1.How to check chemical composition?
As an ultra-deep drawing steel, DC07 requires low carbon and low impurities. Its chemical composition directly impacts its plasticity and formability. Key inspections include:
Carbon (C): ≤0.01% (Excessive concentrations increase hardness, reduce plasticity, and may lead to cracking during deep drawing).
Manganese (Mn): ≤0.2% (Excessive concentrations increase work hardening and affect uniform deformation capability).
Phosphorus (P) and Sulfur (S): Both must be ≤0.02% (Phosphorus can cause cold brittleness, while sulfur can form sulfide inclusions, disrupting the continuity of the steel plate).
Titanium (Ti): ≤0.2% (Titanium stabilizes carbon and nitrogen, refines grains, and improves plasticity. It must be within the specified range).
2.How to test mechanical properties?
DC07's core advantage lies in its ultra-deep drawing performance, with mechanical properties being key verification indicators:
Yield strength: 100-150 MPa (a value too low will result in dimensional instability after forming; a value too high will reduce plasticity, making it prone to wrinkling or cracking during deep drawing).
Tensile strength: 250-310 MPa (must match the yield strength, achieving a reasonable ratio to ensure uniform deformation during stretching).
Elongation at break: ≥44% (a core indicator for ultra-deep drawing; higher elongation indicates better plasticity and greater ability to withstand complex tensile deformation, such as deep drawing of automotive panels).
Hardness: Generally ≤60 HV (excessive hardness reduces plasticity and can be tested with a Vickers hardness tester).
3.How to detect surface quality?
DC07 is commonly used in applications requiring coating or direct exposure (such as automotive bodies and precision electrical appliance housings). Surface quality directly impacts subsequent processing and product life:
Surface Finish: Should be smooth and flat, free of obvious scratches, pitting, or indentations (inspect visually or with a 10x magnifying glass under adequate lighting. Defects that could affect coating are not permitted).
Oxidation/Rust: No yellowish oxide film or red rust (cold-rolled steel is prone to rust due to improper storage, which can disrupt surface continuity and affect lubrication and forming during stamping).
Oil/Impurities: The surface should be evenly coated with anti-rust oil (not too much or too little), free of dust, metal debris, and other impurities (excessive oil can affect paint adhesion, and impurities can cause cracking during stamping).
Edge Quality: The edges should be free of burrs and curling (burrs can scratch the mold or sheet surface during processing).
4.How to detect dimensional accuracy?
DC07 is primarily used for precision forming (such as complex stamping parts). Excessive dimensional deviation can lead to poor mold fit and out-of-tolerance product dimensions.
Thickness Deviation: According to EN 10130, the thickness tolerance must meet the corresponding grade (e.g., ±0.03mm for standard precision, ±0.02mm for high precision). Measure the thickness with a micrometer at different locations (at least five points) on the sheet metal. The deviation must be within the standard range.
Width/Length: Measure with a tape measure or caliper. The deviation should be ≤ ±1mm (to avoid cutting waste or misalignment due to dimensional inconsistencies).
Flatness: The sheet metal should be flat, with no noticeable warping. (Lay the sheet flat and use a feeler gauge to check the clearance from the surface. The general requirement is ≤1mm/m. Otherwise, uneven stress during stamping can cause deformation and cracking.)
5.How to test molding performance?
DC07's ultra-deep drawability requires specialized testing to verify, a key difference from conventional cold-rolled steel:
Cupping Test (Erichsen Test): This measures the steel's plastic deformation capacity during deep drawing. The cupping value (IE) for DC07 should be ≥10mm (a higher value indicates better deep drawability, and this can be tested using a dedicated cupping tester).
Cold Bending Test: The sheet is cold-bent 180° in both the longitudinal and transverse directions (bend diameter = 0 times the sheet thickness). The bends should be free of cracks and delamination (verifying uniform plasticity and avoiding processing failures due to localized brittleness).
Practical Stamping Test: Small batches of complex workpieces (such as deep cylindrical parts and special-shaped curved parts) are tested for defects such as cracking, wrinkling, and necking (simulating actual application scenarios and providing the most direct quality verification).