Variable-Thickness Metal Strip for Lighter Welded Pipe Joints
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Solution Overview
Problem
Existing steel strips with constant thickness gradient in the longitudinal direction lack versatility and structural strength at connection portions, leading to potential cracking and weight issues in long oil-well cleaning pipes.
Innovation Solution
A metal strip with thicker end portions and a thinner intermediate portion, where the thickness ratio between the end and middle portions is between 7% and 50%, is used to form pipes, enhancing joint strength while reducing overall weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If steel strips with uniform thickness are used to manufacture long oil-well cleaning pipes by butt-welding multiple pipe bodies, then the suspended weight increases, but the strength must be increased by using higher grade materials
Solution Approach 1:
The steel strip has different thicknesses at different locations: thicker at end portions (for strong joint portions) and thinner at intermediate portions (for weight reduction). This local quality variation allows the pipe to have reduced suspended weight while maintaining sufficient strength at critical joint areas through the thicker end portions.
2Weight of moving object
If steel strips with constant thickness gradient are used to reduce weight, then the versatility is reduced and structural strength at connection portions is insufficient
Solution Approach 1:
The invention specifies particular thickness ranges for end portions (3.0-20.0 mm) and intermediate portions (2.0-15.0 mm), creating local quality differences that provide both weight reduction and structural strength. The controlled thickness variation maintains versatility while achieving weight reduction goals.
3Weight of moving object
If steel strips with constant thickness gradient are used, then weight is reduced, but cracks occur at step portions during repeated coiling and uncoiling
Solution Approach 1:
The thicker end portions provide enhanced strength and crack resistance at the joint portions where cracks are most likely to occur during repeated coiling and uncoiling operations. This local quality enhancement at critical areas improves reliability while the thinner intermediate portions maintain weight reduction benefits.
4Strength
If the thickness of steel strips is increased uniformly to enhance joint strength, then the weight of the entire pipe increases, requiring reduction of pipe length
Solution Approach 1:
The invention applies increased thickness only at end portions (3.0-20.0 mm) where joint strength is critical, while maintaining thinner thickness at intermediate portions (2.0-15.0 mm). This localized thickness enhancement provides the necessary joint strength without proportionally increasing the total pipe weight, allowing longer pipe lengths to be manufactured.
Data Source
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Figure 4(a)~6
AI summary
Provided is a metal strip for a pipe with which the weight of a pipe can be reduced while maintaining the strength of a joint portion that tends to be structurally the weakest. A metal strip L is formed by rolling. The thickness of each of a head end portion 1a and a tail end portion 1b, which are longitudinal end portions 1, is greater than the thickness of an intermediate portion excluding the longitudinal end portions 1. The metal strips are connected to each other in series by welding, and a pipe is made by performing a pipe-forming operation.