What level of semi-solid forming molds can be achieved now

What level of semi-solid forming molds can be achieved now
Semi solid forming involves slurping the alloy in the solid-liquid two-phase zone and forming it. The mold is subjected to the erosion of high viscosity slurry, with fewer pores but a narrow process window.
The basic logic of craftsmanship
The solid phase ratio of semi-solid forming is usually 30% -50%. The slurry is pressed into the mold cavity like butter, ensuring smooth filling and minimal air entrainment.
Due to the low filling temperature, the thermal impact of the mold is smaller than that of die-casting, and theoretically, the mold life is longer.
However, slurry preparation is complex, temperature control accuracy is required, and the process window is much narrower than die-casting.
Characteristics of mold structure
The pouring system should avoid premature solidification of the slurry. Short flow channels and large cross-sections reduce flow resistance.
The mold temperature needs to be controlled within the stable range of the solid phase ratio of the slurry, usually between 250-350 ℃.
The exhaust system has high requirements. The viscosity of the slurry is high, and the gas is not easily discharged. The exhaust area needs to be increased by 20% -30% compared to die-casting.
Materials and lifespan
The mold material is similar to die-casting molds and H13 is commonly used. Due to its low thermal shock, its lifespan can be 20% -40% longer than that of die-casting molds.
But the erosion of the slurry on the gate is more concentrated, and the wear rate of the gate area is faster than other areas.
Making the sprue into replaceable inserts can reduce maintenance costs.
Applicable scenarios
Semi solid materials are suitable for components with uniform wall thickness and high density requirements, such as steering knuckles and support structures.
Not suitable for thin-walled large items. The flowability of the slurry is limited, and the thin-walled distal end is prone to insufficient filling.
Not suitable for small batches either. The equipment investment for slurry preparation is high, and continuous production is required to flatten it.
Current state of the industry
The application scale of semi-solid forming in China is limited, and the equipment and slurry preparation are not as mature as die-casting.
Automotive structural components are the main direction, but most projects are still in the validation stage and there are not many mass production cases.
Xinfeng Mold mainly uses low pressure and gravity on structural component molds, and semi-solid state belongs to the technical tracking direction.
Comparison with low-pressure casting
The equipment investment for low-pressure casting is low, the process is mature, and it is suitable for small and medium-sized batches.
The semi-solid state has higher density and better mechanical properties, but also higher cost.
Choose based on product positioning. Safe components and large batch size, capable of evaluating semi-solid state; Low voltage is more economical for conventional components.
Implementation suggestions
Perform small batch validation first, do not directly go to the production line. The stability of the slurry requires long-term data support.
Mold design should be jointly reviewed with the slurry preparation party. Designing molds separately can easily overlook the characteristics of the slurry.
Verification of slurry stability
Before continuous production, a sampling of the solid phase rate of the slurry should be conducted every 2 hours. If the solid phase rate fluctuates by more than 5%, there will be batch differences in the quality of castings.
Practical tips
The slurry conveying pipeline needs to be insulated, and a temperature drop of more than 15 ℃ will change the solid phase ratio and the filling state accordingly.
The mold acceptance of semi-solid projects should include a slurry trial run, and only short mold verification cannot explain the problem.
The cooling water circuit of semi-solid molds should be able to switch quickly, with a narrow process window, and lagging adjustment will result in waste products.
Frequently Asked Questions
Q: What is the semi-solid solid phase ratio?
Answer: It is usually 30% -50%, adjusted according to the part type.
Q: Is the lifespan of the mold longer than that of die-casting?
Answer: Theoretically 20% -40% higher, with less thermal shock.
Q: Is it suitable for thin-walled parts?
Answer: Not suitable, the flowability of the slurry is limited.
Q: Is there much mass production in China?
Answer: Not many, most are still in the verification stage.
Q: Is the equipment investment high?
Answer: High, continuous production is required to flatten.
Q: How to choose between low pressure casting and low pressure casting?
Answer: Safety components can be evaluated in large quantities, while conventional components are selected for low voltage.
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