Compared with traditional die steel, carbide mould demonstrates remarkable economy and reliability in the production of high-volume, high-precision parts. Despite the higher initial investment, mould can significantly reduce the unit manufacturing cost by extending mould service life, minimizing downtime for mould maintenance, and improving product qualification rates. Especially under extreme working conditions such as high-frequency impact and severe friction in stamping dies and extrusion dies, the application advantages of carbide mould are more prominent. This paper will systematically elaborate on the application types, performance comparisons, material selection principles, engineering practices and key technical points of mould in the mould field, and look forward to future development trends, providing a comprehensive reference for industry practitioners.
| Kategori |
sınıf |
Composition Elements |
Mechanical Properties |
|
|
|
|
|
|
Bending Strength (MPa) |
Hardness (HRA) |
Compressive Strength (MPa) |
Impact Toughness (J/cm²) |
| Tungsten-Cobalt Cemented Carbides |
YG6 |
WC94%, Co6% |
1400 |
89.5 |
4600 |
2.6 |
|
YG8 |
WC92%, Co8% |
1500 |
89 |
4470 |
3 |
|
YG11 |
WC89%, Co11% |
1800 |
88 |
— |
3.8 |
|
YG15 |
WC85%, Co15% |
1900 |
87 |
3660 |
4.8 |
|
YG20 |
WC80%, Co20% |
2600 |
85.5 |
3500 |
4 |
|
YG25 |
WC75%, Co25% |
2700 |
85.5 |
3300 |
5.5 |
| Steel-Bonded Cemented Carbides |
GT35 (Quenched + Tempered) |
TiC30%, High-Chromium Alloy Steel 70% |
1400-1840 |
85-89 |
— |
5~8 |
|
GT50 (Quenched + Tempered) |
WC25%, High-Chromium Alloy Steel 75% |
1670-2560 |
85-88 |
— |
12 |
| General High-Speed Steel |
W6Mo5Cr4V2 (Quenched + Tempered) |
Fe, C, Mn, P, Cr, Ni, V, Mo, W (Vanadium-Tungsten Alloy Steel) |
4410 |
82 |
5580 |
20.6 (Notched) |
| High-Hardness High-Strength Die Steel |
Cr12MoV (Quenched + Tempered) |
Fe, C, Cr, V, Mo, Si, Mn |
2888 |
81.8 |
— |
40-60 (Unnotched) |
On the surface, the manufacturing cost of carbide mould is 2–4 times that of traditional steel moulds, but its advantages are extremely obvious when measured by the whole-life cycle cost. Taking the stamping of high-strength steel plates in the automotive industry as an example, an automobile manufacturer adopted YG15 mould progressive die to produce chassis parts. Although the initial investment in the mould increased by 300,000 yuan, the service life of the mould increased from 200,000 cycles of the steel mould to 8 million cycles, and the single sharpening interval extended from 5,000 cycles to 30,000 cycles. This not only reduced 15 mould maintenance downtimes (each downtime caused a loss of about 50,000 yuan) but also improved the product qualification rate from 92% to 99.5%, ultimately reducing the unit manufacturing cost by 30%–50%.
Carbide mould is more suitable for large-scale production with an annual output of over 1 million pieces, parts with precision requirements above IT8 grade and material hardness above HRC 30. In contrast, for small-batch production (annual output < 100,000 pieces), simple shapes and light-load scenarios, traditional die steel is more economical.
Application in Carbide Mould in Stamping Dies
Stamping is one of the core processes of metal plastic forming, widely used in automotive, electronics, aerospace, home appliance and other fields. In 2023, the global stamping die market size reached 28 billion US dollars, among which carbide mould stamping dies accounted for about 15% and the proportion is increasing year by year. Complex dies such as progressive dies and high-speed stamping dies need to withstand high-frequency impact of 10–50 times per second, shear stress (up to 500–1000 MPa) and severe friction. Traditional die steel is prone to edge chipping, excessive wear and dimensional deformation. The high hardness and high elastic modulus of carbide mould can perfectly match such working conditions, effectively reducing mould deformation (the deformation is only 1/3–1/5 of that of steel moulds) and ensuring part dimensional accuracy.
Material Selection and Design Optimization of Blanking Dies
The core requirement of blanking dies is to ensure neat part cross-sections with burrs ≤ 0.03 mm, so they have extremely high requirements for the hardness and wear resistance of mould materials. Material selection and design should follow the following principles according to plate thickness and working conditions
Image 1 Blanking Die
Low-cobalt fine-grained carbide mould is selected, with typical grades such as YG8 (Co content 8%, WC grain size 1–3 μm) and YG8X (fine-grained modified version, WC grain size 0.8–1.2 μm). The hardness is HRA 91.5–92, and the wear resistance is 30% higher than that of ordinary YG8 carbide mould. It is suitable for precision parts such as electronic connectors, motor silicon steel sheets and battery tabs. An electronics enterprise applied YG8X mould to blank 0.2 mm thick phosphor copper sheets, and the service life of the carbide mould reached 12 million cycles, which is 60 times that of Cr12MoV steel moulds.
High-cobalt coarse-grained carbide mould is adopted, such as YG15 (Co content 15%, WC grain size 3–5 μm) and YG18C (Co content 18%, coarse-grained). The impact toughness is 20%–40% higher than that of YG8 mould, which can avoid edge chipping during thick plate shearing. An auto parts enterprise used YG15 mould to blank 8 mm thick high-strength steel (tensile strength 1200 MPa), and the service life of the carbide mould increased from 50,000 cycles of the steel mould to 2 million cycles, and the chipping rate decreased from 15% to 0.5%.
Key Design Points
Carbide mould is sensitive to stress concentration. Traditional carbide mould is not recommended for trimming dies with complex edges and significant stress concentration; instead, steel-bonded mould (such as GT35) can be used as a replacement.
Multi-station progressive dies need to adopt high-cobalt fine-grained grades (such as YG15X carbide mould), and the corner fillet radius should be optimized to more than R0.5 mm to reduce the risk of stress concentration.
The matching gap between the punch and die should be controlled at 3%–5% of the plate thickness, which is 1–2 percentage points smaller than that of steel moulds, to reduce burr generation.
Forming process dies (drawing dies, bending dies, flanging dies, etc.) not only require high hardness but also need to have low friction, anti-seizure and shape stability. The polishing performance (up to Ra ≤ 0.01 μm) and low friction coefficient (0.15–0.25, compared with 0.35–0.5 for steel moulds) of carbide mould make it an ideal choice.
Carbide mould with low friction coefficient is selected, such as YG8C (surface polished) and YG6A (fine-grained low-cobalt carbide mould), which can reduce the friction resistance between the blank and the carbide mould, decrease the drawing force by 30%, and inhibit surface scratches on the workpiece. Application of stainless steel sink drawing dies in a home appliance enterprise showed that after using YG8C mould, the drawing force decreased from 1200 kN to 840 kN, the surface scratch rate of products decreased from 12% to 0.8%, and the qualification rate increased from 85% to 99%. If the surface of the mould is coated with TiN coating (thickness 2–3 μm), the friction coefficient can be further reduced to below 0.1, and the service life of the mould can be increased by another 50%.
şekil 2
Simple non-blank holder device drawing die for cylindrical parts
1 – Die shank 2 – Lower template 3 – Punch 4 – Locating plate
5 – Die 6 – Stripper 7 – Spring
Medium-cobalt carbide mould (such as YG11, Co content 11%) is adopted, which balances hardness (HRA 90) and toughness (impact toughness 14 MPa·m¹/²), and is suitable for bending forming of high-strength steel and stainless steel. An automobile factory used YG11 carbide mould to make bending dies for door anti-collision beams, and the bending angle accuracy was controlled within ±0.5°, and the service life of the carbide mould was 20 times longer than that of Cr12MoV steel moulds, avoiding the angle deviation problem of steel moulds caused by wear.
Image 3 Bending Die
For large-size dies (size > 1000 mm × 500 mm) such as automobile panels and large home appliance shells, a composite structure of “carbide mould insert + steel matrix” is adopted. The insert is made of YG8 or YG11 carbide mould with a thickness of usually 10–15 mm, covering the key forming surfaces; the matrix is made of 45 steel or Q235 steel, fixed by bolt connection or interference fit. This scheme can reduce the mould cost by more than 40% and ensure the wear resistance of key forming surfaces at the same time. After application in an automobile panel mould, the service life increased from 80,000 cycles of the steel mould to 1.5 million cycles.
After selecting the appropriate grade, in mould design, if the mould size is too large, the preparation of the integral carbide mould will be difficult and costly. Therefore, carbide mould is often used to prepare mould part inserts, as shown in Figure 1. The radial dimensions of the moulds shown in Figure 1(a) and (c) are small, so integral mould can be used for manufacturing. For the moulds with large overall dimensions shown in Figure 1(b) and (d), mould is used to prepare the working parts of the mould or the parts with high performance requirements in the working parts, which can reduce the manufacturing cost and processing difficulty of the mould.
Figure 4 Carbide Mould Stamping Die Parts
(a) Stamping Combined Punch and Die for Motor End Cover
(b) Punching Die
(c) Drawing Die for Deep Cylinder Parts
Extrusion forming is an efficient near-net-shape processing technology. By applying high pressure to the blank through the die (up to 2000 MPa for cold extrusion and 500 MPa for hot extrusion), plastic flow is generated to obtain parts with special-shaped cross-sections. The material utilization rate is over 95%, saving 30%–50% of raw materials compared with cutting processing. The working environment of extrusion dies is extremely harsh: the die cavity bears huge radial compressive stress and friction wear, and the punch bears axial tension-compression alternating stress and impact load. Therefore, wear resistance and toughness should be emphasized respectively, while meeting the requirements of dimensional accuracy (IT7–IT9 grade) and surface quality (Ra ≤ 1.6 μm).
The plasticity of blanks in cold extrusion is poor at room temperature, and the die needs to withstand high stress, alternating load and certain thermal effects (the temperature can rise to 150–300°C during extrusion). Therefore, material selection and structural design are particularly critical.
Figure 5 Cold Heading Die
High-cobalt carbide mould is preferred, such as YG15 (Co content 15%) and YG20 (Co content 20%) carbide mould, to ensure sufficient impact toughness and compressive strength, avoiding punch fracture failure during cold extrusion. A fastener enterprise used YG20 carbide mould to make cold extrusion punches for M12 bolts, and the service life of the mould punch increased from 20,000 cycles of high-speed steel (W6Mo5Cr4V2) to 500,000 cycles, and the fracture rate decreased from 8% to 0.3%.
A composite structure of “low-cobalt fine-grained carbide mould + prestressed ring” is adopted. The die cavity body is made of YG8 carbide mould (Co content 8%, WC grain size 1–2 μm) with a hardness of HRA 92 and excellent wear resistance; the prestressed ring is made of 45 steel or 40CrNiMo steel, applying pre-compressive stress to the die cavity through interference fit (interference 0.1–0.2 mm) to offset the radial tensile stress during extrusion, increasing the service life of the mould by 3–5 times. A machinery parts factory used this structure to make cold extrusion dies for gears, and the service life of the mould increased from 100,000 cycles of the single mould cavity to 450,000 cycles.
Figure 6 Punch, Combined Punch and Die, Die Insert and Prestressed Ring of Cemented Carbide Extrusion Die
Figure 6 shows the four parts of a set of carbide mould extrusion die: punch, combined punch-die, die insert and prestressed ring. The radial dimensions of the punch and combined punch-die are small, and integral carbide mould is used for preparation. The die cavity of the extrusion die adopts the mosaic method of carbide mould insert and alloy steel prestressed ring, which is widely used in many mould designs. The use of prestressed ring can share the tensile stress borne by the mould insert, make up for the shortcomings of low tensile strength and poor toughness of carbide mould, improve the overall strength of the mould, and reduce the manufacturing cost of the mould.
For complex cold extrusion parts such as special-shaped holes, multi-step and thin-walled parts, traditional carbide mould is prone to failure due to insufficient toughness and poor machinability. Steel-bonded carbide mould (such as GT35 and TLM50) can be selected. Steel-bonded carbide mould uses steel as the binder phase, with a bending strength of 1200 MPa, and its machinability is better than that of traditional carbide mould (it can be processed by turning, milling, drilling and other machining methods). The service life of the steel-bonded carbide mould is more than 10 times that of high-speed steel. An automobile gearbox factory used GT35 steel-bonded mould to make cold extrusion dies for spline shafts, and the average service life reached 500,000 pieces, far exceeding the design requirement of 300,000 pieces.
Figure 7 hot Extrusion Die
Warm extrusion (blank temperature 300–800°C) and hot extrusion (800–1200°C) reduce the deformation resistance of blanks by heating, which can process high-strength alloys (such as titanium alloys and superalloys) and large-size parts, or reduce the number of extrusion steps to lower continuous production costs, reduce processing time and increase output. The working parts of warm/hot extrusion dies bear less force, but due to the temperature rise, the material performance is affected, and new requirements are put forward for the mould material.
The hardness of carbide mould remains above HRA 80 in the range of 600–800°C, which is much higher than that of H13 hot work die steel (HRA 65–70); the thermal conductivity reaches 80–100 W/(m·K), which is 2–3 times that of H13 steel, with better heat dissipation effect, which can reduce the generation of thermal fatigue cracks.
Typical Application Cases
Aluminum alloy round tube warm extrusion die: YG8 carbide mould is adopted, with a working temperature of about 500°C. The service life of the mould can reach more than 100,000 cycles, which is 5–8 times that of H13 steel mould, and the surface roughness of the profile is reduced from Ra 1.6 μm to Ra 0.8 μm without subsequent grinding processing.
Titanium alloy part hot extrusion die: YG10X (fine-grained carbide mould) is selected, with TaC added (content 5%) to improve high-temperature stability. The service life of the mould is 3–4 times that of H13 steel mould. After application in an aerospace enterprise, the extrusion qualification rate of titanium alloy pipes increased from 75% to 92%.
To further improve high-temperature wear resistance and oxidation resistance, the surface of carbide mould can be coated with AlTiN or CrN coating (thickness 3–5 μm). The hardness of the coating can reach above HV 3000, which can increase the service life of the mould by another 20%–30%.
With the unique advantage of “exchanging high initial cost for ultra-long service life, high precision and high efficiency”,
carbide mould has become the preferred material for high-end plastic forming dies. Its material selection rules can be summarized as follows: high-cobalt grades (YG11–YG15 carbide mould) are preferred for separation processes (blanking, shearing), bending dies and extrusion punches, balancing toughness and wear resistance; low-cobalt grades (YG6–YG8 carbide mould) are selected for forming processes (drawing, extrusion die cavities), highlighting high hardness and low friction characteristics.
With the continuous breakthroughs in material innovation, preparation technology and processing technology, the application proportion of carbide mould in the mould field will continue to increase. Especially in strategic emerging industries such as new energy vehicles, aerospace and high-end equipment, carbide mould is expected to become the core support for promoting the upgrading of the manufacturing industry towards high precision, low energy consumption and large-scale production. In the future, the industry needs to further strengthen industry-university-research cooperation, improve the standardization system, reduce application costs, and fully transform the performance advantages of carbide mould into industrial competitiveness.
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