Material Section (1): Application of DC01-DC07 Series Low Carbon Steel Materials

Low carbon steel accounts for a large proportion of materials used in automotive body manufacturing.

As globally accepted products under the European standard system, DC series low carbon steel serves as the basic standard material for all automobile manufacturers. This article will briefly analyze the material characteristics, mechanical properties, CAE simulation models, and specific applications of DC01-DC07 cold-rolled steel plates and DC51D + ZF-DC57D + ZF zinc-alloy galvanized plates in automotive vehicles.

Material Classification and Standard System

DC series low carbon steels are strictly divided into two categories for different application scenarios.

1.1 Cold Rolled Low Carbon Steel Sheets (DC01-DC07)

Applicable Standard: EN 10130:2020 (latest European standard), equivalent to Chinese standard GB/T 5213-2019.

•Key Features: Excellent surface quality, superior formability and lowest cost.

•Its main performance advantages are as follows. Thanks to low carbon content and strict impurity control, the steel boasts outstanding cold formability, which enables easy implementation of basic processes such as bending and stamping. It also has good weldability, and is suitable for high-precision flattening, slitting and cutting with stable dimensional accuracy after processing.

In terms of surface and dimensional performance, cold rolling and finishing processes deliver a smooth surface free of obvious scale, cracks and other defects, so subsequent coating can be performed without extra grinding. In addition, the products feature high precision in thickness and width with good batch consistency.

Grade Designation Definition:

D: Flat steel for cold forming

C: Cold rolled base sheet

Numeral: Represents the forming grade, the larger the number, the better the formability

1.2 Hot-dip Galvannealed Steel Sheets (DC51D+ZF ~ DC57D+ZF)

•Applicable Standard: EN 10346:2022 (the latest European standard), corresponding to Baosteel Standard Q/BQB 420-2020.

•Key Features: A zinc-iron alloy coating is applied on the cold rolled substrate, improving corrosion resistance and paint adhesion by more than three times.

•Grade Designation Definition:

•The first two letters D: Flat steel for cold forming

•Figures 51 to 57: Formability grades corresponding to DC01-DC07 (Grade 55 is omitted in the standard)

•The third letter D: Hot-dip galvanized

•+ZF: Zinc-iron alloy coating (Galvannealed), distinct from pure zinc coating + Z

Core Material Models for CAE Simulation

In automotive collision and stamping simulations, the DC series low-carbon steel is mostly modeled using the following two types:

2.1 Preferred Model for Crash Simulation: MAT_024

Piecewise Linear Plasticity Model, applicable to crash and stiffness analysis of all DC steels.

•General basic parameters (for all DC steels):

•Density ρ = 7.85e-6 kg/mm³

•Young's modulus E = 210 GPa

•Poisson's ratio ν = 0.3

•Strain rate parameters: C = 40.0, P = 5.0 (general recommended values; measured material data shall be used for high-precision simulation)

•Required input: True stress-plastic strain curve (measured data within the plastic strain range of 0 to 0.5 is recommended)

2.2 Preferred Model for Stamping Simulation: MAT_124

3-parameter Barlat Yield Model, which accurately simulates the anisotropy of steel sheets.

•Additional inputs required: Plastic strain ratio (r-value) and work hardening exponent (n-value) (refer to the mechanical property table for different grades)

•Supplementary note: MAT_133 (Barlat Yld2000) is recommended for high-precision stamping simulation for better accuracy.

Typical MAT_24 Model Code for DC04

Mechanical Properties

3.1 Mechanical Properties of Cold Rolled DC01-DC07 (EN 10130:2020)

3.2 Mechanical Properties of Galvannealed Steel DC51D+ZF~DC57D+ZF (EN 10346:2022)

Key Performance Notes

•Yield Strength: For cold rolled low carbon steels DC01~DC07, the higher the grade number, the lower the carbon content and the more microalloying elements added. Accordingly, the yield strength decreases gradually, while the elongation and deep drawability improve. A lower yield strength means less resistance to plastic deformation and better formability. DC07 delivers the optimal formability in this series and is suitable for extremely complex deep drawing processes.

•Elongation: The larger the number, the better the plasticity, and the less likely it is to crack.

•r-value: A core indicator for deep drawability. Higher r-value stands for superior deep drawing performance.

•n-value: A key parameter for stretch forming. Higher n-value means better uniform deformation capacity.

