Sintex Sintered Parts - FAQ section

Under this FAQ section you can find questions and answers within the product area sintered stainless steel - that is in relation to stainless steel sintered components, stainless steel sintered filters and components produced by metal injection moulding.
 

Please notice that this FAQ section is only in English. All questions should also be submitted in English.

 

Currently showing 9 questions and answers:

Product	Question	Answer
MIM	Is it possible to give some design guidelines?	It is difficult to give precise limitations to design, but here are some rules of tumb: o Flow length below 100mm o Weight below 200 grams (preferable also below 100 grams) o Maximum thickness 6mm o Yearly production above 100.000 pieces
MIM	What materials are available?	There is a wide range of materials available for MIM, the most common are: 316L, 17-4PH, 430L and FN02. But it is also possible to MIM Titanium parts and ceramic parts (called CIM for Ceramic Injection Molding).
MIM	Why use Metal Injection Moulding?	The process is very suitable for high production volume parts with a high complexity. There is some limitations on the size, parts above 100 grams are generally more difficult to manufacture than smaller parts. It is possible to achieve tolerances below 0.5% of the nominal.
MIM	What is Metal Injection Moulding (MIM)?	MIM is a process combining the shaping advantages from injection molding, with the mechanical strengths of normal powder metallurgy (PM). The result is a process where it is possible to achieve geometries in a single step, which would otherwise demand either several steps, or not otherwise be possible. The process starts out with injection molding of the part, called a green part. The part is then debound, which can be done thermally, solvent or catalytic. After debinding the part is called a brown part, which is ready for sintering. After sintering it is possible to use a wide variety of processes to complete the part, for instance surface coatings, polishing etc.
Sintered Components	Can you do any tricks to reduce the porosities or increase the corrosion resistance.	PM components can be sintered with addition of a liquid forming agent. This increases the activity during sintering making the remaning pores spherical and closed to the surrounding. This leaves a surface without open pores making pitting initiation more difficult. Furthermore the spherical pores do not act as crack initiators which results in better mechanical properties - especially on the elongation and UTS.
Sintered Components	Can you reach the same corrosion resistance as known from stainless plates and rods?	The corrosion risks in stainless steel is pitting corrosion. As a PM component normally has around 15 volume percentage porosities you can look at the surface as pre-pitted making the pitting initiating attack easier. It is also known the the pore size can be critical for pitting initiation - the smaller pores the more critical. Therefore most components are designed with a relatively large amount of pores (density below 6,6 g/cm) in order to have better corrosion resistance. For components with high demands on corrosion resistance a PM processed component is often choosen in a more noble grade than needed in plate or rod material. In these grades Molybdenum plays a large role as Mo is known as a strong pitting resistance agent. The alloy STX2000 with 3,9%Mo is an example on this where the corrosion resistance is comparable to plate processed AISI 316L (2,3% Mo).
Sintered Components	Can you reach the same mechanical properties as known from stainless plates and rods?	Powder metallurgical process components contains porosities. As the pores acts as crack initiators the mechanical properties are typically lower than known from fully dens parts. Especially elongation is reduced and typically have values between 10 and 20% for stainless grades after sintering in pure hydrogen atmosphere. Furthermore the PM components are fully soft annealed after the sintering process, which can be seen on a low yield strength and low hardness. Both the yield strength and the hardness can be increased in coldforming post processing or by sintering in nitrogen containing atmosphere. The latter though reduces the toughness and the corrosion resistance.
Sintered Components	Can you make the same grades in stainless steel as we know from rolling and forging processes?	The grades produced in powder materials are almost identical to the grades known from other processes. On the chemical side you will often find larger levels of Si and lower levels of Mn in a PM-grade compared to other processes. This is due to the atomisation process and the compaction process where Si secures a low level of oxygen and Mn works as a deformation hardening agent reducing the powder compressibility and hence the green strength of the compacted parts.
Sintermetal	Why use PM?	Powder Metallurgy is a process route where a complex component can be produced in one single operation without any machining of the component. This makes the process economical interesting for many complex applications. Furthermore is the process highly reproducable and fits perfectly production of high volume parts.