Fergana polytechnic insitute mechanical engineering faculty department of mechanical engineering and automation

2.
 
Carbide generators 
:
 
Cr; Mn; W; Mo; V; Ti; Hb; Ta; TS; Hf. 
Figure 6.1 . Dependence of the strength on the number of dislocations and other 
defects. 
Alloying elements increase the strength and hardness of the metal due to 
dislocations 
, phase changes, allotropic changes, and the formation of carbides. Other 
characteristics are also affected. 
Cr - increases resistance to abrasion, increases rust tolerance. With W and G, it 
increases the ability not to be deformed under the influence of temperature. For this 
reason, long-sized ("dlinnye mernye") cutters are made from alloyed XVG steel, for 
example, a protyajka. 
W – resistance to grass. For example, along with Aynika V, this steel is R18 

high-speed steel. Various cutters are made. 
Ni - increases hardness, 
anti-rust 
ni and xk properties. In particular, together 
with nickel chromium: steels in the Cr-Ni system. 

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67 
Marking of alloy steels. 
A - nitrogen, B - niobium, P - phosphorus, D - copper, G - manganese, V - tungsten, F 
- vanadium, K - cobalt, M - molybdenum, N - nickel, R - boron, T - titanium, S - 
silicon, X – chromium, TS – zirconium, Yu – aluminum, CH – rare earth metals. 
18X2N4V,EN154, EP3980,18% - S "Elektrostal" plant P - model. 
2% - X
N - "experimental " 4% - N 154 - serial number 1% - W 
Requirements for structural steels . 
These contain 0.1-0.25% carbon. These steels include trusses, ship hulls, fittings, 
etc. Due to its low carbon content, it welds well. These are also made for reinforced 
concrete pipelines, oil and gas pipelines , and metal pipes . However, it is used 
occasionally for car detailing. These steels St.1; St. 2; .... ;St. 6 will be marked. The 
strength of these steels is equal to 

og 
= 240 Mpa. 
Low-alloyed steels used in construction: 14G2; 17GS; 14XGS; 15XSND (D-
Cu). Stal 15XSND works even in extreme cold (-60 o C) 
, 
because N + D does not 
embrittle even in cold. In addition, they also increase the resistance to corrosion in the 
air. 
In construction and mechanical engineering, sheets and rolled products 

are 
made of low-alloyed steels 14G2AF, 17G2AFB ( 
og =450 MPa). When 
these are added , they 
are refined to form carbonitrides. 
Plastic deformation is not allowed. It is alloyed with silicon and manganese. 
There is a high degree of attachment and attachment . 65; 70; 65G; 60S2; 70S3A; 
60SG; 40XFA. 
Embodied force of different poles is affected. It should be hard , resistant to 
eating and not fatigued ( kontaktnaya ustalost) : SHX4; SHX15; SHX15SG; 
SHX20SG. 
The fire resistance of iron and steel is increased by alloying them with 
chromium, aluminum and silicon. Chromium is the most widely used in alloying iron 
and steel and its content reaches 30%. As the content of chromium in the steel 
increases, and the temperature rises and the time of holding it increases, the amount of 

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68 
chromium in the oxide increases. Alloyed iron oxide replaces chromium oxide, which 
increases fire resistance. 
The more chromium in the steel, the higher the temperature . the time of its use 
will also be long. Refractoriness is determined by the chemical composition of the steel 
(mainly by the amount of chromium) and is less dependent on its structure. 
Additional alloying of refractory steels with additional silicon (2-3%) and 
aluminum (1-2%) increases its service temperature. 
The chemical composition and properties of some refractory steels are given 
below. Steels 08X17T and 15X25T are not heat-resistant with ferrite, therefore, it is 
used for details that are not subjected to great force and do not have impact strength. 
Steels 20X23N18 and 20X25N20S2 is both fire-resistant and heat-resistant, therefore, 
in shoe ovens, floor slabs, used in conveyors. Fire resistant 
6 .Table 1. 
Chemical composition and properties of some refractory steels 
Steel
brand 
Amount of elements, 
% 
Properties 
C 
Cr 
Ni 
Si 
s 
b 
, 
MP a 
d, % 
08X17T* 
≤0.08 
16-18 
0.7 
0.8 
450 
20 
15X28* 
≤0.15 
27-29 
0.8 
1.0 
450 
20 
20X23N18** 
≤0.2 
22-25 
17-20 
1.0 
500 
35 
20X25N20S2** ≤0.2 
24-27 
18-21 
2-3 
600 
35 
Note: Ti=0.4-0.8 in steel 08X17T. 
*-normalized;**- obtained; 
aircraft engine parts (operating at 700-1000ºС) are made of steel; gas pipe plates, 
pipe discs, pipes, etc 
Refractory steels alloyed with Cr and Si are called "silchrome", those alloyed 
with Cr and Al are called "chromal", and those alloyed with Cr-Al-Si are called 
"cylchromal". The melting temperature of "Silkhromal" is very high (850-950ºС). 

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69 
These are fired in oil (1000-1050ºС); released (500-540ºС). Silchromal steel 
10X13SYu fire resistance 950 
0 
C; also works in sulfur environment. 
Steel 36X18N25S2 with high technological properties, fire resistance is 1100ºС, 
it is stable even at a much higher temperature, i.e. it is heat resistant.