PCBA Tech - STM powder density and liquid maintenance points

STM powder density meter is suitable for boiling method and vacuum saturation method measurement, adopts Archimedes principle buoyancy method, and directly reads the measured value accurately. It can directly read the effective porosity, wet density and volume of the structure body density and oil-bearing alloy. Directly read the oil content of sintered oil-impregnated bearings. The STM instrument adopts a large water tank design to reduce the error caused by the buoyancy of the hanging rail.

In STM powder metallurgy, theoretical density is sometimes used. Its purpose is to estimate the quality of test materials; estimate the highest density that the green body can achieve; calculate the density; calculate the target density of powder forging. When calculating the theoretical density, it can be calculated according to the following formula:

D=1/w-1.

Where w=a/da+b/db+..., where: d-theoretical density (g/cm3); a and b- are the mass percentages of a and b components respectively; da and db- are a and b groups respectively The theoretical density of the element (g/cm3). The theoretical density of each component can be found in the manual, and the density of dense parts can also be used in the approximate calculation. For example, the density of pure iron can be used.

Sometimes the material formula in the company will use iron powder as 100%, and other ingredients are used externally, such as iron powder 100%+copper powder 2%+graphite 0.7%+... The material formula of this additional method, for example, can be calculated after the content of each group member is converted into a percentage, otherwise large errors may occur. The conversion percentage can be calculated according to the following formula:

A%=a/∑*100%; B%=b/∑*100%-2.

where ∑=a+b+...; A, B,..., represent the name of each group member; a, b,..., represent the proportion of each group member.

The powder metallurgy density meter STM manufacturer analyzes the theoretical density calculation formula is fundamental, no matter how to calculate it, you must use this formula, but if you don’t analyze it according to the actual situation, you will use this formula unchanged. When dealing with formulas, we must understand its connotation, know the specific conditions of its use, and then use it flexibly according to the actual situation, otherwise it will be a mechanical method.

For the theoretical density of powder metallurgy, it is not the theoretical density in the strict sense. The theoretical density in the strict sense can only be calculated by knowing the composition percentage of each member of the material and its unit cell structure. The composition of powder metallurgy materials is complex, and the material after sintering It is more difficult to determine the various structures and ratios of, so for powder metallurgy materials, the theoretical density in the strict sense is difficult or even impossible to calculate. Although it is not a theoretical density in the strict sense, this thing, whether it is experiment or production, has a certain guiding effect and is of practical significance.

STM liquid specific gravity balance use procedures and maintenance points

The liquid specific gravity balance is a teaching instrument and an indispensable liquid measuring instrument in the laboratory. The liquid specific gravity balance has many requirements in the process of using it, if it is used improperly, it will cause measurement errors. Today, let me introduce the main points of the use of liquid specific gravity balance for everyone:

1. STM balance should be adjusted and balanced before use.

2. Put the liquid to be tested into a glass measuring cylinder and test.

3. Immerse the measuring hammer into the liquid in the glass measuring cylinder. At this time, the beam loses balance; various weights should be added to the V-shaped groove and small hook of the beam to restore the balance of the liquid specific gravity balance. At this time, the V-shaped groove and small hook of the beam The sum of the weights on the hook is the measured specific gravity value of the liquid.

4. After the liquid measurement is completed, all the weights on the V-shaped groove and small hook of the beam shall be removed, and the V-shaped groove and small hook of the beam shall not be left.

5. When the balance needs to be moved, the parts, components and beams that are easy to separate should be disassembled and separated to avoid damage to the knife.

6. According to the frequency of use, regular cleaning work and measurement performance verification should be carried out. When the balance is found to be distorted or doubtful, the use should be stopped before the fault is cleared, and it can be used after the repair verification is qualified.

STM liquid specific gravity balance maintenance guidelines:

1. Clean the blades and agate blade holders regularly. Use handkerchiefs, soft brushes, etc. to clean them. It is strictly forbidden to use coarse cloths and hard brushes, and to prevent scratches and damage.

2. When the balance needs to be moved, the STM parts, components and beams that are easy to separate should be disassembled and separated to avoid damage to the knife.

3. After the liquid measurement of STM is finished, all the weights on the V-shaped groove and small hook of the beam should be removed, and the V-shaped groove and small hook of the beam shall not be left.