1. What is powder metallurgy?
Powder metallurgy is a technology that manufactures metal powder and uses metal powder (sometimes with a small amount of non-metal powder) as raw materials, through mixing, forming and sintering, to manufacture materials or products. It includes two parts
That is: (1) Manufacturing metal powder (including alloy powder, hereinafter collectively referred to as "metal powder").
(2) Using metal powder (sometimes also adding a small amount of non-metal powder) as raw materials, after mixing, forming and sintering, manufacturing materials (called "powder metallurgy materials") or products (called "powder metallurgy products").
2. What are the most prominent advantages of powder metallurgy?
There are two most prominent advantages of powder metallurgy:
(1) Able to manufacture materials and products that cannot be manufactured or difficult to manufacture by other processes, such as porous, perspiration, shock absorption, sound insulation and other materials and products, refractory metal materials and products such as tungsten, molybdenum, and titanium, metal-plastic, Bimetal and other composite materials and products.
(2) It can directly manufacture products that meet or approach the size requirements of the finished product, thereby reducing or eliminating mechanical processing. Its material utilization rate can be as high as 95%. It can also replace copper with iron in some products, achieving "material saving , Energy saving".
3. What is "iron-based"? What is iron-based powder metallurgy?
Iron-based means that the composition of the material is based on iron. Iron-based powder metallurgy refers to the use of sintering (also including powder forging) to manufacture powder metallurgy materials and products (iron-based mechanical parts, anti-friction materials, friction materials, and other iron-based powder metallurgy materials) with iron as the main component The general term for the process.
4. What are the main types of powder manufacturing methods used in powder metallurgy?
There are two main types of powder manufacturing methods: physical and chemical methods and mechanical crushing methods. The former includes reduction method, electrolysis method and carbonyl method, etc.; the latter includes grinding method and atomization method.
5. What is going on in the production of metal powder by the reduction method?
This method uses a reducing agent to extract oxygen from the metal oxide to obtain a metal powder.
6. What is a reducing agent?
Reducing agent refers to a substance capable of depriving oxygen from oxides. The reducing agent used in the preparation of metal powder refers to a substance that can remove oxygen in the metal oxide. As far as metal oxides are concerned, any substance whose affinity with oxygen is greater than that of the metal with oxygen is called the reducing agent of this metal oxide.
7. What is the purpose of powder reduction annealing?
The purpose of powder reduction annealing mainly has the following three aspects:
(1) Remove the oxide film on the surface of the metal powder particles;
(2) Remove foreign matter such as gas and moisture adsorbed on the surface of the particles;
(3) Eliminate the work hardening of particles.
8. What are the general measurement of powder properties used in powder metallurgy?
There are generally three items used in powder metallurgy to determine the properties of powders: chemical composition, physical properties and process properties.
9. What are the main powder physical properties used in powder metallurgy?
The physical properties of powder used in powder metallurgy mainly include the following three items:
(1) The particle shape of the powder;
(2) The particle size and particle size composition of the powder;
(3) The specific surface area of the powder.
10. What are the main properties of powder technology used in powder metallurgy?
The powder process performance used in powder metallurgy mainly includes the following five items:
(1) Bulk density; (2) Tap density: (3) Fluidity; (4) Compressibility; (5) Formability.
11. What determines the shape of powder particles used in powder metallurgy? How many types are there in general?
Due to the different preparation methods of the powder, the particle shape is also different. Generally there are irregular, flake, polyhedral, dendritic, granular, spherical, drop, fibrous...
12. What is the particle size of the powder? What method is usually used to determine it?
Powder particle size refers to the size of powder particles. It is usually determined by the sieving method.
13. What is the particle size composition of the powder?
The particle size composition of the powder, also known as the particle size distribution. It refers to the weight percentage of the powder in the powder to the whole powder.
14. What is the particle size range of the powder?
The particle size range of the powder refers to the size of the powder particles that vary between two specified particle sizes. If the particle size range of a certain powder is -80+150 mesh, it means that the particle size of these powders is equal to or less than 80 mesh and greater than 150 mesh. In other words, these powders passed the 80-mesh sieve, but not the 150-mesh sieve.
15. What is the sieve classification of powder?
The sieve classification of powder refers to the method of sieving the particle size of the powder.
16.What is the sieve analysis of powder?
The sieve analysis of powder refers to the method of sieving the powder sample with a set of standard sieves and calculating the weight percentage of each level of powder to express the particle size distribution of the powder.
17. What is the mesh number of the screen?
The mesh size of a sieve (such as a Taylor standard sieve) refers to the number of all meshes in a length of 1 inch.
18. What is the specific surface area of the powder?
The specific surface area of a powder refers to the total surface area of all particles of 1 gram of powder (C㎡ or ㎡), also known as the specific surface area.
19.What is the bulk density of the powder?
The bulk density of the powder refers to the free flow of the powder into a standard container (measuring cup) under limited conditions, and then it is flattened, and the mass of the powder per unit volume is measured, expressed in g/cm3.
20. What is the tap density of the powder?
When the powder stays freely in the standard container, it forms an arch bridge due to friction between particles. If vibration is applied to the powder under limited conditions to cause the arch bridge to collapse, the measured mass of the powder per unit volume is called the tap density of the powder.
21. What is green density?
The green density is the average value of the actual mass per unit volume of the green compact, expressed in g/cm3.
22. What is the relative density of the green compact and the relative density of the sintered part?
The ratio of the density of the compact to the density of the compact material of the same composition is called the relative density of the compact; the ratio of the density of the sintered part to the density of the compact material of the same composition is called the relative density of the sintered part.