ST13 steel plate is a stamping grade cold rolled low carbon steel, and tensile strength is one of the key indicators of its mechanical behaviour. Engineers ask for the tensile strength range for a practical reason: it sits between the yield strength, which decides how easily the blank deforms, and the elongation, which decides how far it can be stretched before it tears. Getting the balance right is what makes a part formable in production.
ST13 Steel Plate in the St Grade Series
ST13 was one of the grades in the German cold reduced sheet series of DIN 1623, positioned above the basic ST12 grade and below the deeper drawing grades St14 and St15. When DIN 1623 was withdrawn, the grade was re-designated DC03 in EN 10130, so ST13 and DC03 describe the same class of steel. It is a low carbon, aluminium killed, fully annealed material intended for medium forming work, including deep drawing and difficult profiling, rather than for simple bending alone.
Plate, sheet and coil are supplied in the same grade; the word plate usually indicates a cut to length flat product, while coil refers to the as rolled form. Thickness typically runs from 0.3 mm up to 3.0 mm and width from 600 mm up to 1500 mm, with the mechanical property requirements applying after the final anneal and skin pass.
Tensile Strength Range of ST13
According to the German standard series and to the values quoted in normal application data, the tensile strength of ST13 steel plate falls typically in the 300 to 400 MPa range. That moderate level is deliberate. It is high enough to keep a stamped part dimensionally stable and to resist local deformation in service, yet low enough that the material still deforms plastically rather than cracking when it is stretched over a punch.
| Property | Typical value for ST13 | Practical meaning |
|---|---|---|
| Tensile strength | 300 to 400 MPa | Sets the load at which the sheet finally tears |
| Yield strength | 130 to 210 MPa | Sets the stress at which forming begins; kept low for easy flow |
| Elongation | Generally 34 % and above | Allows the sheet to stretch without localised fracture |
| Typical thickness | 0.3 mm to 3.0 mm | Values vary with thickness and with the anneal |
The figures above should be read as typical ranges rather than as fixed numbers. Mechanical properties of cold rolled drawing grades change with thickness, and acceptance values are taken from the property table of the standard named on the purchase order, which for the current equivalent grade is EN 10130 with grade DC03. Anything outside the quoted band should be confirmed against the mill certificate for the specific coil.
How Tensile Strength Is Measured
Tensile strength is determined by pulling a prepared specimen in a tensile testing machine and dividing the maximum recorded load by the original cross sectional area of the test piece. For sheet and thin plate the test is carried out to ISO 6892-1, to ASTM A370 or to JIS Z2241 depending on the standard system of the order, and the elongation result is normally reported on a fixed gauge length. Thin sheet is usually measured on an 80 mm gauge length, which is why the elongation figure for ST13 is quoted as an A80 value rather than on the 50 mm gauge length common for plate.
Three practical points matter when comparing certificates. First, the specimen axis should be transverse to the rolling direction for the values to be comparable with the standard table. Second, the strain rate must be controlled, because a fast test can report a tensile strength a few tens of megapascals higher than a slow one. Third, ageing of an aluminium killed sheet is limited but not impossible, so a coil stored for a long time and then tested can show a higher yield strength than when it left the mill.
Why the Balance Between Strength and Elongation Matters
ST13 performs well in the press because its yield strength and tensile strength are well balanced, with yield strength in the 130 to 210 MPa band and tensile strength in the 300 to 400 MPa band, and because its high elongation, generally 34 % or more, allows the material to coordinate deformation during stretching. A low yield to tensile ratio means the material has a wide window between the onset of plastic flow and final fracture, so the press can push it into shape without the part failing.
That combination reduces the risk of localised fractures. In practice, a stamping that tears usually does so at a corner or a tight radius, and the cause is either insufficient elongation or a sheet with yield strength at the top of the permitted range. When a part is marginal, checking the actual yield strength of the coil is more useful than checking the tensile strength alone, because it is the yield point that determines how much force the blank needs before it starts to flow.
Typical Applications of ST13 Plate
Automotive panels and inner panels produced by medium depth stretch forming
Appliance housings, doors and side panels for white goods
Furniture frames, cabinet components and shelving formed on press brakes and presses
Electrical and control enclosures and general pressings that need a smooth surface
Substrates for painting, powder coating and organic coating where the coating hides the surface
Where the drawing depth or the complexity of the profile increases beyond what ST13 can supply, the next grades in the series are DC04 and the titanium stabilised interstitial free grades DC05 and DC06, which offer lower yield strength and higher elongation and can therefore be formed into the most demanding shapes. Selecting the lightest grade that will make the part keeps material cost and tooling load under control.
Frequently Asked Questions
Q: What is the tensile strength of ST13 steel plate?
It typically falls in the 300 to 400 MPa range. Exact values depend on thickness and on the anneal, and the acceptance figures come from the property table of the standard named on the order.
Q: What is the yield strength of ST13?
Yield strength is typically between 130 and 210 MPa, deliberately kept much lower than the tensile strength so that the material flows easily in the press.
Q: What is the elongation of ST13 steel?
Elongation is generally 34 % or more, measured on an 80 mm gauge length for thin sheet, which is what allows medium depth stretch forming without tearing.
Q: Is ST13 the same as DC03?
Yes in practical terms. ST13 was the designation in the withdrawn DIN 1623 series and DC03 is the equivalent grade in EN 10130, so current orders are usually placed against DC03.
Q: Is ST13 suitable for deep drawing?
It is suitable for medium forming including deep drawing and difficult profiling. For the most severe drawing operations, DC04, DC05 or DC06 provide better forming limits.
Q: How is the tensile strength of ST13 verified?
By a tensile test to ISO 6892-1, ASTM A370 or JIS Z2241 using a transverse specimen, with the result reported on the mill inspection certificate for the coil concerned.