Конструкциялық материалдар және термоөңдеу Конструкционные материалы и термообработка Constructional materials and heat treatment Учебное пособие для специальности: 5В071200– «Машиностроение»

237 
heating. Application of mineral-cotton plates glued by phenolic pitch or 
bituminous emulsion is possible as well. 
Electroinsulating materials. 
As electroinsulating materials only such materials which don't carry out an 
electric current or carry out it very poorly can be applied. They have to possess 
also necessary mechanical durability, warm and moisture resistance. Such 
materials are wood materials already considered by us, plastic, and also rubbers, 
electroinsulating varnishes, asbestos, fiber, layered plasticity. 
Paper - is the sheet material made of vegetable fibers and cellulose. Cellulose - 
is the vegetable fibers cleared of pitches and other components. Cardboard - is a 
specially processed thick paper (thickness 0,25-3 mm). Depending on a way of 
processing, cardboard gets oil - and benzine resistance, electro - and thermal 
insulating. Paper and cardboard are applied as electroinsulating, pro-masonry 
and sealing material. 
Fiber - is a version of paper material, it is produced from paper impregnated 
with solution of chloride zinc. Differs high durability and well machinable, oil - 
and petrolrack. Lack of a fiber - considerable hygroscopicity therefore when 
moistening it is deformed. Fibers are applied to production of washers, laying 
and plugs. 
The press-spahn - is produced in the form of firm cardboard sheets. It is 
produced from paper stock impregnated with linseed oil. It is applied to isolation 
in electric cars. 
Mica - represents the refractory layered mineral which is easily splitting on 
thin transparent leaflets. Mica possesses high electroinsulating properties and is 
applied as dielectric in condensers, collectors, electric generators and starters, in 
electric heaters. 
The leaflets of mica which have been stuck together by glyptal pitch under hot 
pressing, is called micanite. 
Insulating varnishes (№ 458, 460, 447, 13, 1154, etc.) represent a mix of 
asphalt or bitumen, vegetable oil, organic solvent and desiccant. They are 
applied to isolation of polar coils windings of generators and starters, and also to 
protection of electrodetails against moisture and oil products. 
The insulating rubberized tape represents the severe fine cotton fabric (muslin) 
impregnated from one or two parties with a sticky crude rubber mix. 
The sticky insulating tape is the film plastic covered with a layer of 
perchlorovinyl glue. Insulating tapes are produced of various sizes and colors. 
Materials for drawing coverings. 
Coverings from metals and alloys. 

238 
In mechanical engineering providing the set characteristics of materials not in 
all volume of a product, and only in its blanket with preservation in a core of a 
product of properties of an initial material is often required. It belongs to such 
important characteristics of materials in operation of products as durability, wear 
resistance, resistance to electrochemical corrosion and oxidation. 
Except methods superficial thermal and chemical heat treatment, change of 
properties of products surface can be achieved by drawing of coverings on the 
main material - rather thin layers of other material with demanded properties. 
Coverings from metals and alloys are used mainly for increase of corrosion 
resistance and wear resistance of metal products. For this purpose most often we 
apply coverings from aluminum, cadmium, nickel, tin, lead, chrome, zinc and 
their alloys. For increase of reliability of electric contacts work they are covered 
with precious metals and alloys. 
For drawing of anticorrosive coverings we use: 
-galvanic sedimentation, 
- metallization by dispersion, 
- immersion in fusions. 
In mechanical engineering, the greatest distribution was gained by coverings: 
- zinc (galvanizing), 
- nickel (nickel plating), 
- cadmium (cadmium plating), 
- chrome (chromium plating). 
Galvanizing is applied to protection against corrosion of steel and cast iron 
details at influence of water and damp air on them. The covering is most 
efficient up to the temperature plus 70ºС. 
Nickel plating is used for receiving protective and decorative and wearproof 
coverings on surfaces of details of the cars working in the atmosphere at 
temperatures to 60ºС. When processing steel details, nickel plating is made on a 
copper underlayer to eliminate influence of covering porosity. 
Cadmium plating is applied to protection against atmospheric corrosion of 
products from staly, cast iron and copper alloys. 
Chromium plating of details is carried out for their protection against 
corrosion in the atmosphere of gases, in the damp environment, alkalis and 
acids. Thicker coverings (5-100 mkm) are applied to increase wear resistance of 
the details working in severe constraints. 
Coverings from inorganic materials. 
Coverings from inorganic materials are put on surfaces of metal products for 
the purpose of their protection from corrosion, decrease in coefficient of friction, 
increase heat- and wear resistances. 
Such coverings as oxides, carbides, nitrides and phosphates of metals, enamels 
and firm greasings belong to the main materials. 

