![]() ![]() It’s the pivot point between the two units and because if this it receives a great deal of wear and tear making eventual repair or replacement necessary.įailure of the king pin means that the steering system will not work properly, and improperly working steering systems can be dangerous. The receiving piece on the truck is a horse-shoe shaped platform attached to the tractor. This is a pin which connects the trailer to the fifth-wheel. Smith Co., we offer a complete range of king pin replacement, king pin servicing, and king pin repair services.Įvery semi-truck or trailer depends on one small piece of equipment for its connection. There would not be much point in getting overly enthusiastic with the tempering.At Harry J. That temperature is not high enough to relieve the brittleness of an unsuitable core steel.Īfter all, the purpose of case hardening is to provide a very hard, wear resisting surface with a tough core. The only tempering, if any, of a case hardened part that is normally done is done at a low temperature, to provide a small measure of stress relief. The point remains, the steel has to be quenched from above the critical temperature, and if the core steel is then too hard, that's it-it's too hard. That will do the hardening, and then it's a matter of tempering as needed.Yes, of course, and I also didn't state that the long time deal is with the steel surrounded by a carbon providing medium, protected from atmospheric oxygen, or any of the other niceties or necessities of the case hardening process. The hardening is after that, ideally right from the case process into the quench, as I understand it. I would think this job needs to be professionally case hardened.Ī steel like this results in a hard surface (for wear) and a tough core for strength.Īctually that long time deal is for the driving in of the carbon. Atlas call their version Impacto, but 8620 is a more common designation I think. AISI/SAE 8620 which is suitable for case hardening. My old Atlas Steels handbook recommends an alloy steel (not a toolsteel) for kingpins. Silver steel is supplied unhardened and can be machined fairly easily. BTW, there is no way that 61HRC is "easily machinable" by normal methods. Silver steel is used for cutting tools and other through-hardened applications. Silver Steel (Drill Rod) is "01" toolsteel and not suitable as a kingpin. It has typical UTS 40-60 tons/in 2 (550-830 MPa) and typical yield strength of 35-50 tons/in 2 (480-690 MPa).Spinneyhill, sheet from the supplier - can I attach a pdf file? It is supplied tempered to 61 HRC and is easily machinable. I was thinking I could use it for this job. A specific recommendation would be outside my area of competence.Ī locally available steel is silver steel, made to BS1407. I think what is wanted is a steel designed to be case hardened while leaving a tough core. If an unsuitable steel is used, this may result in too high a hardness and low ductility (brittle and susceptible to fracture). Quenching after the case harden heat soak will re-harden the steel. That will conflict with the previous heat treat and temper for toughness. They are definitely softer under the surface, (put a file to a worn one) and glass hard on the surface, so I would go for a very tough grade of steel, machine, heat treat and temper for toughness, and then case harden and polish to exact size.Case hardening will require a long time at high temperature. I don't know that a silver steel hardened all the way through will fit the bill for the shock loading a king pin has to withstand. Never made a king pin before, but fitted "just a few" but looking at the job they have to do, it will need to be tough on the inside, and glass hard on the surface. If not a threaded draw key, drive in with a drift and stake with a center punch. Threaded draw keys don't always seat when drawn by the nut. Drive the draw key in with a hammer until it seats. No radius is a guaranteed failure in this application. Grind the draw key slot making sure to have the radius at both ends of the slot. I would suggest buying/borrowing a set of hardness files to know if it is Rc40, 45, 50 or 55. If it is softer than Rc60 it is probably through hardened 4140 or similar material as Tiers suggests. This is what is done for heavy truck king pins. That means machine it oversized with the flat, send it out for carburization then grind it back to round and the correct diameter. If it doesn't scratch, it was probably carburized. This will point you in the right direction.įirst run a file across the existing part in an area with no wear or rust. ![]()
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