Table of Contents
Introduction to Cr12MoV Cold Work Die Steel
Cold work die steel is primarily used for manufacturing dies that facilitate cold metal deformation, requiring high hardness, excellent wear resistance, and sufficient toughness. During heat treatment, high hardenability and minimal quenching distortion are essential requirements.
Cr12MoV steel is a high-carbon, high-chromium ledeburitic steel widely used in cold work die applications. This grade exhibits minimal heat treatment distortion and offers wear resistance 3-4 times greater than conventional low-alloy tool steels. Cold work dies typically operate under demanding conditions, experiencing high cyclic stresses and impact forces, with wear being the primary failure mode.
“Continuous casting technology for high-carbon, high-alloy tool and die steels offers significant process advantages, including dramatically improved production efficiency, reduced costs and energy consumption, higher yield rates, and potentially finer ledeburitic eutectic structures with more uniform composition stability.”
Traditional domestic production of high-carbon, high-alloy cold work die steel primarily employs the long process route: Electric Arc Furnace (EAF) melting → LF refining → VD vacuum degassing → die casting → multi-fire forging or rolling breakdown → final rolling. This multi-fire forging breakdown process suffers from low efficiency, poor yield rates, and high costs.
Chemical Composition Control
For continuous casting production of Cr12MoV steel, higher requirements are placed on steel castability and production continuity, while casting quality and stability present new considerations. Chemical element control targets are established based on their effects on steel properties, with particular attention to controlling harmful elements including phosphorus, sulfur, oxygen, nitrogen, and hydrogen.
The stability of chemical composition directly affects heat treatment process design, product quality consistency, material service life, and mechanical properties. Cr12MoV steel production requires narrow composition control as the target, minimizing variations within the same batch. Reducing P and S content improves impact toughness and brittleness characteristics while enhancing fatigue performance. Controlling oxygen content reduces inclusions, improves steel purity, and further enhances overall material performance.
Table 1: Cr12MoV Steel Chemical Composition (Mass Fraction %)
| Element | C | Si | Mn | P | S | Cr |
|---|---|---|---|---|---|---|
| Standard | 1.50-1.60 | 0.10-0.30 | 0.20-0.35 | ≤0.025 | ≤0.010 | 11.40-11.60 |
| Measured | 1.55 | 0.18 | 0.26 | 0.020 | 0.003 | 11.47 |
| Element | V | Mo | O | N | H |
|---|---|---|---|---|---|
| Standard | 0.15-0.30 | 0.40-0.50 | ≤0.0015 | ≤0.0150 | ≤0.0001 |
| Measured | 0.19 | 0.43 | 0.0009 | 0.0078 | 0.00003 |
Short Process Production Technology
Process Flow Overview
The innovative short process production route for Cr12MoV steel follows this sequence:
Raw Materials
→
90t EAF
→
90t LF
→
90t VD
→
Continuous Casting
→
Hot Transfer
→
Rolling
Electric Arc Furnace (EAF) Control
The electric arc furnace employs horizontal continuous charging with door oxygen lance and wall-mounted multi-function oxygen lance for oxygen injection assistance. Key process parameters include:
- Lime addition in 3 batches (1.5 tons total) for foaming slag formation
- Low-temperature dephosphorization achieving P ≤ 0.06%
- Tapping with residual steel (30-40 tons), preventing oxidizing slag carryover
- Tapping carbon content C ≥ 0.15%
- 50 kg aluminum block addition during tapping for deoxidation
- Pre-melted ferromolybdenum, ferrovanadium, and high-carbon ferrochrome added to ladle
LF Furnace Refining Control
Given the substantial alloy addition requirements for Cr12MoV steel, the LF process emphasizes rapid power-on heating, slag formation, and composition analysis. Key operations include:
- 300 kg specialized refining slag former addition
- 100 m aluminum wire feeding for precipitation deoxidation
- Diffusion deoxidation with 150 kg carbon powder, 120 kg aluminum powder, and 80 kg calcium carbide
- Submerged arc operation throughout the entire process
- White slag time ≥ 30 minutes
- Bottom argon stirring for temperature and composition homogenization
VD Vacuum Degassing Control
The VD vacuum process dynamically controls vacuum degree and argon flow rate to prevent slag overflow. When vacuum degree ≤ 67 Pa, vacuum treatment time is maintained at ≥ 20 minutes, followed by soft argon blowing ≥ 20 minutes to promote inclusion flotation.
Continuous Casting Parameters
The continuous casting machine features a 6.5 m arc radius, two-machine two-strand vertical-bending configuration. The trial steel casting section is 150 mm × 630 mm rectangular billet.
Critical Casting Parameters:
| Parameter | Value |
|---|---|
| Tundish Superheat | 25-40°C |
| Casting Speed | 0.80 m/min |
| Mold Oscillation Frequency | 80-180 cycles/min |
| Oscillation Amplitude | 3.0-6.0 mm |
| Level Fluctuation Control | ±3 mm |
| Secondary Cooling Specific Water | 0.10-0.18 L/kg |
| EMS Forward/Reverse Pattern | 15s – 5s – 15s |
Technical Note: Cr12MoV steel exhibits high crack sensitivity with significant structural stress during cooling. Therefore, secondary cooling employs weak cooling strategy with specific water ratio of 0.10-0.18 L/kg. Full-process protective casting is implemented with integral tundish nozzle and ladle long nozzle with sealing ring and argon protection.
Rolling Process Control
The 150 mm × 630 mm rectangular continuous casting billet undergoes heating to 1,180°C with 2-hour soaking time. Rolling commences at 1,050°C with finishing temperature above 850°C. High-pressure descaling pressure is maintained at 32.0 MPa.
Table 2: Rolling Process for 19 mm Thick Flat Steel (15-Pass Schedule)
| Pass | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|---|---|---|---|---|---|---|---|
| Gap (mm) | 140 | 125 | 110 | 95 | 80 | 65 | 61 | 47 |
| Pass | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
|---|---|---|---|---|---|---|---|
| Gap (mm) | 37 | 35 | 31 | 26 | 22 | 20 | 19 |
Rolled flat steel undergoes annealing followed by specialized finishing line processing: Loading → Leveling → Online Inspection → Surface Examination → Automatic Sawing → Marking → Weighing Collection → Warehousing.
Product Quality Analysis
Continuous Casting Billet Quality
Samples were taken from the entire cross-section of the 150 mm × 630 mm rectangular continuous casting billet according to GB/T226-2015 standard, with macrostructure evaluation performed according to YB/T4003-2016 standard.
Table 3: Low Magnification Structure of Cr12MoV Steel Continuous Casting Billet (Rating)
| Section (mm) | Center Porosity | Center Segregation | Internal Cracks | Corner Cracks | Triangle Zone Cracks |
|---|---|---|---|---|---|
| 150 × 530 | 1.5 | 0.5 | 0 | 0 | 0 |
| 150 × 680 | 1.5 | 1.0 | 0 | 0.5 | 0 |
| 150 × 630 | 1.5 | 0.5 | 0 | 0 | 0 |
Using metal in-situ analysis (OPA) across the entire cross-section of the 150 mm × 630 mm rectangular continuous casting billet, no obvious carbon segregation was observed, with overall segregation well controlled. The microstructure from surface to center shows uniform distribution with relatively small dendrite spacing and finely dispersed eutectic carbides.
Finished Flat Steel Quality
Compared with traditional die casting processes, the short process features larger furnace capacity with full-process protective casting, facilitating complete flotation and removal of deoxidation products. Non-metallic inclusion control is superior to traditional die casting. Despite reduced total thermomechanical deformation ratio, finished flat steel of various thicknesses meets GB/T1299-2014 Group I ≤ 3 grade requirements for eutectic carbide unevenness.
