European Standard (EN) Steel Grades: Quick Reference for Heat Treatment, Coating & Plating Suffix Codes
When selecting and specifying European standard steel grades, the suffix codes marked with the “+” symbol are critical technical identifiers. These codes clearly define the heat treatment state, delivery condition, mechanical properties, surface coating, plating, and special performance requirements of steel products. They directly determine the processability, service performance, and application life of steel in construction, automotive, machinery, pressure equipment, electrical engineering, and other industrial fields.
This article provides a complete quick reference of common EN steel suffix codes, with detailed explanations and practical application examples. It helps global steel buyers, engineers, production technicians, and procurement professionals quickly interpret steel designations and choose the most suitable materials for their projects.
01 Steel Product Processing & Heat Treatment Symbols
Core Purpose
Identify the processing or heat treatment state of steel products and reflect their process characteristics and targeted mechanical properties.
Symbol Rule
All suffix codes are separated by a “+” sign from the base steel grade name.
Main Symbols and Meanings
| Code | Meaning |
| +A | soft annealed |
| +AC | Annealed to achieve spheriodised carbides |
| +AR | as rolled (without any special rolling and/or heat treatment conditions) |
| +AT | solution annealed |
| +C | cold work hardened |
| +Cnnn | cold work hardened with a minimum tensile strength of nnn MPa |
| +CPnnn | cold work hardened with a minimum 0.2% proof strength of nnn MPa |
| +CR | cold rolled |
| +DC | delivery condition at manufacturer’s discretion |
| +FP | treated to ferritic-pearlite structure and hardness range |
| +HC | hot rolled followed by cold hardening |
| +I | isothermically treated |
| +LC | skin passed (temper rolled or cold drawn) |
| +M | thermomechanically formed |
| +N | normalised or normalised formed |
| +NT | normalised and tempered |
| +P | precipitation hardened |
| +Q | quenched |
| +QA | air quenched |
| +QO | oil quenched |
| +QT | quenched and tempered |
| +QW | water quenched |
| +RA | recrystallisation annealed |
| +S | treated for cold shearing |
| +SR | stress relieved |
| +T | tempered |
| +TH | treatment to hardness range |
| +U | untreated |
| +WW | warm worked |
02 Steel Product Coating, Plating & Special Property Symbols
Core Purpose
Mark special performance and surface treatment requirements of steel products, including hardenability, through-thickness performance, corrosion resistance, and various metallic/non-metallic coatings.
Symbol Rule
Consistent with heat treatment codes: separated from the base grade by a “+” sign.
Main Symbols and Meanings
| Code | Meaning |
| +CH | core hardenability |
| +H | hardenability |
| +Z15 | through thickness property; min. reduction of area = 15% |
| +Z25 | through thickness property; min. reduction of area = 25% |
| +Z35 | through thickness property; min. reduction of area = 35% |
| +A | hot dip aluminium coating |
| +AS | aluminium silicon alloy coating |
| +AZ | aluminium zinc alloy (>50% Al) coating |
| +GE | electrolytic chromium/chromium oxide coating (EGCS) |
| +CU | copper coating |
| +IC | inorganic coating |
| +OC | organic coating |
| +S | hot dip tin coating |
| +SE | electrolytic tin coating |
| +T | hot dip lead tin alloy (terne) coating |
| +TE | electrolytic lead tin alloy (terne) coating |
| +Z | hot dip zinc (galvanised) coating |
| +ZA | hot dip zinc aluminium (>50% Zn) coating |
| +ZE | electrolytic zinc coating |
| +ZF | hot dip zinc iron (galvannealed) coating |
| +ZN | electrolytic zinc nickel alloy coating |
03 Practical EN Steel Grade Selection Examples
Combining base steel grades with correct suffix codes is the core of European standard steel material selection. Below are 4 typical industrial application cases.
Example 1: High-Strength Plate for Bridge Structures
Demand: Withstand load & outdoor corrosion; prevent lamellar tearing (requires through-thickness performance).
- Through-thickness property (25% reduction of area): +Z25
- Hot-dip galvanised coating for corrosion resistance: +Z
- Base grade: S355J2Final designation: S355J2+Z25+Z
This grade delivers high strength, good low-temperature toughness, and long outdoor service life, widely used in bridge and structural engineering.
Example 2: Cold-Stamped Parts for Automotive Chassis
Demand: Good cold stamping formability; strengthened by cold work hardening; suitable for phosphating.
- Cold-rolled base: +CR
- Cold work hardening (min. 300MPa tensile strength): +C300
- Base grade: DC04Final designation: DC04+CR+C300
Ideal for automotive chassis and body structural parts, balancing formability and strength.
Example 3: Pressure Pipes for Chemical Equipment
Demand: Uniform mechanical properties; resist high-temperature & chemical corrosion.
- Improved hardenability: +H
- Electrolytic chromium coating (corrosion resistance): +GE
- Base grade: 13CrMo4-5Final designation: 13CrMo4-5+H+GE
Widely used in pressure vessels and chemical pipelines requiring high uniformity and corrosion protection.
Example 4: Silicon Steel for Motor Cores
Demand: Low iron loss; stable magnetic performance; high lamination efficiency (no coating).
- Soft annealed for stress relief: +A
- No coating required
- Base grade: 50W400Final designation: 50W400+A
Optimised for motor and transformer cores, reducing energy loss and improving assembly efficiency.
Conclusion
Mastering EN steel heat treatment codes, steel coating codes and steel plating symbols is essential for accurate material selection, quality control, and cost control in global steel trade and manufacturing. Correct use of these suffixes ensures that steel products fully meet design and application requirements.
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