1．The meaning of all kinds of symbols and numbers
（1）The meaning of various symbols, the meaning of various symbols see Table 1。
Table 1 All kinds of symbols and meanings
| Symbol |
Meaning |
Symbol |
Meaning |
| M |
open health steel |
X |
High alloy symbol |
| E |
Electric furnace steel； carburizing and quenching |
G |
Casting；Soft annealing |
| W |
Converter steel； quality grade |
GG |
Gray iron castings |
| U |
Not killed pouring；Without heat treatment |
GGG |
nodular cast iron |
| H |
Semi killed casting；quench |
GT |
malleable cast-iron |
| R |
Calm pouring |
GS |
cast steel |
| A |
Engage in time；tempering |
HF |
flame hardening |
| N |
N；normalizing |
HI |
Induction quenching |
| S |
Stress relief annealing |
NT |
nitridation |
| V |
vanadium；QT |
K |
Requires low S, P content |
When a symbol has two meanings, the meaning of the symbol should be determined in the position of the brand.
- the representation of alloying elements in alloy steel by means of the average content of alloying elements multiplied by the coefficient in Table 2 represents the value of the gold element content.
Table 2 Coefficient of alloying elements
| alloying element |
coefficient |
| Cr 、 Co 、 Mn 、 Ni 、 Si 、 W |
4 |
| Al 、 Be 、 Cu 、 Mo 、 Nb 、 Pb 、 Ta 、 Ti 、 V 、 Zr |
10 |
| Ce 、 N 、 P 、 S |
100 |
| B |
1000 |
The content of alloy elements is less than or equal to 5%, using the above table coefficient multiplication, content of alloy elements > 5%, but no longer multiplied by the coefficient, such as the outright.
2．A sample of the steel grades according to the strength grade
The grade representation method is only applicable to the DIN-EN.S235JR standard of the non alloy steel, which is equivalent to the old brand St37-2.235 tensile strength (MPa) minimum value, and the old and new grades are shown in Table 3
Table 3 Examples of new and old brands
| New Grade |
Old Grade |
New Grade |
Old Grade |
| S185 |
St33 |
S275JQ |
St44-3U |
| S235JR |
St37-2 |
S275J2G3 |
St44-3N |
| S235JRG1 |
USt37-2 |
S355JR |
St52-3U |
| S235JRG2 |
RSt37-2 |
S355J2G3 |
St52-3N |
| S235J0 |
St37-3U |
E295 |
St50-2 |
| S235J2G3 |
St37-3N |
E355 |
St60-2 |
| S275JR |
St44-2 |
E360 |
St70-2 |
3．An example of a chemical composition of steel
This designation is applicable to non alloy steel, low alloy steel and high alloy steel. Non alloy steel grades non alloy steel carbon steel as example, technical conditions and other performance requirements higher than the steel strength indicator, the chemical composition of commonly used representation methods to represent trademarks.
Grade prefix symbol for C, followed by the average content of carbon (in very few dollars) percentage, plus symbols with special requirements. Ck control with P, S amount of high-quality steel Cq cold heading steel, examples are as follows：
C20— The average carbon content of W (C) of 0.20% carbon steel .
C20E— Carburizing and quenching of the average carbon content of (C) is 0.20% of the carburizing steel.
C35E —The normalized average carbon content w (C) of 0.35% carbon steel.
• Carbon tool steel grades that the method of carbon tool steel is also a non alloy steel, often included in the tool steel series. Grade with a non alloy steel grade representation method, and the other with the suffix letter W1, W and W2, said different grades.
In recent years, in order to facilitate the same European standards (EN) and international standards (ISO), part of the carbon tool steel grades are also available ISO standard grades, such as C70U equivalent to C70W1
• Low alloy steel and alloy steel grade method only when the alloying elements in Steel w (Si) = 0.50%, w (Mn) = 0.80%, w (Al) and w (Ti) = 0.10% respectively and w (Cu) = 0.25%, these elements can be called alloy elements, this is our alloy elements the content of the limit value (see table 1-2). A slightly different grades is composed of 00 * * - *, 00 w (C)% average content value, * * symbol and content of alloy elements, content values in table 1-25. Set the execution, - x for the specified suffix symbol. The example is as follows
15Cr3 - the average carbon content of W (C) 0.15%, the average content of chromium (Cr) w (3/4)% (0.75%) of the steel.
15Cr3E - the average carbon content of W (C) 0.15%, the average chromium content w (Cr) 0.75%, subject to the carburizing and quenching steel.
25CrMo56V+65S - the average carbon content of W (C) 0.25%, the average chromium content w (Cr) 1.25, the average content of molybdenum (Mo) 0.60%, Omega quenched and tempered the tensile strength of the minimum value of 65kgf/mm 2 (635MPa), and the elimination of alloy steel stress treatment.
• Usually when a high alloy steel element content in alloy steel is more than 5%, this kind of steel is called high alloy steel grades. The first is composed of X (dubbed the letter said, then high alloy) is that the average carbon content of numbers (in very few dollars) and alloy element content by alloy element content, and from the main character the average percent of the alloy. The numerical examples are as follows
X10CrNi18-8 - (C) 0.10%, (Cr) 8%, stainless steel (Ni) 18%.
• High speed tool steel grade designation letter is most preceded by the letter S high speed tool steel, followed by a combination of numbers (three or four group) said the mass percentage of alloying elements, each with a number between short-term separated. General Cr content shall not be marked, followed by W, Mo, V, Co mark. The order of high speed tool steel without Mo, the combination of numbers 0, and not containing cobalt high speed steel, only the first three numbers.
Similarly, in line with the European standard (EN) and international standards (ISO), can also be used to replace S HS, both generic examples are as follows：
S18-0-1 (HS18-0-1) W18Cr4V high speed tool steel equivalent to China. In addition, according to the common cold heading steel steel in China named, free cutting steel, spring steel and bearing steel, stainless steel, heat-resistant steel and alloy tool steel, according to the relevant provisions of the said their grades, no longer list。
4．Method for the representation of cast steel grades
The cast steel is divided into non alloy steel (i.e., carbon steel, alloy steel and high alloy) are usually three categories. According to the chemical composition (mass fraction) represents the grade of steel, some non alloy steel according to the strength value of grade grades. Can also be said that the cast steel grades before deformation, with all kinds of brand steel said different letters and symbols to cast steel, for example：
GS-45 —Non alloy cast steel for general engineering.
GS-20Mn5 —Low alloy cast steel for welded structure.
G-X20Cr14 —Stainless steel, corrosion resistant cast steel.
G-X120Mn13 — high manganese cast steel.
5．Method for the representation of cast iron
There are two types of representation can be expressed a kind of cast iron grades. Grades by prefix letters and numbers. A set of digital brands, said only the minimum tensile strength (MPa); group two digital grades, after the group number indicates the elongation (%) minimum value. Examples are as follows:
GG-20 Grey cast iron, tensile strength is more than 196MPa (20kgf/mm^2).
GTS-35-10 —FCMB, tensile strength more than 343Mpa (35kgf/mm^2).
Another type of brand is made up of the prefix letters, symbols and numbers of the alloy elements, the number of the main alloying elements of the mass fraction content:
G-X300NiCr42 —The average content of each element of W (C) 8% (Ni), Omega 4% and omega (Cr) 2%. Wear resistant white cast iron
