Nitrided Steel Cooking Vessel With Aluminum Heat-Diffusing Bottom
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Solution Overview
Problem
Cooking vessels made of nitrided steel exhibit inhomogeneous bottom temperature distribution leading to hot spots and poor heat transfer, especially during gas heating, which results in increased cooking times and smoke formation.
Innovation Solution
A method involving the production of a cooking vessel with a nitrided steel substrate treated by nitrocarburizing and oxidation processes, followed by mechanical pickling and the assembly of an aluminum heat-diffusing element via hot stamping, to enhance corrosion resistance and heat distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a cooking vessel is made of nitrided steel with ordinary carbon steel substrate, then production cost is reduced compared to stainless steel, but the bottom temperature distribution becomes inhomogeneous leading to hot spots
Solution Approach 1:
The patent applies composite materials by combining nitrided steel (for corrosion resistance and cost-effectiveness) with an aluminum heat-diffusing element (for improved thermal distribution). The aluminum element is assembled to the outer surface of the nitrided steel cooking vessel, creating a composite structure that leverages the advantages of both materials: the nitrided steel provides economical production and corrosion resistance, while the aluminum layer ensures homogeneous heat distribution across the bottom surface, eliminating hot spots.
2Temperature
If the central part of the bottom is heated to achieve sufficient temperature for wok cooking, then cooking temperature is improved, but very high temperatures in the heating zone promote smoke formation
Solution Approach 1:
The patent applies local quality by creating different thermal properties in different zones of the cooking vessel bottom. The aluminum heat-diffusing element is strategically placed to modify the thermal characteristics of the bottom surface, ensuring that heat is distributed more evenly across the heating zone rather than concentrating in specific areas. This prevents localized overheating that would cause smoke formation while still achieving sufficient cooking temperature in the central area.
3Manufacturing precision
If mechanical pickling is performed on the oxidized surface layer, then surface roughness is improved for better heat diffuser attachment, but the oxidized protective layer is removed
Solution Approach 1:
The patent applies preliminary action by performing mechanical pickling of the oxidized surface layer before assembling the heat diffuser element. The pickling process creates a roughened surface that provides excellent mechanical interlocking for the subsequent hot-stamping attachment of the aluminum heat diffusing element. The oxidized layer is intentionally removed in the specific area where the heat diffuser will be attached, as this localized removal does not compromise the overall corrosion resistance of the vessel, since the oxidized layer remains intact on the rest of the surface.
4Productivity
If hot stamping is used to assemble the aluminum heat diffuser element, then assembly cycle time is reduced compared to brazing, but assembly temperature must be controlled to preserve the oxidized black appearance
Solution Approach 1:
The patent applies parameter changes by optimizing the hot stamping process parameters (temperature, pressure, and time) to achieve proper bonding of the aluminum heat diffuser element while maintaining the oxidized black appearance of the nitrided steel surface. The process parameters are carefully controlled so that the heating temperature remains below the threshold that would cause discoloration or degradation of the oxidized layer, while still providing sufficient thermal energy for effective metallurgical bonding during the shortened assembly cycle.
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 solution achieves improved heat distribution and corrosion resistance, reducing cooking times and preventing smoke formation by ensuring a more uniform temperature across the bottom of the cooking vessel.
Implementation Method 1
production on the tank of a nitrocarburizing treatment and an oxidation treatment, forming on the substrate a nitrided intermediate layer covered with an oxidized surface layer
Implementation Method 2
The oxidation treatment makes it possible to passivate the nitrided layer by the formation of iron oxide Fe 3 O 4 , which provides better corrosion resistance to the entire surface of the tank
Implementation Method 3
assembly by hot stamping an aluminum heat-diffusing element on said outer surface
Implementation Method 4
assembly by hot stamping an aluminum heat-diffusing element on said outer surface
Data Source
Figure 1~4
Figure 5~7
AI summary
The invention relates to a method of obtaining a cooking vessel, comprising the following steps: a vessel (10) is produced by drawing an ordinary steel substrate (16); a nitrocarburizing treatment and an oxidizing treatment are carried out on said vessel (10), forming on the substrate (16) a nitrided intermediate layer (17) covered with an oxidized surface layer (18); the oxidized surface layer (18) is mechanically abraded on an outer surface of said vessel (10), the outer surface comprising at least a portion of the bottom (11) of the vessel (10); and a heat-diffusing element (20) made of aluminium is assembled by hot stamping on said outer surface. The invention also relates to a culinary article or an electrical cooking apparatus comprising a cooking vessel obtained according to the aforementioned method.