Table 4: Quality Inspection Results of Finished Flat Steel (Rating)
| Flat Steel Size (mm) | A Fine | A Coarse | D Fine | D Coarse | DS | Eutectic Carbide | Ingot Segregation | Center Porosity |
|---|---|---|---|---|---|---|---|---|
| 10 × 560 | 0.5 | 0 | 0.5 | 0.5 | 0 | 1.5 | 1.0 | 1.0 |
| 20 × 410 | 0.5 | 0.5 | 0.5 | 0.5 | 1.0 | 1.5 | 1.5 | 1.5 |
| 31 × 510 | 0.5 | 0 | 0.5 | 0.5 | 1 | 3 | 2.0 | 2.0 |
| 40 × 460 | 0.5 | 0.5 | 0.5 | 0.5 | 1.0 | 3 | 1.5 | 1.5 |
| 51 × 510 | 0.5 | 0 | 0.5 | 0.5 | 0 | 3 | 1.5 | 2.0 |
Ultrasonic testing according to GB/T4162-2008 standard confirms that flat steel products achieve Grade A and AA quality levels.
Economic Benefits and Performance
The short process production of Cr12MoV series high-carbon, high-alloy cold work die steel offers significant advantages compared to traditional die casting followed by multi-fire forging or rolling processes:
Yield Rate Improvement
92%
Comprehensive yield from billet to finished product (vs. 80.12% for traditional process)
Energy Reduction
>20%
Lower process energy consumption compared to conventional methods
Annual Production
~40,000
Tons of Cr12MoV cold work die steel produced annually
Industrial Achievement: The specialty steel facility has implemented industrial-scale production using the short process technology. Production reached nearly 40,000 tons in 2022, demonstrating excellent economic benefits while meeting all quality standard requirements.
Key Conclusions
- Successful Industrial Implementation: The short process production practice successfully produces Cr12MoV cold work die steel flat products, now in full industrial production.
- Excellent Billet Quality: Cr12MoV steel continuous casting billets exhibit good macrostructure with center porosity at 1.5 grade, center segregation below 1 grade, and satisfactory macroscopic carbon distribution.
- Superior Product Quality: Finished Cr12MoV flat steel products demonstrate good center porosity and ingot segregation characteristics, with eutectic carbide unevenness consistently ≤3 grade.
- Outstanding Economic Performance: The short process simplifies production workflow, shortens manufacturing cycles, achieves 92% comprehensive yield, and reaches annual production of nearly 40,000 tons with excellent economic returns.
Frequently Asked Questions
What is the short process production method for Cr12MoV steel?
The short process production method involves EAF (Electric Arc Furnace) melting → LF refining → VD vacuum degassing → rectangular billet continuous casting → single-fire heating and rolling. This eliminates the traditional multi-fire forging steps required in conventional die casting processes, significantly streamlining production while maintaining product quality.
What yield rate can be achieved with continuous casting of Cr12MoV steel?
The continuous casting short process can achieve a comprehensive yield rate of 92%, compared to only 80.12% for the traditional die casting long process. This represents an improvement of nearly 12 percentage points, significantly reducing material waste and production costs.
What quality standards does the continuously cast Cr12MoV steel meet?
The continuously cast Cr12MoV steel achieves center porosity of 1.5 grade, center segregation ≤1.0 grade, eutectic carbide unevenness ≤3 grade (meeting GB/T1299-2014 Group I requirements), and ultrasonic testing quality reaching Grade A and AA levels according to GB/T4162-2008 standards.
What are the energy savings of the short process compared to traditional methods?
The short process production method reduces energy consumption by more than 20% compared to the traditional die casting and multi-fire forging process. This is achieved by eliminating multiple heating cycles and forging operations while maintaining the same or better product quality.
What casting parameters are critical for Cr12MoV continuous casting?
Critical parameters include tundish superheat of 25-40°C, casting speed of 0.80 m/min, mold oscillation frequency of 80-180 cycles/min with amplitude of 3.0-6.0 mm, secondary cooling specific water ratio of 0.10-0.18 L/kg (weak cooling to prevent cracking), and electromagnetic stirring in both mold and secondary cooling zones with 15s-5s-15s forward/reverse pattern.
About FUSHUN METAL
FUSHUN METAL is a professional supplier of tool steel, die steel, and specialty steel materials. We are committed to providing high-quality steel products and technical solutions for customers in the tooling, mold manufacturing, and precision engineering industries worldwide. Our expertise spans cold work die steel, hot work die steel, plastic mold steel, and high-speed steel products meeting international quality standards.
