The technical characteristics of powder metallurgy make it widely used, but the phenomenon of burr can not be avoided, we can only control in a certain range, otherwise the burr phenomenon is too large will have a negative impact on the product quality and performance, so what is the impact of burr on the quality of powder metallurgy products?
The causes of burrs on powder metallurgy parts are as follows:
Clearance in the die: There must be a matching clearance between the negative die and the punch and between the relative motion of the die punch and the mandrel. The flow or plastic deformation occurs when metal powder or finished sintered blanks are formed under pressure in the die. The filling effect of molded parts at the mold gap is the root cause of burrs.
Precision of the equipment: Insufficient precision of the equipment leads to deterioration of the working conditions of the mold, prompting the generation of burrs. In addition, such as loading powder height exceeds the range of travel equipment, pressing pressure is too large resulting in insufficient tonnage of equipment, resulting in unstable equipment operation, will also produce burrs, this kind of burrs are mostly randomly distributed on the surface of the parts.
Damage to the mold: due to the complex shape of the mold, manufacturing costs are high, so often in the premise of not affecting the final quality of the product (i.e., the defects of the powder metallurgy blank can be eliminated in the subsequent process, does not affect the quality of the product factory) is still in service, there will be a fly-edge burr, the shape of the burr is more regular, exists in the mold defects.
The burr of powder metallurgy has the following effects on product quality:
1、Positioning performance and assembly performance: the existence of burrs will inevitably lead to positioning errors, thus affecting the processing accuracy of the hole. For some structural parts with high assembly requirements, the presence of burrs can easily cause interference and jamming of matching parts, such as motor bushings, automobile shock absorber guide bushings, valve seats, pistons, etc. The presence of burrs directly affects the assembly requirements.
2, the use of performance: mechanical operation process, under the action of friction, burrs are easy to fall off, exacerbate wear and tear, resulting in early failure of parts. In the hydraulic system, the shedding of burrs with the hydraulic oil into the hydraulic system circuit, affecting the normal operation of the hydraulic system, crawling, shaking phenomenon.
3, heat treatment performance: parts with burrs by heat treatment, easy to stress concentration, resulting in cracks, resulting in reduced fatigue strength of the parts. This can not be ignored for parts subjected to high loads and high-speed movement.
4, surface quality: burrs affect the surface finish of the product, in the surface quality requirements of the higher occasions, resulting in unqualified parts, such as some gear pump
side plate due to the parts are not removed or removed unclean burrs and can not be used.
The above is the impact of powder metallurgy burrs on the product, burrs produce a serious impact on the use of precision powder metallurgy parts performance, limiting the scope of application of powder metallurgy parts, can be assembled from the mold clearance, mold manufacturing precision, mold damage, mold installation and use as well as the precision of the equipment and other five aspects of the systematic analysis of powder metallurgy parts burr causes.
Powder metallurgy is required through the production of powder, compression molding, sintering, post-treatment and a series of processes can be manufactured. Among them, powder metallurgy sintering is a high-temperature treatment process to make the pressed billet or loosely packed powder body further combined to improve the strength and other properties. However, due to the different should, powder metallurgy sintering method is also divided into many kinds.
So what are the common powder metallurgy sintering methods?
1、Liquid phase sintering
If there are more than two kinds of components in the powder billet, the sintering may be carried out above the melting point of a certain component, and thus a small amount of liquid phase appears in the powder billet during sintering.
In the sintering, the powder body pressure to promote its densification process. Pressurized sintering is sometimes synonymous with hot pressing (hot pressing), hot pressing is a combination of powder forming and sintering, directly to the product process.
3, activation sintering
In the sintering process using some physical or chemical measures, so that the sintering temperature is greatly reduced, the sintering time is significantly shortened, while the sintered body properties are improved and enhanced.
Powder body in the molding press into the direct current and pulse electricity, so that the powder particles produced between the arc and sintering; in the sintering gradually exert pressure on the workpiece, the molding and sintering of the two processes are combined together.
The content introduced above is the common four powder metallurgy sintering methods, through these sintering methods, you can effectively complete the powder metallurgy sintering process. Because, in the powder metallurgy sintering process powder particles to occur mutual flow, diffusion, melting, recrystallization and other physicochemical processes, so that the powder body is further densified, eliminating some or all of the pores.
Harber Metal is professional China metal injection molding company which is located in China Guangdong Province. We are directly MIM factory founded in 2014. As a professional manufacturer and solution provider of metal injection molding process(MIM) and PM process. We have 350 employees, including 80 technicians, 60 senior engineers. Our factory covers an area of 108,000 square meters.