plain carbon steels), finer grain size, and paying attention to the details of loading, time at temperature, and quenchant delivery are all steps that can minimize warpage distortion, even when part design is less than optimum.
For the Precision Machining Industry, a strong case can be made that our sales are recovering.
PMPA’s Index of Sales of Precision Machined Products rose to 82, just one point below January’s high of 83.
This is an 11 percent rise in the sales index compared to August, and documents the 95 reporting companies in aggregate are showing a 26% recovery in sales compared to the 2009 year low of 65 in May, 2009.
Fifty-two percent (52%) of our particpants reported double digit sales increases in September.
The outlook for sales in the short term has stabilized, with only 19% of respondents expecting a decline in sales overthe next three months.
For almost a year, Tom Brady sat on the sidelines, working on his recovery. In the sixth week of this new season, he set an NFL record for touchdown passes in one quarter. What a comeback!
The Precision Machining Industry is still on the field despite being hamstrung last fall by the economic meltdown. Our performance continues to be 100% on time and zero ppm. We just need more time on the field. Comeback in progress!
See the full report.
We have open time on our machines. How can we help you?
So much for Change…
The Associated Press reports that “the Obama administration on Thursday declined to name China as a country that is manipulating its currency to gain unfair trade advantages.”
“The Treasury Department did say it has “serious concerns” about a lack of flexibility in the value of China’s currency against other currencies, and the country’s rapid accumulation of foreign exchange reserves including U.S. dollars.”
“The administration’s decision came in a report the Treasury is required to submit to Congress twice a year. Based on a 1988 law, the administration must designate countries judged to be manipulating their currencies to boost their exports to the United States or make U.S. products more expensive in overseas markets.”
Hmmmm…
Obama promised to take a tougher stance against China on trade issues
during his campaign for the White House last year. He pledged to take a tougher approach to China than the Bush administration did. He said the failure by Bush and Paulson to label China a currency manipulator was “unacceptable,” and he endorsed legislation to let US companies seek import duties to compensate for the advantage an undervalued currency gives their Chinese competitors.
But in both the April and the current October report, the administration declined to name China a currency manipulator.
Here’s the story from the AP: http://tinyurl.com/ygw5afp
Of course prices have risen.
We finally are back to manufacturing expansion following 18 months of contraction in the manufacturing sector. Supply chain pretty much destocked. Low inventories. Domestic mills operating at 47% of capacity. Global influences on scrap and raw materials. You need a program to follow this game. We’re providing you one with this edition of PMPA’s Material Impacts Report.
The prices of the raw materials that we track have continued to rise with double digit percentage gains over January with one exception: China Coke. Year over year, all prices are still down significantly.
- Aluminum: Up 18.65% from January
- Copper: Up 86.67% from January.
- Nickel: Up 27% from May, up 4.44 % since January.
- Steel Busheling: Up 26.67% from January.
- China Coke: Down 2.73% from January.
We have seen price increase announcements in addition to surcharge increases since our last report.
Details in PMPA’s Material Impacts Report.
(OSHA) is initiating a national emphasis program (NEP) on recordkeeping to assess the accuracy of injury and illness data recorded by employers.
This new NEP will involve inspecting occupational injury and illness records prepared by businesses and appropriately enforcing regulatory requirements when employers are found to be under-recording injuries and illnesses.
The NEP will focus on selected industries with high injury and illness rates. The inspections include a records review, employee interviews, and a limited safety and health inspection of the workplace.
Now is probably a good time to do a self audit to assure your records are in order.
If you are the lucky recipient of one of these visits, how did it go?
On Friday, October 9, 2009 PMPA’s Director of Marketing and Communications, Robert Kiener, testified before the Senate Banking Subcommittee on how unavailability of credit impacts the precision machining industry and small manufacturers.
NPR radio story: http://marketplace.publicradio.org/display/web/2009/10/09/am-manufacturer-credit/
Buffalo News coverage: http://www.buffalonews.com/145/story/823625.html
Senate Banking Committee Web Site: http://banking.senate.gov/public/
CSPAN Video coverage: (Rob Kiener’s testimony begins at 12:03 into this video.) http://www.c-spanvideo.org/program/id/213648
You can find the presented testimony on the PMPA Website here.
As machinists, we are used to handling materials in the bulk world.
As machinists, our ease in obtaining productivity is influenced by the microscopic world of phases, microstructures, and chemistry.
Underneath this microscopic world lies the world of molecules and atoms themselves.
This is the chemical formula for pentacene. It is used in organic thin film transistors.
Recently researchers from IBM research team in Zurich used an atomic force microscope to capture an image of a single molecule of this substance.
This image of a single molecule shows the five rings of six carbon atoms and suggests the hydrogen bonds along the edges.
The precision needed to resolve at this atomic level requires both extremely high vacuum and frighteningly cryogenic temperatures. And you thought you had temperature control issues in your metrology lab.
Our industry will not be at this atomic-level nanoscale any time soon, at least not for our production processes.
We hope this glimpse of what makes up our material world from the frontiers of science gives you a better appreciation for the work of all the chemists, metallurgists and engineers in the supply chain that produce our raw materials, tools, and metalworking fluids. For all of history, scientists have struggled to make sense of their observations, develop theory, structure and formulas that made sense. This IBM image confirms that we’re on the right track.
Full story care of BBC .