239 
Methods of formation of coverings: 
- heat and chemical treatment, 
- surfacing from powders, 
- chemical sedimentation from a gas phase, 
- cathodic dispersion in vacuum. 
Protective oxidic coverings are formed on a product surface as a result of 
oxidation of their blanket under chemical influence. Widespread methods of 
processing steel are: 
- thermal oxygenating (burnishing), 
- chemical oxygenating in boiling caustic rub, 
- phosphate coating (formation of a phosphatic film). 
High-strength and wearproof coverings from oxide of aluminum are put on 
products from metals, firm alloys and ceramics with methods of a plasma 
dusting. 
Carbide, nitride and carbonitride coverings are put on products from steel and 
firm alloys for increase of their wear resistance and corrosion resistance with 
methods of plasma dusting and chemical sedimentation from a gas phase. 
Materials for coverings are carbide, nitride and titanium carbonitride, and also 
chrome and molybdenum carbides. 
Silicate coverings (enamels) combine strength properties of metals with 
corrosion, thermal and abrasive resistance of silicates. They are put in the form 
of powders on products from steel and cast irons and then subject to annealing at 
the temperature 1000ºС. To products from aluminum alloys, coverings from 
fusible enamels with the high content of lead are applied. 
Coverings from polymers and rubber. 
In recent years, independent value was gained by the coverings received from 
firm powdery polymers. They are widely used not only as protective and 
decorative, but also as wearproof and antifrictional coverings, and also as facing 
of products and components of composite coverings of a universal purpose. 
Originally for drawing coverings, generally thermoplastics - polyamides, 
polyolefins were used, and then more considerable application was received by 
thermosets. 
In most cases polymers when drawing coverings are combined with various 
ingredients - softeners, stabilizers, hardeners, fillers. 
Glues. 
Glues are intended for creation from various materials of one-piece 
connections of the demanded durability. 
Process of pasting is based on coupling of glue with a surface of materials. 
The way of pasting simplifies and accelerates technological process of a product 

240 
production. Glue connections in certain cases are the unique types of 
connections among themselves diverse materials. 
Modern glues stick together various plastics, silicate and organic glasses, 
natural and artificial skin, rubbers, ceramics, products from paper and cardboard, 
various breeds of tree, cotton and woolen fabrics, products from synthetic fibers, 
and also metals and alloys, nonmetallic materials and their combinations. 
Indicator of mechanical durability of glue compounds of metals is strength at 
shift. High durability of glue connection can be provided only at application of 
glue of the relevant structure and observance of technological process of 
pasting: 
- cleaning and roughening of connected surfaces, 
- their degreasing, 
- putting glue by a thin layer and its drying, 
- pressing of stuck together details, 
- heating for heat treatment of glue connection. 
Common fault of glue connections is low temperature firmness. 
At car repairs, glue has found application for connection of frictional slips 
with brake shoes and coupling disks. VS-10T glue is used for this purpose 
represents solution of synthetic pitches in organic solvents. It is uniform 
transparent liquid of dark red color without foreign impurity. VS-10T glue can 
be applied to pasting of steel details, dural, plastic and other materials. It 
possesses high heat resistance, oil - and benzine resistance, protective ability 
against corrosion, is ecologically harmless. 
The pasted worn-out frictional slips are removed by cutting, location in hot 
alkaline solution or the warmed-up formic acid or, most often, heating to 
temperature of a slips carbonization (300-320ºС). 
Pasting of frictional slips with brake shoes and coupling disks instead of their 
connection on rivets provides considerable economic efficiency mainly at the 
expense of increase in the used thickness of slips and, therefore, increase in term 
their service. VS-10T glue is applied also at repair of plastic details. 
Details from thermoreactive plastic stick together with the VIAM B-3 pitch 
glues, BF-2, BF-4, K-17 on the basis of phenolformaldehyde, epoxy and other 
pitches. Pasting of details is provided with swelling of stuck together surfaces 
and emergence of glutinosity. 
The dichloroethane or the glue representing solution of sawdust of organic 
glass in formic acid or in a dichloroethane is applied to pasting of organic glass. 
The glue widely applied at production and repair of wooden details can be of 
two types: 
- casein (proteinaceous) for the details protected from moisture, 
-synthetic (pitch) for the details which are exposed to influence of moisture, 
demanding the increased durability of connection and protection them from 
destruction by fungus. 

241 
The casein glues - represents water solution of casein powder (product of milk 
processing). 
Synthetic glues consist of pitch (thicket phenolformaldehyde, epoxy) or 
difficult vinyl air (PVA, PVB) and solvent (acetone, ethyl alcohol) and hardener. 
Pasting by casein and synthetic glue is possible at the room temperature. The 
prepared glue needs to be used within 3 hours. Humidity of stuck together wood 
shouldn't exceed 18%. 
Connection of gaps, imposing of patches at repair of bodies is made by means 
of synthetic BF-6 glue. PVB is also widely used for preparation of films, 
varnishes and sheetings. PVA-polyvinyl acetate represents a product of 
polymerization of vinyl-acetic ester. Possesses good film-forming properties, 
can be dissolved in many solvents, therefore the main application of PVA-
pasting of paper, fabrics, skin, glasses, ceramics, tree. A number of paints on the 
basis of water dispersions of PVA is developed. 
The repaired place after putting synthetic glue is pressed through a damp rag 
by the iron heated to 130ºС during 12-15 with short breaks. Upholstery gluing to 
wooden details is made by AK-20 nitroglue and to cardboard – glue № 4010. To 
gluing of rubber details to the metal, we apply glue №88, №88Н, №66. 

жүктеу/скачать 1,99 Mb.

Достарыңызбен бөлісу: