Steel key
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Introduction
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Classification of carbon steels
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Steel Classification Standard
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German standardDIN
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American StandardAISI/SAE
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StandardUNS
1-Introduction
Steels are a group of alloys of iron-carbon and other elements that are most widely used in industry and technology. The wide application of steels is due to their completely diverse properties, which is possible by changing the percentage of carbon or changing the percentage of alloying elements or changing the type of heat treatment. The wide range of diverse properties of steels is due to the type, amount, size and distribution of different phases..
Engineers, drafters, purchasing agents and suppliers all speak the same language of steel, aluminium and copper and are assured of the same products. A metal standard is an industry-wide agreement to define metals. This definition contains a lot of information about the chemical composition, manufacturing process, heat treatment and other information related to the metal. The standard usually attempts to specify all the different characteristics of a metal in a simple code consisting of numbers and letters. The most important use of these standards is the exchange of information..
Just as there are different languages to speak, there are also different standards around the world..
International metal standards include::
America: ASTM, AISI, SAE, UNS
Canada: CSA
Germany: DIN
France: AFNOR
England: BS
Italy: UNI
Japan:JIS
Here, a number of these standards are introduced and then the relationship between these standards is examined. There are also various classifications based on different systems for steels, and here we will mention some of these classifications. These classifications may be based on the following::
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Chemical composition: Such as carbon steel, low alloy, stainless steel,…
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Production method: Such as Siemens Martin, oxygen steelmaking, electric furnace method,…
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Payment method: Such as hot rolling, cold rolling,…
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Product shape: Such as rebar, sheet, strip, pipe or structural form
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Oxygen removal operation: Such as calm, semi-calm or uncalm steel
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Microscopic structure: Such as ferritic, pearlitic, martensitic steel
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Strength : Required strength level specified in the ASTM standard
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Heat treatment: Such as annealing, quenching, tempering and thermomechanical processes
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Desired quality such as forged quality or economic quality
2 – Classification of carbon steels
Carbon steels are alloys of iron and carbon that usually contain no more than 1 percent carbon, no more than 1.65 percent manganese, and no more than 0.6 percent copper and silicon. Other alloying elements are usually not significant. The properties and weldability of these steels depend on their carbon content, with other elements having a limited effect..
Carbon steels are classified into subclasses based on oxygen content.:
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Unalloyed steels: A type of low-carbon steel that has not been deoxidized..
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Cast steel: similar to semi-quiet steel
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Semi-calm steel: Deoxidizers such as silicon are added to this steel in a small amount of about 0.1%..
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Calm steel: Steel in which the oxygen is completely removed by manganese and silicon or aluminum before casting. The deoxygenation process and steelmaking processes affect the characteristics and properties of the steel..
Changes in carbon content have the greatest effect on mechanical properties, and hardness and strength increase with increasing carbon content. Carbon steels are usually classified based on the percentage of carbon, as shown in Table (1)..
Table (1): Classification of carbon steels based on carbon percentage
Application |
Common difficulty |
Carbon percentage |
Title |
plate and sheet shapes |
60HRB |
0.15max |
Low carbon steel |
structural shape |
90HRB |
0.15-0.30 |
Mild steel |
machine parts and tools |
25HRB |
0.30-0.50 |
Medium carbon steel |
Spring, Dies |
40 HRB |
0.50-1.00 |
High carbon steel |
Plain carbon steels are divided into four categories::
2-1- Low carbon steels with a maximum of 0.15% carbon
2-2- Steel with partial carbon (normal) between 0.3-0.15% carbon
2-3- Medium carbon steel between 0.3-0.5% carbon
2-4- High carbon steel (high carbon) between 0.5-1% carbon
2-1- Low carbon steels:
The carbon percentage of these steels is maximum 0.15%, in the industry they are sometimes known as tensile steel. Because they have a high relative length change, they are mostly produced as thin sheets and sometimes used as wires or rods. These steels also have high magnetic properties and good weldability and do not have any particular problem in welding. These steels have low hardenability..
2-2- Steel with low carbon content
These steels have a lower relative elongation than low carbon steels but have better tensile strength. They are usually produced in sheet form and sometimes in angle and rebar. The most popular steels in this category are:St37. These two groups of steels, namely low-carbon and low-carbon steels, are known as structural steels and are called ironworks in the industry. The percentage of carbon in these steels is 0.3-0.15% and they have good weldability. In other words, carbon steels containing 0.15 to 0.3% carbon are called soft steels. If carbon steel contains about 0.3 and 1.4% carbon and manganese, respectively, welding is possible, but the weld metal is prone to cracks adjacent to the weld due to increased hardness and strength.
2-3 – Medium carbon steels
Medium carbon steels are widely used in tool steels. Many of these steels are selected for their high wear resistance and are heat treated to achieve the desired properties. Welding may occur before the final heat treatment. Therefore, the selection of filler metal and welding procedures should be based on this. Whenever welding occurs before heat treatment, special considerations must be made in the selection of filler metal to ensure that the properties of the weld metal match those of the base metal..
2-4- High carbon steel
High carbon steel is usually used for applications where high hardness or wear resistance is required, these properties are achieved by heat treatment. The steel should be welded in the annealed condition and then heat treated. Annealing is usually recommended before repair welding of broken sections..
3- Steel classification standard
DIN-1-3 – German standard
Steels can be classified in the following way::
– General structural steels:
These are steels for which heat treatment is not foreseen. The most important characteristics of these steels are their mechanical properties (tensile strength, yield stress and elongation), their quality group and their characteristics for forming. The yield stress depends on the thickness of the product. For example, in structural steelSt50-2 with a thickness of 16mm has a yield stress of 295 Mpa and in a thickness of 0-80 mm the yield stress is 265 Mpa. That is, the yield stress decreases with increasing thickness. The elongation decreases with increasing strength, meaning that the steel becomes brittle. St37-2 steel and St70-2 steel have 25% and 10% elongation, respectively. Having the same mechanical properties, steel is divided into two quality groups 2 and 3 in terms of insensitivity to brittleness and welding characteristics. Quality group 3 steel is of high quality in that it has less phosphorus, sulfur and nitrogen.
General structural steels are used for parts that are not subject to wear and do not require hardening. For example, die tails, backs, handles, etc. Sheets and strips are made of non-alloyed, soft steel, often produced by cold rolling. In thicknesses of 0.3-5 mm, called fine sheet, it is used for shaping, for example, deep drawing. Depending on the subsequent application, fine sheet is divided into surface type and appearance and quality group. Very fine sheet and white sheet(DIN 1616) is less than 0.5 mm thick. These sheets are delivered with different hardness grades and thicknesses. For example, the specification DIN1616-0, 30T52 is a very fine sheet, meaning: thickness 0.3 mm, hardness grade = 52T and maximum hardness according to T30 HR is 56.
The assignment of formability is done with another characteristic letter in the standard code, which is given in Table (2)..
Table (2): Shaping capability allocation
Short description |
Meaning |
Example |
Q |
Bendable, malleable |
QST37-3 |
Z |
Stretchable |
ZST44-3 |
K |
Reshapeable |
KST53-3 |
– Good cutting steels (free cutting):
Free-cutting steels are high-quality, unalloyed or low-alloyed steels that have high sulfur, phosphorus, manganese, or lead content. These steels are mostly used for mass-produced parts on automatic lathes. Alloying elements such as sulfur or lead cause chips to become brittle, which in turn increases the speed of chip removal..
-Carburized steels:
Carburized steels are used for components that are subject to increased wear and bending. Therefore, they must have a hard, wear-resistant surface and a soft, tough core with high strength. Carburized steels are divided into two types: non-alloyed carbide steels with a carbon content of less than 0.2%, for example:C10, C15, Ck10, Ck15 and alloyed carbide steels alloyed with manganese.
– Heat-treated steels:
Tempering steels are used for components that are subjected to severe tensile, bending and torsional loads of the sudden type. With special heat treatment, these steels have very high tensile strength and high toughness (energy absorption capacity)..
Heat-treated steels;
V in improved condition with letter
N in the normalized annealing condition with the letter
andG in the open-baked state softened with the letter
It is determinedB. In heat treated condition for better machining with letter
-Nitrided steels:
Nitrided steels are used for components that are particularly exposed to high and variable abrasion loads and also because they should not change in size or warp during heat treatment. By penetrating nitrogen into the surface of the workpiece, a special anti-wear layer of iron nitride is formed. Nitrided steels are low-alloy steels whose nitrides are made by the elements aluminum, chromium and vanadium..
-Special steels:
These steels include:
Spring steels (e.g.C75,66Si7 (
High temperature resistant steels, for exampleX4NiCrTi-25-15
Fireproof steels, for exampleX15CrNiSi-25-20
Stainless steels, for exampleX15CrNi-l8-8
Stainless steels (non-magnetic, for example) (X40MnCr-18.
-Non-alloy tool steels:
Non-alloy tool steels are used to make tools that are not subjected to high thermal stress. These steels have no core or depth hardness and lose their high surface hardness at 200°C and heavy loads are tolerated by their tough core. The carbon content of these steels is 0.5 to 1.5% and the higher the carbon content, the higher the maximum hardenability. Non-alloy tool steels are produced in three quality groups:.
-Alloy tool steels
In toolmaking and diemaking, the temperature of the workpiece during deformation is a determining factor in the selection of steel. Tools whose surface is heated to 200°C during machining are made of cold-work steels. Alloying ElementsCr, Ni, W, Mn, Mo ensure that these steels are work-hardened even in large sections and do not undergo severe deformation.
-Cold work steels
Cold-work steels must have high wear resistance, as well as high compressive strength and toughness. They have good machinability in the annealed state and are less subject to dimensional change and distortion during heat treatment (Table 3)..
Table 3: Examples of cold-worked steels
Material number |
Short description according toDIN17006 |
Application examples and special features |
1.2004 |
85Cr1 |
Measuring tools and equipment |
1.2083 |
X42Cr13 |
Special synthetic material molds made of corrosion-resistant fiberglass with high dimensional stability |
1.2436 |
X210Crw12 |
Cutting dies. High volume. Drawing dies |
1.2710 |
45NiCr6v |
Thermoplastic molds. Good toughness. Polishable. Nitriding-capable. |
1.2721 |
50Nicr13 |
Plastic round molds. Resistant to pressure and abrasion. High dimensional stability. Polishable. |
1.2842 |
90MnCV8 |
Low-volume cutting dies. Order measuring devices |
1.3247 |
52-10-1-821 |
Cold extrusion dies. Cutting punches |
-Hot work steels
The strength, hardness and wear resistance of hot-worked steels change only slightly even at high temperatures. These properties, as well as increased heat strength, thermal toughness, rebound resistance and resistance to temperature fluctuations, are due to the alloying elements chromium, vanadium, tungsten, nickel and molybdenum (Table 4)..
Table (4): Example of hot-worked steels
Material number |
Short description according toDIN I7006 |
Application examples and special features |
1.1730 |
C45W |
Simple forging steels, hammers, cutting blades, screwdrivers, knives |
1.2323 |
48CRM0V67 |
Injection and pressing molds |
1.2343 |
X38CRM0V51 |
Light metal injection molding Extrusion molding |
1.2365 |
X32CRM0V33 |
Injection molds under pressure. Punching and drilling in extrusion molds High return stability for narrow sections that are not core-hardened |
1.2713 |
55NICRM0V6 |
Forging dies and pond liner dies are not brain-hardened. |
DIN- Steel Nomenclature System according to 2-3
Non-alloy steels contain a number of associated elements whose amounts never exceed the values stated below. These associated elements enter the steels through the melting of the raw materials..
P<0.09. S<0.06./. Ti<0.1./. Si<0.5./. Mn<0.8./. Al<0.1./.
We divide these non-alloy steels into two parts. This division is based on whether this steel is intended for heat treatment or not..
First category: Bulk steels marked by the symbolIt is indicated by St followed by a two-digit number indicating the minimum tensile strength. According to this standard, the production method and special cases are sometimes indicated by the letters that precede St. These categories are not intended for heat treatment.
The second category: These are high-quality steels that are intended for heat treatment. In this type of steel, the wordC is used as its characteristic, after which the average percentage of carbon is presented as a hundredfold. In order to distinguish non-alloy steels or to indicate its affiliation to a certain group of steels, the following letters with certain meanings come after the symbol:
Cf53: Steel for flame and induction hardening, e.g. f
Ck53: Noble steel with low phosphorus and sulfur content, e.g. K
Cm35: Noble steel with a certain range of – not just the upper limit – sulfur content, e.g. m
Cq35 Carburizing and tempering steel for cold heading, for example: q
Sometimes, after the carbon content number, the following letter also appears::
C80W1 First-class quality tool steel, for example: W1
C80W2 Second-grade quality tool steel, for example: W2
In the German standard, the following letters are used to specify the production method:.
B: Bessemer steel
E: Electrical steel
M: Siemens Steel
T: Thomas Steel
U: Unstressed steel
Alloy steels
Alloy steels are named only according to their chemical composition. This method expresses the exact characteristics of the steel. In addition, this method allows for a clear naming of the steel in the raw cast block state. Of course, it is not possible to know the type of process and heat treatment that is performed on it or its strength properties that are obtained later, for example, by tempering..
The full nomenclature of an alloy steel is as follows::
1- Letters identifying the type of casting
2- Letters identifying properties that are conditional on the melting and curing process.
3-Characteristic number of carbon
4-Chemical symbol of alloying elements
5- Guaranteed range identification number
6- Letters indicating the heat treatment status
7- Guaranteed tensile strength characteristic number or other determining properties
– Carbon characteristic number
One hundred times the carbon content is considered as the carbon characteristic number. In order to distinguish very similar brands, if necessary, its value is shown by increasing or decreasing by 1 unit. In alloy steels, in order to shorten the symbolC is omitted. This symbol is placed before the C designation number only in non-alloy steels. The C designation number is placed first.
– Chemical symbol of alloying elements
Chemical symbols are generally used to characterize alloy components. These symbols are placed immediately after the characteristic.C is placed. Of course, in order of percentage value, if the percentage value is the same, the symbols are arranged alphabetically. After this group of symbols, the alloy characteristic numbers come in the same order as the symbols. In fact, the group of numbers comes together. As a rule, it can be said that alloying elements are selected for naming, which are necessary for the characteristic of the steel or its distinction from other similar steels. Therefore, the characteristic numbers are related to these alloys.
– Characteristic numbers of alloying additions and coefficients
The concept and purpose of using coefficients is to make the characteristic numbers as small as possible (also without decimals), which, together with the chemical symbols, are placed in specific groups depending on their percentage value. In this way, each steel can be sorted depending on the type and amount of its alloy..
– Low alloy steels
In this type of steel, the percentage of alloying elements is less than 5% by weight. Here the standard DIN, which is that instead of the letters C or St used in non-alloy steels, a number is used that indicates one hundred times the average carbon content in percent. Then, the symbols of the alloying elements are used in order of the abundance of that element, and certain coefficients are also selected to indicate the percentage of these alloying elements. So that these coefficients are multiplied by the average percentage of that alloying element.
These coefficients for the elements:
4————–W.Si. No. Mn, Cr.Co |
10 ——————–Ti .Mo .Ai .V .Cu |
100……….NC |
For example 15Cr3 is a low-alloy steel with an average carbon content of 15% and an alloying element of about 0.75% chromium. E36CrNiMo4V is a steel produced using an electric melting furnace and heat treated, with a carbon content of 0.36%, chromium content of 1%, and nickel and molybdenum content.
Number |
DIN mark |
Analzye |
||||||||
C% |
Yes% yes |
Mn% mn |
P% |
S% |
Cr% |
Mo% |
Ni% |
V% |
||
1.2838 |
145V33 |
1.4-1.5 |
0 02-035 0 |
0.5-0.3 |
0.03 |
0.03 |
– |
– — |
– – |
3-3.5 |
1.2826 |
60MnSiCr4 |
58%-65% |
0.8-1.2 0 |
0.03 |
0.03 |
0.03 |
02-04 |
– – |
– |
– |
1.2726 |
226NiCrMoV5 |
0.22-0.3 |
0.3-0.5 0. |
0.2-0.4 |
0.03 |
0.03 |
0.6-0.9 |
0.2-0.4 |
13-16 |
0.15–020 |
-High-alloy steels
The percentage of alloying elements in them is more than 5%. Here, first of all, the letterX is used and then we give the weight percentage of carbon and then, like low alloys, we give the abbreviations of the alloying elements in order from highest to lowest in the steel, with the difference that here carbon has a coefficient of 100 and we give the alloying elements in order from highest to lowest in the steel and they have a coefficient of one.
Ni |
Mo% |
Cr% |
S% |
P% |
Mn% |
Si% |
C% |
dinsign |
Number |
19-21 |
– |
24-26 |
0/035 |
0.035 |
<2 |
18-2.3 |
<0.15 |
X11115CRNISI252O |
1.2782 |
<1 |
0.9-1.3 |
12-14 |
0.03 |
0.045 |
<1 |
<1 |
0.17-0.22 |
X20CRMO13 |
1.4120 |
If the carbon content characterizing number is omitted due to unimportance, in order to shorten the steel characterizing number, the symbol is omitted.X is also ignored.
DIN 17006 Complete specification of steels according to
Naming of steels according toDIN17006, as mentioned, consists of three parts, as shown in the following example:
Y30CrNiMo8V130
Production department(Y): Oxygen-blasted steel
Composition section(30 CrNiMo8) :
30: Carbon percentage 0.3% and Cr and 8: 8.4=2% Chromium and Ni and Mo in small amounts
Heat treatment department:
V: Improvement and 130: Strength 1275 MPa
Given that steels have different types of production, composition, and heat treatment, the characteristics of steels mentioned in the naming of steels are expressed in the table below.:
Steel production sector |
Steel composition section |
Steel heat treatment department |
|||||
Symptoms of castration |
F |
Flame or induction hardening possible |
Heat treatment status |
||||
G |
General casting |
K |
Low sulfur and phosphorus content |
A |
Returned |
||
GG |
Gray cast iron |
M |
Guaranteed sulfur content in non-alloy steel |
AH |
Old age has become hard. |
||
GH |
Ductile iron |
S |
Range of sulfur content in steelAlloy |
AL |
Heated deposition |
||
GS |
Cast steelMalleable cast iron. Ductile iron. |
ST |
Steel without mention of composition |
B |
MachinabilityGood |
||
GTW |
Malleable cast iron, black core |
Chemical element |
Chemical element |
Coefficient |
E |
Carburized Hardening |
|
GGL |
Austenitic flake graphite gray cast iron |
A1 |
Aluminum |
10 |
G |
Soft annealing |
|
GGG |
Spheroidal graphite cast iron |
B |
On |
1000 |
G |
Shiny |
|
GK |
Casting in metal molds |
BE |
Beryllium |
10 |
GKZ |
Annealed spherical cementite |
|
GZ |
Centrifugal casting |
C |
Carbon |
100 |
H |
Hard-working |
|
Casting process |
Ce |
Cerium |
100 |
HF |
Flame hardened surface |
||
B |
Bessemer steel |
CO |
Cobalt |
4 |
HJ |
Induced surface hardening |
|
B |
MB game for example |
CR |
Cream |
4 |
K |
Cold forming |
|
E |
Electro steel |
CU |
Copper |
10 |
KBK |
Tension of the armature |
|
F |
Flame furnace melting |
FE |
Iron |
– |
L |
Solution annealing |
|
J |
Electro-steel (in induction furnace) |
MG |
Magnesium |
– |
M |
Matte |
|
M |
SteelSiemens Martin |
MN |
McKenzies |
4 |
N |
Normalized annealing |
|
PP |
Pudlazh steel |
MO |
Molybdenum |
10 |
NT |
Nitrided |
|
ss |
Welding fold |
N |
Nitrogen |
100 |
R |
Weber |
|
t |
Thomas F. Steel |
Nb |
Niobium |
10 |
S |
Stress relieving annealing |
|
you |
Steel crucible |
no |
Nickel |
4 |
Sh |
Peeled |
|
V |
Vacuum steel |
p |
Phosphorus |
100 |
U |
Bad van heat treatment |
|
WT |
Weather-resistant steel |
PB |
Lead |
10 |
V |
Improved |
|
Y |
Oxygen-breathing steel |
S |
Sulfur |
100 |
W |
Non-alloy tool steel |
|
Y |
Oxide, for exampleMY |
SI |
Cecilium |
4 |
W |
Tool steel quality group =1-2-3 |
|
Casting type |
SN |
Tin |
– |
W.K. |
Hard work, hot and cold |
||
H |
Casting type |
Ta |
Tantalum |
10 |
Guaranteed Limited Characteristic Number |
||
U |
Uneasy spilled |
TI |
Titanium |
10 |
.1 |
Yield stress |
|
R |
Calm and semi-calm poured |
V |
Vanadium |
10 |
.2 |
Bending and bending test |
|
RR |
Special poured Aram |
W |
Tungsten |
4 |
.3 |
Impact toughness |
|
Special properties |
Zn |
On |
– |
.4 |
1+2 |
||
A |
Weather-resistant steel |
Zr |
Under the hood, under the hood |
10 |
.5 |
2+3 |
|
G |
High contentP. |
.6 |
1+3 |
||||
K |
Low contentP.P |
.7 |
.1+.2+.3 |
||||
L |
Stable to alkali |
.8 |
Thermal and fatigue strength |
||||
Q .q |
Capable of being beaten |
.9 |
Electrical or magnetic properties |
||||
s |
Fusion welding capability |
||||||
x |
High alloy (factor 1) |
||||||
z |
Stretchable |
||||||
p |
Forging direction of closed die |
||||||
Ro |
For welding pipes |
||||||
Material numbering system for steels and cast steels according toDIN1700
The material number is a six-digit number as follows::
X.XXXX.X
-Characteristic numbers of the main group of materials
For the main group of materials, we can write:
0: Pig iron, cast irons and alloys
1: Steels
2: Heavy metals other than Fe
Light metals: 3
Non-ferrous metals: 8 to 4
Free for indoor use: 9
(Fe) is the most abundant element in all materials in which iron is present. Main group 0.1
-Type number
The first two digits are the steel type number and the next two digits are the counter digits. Steel types are divided into the following groups:.
Basic and high-quality steels and noble steels.
These groups are further divided into smaller subgroups based on their chemical composition and significant characteristics resulting from the technical conditions of use and production..
No conclusions can be drawn from the counter figures regarding the amount of carbon and alloying elements..
Type grade |
Type number |
Type grade |
Type number |
Noble alloy steels |
Low carbon steels and quality alloys |
||
Tool steels |
20………28 |
Base steels |
00 |
High-speed steels |
32……..33. |
Non-alloy structural steels |
01….02 |
Wear-resistant steels |
34 |
High-quality non-alloy steels |
03………07. |
Rolling bearing steel |
35 |
Quality alloy steels |
08………09 08 |
Ferrous materials with special physical properties |
36.. .39 |
Special types of base steels |
90 |
Stainless steels |
40….45 |
Other special types |
91……..99 |
Heat-resistant steels |
47…48 |
Non-alloyed noble steels |
|
High temperature materials |
49 |
||
Structural steels |
50….84 |
Steel with special physical properties |
10 |
Nitrided steels |
85 |
Structural steels |
11……..12 |
Hard alloys |
88 |
Tool steels |
15………18 |