Induction Heating for Heavy-Wall Seamless Steel Pipe Toughness
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Solution Overview
Problem
Conventional heat treatment methods fail to achieve sufficient toughness in heavy-wall seamless steel pipes due to limitations in heating rate and grain refinement, particularly when using atmosphere temperature control type heating furnaces, which result in decreased toughness and grain size refinement.
Innovation Solution
The method involves using induction heating at a frequency of not more than 200 Hz for quenching and tempering, with a temperature range of at least 750°C to 1000°C, combined with preliminary heating in an atmosphere temperature control type furnace and water cooling, to achieve rapid and uniform heating and refine grain structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If atmosphere temperature control type heating furnace is used for thermal refining, then heating can be performed, but grain refinement is insufficient and toughness decreases
Solution Approach 1:
The patent changes the heating rate parameter from conventional slow heating to rapid heating (heating rate of 100°C/min or more). This parameter change enables sufficient grain refinement in heavy-wall steel pipes while maintaining the required heating temperature, thereby improving toughness without sacrificing manufacturing feasibility.
2Strength
If wall thickness of seamless steel pipes increases, then pipe strength and load-bearing capacity improve, but toughness becomes difficult to ensure
Solution Approach 1:
The patent applies rapid heating (heating rate of 100°C/min or more) as a parameter change to achieve sufficient grain refinement in heavy-wall steel pipes. This enables the pipe wall to be thickened for strength while maintaining toughness through improved grain structure, resolving the trade-off between strength and toughness.
3Ease of manufacture
If conventional heat treatment is applied to heavy-wall steel pipes, then heat treatment can be performed, but expected grain refinement is not achieved and toughness decreases
Solution Approach 1:
The patent modifies the heating rate parameter to 100°C/min or more, transforming conventional heat treatment into rapid heating treatment. This parameter change makes grain refinement feasible in heavy-wall steel pipes while maintaining manufacturing simplicity, thereby improving toughness without complicating the manufacturing process.
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 approach enables the production of heavy-wall seamless steel pipes with improved toughness and refined grains, ensuring high strength and durability, particularly for applications in oil and gas well drilling and transmission.
Implementation Method 1
heating the steel pipe to a temperature in the range of not less than 900°C but not more than 1000°C at a heating rate of not less than 100°C/min by use of induction heating
Implementation Method 2
subsequently performing quenching by water cooling
Data Source
AI summary
In subjecting a steel pipe with a wall thickness over 30 mm to heat treatment of quenching and tempering, the pipe being made through a pipe making step by hot working, specifically in a temperature range of at least not less than 750°C during the heating stage, performing a quenching and tempering steps as below, in the order as described, makes it possible to perform uniform rapid heating in quenching and to obtain a heavy-wall seamless steel pipe having excellent toughness by resulting grain refinement, wherein (a) the quenching step involves quenching by performing water cooling after heating the steel pipe to a temperature in the range of not less than 900°C to not more than 1000°C by using, as a heating means, induction heating at a frequency of not more than 200 Hz, and (b) the tempering step involves tempering the steel pipe at a temperature in the range of not less than 500°C to not more than 750°C. In the quenching step of (a), it is preferred that after the heating by induction heating, a soaking treatment is further performed in the temperature range of not less than 900°C to not more than 1000°C for 10 minutes or less, and subsequently quenching by water cooling is performed.