Why DC04 Is Ordered for Severe Forming
DC04 is a cold-rolled, unalloyed low-carbon flat product defined in EN 10130 for deep-drawing duty. Its advantage is not extra strength but extra reserve: a very low carbon and phosphorus analysis, killed and annealed under controlled conditions, produces a high plastic strain ratio so the material thins uniformly across a punch instead of localising into a neck. That reserve is what allows a refrigerator liner, a washing-machine tub wall or a deep filter housing to be drawn in one or two operations without splitting.
The same reserve explains the grade's secondary benefits. A DC04 coil is rolled to close thickness and width tolerances and to a fine, even surface roughness, so it can be used either as a visible part after painting or as a substrate for zinc or organic coating. Process stability across a coil and between coils is the other reason the grade is specified: a fabricator running several hundred strokes an hour cannot absorb a yield-strength swing of fifty megapascals between coils.
Composition and Property Windows Across the DC Series
EN 10130 keeps carbon, manganese, phosphorus and sulphur low, tightening them as the grade number rises. The table below collects the composition ceilings and the base mechanical windows for the grades most often traded side by side.
| Grade | C max % | Mn max % | P max % | S max % | Re MPa | Rm MPa | A80 min % |
|---|---|---|---|---|---|---|---|
| DC01 | 0.12 | 0.60 | 0.045 | 0.045 | 140 - 280 | 270 - 410 | 28 |
| DC03 | 0.10 | 0.45 | 0.035 | 0.035 | 140 - 240 | 270 - 370 | 34 |
| DC04 | 0.08 | 0.40 | 0.030 | 0.030 | 140 - 210 | 270 - 350 | 38 |
DC05 and DC06 continue the trend with still lower carbon and a wider elongation floor, and are ordered by the deep-drawing indices given in the standard. Two consequences follow for a buyer. First, a tensile test alone does not prove drawability - the tensile window is broad and the top of it is unusable for a difficult part. Second, an incoming coil that sits at the upper end of the yield window will spring back more and flatten less, even though it is fully compliant.
Where Q195 and SPCC Sit in the Same Picture
Q195 belongs to the Chinese structural and general-purpose carbon steel family in GB/T 700 and is characterised by a low minimum yield strength of 195 MPa with a correspondingly wide tensile range. It is a hot-rolled-oriented specification that is also produced in cold-reduced form for light bends and flat parts, but it is not a deep-drawing grade: the analysis is not held to the phosphorus and sulphur ceilings of EN 10130, so its forming reserve is lower and its scatter is wider.
SPCC from JIS G 3141 is the closer commercial match to DC01, with carbon to 0.15%, manganese to 0.60%, phosphorus to 0.100% and sulphur to 0.050%, and a specified minimum tensile strength of 270 MPa. SPCD and SPCE extend the series toward drawing and deep drawing. In practice, Q195 is chosen for economy and weldability in structures and simple stampings, SPCC for general light forming with a good surface, and DC03 or DC04 where the tool actually needs drawability.
Surface Finish, Coating and Flatness Requirements
Deep-drawing stock is normally supplied with a controlled surface roughness produced by temper rolling, because a fully bright surface traps lubricant poorly and a fully matt surface drags in the die. Surface quality classes set in EN 10130 distinguish general forming quality from an improved class intended for visible parts, and the number and size of admissible imperfections must be agreed before the order is placed if the part will be painted without filler.
Where the formed part is to be zinc coated, the substrate is usually ordered as an electrolyte-zinc-coated DC grade to EN 10152 rather than as bare cold-rolled coil, so that the coating is applied before drawing and the die never sees a dry surface. For parts that will be hot-dip galvanized after forming, the drawing grade must still satisfy the tool, since galvanizing adds no ductility and the zinc-iron reaction at the coating temperature does not repair a forming crack.
Drawing Practice That Keeps DC04 Parts Sound
Four parameters decide whether the draw succeeds. The die radius should be generous relative to thickness, typically several times the sheet thickness for the first draw. Blank-holder force must be set high enough to suppress wrinkling but low enough to avoid stretching the wall. Lubricant must be applied to the whole blank rather than poured at the corners. Blank development should be calculated from the true developed length rather than drawn from the finished outline, because insufficient blank material, not poor steel, causes most split corners.
Tooling should also be validated on the actual grade and heat that will be used in production. A tool proved on DC01 will not necessarily run on DC04 without adjustment to springback compensation, and a tool proved on a single trial coil is not proved at all if the production supply is allowed to drift to the top of the yield window.
Frequently Asked Questions
Q: What is the main difference between DC01 and DC04?
A: Both are cold-rolled unalloyed quality steels, but DC04 carries a lower carbon and phosphorus ceiling, a narrower yield window and a higher elongation floor, which gives it the deep-drawing capacity DC01 lacks.
Q: Can DC01 be used instead of DC04?
A: Only if the part is actually a light forming job. On a validated deep draw, DC01 will thin faster at the punch radius and is likely to tear, so a substitution must be proved by tool trial rather than by grade equivalence tables.
Q: Is Q195 an acceptable substitute for DC03 or DC04?
A: No. Q195 is a general-purpose carbon steel grade with a wide tensile range and no deep-drawing classification, so it suits flat parts, brackets and welded structures rather than severe draws.
Q: How is deep-drawing quality verified?
A: By chemistry check against EN 10130, by the yield and tensile windows, and by the plastic strain ratio and strain-hardening exponent where the standard specifies them. Tensile strength alone does not demonstrate drawability.
Q: What surface conditions are available for DC04 coil?
A: General forming quality or an improved class for exposed parts, with the roughness and defect acceptance level agreed at order stage; temper-rolled matt and bright finishes are both common.
Q: Why does the coil need rust-preventive oil?
A: Cold-rolled low-carbon steel has no alloying protection, so a thin oil film is applied to prevent condensation rust during transport and storage; it is normally compatible with drawing and with spot welding.
Q: Which industries use DC04 most?
A: Domestic appliance housings and drums, automotive interior and structural stampings, lighting and enclosure parts, and coated-substrate applications where a defect-free draw is required.