Detection method and characterization method of microporous defects in cold-drawn seamless steel pipes

A technology of seamless steel pipe and detection method, which is applied in the directions of optical testing flaws/defects, preparation of samples for testing, etc., can solve the problems such as the lack of detection methods and evaluation standards for microporous defects in the core of cold-drawn seamless steel pipes. Achieving the effect of solving quality inspection problems

Active Publication Date: 2018-03-16
PANGANG GROUP CHENGDU STEEL & VANADIUM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] At present, there is no detection method and evaluation standard for microporous defects in the core of this type of cold-drawn seamless steel pipe.

Method used

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  • Detection method and characterization method of microporous defects in cold-drawn seamless steel pipes
  • Detection method and characterization method of microporous defects in cold-drawn seamless steel pipes
  • Detection method and characterization method of microporous defects in cold-drawn seamless steel pipes

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preparation example Construction

[0047] (3) The preparation of the sample, generally after grinding and polishing, a certain number of pits are inevitably distributed on the grinding surface of the sample, and foreign matter such as polishing agents, polishing fabrics, sand grains, etc. are often distributed in the pits, These foreign bodies have a strong binding force with the matrix, and it is not easy to clean them by conventional methods. In this way, when observing under a microscope, the above-mentioned pits are easily confused with microporous defects, thereby affecting the inspection efficiency and quality; in order to solve the above problems, the present invention The applicant chooses clean silk cloth as the polishing fabric, and clear water as the polishing agent. Firstly, the sample polished in the previous step is polished on a polishing machine to remove the polishing agent, polishing fabric, sand, etc. attached to the sample and inside the pit. Foreign matter, and then use alcohol and hot water...

Embodiment 1

[0051] The specification of embodiment 1 is Detection of Microporous Defects in Cold-drawn Seamless Steel Tubes for 25Mn Ordinary Structures and Their Grading

[0052] Specific steps are as follows:

[0053] a. Cut a section of horizontal pipe section from the cold-drawn seamless steel pipe, the longitudinal length of which is not less than 40 mm, and take a metallographic sample with inner and outer surfaces every 90 degrees in the horizontal direction of the pipe section, and take a total of 4 samples , the longitudinal length of which is not less than 30mm, and the sample includes the sample cut from the thinnest wall thickness of cold-drawn seamless steel pipe;

[0054] b. The longitudinal surface of the sample is used as the inspection surface;

[0055] c. Preliminarily grind the sample on the grinder, rinse the ground sample with clean water, and then put the grinding surface on the metallographic sandpaper of 280#-600#--800#--1000# in turn Fine grinding; each time w...

Embodiment 2

[0059] Embodiment 2 specification is Detection of Microporous Defects in Seamless Steel Tubes of 30CrMo Gas Cylinders and Their Grading

[0060] Specific steps are as follows:

[0061] a. Cut a section of horizontal pipe section from the cold-drawn steel pipe, the longitudinal length of which is not less than 40 mm, and take a metallographic sample with inner and outer surfaces every 90 degrees in the horizontal direction of the pipe section, and take 4 samples in total, of which The longitudinal length is not less than 30 mm, and the sample includes the sample cut from the thinnest area of ​​cold-drawn seamless steel pipe;

[0062] b. The inspection surface is the longitudinal inspection surface of the sample;

[0063] c. Preliminarily grind the sample on the grinder, rinse the ground sample with clean water, and then put the grinding surface on the metallographic sandpaper of 280#-600#--800#--1000# in turn Fine grinding; each time when the next finer sandpaper is changed...

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Abstract

The invention relates to a detection method and a rating method for defects of cold-drawn seamless steel pipes, belonging to the field of metal materials produced in the metallurgical industry. The invention provides a method for detecting microporous defects in cold-drawn seamless steel pipes, which comprises the following steps: 1) cutting a section of horizontal pipe section on the cold-drawn seamless steel pipe, the longitudinal length of which is not less than 40 mm, and every Take 4 to 8 metallographic samples at intervals of 45° to 90° to retain the inner and outer surfaces, and their longitudinal length is not less than 30 mm; the metallographic samples include at least one region with the thinnest wall thickness from cold drawn seamless steel pipe 2) take the longitudinal inspection surface of the metallographic sample as the inspection surface and grind and polish it; 3) observe the inspection surface of the metallographic sample under a microscope, and the holes distributed on the inspection surface are microscopic Hole defects. The method of the invention can quickly and accurately detect the distribution of microporous defects in the core of the cold-drawn seamless steel pipe, and evaluate the quality status.

Description

technical field [0001] The invention relates to a detection method and a rating method for defects of cold-drawn seamless steel pipes, belonging to the field of metal materials produced in the metallurgical industry. Background technique [0002] In the production process of cold drawn seamless steel pipe, if the tube blank has not been annealed or tempered heat treatment and the tube blank annealed or tempered heat treatment effect is not good, pickling, phosphating, saponification effect is not good, cold drawing process parameters are improper 1. If the wall thickness of the steel pipe is uneven, microporous defects may be formed in the center between the inner and outer walls of the cold-drawn seamless steel pipe. [0003] There are microporous defects in the core of cold-drawn seamless steel pipes, which not only cause high stress concentration at the defect, and are easy to form fatigue sources or crack sources, but also reduce the mechanical properties such as elongat...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N1/32G01N21/95
Inventor 陈雨杨其光张先华
Owner PANGANG GROUP CHENGDU STEEL & VANADIUM
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