Steel grade
|
DIN EN 10027 |
|---|---|
| Area | Materials |
| title | Designation systems for steels - Part 1: Short names, Part 2: Numbering system |
| Latest edition | 2017-01 / 2015-07 |
| ISO |
As steel grade the different types of steels referred. In the past, the terms steel brand or steel quality were also common. By specifying the steel grade, the manufacturer guarantees certain properties that depend on the composition and thermal treatment of the raw material.
The designation of steels is specified in EN 10027-1 and 10027-2. In addition to the brief classification according to material numbers , each steel is also given a short material name , which is mainly based on its intended use. It is also common to classify steel according to its chemical composition, i.e. its alloy components.
Short material name
Unalloyed steels
Bulk steels for machine and steel construction
| EN 10025 (current) | EN 10025 (old) | DIN 17100 (old national) | Remarks |
|---|---|---|---|
| S235JR + AR | S235JRG2 | RSt 37-2 | Calmed steel, yield point of 235 N / mm² for the smallest product thickness, quality group JR, not normalized (+ AR). |
| S355J2 + N | S355J2G3 | St 52-3 N | Calmed steel, yield strength of 355 N / mm² for the smallest product thickness, quality group J2, normalized (+ N). |
In the structure of steels according to EN 10025, structural steels are given the prefix S for “structural steel”. The following number indicates the characteristic yield point in N / mm². According to the now withdrawn DIN 17100 standard , structural steels were designated St x in Germany , where x stood for one tenth of the tensile strength value in N / mm² (or for the tensile strength value in the unit kp / mm² used at the time). This term is still widely used in everyday life. Structural steels are only characterized according to their mechanical properties. A steel with the same designation can therefore have a significantly different chemical composition depending on the manufacturer and batch.
The first letters after the yield point provide information about the notched impact strength . The following letters identify further mechanical properties or the intended use of the steel produced. Examples:
- K: cold worked
- A: annealed
- N: normalized
- V: remunerated
The oxygen content of the steel can be characterized by the following codes:
- FU: poured without calming (i.e. contains a lot of residual oxygen and distinct segregation zones )
- FN: simply shed calmly (i.e. contains less residual oxygen)
- FF: double soothes (also fully killed ) shed (i.e., virtually all of the oxygen is slagged.).
Calm potting means that either silicon or aluminum ("single calming") or silicon and aluminum ("double calming") is added to the liquid steel when converting pig iron to crude steel using the Linz-Donawitz process . The oxygen present in the melt reacts with these metals and is slagged .
The steel is said to "calm down" because the solubility of the oxygen in the liquid iron falls during cooling and is therefore bubbled out of the molten steel when it is poured. By adding the aluminum or silicon, the precipitation process is intensified until the oxygen is completely absorbed. Only killed steel can be processed in the continuous casting process. Due to the hardly or nonexistent air inclusions and the low degree of segregation in segregation zones, cast steel has better mechanical properties and weldability .
A quality label was planned up to October 2004 that provided information about the calming and heat treatment status of the product:
- G1: unkilled steel. Hardly produced today because it cannot be processed in a continuous casting process. Chill casting is possible, but not economical.
- G2: Killed but not normalized steel
- G3: Fully killed and normalized steel
- G4: Heat treatment at the choice of the manufacturer. For example:
- normalized
- thermomechanically rolled
- tempered (water, air and / or oil tempered )
Unalloyed quality steels
Unalloyed quality steels are types of steel for which certain requirements apply in most cases (such as toughness, grain size or formability), but which do not correspond to the characteristics of unalloyed stainless steels . The carbon content is 0.2 to 0.65%
- Designation: Cx with x = carbon content in percent by mass multiplied by 100
- reduced content of phosphorus and sulfur compared to bulk steels (less than 0.045 mass percent)
- usually no heat treatment provided
- Example: C60 is a quality steel with a carbon content of 0.60 percent by mass.
Previously, the designation was written with spaces; according to the new standard, the space between C and percentage is no longer required.
