Triloy  TM is a product of Kennametal Inc

Following is an interview with former Tricon Metals metallurgist Grant Murphy about Triloy TM shafting.

Q:  Triloy TM is listed as an exclusive composition, what does that mean?
A:  We start out with a modified 4340 alloy bar which has slightly higher carbon and nickel levels.  It is then injected with calcium silicate during the melt process to control the shape of manganese-sulfur inclusions.  If the other suppliers do not list this treatment, the extra steps have not been taken.  Compare carefully.

Q:  Aren’t all 4340 shafts are the same?
A:  Definitely not.  4340 can be many different strengths depending on the tempering and heat treatment.  When you buy Triloy TM, it has always been heat treated the exact same way, for extremely consistent results.   You can obtain 4340 anywhere from annealed bar which is soft (140 BHN) and low in strength, to 600 BHN and unless you specify what hardness you want, you cannot be certain of what you will be getting.  Triloy TM will always be from 285 to 341 BHN, every time.

Q:  Do we add sulfur to the steel to make it easier to machine?
A:  Lower priced 4340 steels have sulfur added to improve machinability, however the more sulfur you add, the more brittle the steel becomes.  Sulfur has a string-shaped molecule.  When they line up, they form inclusions and create a high fracture potential, meaning possible failure is quite high.

Q:  Triloy TM is listed as triple heat-treated, what additional steps are taken?
A:  After the bar is rolled to size, it is heated to about 1600° F, and quenched in oil, to temper it.  Going through that process sometimes causes it to distort, requiring you to straighten the shaft.   It is straightened by cold working it, which induces stress into the metal.  It is then tempered again to stress relieve it.  Triloy TM is therefore quenched, tempered and stress relieved.  Since it removes the internal stresses, this makes the shaft not distort during machining.

Q: Are the bars rolled or forged?
A:  Steel mills will roll bars up to about 10” diameter.  Above that, or for a step shaft, they are made from a forging.  The equipment available at the rolling mill in the US determines the sizes available.

Q:  Can only certain areas be induction hardened for wear resistance on the shaft?
A:  Absolutely.  That is a common application for bearing areas or for gudgeon pins, which attach screw conveyors together.

Q:  What are the advantages to Triloy TM over less expensive steels?
A:  Greater strength and higher harden-ability.  Less expensive 1050 steel can also be surface or casehardened.  Triloy TM will harden much deeper in cross section for more wear resistance.  This is more important the greater the diameter of the bar.

Q:  Increased machine cutting speeds of 20% to 40% can be expected.  Why is that?
A:  The harder the steel, the tougher the machinability and cutting speeds slow down.  By controlling the sulfur shapes, it acts to lubricate the cutting tools for faster stock removal.  Triloy TM not only increases your cutting speeds, it maintains high strength without becoming brittle.

Q:  What is the straightness tolerance and finishes available on Triloy TM?
A:  Straightness is 0.002” TIR.  We stock it from 1” through 6” in 1/16” increments.   Available in standard hot rolled finish.

Q:  Is Triloy TM pin stock the same as Triloy TM shaft material?
A:  The pin stock is the same chemistry, however, it is de-sulfurized and heat-treated to 369 to 430 BHN.  This eliminates the sulfur, which could cause cracking potential in the high hardness.    The surface can then be induction hardened ½” or deeper up to 700 BHN, for a very durable, wear resistant surface.

Q:  What does vacuum de-gassed mean?
A:  When steel is melted in the air it picks up hydrogen and oxygen from the atmosphere.  Adding aluminum or silicon can eliminate oxygen.  The only way to get rid of hydrogen is to insert the molten steel into a vacuum chamber, which de-gasses or removes both the oxygen and hydrogen.  Oxygen in the steel causes voids in the steel, while hydrogen causes internal cracks in the steel resulting in a future failure.

Q:  What about resistance of the shaft to bending and breaking with Triloy TM?
A:  The higher the strength, the less susceptible it is to bending.  Triloy TM has 160,000 Psi tensile strength.

Q:  Why is this material specified in the pulp & paper industry?
A:  For the excellent strength and fatigue resistance.  Reel spool journals are a good example because they are constantly turning and the higher the strength, the longer the product will last.

Q:  Is Triloy TM TG&P available in metric sizes?
A:  Yes.  The shafts are centerless ground to the dimensions required, metric or standard.  We have a few metric sizes in stock.  Please advise your requirements.

Q:  What about a step down shaft with a 6” diameter shaft that has one area that is 14” diameter?
A:  By using a step down forging to your specifications, it is more economical.  Because they are created for your unique application, there is a longer lead time.  The steel used in the forging is still the same Triloy TM alloy.