Black Heart Malleable Cast Iron Plating Without Pickling
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Solution Overview
Problem
Conventional methods for producing black heart malleable cast iron members with a plating layer require shot blasting or pickling, which increase production costs and pose environmental and safety hazards due to the use of acidic solutions.
Innovation Solution
A method involving graphitization in a non-oxidizing and decarburizing atmosphere, followed by immersion in a flux and hot-dip plating, to suppress oxide formation and eliminate the need for shot blasting or pickling, using a converted gas generated by combustion of a mixed gas of combustion gas and air to reduce production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shot blasting or pickling is performed to remove oxides from the surface, then the plating layer adhesion is improved, but production cost increases and environmental/safety hazards arise
Solution Approach 1:
The patent applies this principle by performing graphitization in a non-oxidizing atmosphere (such as nitrogen or argon atmosphere, or vacuum environment) to prevent oxide formation on the black heart malleable cast iron surface. By eliminating oxygen during the heat treatment process, the surface remains clean and free from oxides that would interfere with plating adhesion, thus removing the need for subsequent shot blasting or pickling operations.
Solution Approach 2:
The patent applies this principle by performing graphitization in a non-oxidizing atmosphere before the plating process to prevent oxide formation in advance. This preliminary protective measure ensures that the surface is already clean and ready for plating, eliminating the need for subsequent oxide removal steps and streamlining the manufacturing process.
2Manufacturing precision
If pickling with acidic solution is used to remove oxides, then the plating surface quality is improved, but worker safety and environmental burden worsen due to poisonous gases and waste disposal
Solution Approach 1:
The patent replaces the harmful pickling process with graphitization in a non-oxidizing atmosphere. By conducting the heat treatment in an inert or reducing atmosphere, oxides are prevented from forming on the surface, eliminating the need for acidic pickling solutions and the associated safety and environmental hazards while still achieving a clean plating surface.
Solution Approach 2:
The patent converts the potential harm of oxide formation during graphitization into a benefit by deliberately controlling the atmosphere to be non-oxidizing. Instead of allowing oxides to form and then removing them with harmful chemicals, the process uses the graphitization step itself to create a clean surface by preventing oxide formation, thus turning a potentially harmful process into a beneficial one.
3Reliability
If conventional plating process is used with oxide removal steps, then the plating layer adhesion is ensured, but production time and complexity increase
Solution Approach 1:
The patent merges the graphitization process with the surface preparation for plating by performing both functions in a single step. By conducting graphitization in a non-oxidizing atmosphere, the process simultaneously achieves the microstructural transformation needed for mechanical properties and the surface cleaning needed for plating adhesion, thereby eliminating separate oxide removal steps and reducing overall process complexity.
Solution Approach 2:
The patent performs surface preparation in advance during the graphitization step itself by preventing oxide formation through atmospheric control. This preliminary action ensures the surface is ready for plating before the actual plating process begins, eliminating the need for subsequent separate preparation steps and simplifying the overall manufacturing sequence.
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
This method reduces production costs and environmental burden by omitting shot blasting and pickling, while ensuring a robust and adhesive plating layer on the black heart malleable cast iron members without exposing workers to hazardous materials.
Implementation Method 1
the cast metal is heated to and held at a temperature of 720° C. or higher, so that the cementite is decomposed to precipitate graphite. Herein, the step of precipitating graphite by heat treatment is hereinafter referred to as 'graphitization'.
Implementation Method 2
using a converted gas generated by combustion of a mixed gas of combustion gas and air to reduce production costs
Implementation Method 3
immersing a black heart malleable cast iron member obtained after the graphitization, in a flux for 3.0 minutes or more
Implementation Method 4
performing hot-dip plating on the heated black heart malleable cast iron member
Data Source
AI summary
Provided is a method capable of producing a plated black heart malleable cast iron member having a plating layer with excellent adhesiveness to a black heart malleable cast iron member, while having less burden on the environment, compared to conventional methods.