1. What is powder metallurgy?
Powder
metallurgy is a technique for making metal powder and making a material
or product by mixing, forming and sintering the raw material of a
self-lubricating composite bushing with metal powder (and sometimes
adding a small amount of non-metallic powder). It consists of two parts, namely: (1) the manufacture of metal powder
(including alloy powder, hereinafter referred to as "metal powder").
(Known
as "powder metallurgy materials") or articles (referred to as "powder
metallurgy products"), which are made of metal powder (sometimes with a
small amount of non-metallic powder) as a raw material, mixed, ).
2, powder metallurgy What are the most prominent advantages?
The most prominent advantages of powder metallurgy are two:
(1)
It is possible to manufacture materials and articles such as porous,
sweat, shock, noise and other materials and products such as tungsten,
molybdenum, titanium and other refractory metal materials which can not
be manufactured or difficult to manufacture or difficult to manufacture
copper-based self- Products, metal - plastic, bimetallic and other composite materials and products.
(2)
can directly produce products that meet or meet the requirements of the
finished product size, thereby reducing or eliminating the mechanical
processing, the material utilization rate can be as high as 95% or more,
it can also be in some products to iron on behalf of copper, , Energy saving ".
3, what is the "iron base"? 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 (including powder
forging) method, the manufacture of iron as the main component of the
powder metallurgy materials and products (iron-based mechanical parts,
wear materials, friction materials, and other iron-based powder
metallurgy materials) Process collectively.
4, powder metallurgy for the powder manufacturing methods which are several categories?
Powder manufacturing methods are mainly physical and chemical methods and mechanical crushing two categories. The former includes reduction, electrolysis and carbonyl method; the latter includes grinding and atomization.
5, with the reduction method of manufacturing metal powder is how is it?
The method is a method of obtaining a metal powder by removing the oxygen in the metal oxide with a reducing agent.
6, what is the reduction agent?
Reducing agent refers to the ability to capture oxygen in the oxide material. The reducing agent used to prepare the metal powder refers to a substance capable of removing oxygen from the metal oxide. In the case of metal oxides, a substance that is greater than the
affinity of the metal with oxygen is known as a reducing agent for such a
metal oxide.
7, what is the purpose of powder reduction annealing?
The purpose of powder reduction annealing is as follows: (1) removing
the oxide film on the surface of the metal powder particles; (2)
removing the foreign matter such as gas and moisture adsorbed on the
surface of the particles; and (3) eliminating the hardening of the
particles.
8, for the powder metallurgy powder performance measurement which generally?
Powder
metallurgy for the determination of the performance of the powder
generally have three: chemical composition, physical properties and
process performance. 9, powder metallurgy for the physical properties of the powder mainly include that several?
The physical properties of the powder used in powder metallurgy mainly
include the following three: (1) the particle shape of the powder; (2)
the particle size and particle size of the powder; and (3) the specific
surface of the powder.
10, powder metallurgy for the powder process performance which includes several items?
Powder metallurgy powder technology performance mainly includes the
following five: (1) loose density; (2) tap density: (3) mobility; (4)
compression; (5) formability.
11, for the powder metallurgy powder particle shape is determined by what? What about that?
As the powder preparation method is different, its particle shape is also different. Generally irregular, flaky, polyhedral, dendritic, granular, globose, drop-like, fibrous ... ....
12, what is the particle size of the powder? What is the usual method?
The particle size of the powder refers to the size of the powder particles. Usually by sieving method to determine.
13, what is the particle size of the composition of the powder?
The particle size of the powder, also known as particle size distribution. Refers to the powder in the powder at all levels of the overall weight percentage.
14, what is the particle size of the powder range?
The
particle size range of the powder refers to the particle size of the
powder particles that vary between the two specified particle sizes. If
a powder has a particle size range of -80 + 150 mesh, it means that the
powder has a particle size equal to or less than 80 mesh and greater
than 150 mesh. In other words, these powders pass through the 80 mesh sieve, but pass the 150 mesh sieve.
15, what is the sieve grade of the powder?
The sieve grade of the powder is a method of classifying the powder particle size by sieving.