Unalloyed stainless steels
Unalloyed stainless steels have a higher degree of purity than quality steels (especially with regard to non-metallic inclusions). In contrast to the colloquial use of the term, stainless steel is not to be equated with stainless steel . Unalloyed stainless steels are defined in EN 10020 as steel grades that meet one or more of the following requirements:
- defined minimum value of the impact energy (see toughness ),
- defined hardening depth or surface hardness ,
- very low content of non-metallic inclusions,
- even lower content of phosphorus and sulfur than in quality steels (<0.025%)
- electrical conductivity over 9 S * m / mm²
- micro-alloyed steels with niobium , vanadium and / or titanium below the respective alloy limit
- Prestressed concrete steels
- Nuclear reactor steels with limited contents of copper (≤0.1%), cobalt (≤0.05%) and vanadium (≤0.05%)
The designation corresponds to the unalloyed quality steels, but with the letter E attached: CxE (with Cx carbon content in percent by mass multiplied by 100)
Example: C45E is a heat treatable steel with a carbon content of 0.45 mass percent. Former designation according to DIN 17200 (withdrawn 1991): Ck 45
Alloy steels
Micro-alloyed steels
Microalloyed steels are added 0.01 to 0.1 percent by mass of aluminum , niobium , vanadium and / or titanium in order to achieve high strength through the formation of carbides and nitrides and grain refinement . Their short names, like the designations of structural steels, are based on the minimum yield strength.
Example for steel with material number 1.0545:
- new designation according to EN 10113: SxN , example: S355N
- old designation according to DIN 17102: StE x with x = the minimum elasticity limit in N / mm Example: StE 355
The alloy elements partially dissolve when heated to the forming temperature. With targeted cooling, they form carbides with carbon and nitrides with nitrogen. These are finely distributed in the ferrite and in the ferrite of pearlite . This creates what is known as precipitation hardening, which in this case results in greater strength. A further increase in strength is achieved by the normal annealing treatment , with the resulting grain refinement being improved by the micro-alloy elements which inhibit grain growth. With this increase in strength, the toughness is not reduced.
Low alloy steels
As a low-alloy is known steels in which the sum of the alloying elements does not exceed a level of 5 percent by mass.
Designation:
- First is the carbon content in percent by mass times 100, followed by the chemical element symbols of the alloy elements in the order of decreasing mass fractions. Finally, the mass fractions of the alloy elements listed above are given in the same order, separated by hyphens.
In order to arrive at whole numbers as possible, the actual alloy proportions are multiplied by the following factors:
- × 1000: B
- × 100: C, N, P, S, Ce
- × 10: Al, Cu, Mo, Ti, V, Be, Ta, Zr, Nb, Pb
- × 4: Cr, Co, Mn, Ni, Si, W
- Example: 30NiCrMo12-6 is a steel with 0.3% carbon (0.3 = 30 : 100), 3% nickel (Ni: 3 = 12 : 4), 1.5% chromium (Cr: 1.5 = 6 : 4) and a small, unspecified proportion of molybdenum (Mo).
In order to be able to remember which factor is used for which elements, there are some donkey bridges :
- for the factor 4:
- " C h r om Co might M a n Ni CHT Si cher W ahrnehmen."
- " M a n Si eht Ni e 4 W hite Cr o Co dile."
- " W o Si eht M a n the Cr o Co ? Dil On Ni l - it has four legs."
- for the factor 10:
- "AlCuMoTaTiV"
- " Al le 10 Cu baner Mo Want Ta nth Ti nas V OGEL"
- for 100 times: "With 100 P S N oh Ce ll". Here Celle stands for both C and Ce .
High alloy steels
As a high-alloy is referred to steels in which the mass content exceeds at least one alloying element 5%.
Designation:
- High-alloy steels are marked with an X at the front (internationally possibly also with a Y ). This is followed by the carbon content multiplied by a factor of 100 in percent by mass and the chemical element symbols of the alloy elements in the order of decreasing mass proportions. Finally, the mass fractions of the alloying elements listed above are given in the same order, separated by hyphens and in mass percentages ( without multipliers!).
- Example: X12CrNi18-8 is a steel with 0, 12 % carbon, 18 % chromium (Cr) and 8 % nickel (Ni).
High speed steels
High- speed steels (abbreviation HS (formerly HSS high- speed high-speed steel )) are characterized by high wear resistance, tempering resistance and hot hardness up to 600 ° C. You will e.g. B. used as broaches , twist drills , milling tools , turning tools and indexable inserts .
The carbon content is usually between 0.8 and 1.4%, some varieties have contents of 2.1%.
