![<?echo $_SERVER['SERVER_NAME'];?>](/template/twentyseventeen/skin/images/header.jpg)
As described above, it is not difficult to find that the surface layer of the stainless steel powder has such a passivation layer, which greatly hinders the progress of the sintering reduction, thereby making the sintering of the powder metallurgy stainless steel very difficult.
In order to overcome this difficulty, the law of oxidation-reduction reaction of chromium oxide in hydrogen has been studied. From the relevant reaction diagrams, it can be seen that the dew point (critical value) of the atmosphere required for pure Fe--Cr stainless steel at different sintering temperatures does not appear to be particularly harsh (eg, about -23 ° C at 1150 ° C). ). But this is just the dew point of the atmosphere necessary for chromium oxide to begin to be reduced.Industrial practice has shown that in order to fully ensure the continuous successful sintering of stainless steel powder compacts, more influencing factors must be considered, such as no contamination during sintering and cooling, and alloys requiring other components, generally requiring lower atmospheric dew points. There should also be a certain safety factor and so on. Therefore, in order to ensure the normal progress of stainless steel sintering, it is not only required to introduce the decomposed ammonia dew point to dry to -60 ° C, more importantly how to remove the water vapor generated by redox. In order to always keep the dew point of the furnace atmosphere within the corresponding requirements.
(2) Main technical measures. According to the above, through the trial and exploration, a number of technical measures have been taken, so that the original equipment in the whole process of sintering ensures that the "lubrication in the furnace" meets the requirements of stainless steel sintering, thereby achieving successful sintering. The main points of its technical measures are:
â— Powdered raw materials require low carbon and oxygen content; all materials related to sintering are required to maintain high dryness;
â— Modification of the structure of the existing sintering furnace. If a pre-sintering section is added, the size of the furnace tube is changed and the flow rate of the reducing gas and its flow direction are adjusted;
â—Change the ammonia decomposition unit and strictly select the anhydrous liquid ammonia and change the drying cycle process rules;
• Use a higher sintering temperature (such as 1250-1300 ° C) and properly control the productivity to reduce the dew point requirement.
The third stage of the development is to further solve the problems of dimensional accuracy, mechanical physical performance indicators and appearance compliance (all imported parts are standard). Since the parts are in the shape of a sheet, and the steps, the inverted cone and the slope have certain precision requirements, and the high-temperature sintering shrinkage deformation is large, the adjustment of the size and weight of the blank is adjusted several times. . In addition, through continuous testing, we also explored the best post-processing equipment and processes, so that the surface finish of the parts also meets the standards of imported parts.
Corrosion resistance test of parts
(1) Selection of test methods:
In fact, all metal or alloy materials are difficult to guarantee that they will never rust. Whether they cause corrosion depends on the conditions of their working environment. However, due to the various combinations and changes of the working environment conditions of the parts and the factors of the materials themselves, it is obviously unrealistic to develop a general test method to determine the corrosion resistance of the materials in the face of such extremely complicated situations. Only certain test methods may be formulated or selected according to actual needs. The usual test methods are:
The first is the actual use test. It takes a long time (some years), is expensive, and is not easy to obtain quantitative results.
The second is the laboratory test. It is divided into analog test and accelerated test. The former is tested in a small simulation load to artificially simulate various media and conditions formed by nature as accurately as possible. The accelerated test is to strengthen one or a few control factors in the actual conditions, so that it is easy to make a judgment in a short time. Because it is convenient to freely choose and strictly control the various influencing factors, it can be accurately measured, the test time is short, the result is reproducible, and so on, and there are many methods for formulating corresponding national or industry standards. Such as "artificial atmosphere - salt spray corrosion test" and "wet hot corrosion test", etc. belong to this category. This part is selected by the “wet hot corrosion test†method.
Throttle Cut-Off Vent Valve,Manual Flange Adjustment,Large Diameter Vent Valve,Large Diameter Globe Valve
Zhejiang Meide Machinery Co.,Ltd , https://www.meidemachinery.com