16, what is the powder sieve analysis?
The sieve analysis of the powder refers to the method by which the
powder sample is sieved with a set of standard sieves and the weight
percentage of each grade powder is obtained to show the particle size
distribution of the powder.
17, what is the mesh mesh?
The mesh size of the screen (eg Taylor standard sieve) refers to the number of all meshes on the length of 1 inch.
What is the specific surface of the powder?
The specific surface of the powder is the sum of the surface area of
all the particles of 1 gram of powder (C ㎡ or ㎡), also known as grams
of surface.
What is the loose density of the powder?
The bulk density of the powder means that the powder is allowed to
flow freely into the standard container (measuring cup) under limited
conditions and then flattened to measure the mass of the powder per unit
volume, expressed in g / cm3.
What is the real density of the powder?
Powder
in the free admission to the standard container, due to friction
between particles and other reasons to form arch bridge. If the vibration of the powder is carried out under limited
conditions, the arch bridge is collapsed and the measured mass per unit
volume of powder is called the tap density of the powder.
21, what is the density of green?
The green density is the average of the actual mass of the compact volume per unit volume, expressed in g / cm3.
What is the relative density of the compact and the relative density of the sintered parts?
The ratio of the density of the green compact to the density of the
dense matter of the same component is called the relative density of the
compact; the ratio of the density of the sintered member to the density
of the dense matter of the same component is called the relative
density of the sintered member.
23, what is the flow of powder?
The flowability of the powder is a qualitative term that describes the nature of the powder flowing through a defined pore. Usually with 50 grams of powder all through the export aperture of
2.54mm, cone angle of 60 degrees flow rate funnel used time (s) to
represent.
24, what is the compression of the powder?
The
compressibility of the powder is the degree to which the powder can be
compressed at a prescribed unit pressure (e.g., 392 MPa, i.e., 4 tf /
cm2). With a compact density.
25, what is the shape of the powder?
The formability of the powder is the ability of the powder to maintain a certain shape after forming. The drum test can be used to determine the compressive strength or bending strength of the compact.
26, what is the shape of the powder?
Powder forming refers to the process of making the powder a compact having a certain property, size, density and strength.
27, what kind of special powder forming method?
Special powder forming methods are the following five: (1) isostatic
pressing; (2) continuous forming; (3) no pressure forming; (4)
high-energy forming; (5) injection molding.
28, what is the purpose of powder?
Through the powder, can make the performance of different powder
components to form a uniform mixture, in order to facilitate the
suppression and sintering, to ensure that the material evenly, stable
performance.
29, the length of powder mixing time on the powder have any effect?
The mixing time must be based on the specific requirements and equipment for the powder. Time is too short, the mixing is not uniform; and too long will
produce many unfavorable factors, such as iron, copper and other metal
powder will produce hardening, will also make the particle shape and
particle size distribution changes.
30, the use of the main parts of the die is what?
The
use of the main parts in the press mold is: the mold, the forming
surface of the forming compact; the upper punch, the upper end of the
forming compact; the lower punch, the lower end face of the forming
compact, The surface and the end face of the forming compact.
35, the manufacture of powder metallurgy mold material selection principle is what?
1
manufacturing powder metallurgy mold main parts according to its
specific use, the material wear resistance, processing, cost and other
factors, a comprehensive consideration, a reasonable choice. Its hardness must reach HRC55 above. Selection of carbon tool steel, alloy tool steel and hard alloy, etc., can meet the hardness and strength requirements.
32, press the mold is made of what parts of the material?
(T10A,
T12A, etc.), alloy tool steel (GCr15, Cr12, 9CrSi, Cr12Mo, Cr12W,
Cr12MoV, CrWMn, CrW5), high speed steel (W18Cr4V, W9Cr4V, W12Cr4V4Mo),
hard (T8A,
T10A), alloy tool steel (GCr15, Cr12, 9CrSi, Cr12Mo, CrWMn, CrW5);
pressure sets can be used alloy (steel alloy, YG15, YG8) Tool steel (GCr15, 9CrSi, Cr12, Cr12Mo, CrWMn, CrW5).
