Carbon Casting Mold Coated with Pyrolytic Carbon
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Solution Overview
Problem
Continuous casting molds made of graphite wear out quickly due to corrosion from molten metal, leading to reduced surface quality and dimensional accuracy of semi-finished products, necessitating frequent replacements and increased production costs.
Innovation Solution
A method for producing a casting mold predominantly made of carbon, coated with pyrolytic carbon and/or boron nitride using a combination of CVI and CVD processes at controlled temperatures, which seals pores and enhances mechanical and chemical resistance, forming a diffusion barrier against molten metal and gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a graphite mold is used for continuous casting, then the mold can be made entirely of carbon material suitable for non-ferrous metals, but the mold suffers from rapid wear and corrosion by molten metal leading to frequent replacement
Solution Approach 1:
The patent applies a coating layer of pyrolytic carbon or boron nitride on the graphite mold surface, creating a composite structure that combines the advantages of graphite (thermal conductivity, cost-effectiveness) with the advantages of the coating material (corrosion resistance, low reactivity with molten metal). This composite approach resolves the contradiction by maintaining adaptability for non-ferrous metal casting while significantly improving mold service life through enhanced corrosion resistance.
2Reliability
If the mold is coated with pyrolytic carbon using CVD process at high temperature (1700-2300°C), then the coating provides good corrosion resistance, but the process becomes complex and costly
Solution Approach 1:
The patent introduces a two-stage coating process where the first stage uses CVI at lower temperature (500-1000°C) to form a preliminary coating layer, and the second stage uses CVD at higher temperature (1700-2300°C) to form the final protective layer. This parameter change approach (temperature and process sequence) allows achieving good corrosion resistance while reducing overall process complexity compared to direct high-temperature CVD, as the lower-temperature CVI stage prepares the surface more efficiently.
3Reliability
If a thicker pyrolytic coating is applied to improve corrosion resistance, then the mold service life increases, but the coating process duration and cost increase
Solution Approach 1:
The patent uses the CVI process in the first stage to apply a preliminary coating layer at lower temperature, which prepares the mold surface and provides initial corrosion protection. This preliminary action reduces the burden on the subsequent CVD stage, allowing the final protective layer to be applied more efficiently. The two-stage approach with preliminary CVI coating reduces total process duration while achieving the required coating thickness and corrosion resistance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method significantly extends the service life of the casting mold, reducing replacement frequency and production costs by improving corrosion resistance and maintaining product quality over a longer period.
Implementation Method 1
within a first process section using a CVI process at a first temperature
Implementation Method 2
subsequently within a second process section using a CVD process at a second temperature
Implementation Method 3
a coating of the mold is applied at a temperature of 500 °C to 1900 °C
Data Source
Figure 1~3
AI summary
The invention relates to a method for producing a casting mould and to a casting mould (10), in particular a continuous casting mould or similar. Said casting mould is made from a material which is essentially made from carbon, and the casting mould is coated with pyrolytic carbon and/or boron nitride.