Designation according to EN ISO 4957 (tool steels): Code letters HS and following numbers that indicate the mass fractions in whole, rounded numbers in the order W, Mo, V and Co.
Example: HS2-10-1-8
- HS: high speed steel
- 2: 2% W (tungsten)
- 10: 10% Mo (molybdenum)
- 1: 1% V (vanadium)
- 8: 8% Co (cobalt)
Sometimes there is also the designation S , followed by three to four digits. If only three digits are given, the high-speed steel does not contain any cobalt.
Example: S6-5-2
- 6% W (tungsten)
- 5% Mo (molybdenum)
- 2% V (vanadium)
- 0% Co (cobalt)
As in almost all high-speed steels, S6-5-2 also contains around 4% chromium, which is just as little apparent from the abbreviation as the C content.
Case-hardening steels and heat treatable steels
The properties of case- hardened steel and heat-treated steel are largely determined by their carbon content, which is also reflected in the nomenclature.
- Designation: Cx
Here x stands for the carbon content in percent by mass multiplied by 100. (With a carbon content below 0.25%, the steel can be case- hardened , above that it can be tempered .)
Cast steel
As a cast steel is known types of steel that is designed for direct casting in its final form (without significant deformation processes).
Designation:
- Corresponds to the low-alloy steels, but with a prefixed G.
- Example: G-17CrMo5-5 is a cast steel with 0.17% carbon , 1.25% chromium (Cr) and 0.5% molybdenum (Mo) according to the standard.
- High alloy according to:
- Example: GX210CrNiMo18-8 would be a high-alloy cast steel with 2.1% carbon, 18% chromium, 8% nickel, and a small proportion of molybdenum
- unalloyed similar to steels for mechanical engineering
- Example: GE395 is a cast steel with a yield strength of 395 N / mm²
Material numbers
Material numbers are assigned in Europe by the steel institute VDEh .
Designation: X.YYZZ (AA) with
- X: main group
- Y: variety numbers
- Z: count numbers
- A: Extended counting numbers when the increase in the number of steel grades makes it necessary.
The main group X for steel and cast steel grades is "1". The variety numbers YY are used for classification, the two counting numbers ZZ are assigned chronologically.
Examples:
1.7218 translates into [steel], [stainless steel with Cr and <0.35 mass percent Mo], [0.25 mass percent C, 1.0% Cr, 0.65% Mn] . The short name would be 25 CrMo 4.
A well-known material number in the steel industry is 1.4301 , which was assigned to the first stainless steel. Its short name is X5CrNi18-10.
According to the withdrawn DIN standard DIN 17007-2: 1961-09, positions 6 were also standardized as the steelmaking process and 7 as the treatment status, but this was mostly omitted.
Designation according to intended use and minimum yield strength
| Usage | Name / example | additions | Requirement class | Material standard |
|---|---|---|---|---|
| Steels for steel construction | Designation S + minimum yield strength
|
|
EN 10025 | |
| Steels for pressure vessels | Designation P + minimum yield strength
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|
EN 10028 | |
| Steels for line pipes | Designation L + minimum yield strength + addition + requirement class, L
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|
EN 10208, EN 10224 |
| Steels for mechanical engineering | Designation E + minimum yield strength
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EN 10305 | ||
| Cold-rolled flat products made of high-strength steels | Designation H + minimum yield strength
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|
EN 10268, EN 10292, SEW 094 | |
| Flat products for cold forming | Designation D + code letter type of rolling
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|
EN 10130 | |
| Further | Designation B, Y, R, T, M |
In the case of steels whose composition is of greater interest than the minimum yield strength, the composition is specified according to a defined key.
Other names
The designation of the steels is clearly defined. However, the intended markings have been changed several times in recent years. Furthermore, brand names and traditional designations such as St 52, V2A , Invar and Nirosta are used for certain steels , which makes naming the steels a bit confusing. In the USA, steel grades are designated according to the system of the American Iron and Steel Institute (AISI).
literature
- Manfred Riehle, Elke Simmchen: Fundamentals of materials technology . 2nd edition, German publishing house for basic industry, Stuttgart 2000, ISBN 978-3-342-00690-9 .
See also
Individual evidence
- ↑ Dubbel - Taschenbuch für den Maschinenbau , Ed. W. Beitz, KH Grote Springer Berlin Heidelberg Tokyo, 20th edition 2001, p. E43 ISBN 3540677771