33, how to choose the use of mold materials?
To
suppress the bulk of the large pieces of pressure, to be used with good
wear resistance materials, such as high-speed steel, carbide, etc .;
repression of small pieces of pressure, can be used carbon steel and
other cheap materials. The
use of carbon tool steel or alloy tool steel; suppression of tungsten,
molybdenum and other hard metal powder (such as the use of carbon steel
tools, steel and other materials); the use of alloy tool steel and other
easy to process and heat treatment deformation of small materials; Materials, as well as cemented carbide, friction material, shall be made of cemented carbide material. To suppress high-density presses, should wear a good material; for
high-precision die, should use wear-resistant materials, and to use as
much as possible carbide.
34, powder metallurgy press the main parts of the heat treatment hardness is how much?
Powder
metallurgy pressing die The main parts of the processing hardness is:
female mold, the requirements of steel for the HRC60-63, steel cemented
carbide HRC64-72, carbide parts HRA88-90; mandrel, required for HRC60-63 ,
The hardness of the mandrel mandrel can be appropriately reduced, the
local hardness of the mandrel bar connection HRC35-40; punch, the
requirements for the HRC56-60; pressure sets, the requirements for the
HRC53-57. Protective cover, no heat treatment; or quenched and tempered, hardness HRC28-32.
35, what is a single layer of compact, double compact?
The single layer compact is a compact which is made of the same
composition powder; the double layer compact is a compact having two
different layers of powder; the multi-layer compact is a compact made of
two or more different composition powders.
36, the common crater defects and the reasons for what?
Common crust defects and the reasons are as follows:
(1) density is not uniform.
2)
mold finish is low, increase the friction resistance; 3) lack of
lubrication; 4) parts size is unreasonable (aspect ratio is too large,
long wall thickness is too large ... ...) ); 5) the way to suppress wrong.
(2) crack.
The reasons are: 1) uneven density; 2) powder formability is poor, the
billet elastic effect is large; 3) stripping mode is not right; 4) mold
rigidity difference; 5) mold with inverted taper.
(3) fall off the corner.
The reasons are: 1) powder formability is poor; 2) compact density is low.
(4) surface scratches.
The reasons are: 1) mold surface scratches; 2) appear tumor.
37, what is powder metallurgy sintering?
Sintering is one of the main processes of powder metallurgy. Generally, the powder or green compact is heated to a temperature of
2/3 to 4/5 of the melting point of the main component, and the physical
and chemical processes such as the adhesion between the particles are
made to have the desired process of the material or the product.
38, what is the sintering protection atmosphere? What is its role
Sintering protection atmosphere refers to the atmosphere when the
powder product is sintered to prevent the product from being oxidized.
The protective atmosphere can prevent the oxidation of the sintered
parts, but also reduce the oxide on the surface of the powder particles
to remove the gas and moisture adsorbed on the surface of the powder
particles. For the iron-based powder products, it can also ensure that
it does not decarburize or carburize.
39, commonly used sintering protective atmosphere which?
Sintering protection atmosphere is generally a reducing or neutral
gas, such as hydrogen, ammonia decomposition, carbon monoxide, nitrogen
and vacuum.
40, powder metallurgy materials What are the characteristics of porous features?
Porous is one of the important characteristics of powder metallurgy materials. With this feature, you can:
(1) manufacture sweating materials. That
is, ordinary powder metallurgy materials in the pores containing low
melting point substances, in high temperature work, the impregnation of
exudate, so that the material "sweating" heat. This can be replaced by ordinary materials, expensive heat-resistant
alloy, and further improve the use of heat-resistant parts of the
temperature.
(2) manufacturing filter material. For the filter gas, filtrate and so on.
(3) impregnated with anti-wear agent, the manufacture of oil and
oil-free lubricating bearings; impregnated spices, manufacturing incense
and other crafts.
(4) in some cases with iron instead of copper, lead and other non-ferrous metals.
(5) manufacturing vibration, noise, insulation and other materials.
(6) to increase the material than the surface, with its role as a carrier (such as carrying a catalyst, etc.).
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