Nitrided Rolling Rod for Seamless Pipe Production
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rolling rods used in the production of seamless metallic hollow bodies, particularly those made of chromium-containing steels, face reduced service life and increased risk of defects due to thermal loading and abrasion, with existing nitriding solutions not effectively addressing these issues and posing environmental concerns from chromium plating and borax deoxidation.
Innovation Solution
A rolling rod with a nitriding layer on a heat-resistant steel material having a chromium equivalent of more than 6.5, minimum hardness of 200 HV 0.5, yield point of at least 450 MPa at 500°C, and tensile strength of at least 600 MPa, combined with a specific nitriding layer depth and lubrication process, is used to enhance service life and reduce inner surface defects during the stretch-forming of metallic hollow blocks in a multiple-stand rolling mill.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rolling rod is used for stretch-forming of hollow blocks made of chromium-containing steels, then the production of seamless metallic hollow bodies is achieved, but the service life of the rolling rod is reduced due to thermal loading and abrasion
Solution Approach 1:
The rolling rod combines a heat-resistant steel base material with a nitriding layer surface treatment to create a composite structure that provides both thermal resistance and abrasion resistance, thereby extending service life while maintaining productivity in processing chromium-containing steels
Solution Approach 2:
The invention changes the surface properties of the rolling rod by applying a nitriding layer with specific depth (>0.15mm) and hardness (>950 HV 0.5), transforming the surface to withstand thermal loading and abrasion from chromium-containing materials, thus extending the rolling rod's service life
2Strength
If chromium plating is applied to the rolling rod surface, then wear resistance is improved, but environmental harm is caused due to toxic chromium IV release
Solution Approach 1:
The invention replaces harmful chromium plating with a nitriding layer that provides equivalent or superior wear resistance without releasing toxic substances, converting the harmful chromium-based solution into a beneficial environmentally-friendly nitriding process
3Ease of operation
If borax deoxidation is used to dissolve oxide scale, then lubrication is improved, but gene-altering effects are caused
Solution Approach 1:
The invention eliminates the use of borax deoxidation by relying on the nitriding layer's inherent lubrication properties and controlled oxide scale formation, thereby removing the gene-altering hazard while maintaining adequate lubrication conditions for the rolling process
4Duration of action of moving object
If a nitriding layer is applied to the rolling rod, then service life is extended, but manufacturing complexity increases
Solution Approach 1:
The nitriding layer is applied by controlling parameters such as layer depth (>0.15mm) and surface hardness (>950 HV 0.5) to achieve the required performance, transforming a complex manufacturing challenge into a manageable process through defined parameter specifications
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 proposed solution significantly increases the service life of rolling rods and minimizes defects on the inner surfaces of pipes, particularly for chromium-containing materials, while avoiding the need for borax deoxidation and improving lubrication efficiency, leading to more reliable and cost-effective production of seamless metallic hollow bodies.
Implementation Method 1
having a surface comprising a nitriding layer
Implementation Method 2
the rolling rod is provided with a liquid lubricant and which is subsequently dried
Implementation Method 3
prior to the commencement of rolling, i.e. the beginning of threading the rolling rod into the hollow block, the rolling rod is provided with a liquid lubricant and which is subsequently dried
Data Source
AI summary
A rolling rod configured as an inner tool in the production of seamless hollow bodies, such as seamless pipes. The rolling rod has a nitrided surface layer and may consist of a heat-resistant steel material having a chromium equivalent calculated by a formula, as well as has a minimum hardness, yield point and tensile strength. A seamlessly hot-rolled, metallic hollow body is produced by a stretch-forming procedure in a multiple-stand rolling mill via the rolling rod which is threaded into the hollow block. Prior to threading the rolling rod into the hollow block, the rolling rod is provided with a liquid lubricant and is subsequently dried. The rolling rod is threaded in with a clearance with respect to the inner diameter of the hollow block. Prior to threading-in the rod, the hollow block may have an average temperature of at least 1000° C., with the rod having a determined speed.