"Wear It's At"
Volume 1 Issue 11
Tuesday, December 14, 1999
In This Issue
2. Postle Announces New Alloy
3. Cracking Problem in Dissimilar Weld Joint
4. A Little Humor
I would like to extend a warm welcome all new subscribers to the "Wear It's At" newsletter. We are very glad to have you aboard.
2. Postle Industries Announces New Alloy
Postle Industries, Cleveland, Oho ( http://www.postle.com ) has announced a new tool steel alloy called Postalloy 2868-SPL. This is an abrasion resistant, gas shielded, high speed tool steel wire designed for application where edge retention is a primary concern. Weld Deposits are martensitic with micro carbides evenly dispersed throughout the deposit. These properties create a fracture resistant cutting edge even under high compressive loads. Postalloy
2868-SPL is alloyed with Molybdenum and Tungsten for superior high temperature hot hardness. This property helps maintain a sharp edge under localized high heat conditions created by extreme friction. Applications include all types of knives, shearing punches, sheer blades and cutting tools. Typical hardness is 60 - 65 Rc. Good Hot Hardness up to 1150ºF. This alloy is limited to 2 to 3 Layers and is non-machineable . It is available in ether 1/16" and .045" diameters.
3. Cracking Problem in Dissimilar Weld Joint
Dissimilar weld joints are not always easy as they sometimes appear. I recently had the opportunity to investigate a failed component with a dissimilar weld joint. There were a number of reasons for the failure, but the main problem focused around a dissimilar weld joint of a (high carbon) rail section and a 304 stainless structural member. A recommendation of a 308 or 309 stainless electrode was made and the company followed all the preheat and interpass temperature rules. Almost immediately
upon cooling, a crack developed longitudinally along the length of the weld. After cross sectioning and observing under the microscope it was determined that the weld deposit was fully austenitic. There was no doubt that the weld failed because of this.
But how did it happen?
Well, while 309 is a good alloy in some dissimilar weld joints it was not good enough for this joint because of the high carbon rail. High carbon in a stainless deposit has a bad habit of causing a reduction in Ferrite. What is Ferrite? Stainless electrodes are designed with a small amount of Ferrite in the deposit. It is magnetic and can be detected in most austenitic stainless deposits, such as a 308 r 309. Ferrite can be thought of as a garbage collector for impurities and carbon.
Actually it offsets the bad effects of carbon. In this case the high carbon rail was simply too overwhelming for the 309 deposit, which normally contains about 15 Ferrite. The carbon drove the Ferrite down to zero, thereby rendering it fully austenitic. Fully austenitic welds are very crack sensitive. Thus the failure.
And what could have been done to avoid this failure?
Well, a 312 Stainless electrode would have probably had enough Ferrite to handle the high carbon. 312 typically has about a 25 Ferrite Number. With careful buttering of all sides of the weld joint, prior to filling the joint would have ensured its success.
This problem is just not confined to joints. Overlays are also affected in the same way. Dilution, penetration and welding parameters all play a significant roll in the outcome of a successful stainless overlay, but that is a subject for another newsletter.
3. A Little Humor
On the lighter side, I thought you might be interested in this little piece of wisdom.
The Buffalo Theory: Why You Should Drink More Beer
A herd of buffalo can move only as fast as the slowest buffalo, and when the herd is hunted, it is the slowest and weakest ones that are killed first. This natural selection is good for the herd as a whole, because the general speed and health of the whole group keeps improving by the regular killing of its weakest members. In much the same way the human brain can only operate as fast as the slowest brain cells. Excessive intake of alcohol, we all know, kills off brain cells, but naturally
it attacks the slowest and weakest brain cells first. In this way, regular consumption of beer eliminates the weaker brain cells,
constantly making the brain a faster and more efficient machine.
The results of this in-depth epidemiological study verify and validate the causal link between all-weekend parties and engineering performance. It also explains why, after a few short years of leaving university and getting married, most engineers cannot keep up with the performance of new graduates. Only those few who stick to the strict regimen of voracious alcoholic consumption can maintain the intellectual levels they achieved during their university years.
So this is a call to arms. As our country is losing its technological edge we should not shudder in our homes. Get back into the bars! Quaff that pint! Your company and your country need you to be at your peak, and you shouldn't deny yourself the career you could have.
Be all that you can be.
Kristen K. Brewer, Ph.D.
Department of Psychology
Bohler Thyssen Welding USA Inc. (http://www.btwusa.com) A single source supplier of practical high quality electrodes, wires and fluxes.
Postle Industries Inc.( http://www.postle.com ) Postle offers a complete range of hardface welding alloys to protect equipment from all types of wear.
Sure Alloy Steel Corporation (http://www.surealloy.com) Wear Control - Design, engineering, and fabrication with over 40 years experience.