From: Edward ® 23/09/2001 14:17:50 Subject: Sintered Stainless Steel post id: 424501 The grinding mechanism in my new pepper grinder is made from sintered stainless steel. I have a basic understanding of the sintering process, but no idea about the properties of the end product. Why would sintered stainless steel be chosen over regular stainless? What is it about the sintering process that gives the product these qualities? (I tried a 'net search, but all I got were companies advertising their sintered products) Thanks SSSF'ers. From: Zardoz ® 23/09/2001 14:33:05 Subject: re: Sintered Stainless Steel post id: 424511 Powdered metal parts & high volume capacity have been at the core of Sterling Sintered Technologies since its inception in 1955. Sterling's forty-five year history in the custom fabrication of powdered metal parts & high volume capacity involves innovative designs, ranging from the simplest basic parts to complex precision parts, ultimately employed in specialty toolmaking and secondary manufacturing operations. Sterling Sintered Technologies produces its custom made components in various grades of sintered brass, sintered stainless steel and sintered bronze, for use in structural pieces and self lubricating bearings, as well as in applications geared for continuous improvement in performance and product development. The manufacturing of powdered metal parts & high volume capacity components, which Sterling Sintered specializes in, is a highly developed process of mixing metals in a powder state, whether the pure element or an alloy, then compressing the mixture in a mold and shaping the material according to the customers needs. The parts are then sintered by heating the shapes in a furnace, to cause the shaped particles to bond metallurgically. The initial P/M manufacturing process can be expanded to result in operations which will also produce bearings and or bushings in sintered stainless steel, sintered brass, and sintered bronze, as well as other metals which can be processed after the metal powders have been compressed into shape. There are three basic steps in producing P/M components. Whether the final result is sintered brass, sintered stainless steel, sintered bronze, or any other powder based element, the three production steps are the same. THE SINTERING OPERATION . The pressed compact is prepared for sintering by being placed on a mesh conveyor belt and moved into a controlled-atmosphere furnace. In the furnace, the compacted P/M pieces are heated to below the melting point of the base element, then held at this sintering temperature, until the particles bond metallurgically. Sintering temperatures can range anywhere between 1450-1550 degrees for bronze, to 2050-2100 degrees for other ferrous alloys. The sintering times average from 1-1-1/2 hours for a small part such as a bushing, to 2-3 hours for an average size ferrous part. Hardening sintered pieces involves applying a controlled cooling rate in a separate cooling section of the conveyor belt driven sintering furnace. Lastly, P/M components are more often than not user-ready following the sintering process. There are times, however, when special properties must be applied. These special properties can include, but are not limited to, repressing, impregnating, machining, tumbling, plating and heat-treating. Sterling Sintered Technologies can work within their customers specific needs. Initial contact with the engineering professionals in the P/M field can shed new light on this innovative P/M manufacturing process, for those unfamiliar with or just starting to implement the use of different types of sintered components. Additional information concerning powder metallurgy may be found at the address www.sterlingsintered.com. http://www.sterlingsintered.com/powdered-metal-parts-ge.htm Powdered metal parts & high volume . From: Procrastination inc ® 23/09/2001 16:53:52 Subject: re: Sintered Stainless Steel post id: 424625 The biggest reason to choose sintering for this component is the cost. Considering the volumes of this item produced (large), machining that component from bar, even using modern CNC equipment, would take a couple of minutes each unit. That time costs the manufacturer in man hours and over heads, plus the cost of the wasted material that has been cut away. Sintering is a much quicker process, the expensive tooling costs are offset by the high volumes produced by the dies and the speed of production. Sintering has really only come of age over the last few decades. Some sintered components are actually superior to machined equivalents for their application. Sintered bronze bearings exhibit porosity that holds lubricant, machined versions don't. This extends the life of the bearing over machined units. Sintering is now used in high volume gear manufacture. Very high loads are experienced in this application, it surprises me that the process can produce these components. Stainless was chosen for its corrosion resistance and hardness, both important in a food grinding application From: Alan™ ® 23/09/2001 18:44:28 Subject: re: Sintered Stainless Steel post id: 424684 Looks like I should be doubling my consultancy fees, with the current popularity of metallurgist in the SSSF :-^) OK, the short answer is that it was a cost effective means to obtain the grinder, with suitable properties. So for starters it is compromise, the most cost effective way of producing the part, won't necessarily provide a part with suitable properties, nor will using a part that with the best properties be necessarily cost effective. So why sintering? Basically the part will be difficult to machine, where as a casting will produce the component much more simply. In some extreme cases the component, because of it's design, may not even be possible to machine, without having to assemble it in pieces (possibly requiring welding). However there is an extremely small range of alloys available using the casting process, because the viscosity of the molten metal becomes a major issue, if you need to heat the metal to hot to achieve the correct viscosity, you then can have unacceptable oxidation of the molten metal. If you use another alloy which can be cast, you can then end up with a grinder which deforms when you attempt to grind the metal or even cracks. The main advantage sintering has over other manufacturing processes, is the ability to relatively cheaply manufacture complex parts using more exotic alloys. value=424501> This forum is un-moderated. The views and opinions expressed are those of the individual poster and not the ABC. The ABC reserves the right to remove offensive or inappropriate messages.