Targeted Applications on Vehicle Components

4.1 Exterior Body Panels

Galvanized steel sheets are predominantly used for exterior body panels of mainstream passenger vehicles, while a small number of cold rolled steel sheets are still applied on low-end commercial vehicles.

Figure 1: Body Side Outer Panel (DC56D+ZF / 0.7mm) – The largest and most complex exterior panel of vehicle body

4.2 Interior Body Panels and Structural Components

Figure 2: Front Floor Assembly (DC04 / DC54D+ZF / 0.8mm) – Large-area stamped part

4.3 Chassis and Special Components

Plastic fuel tanks are widely adopted in passenger vehicles, while metal fuel tanks are still used for commercial vehicles and some special-purpose vehicles.

Figure 3: Vehicle Spare Wheel Well (DC06/DC56D+ZF/0.8mm) – Deep drawn component

Plain Text

Step 1: Determine corrosion resistance requirements

├─ Dry interior environment → Select cold rolled steel (DC01-DC07)

└─ Exterior exposed areas / Chassis / Humid environment → Select galvannealed steel (DC51D+ZF-DC57D+ZF)

Step 2: Judge component forming complexity

├─ Simple bending/flanging / Small brackets → DC01/DC51D+ZF

├─ Normal drawing / Reinforcement plates / Crossmembers → DC03/DC52D+ZF

├─ Deep drawing / General inner panels / Floor panels → DC04/DC53D+ZF

├─ Extra deep drawing / Complex inner panels / Wheel housings → DC05/DC54D+ZF

├─ Ultra-deep drawing / Outer panels / Spare wheel wells → DC06/DC56D+ZF

└─ Extreme deep drawing / Metal fuel tanks → DC07/DC57D+ZF

Step 3: Cost optimization verification

├─ Prioritize lower-grade steels if performance requirements are met

├─ For the same grade: Cold rolled steel is approximately 8%-12% cheaper than galvannealed steel

└─ DC01 costs roughly 10%-15% less than DC06

Comparison Table of Main Grades at Home and Abroad

6.1 Grade Comparison of Cold Rolled Low Carbon Steel Sheets

6.2 Grade Comparison of Hot-Dip Galvannealed Steel Sheets

Supplementary Note: Chinese national standard grades adopt the DX prefix, which has identical performance to European DC prefix grades and can be used interchangeably.

Industry Trends and Notes

7.1 Three Major Development Trends

1. Complete replacement of galvanized sheet：Mainstream automakers have achieved 100% galvanization for body outer panels. The galvanization rate of inner panels rose from 60% in 2020 to over 85% in 2025.

2. Growing consumption of ultra-deep drawing steel: With increasingly complex automotive designs, the proportion of DC06/DC07 and DC56D+ZF/DC57D+ZF used has increased from 10% to 25%.

3. Thin specification: Through optimizing the forming process, major car manufacturers have generally replaced 0.7mm steel with 0.65mm steel, and some models have begun to use 0.6mm or even 0.55mm steel.

7.2 Common Material Selection Misconceptions

•❌ Blind selection of high-grade steel: Using DC07 for components applicable to DC06 will raise material costs by approximately 5%-8%.

•❌ Neglect of coating differences: The zinc-iron alloy coating (+ZF) delivers over 30% better weldability and higher paint adhesion than pure zinc coating (+Z), making it more suitable for automotive bodies.

•❌ Ignorance of strain rate effect: Exclusion of C and P parameters in crash simulation will lead to results about 15%-20% softer than actual conditions.

•❌ Using uniform material parameters: High-precision simulations must use the actual measured data provided by the supplier for the materials, and cannot directly use general parameters.

Quick Reference: Common Stamping Defects of DC Series Steel & Solutions

8.1 General Defects (Applicable to both cold rolled steel and galvannealed steel)

8.2 Defects Specific to Galvanized Steel Sheets (DC51D+ZF ~ DC57D+ZF)

8.3 Reference Stamping Process Parameters for Different Grades of DC Steel

Conclusion

DC series low-carbon steel serves as a cornerstone of the automotive industry and is a fundamental material that all automotive engineers need to master.

A thorough understanding of property differences among various grades and solutions to common stamping defects enables the optimal balance of performance, quality and cost in product design.

With the advancement of automotive electrification, DC series low-carbon steel is continuously upgraded. It complements high-strength steel and aluminum alloy, jointly underpinning the sustainable development of the automotive industry.