阅读说明：本技术 一种准确评估焊接用钢盘条拉拔加工性能的方法 (Method for accurately evaluating drawing processing performance of steel wire rod for welding ) 是由 亓奉友 李阳 侯建伟 王广顺 张吉伟 唐庆 于 2021-07-26 设计创作，主要内容包括：本发明提供一种准确评估焊接用钢盘条拉拔加工性能的方法,所述方法为：在盘条代表性位置取金相样棒；将金相样棒横截面进行热镶嵌制成金相样品后,进行机械磨抛并腐蚀；把金相样品放在光学显微镜下观察,找出马氏体和/或贝氏体组织并拍摄照片；根据显微组织照片中马氏体贝氏体组织所占的比例大小准确判定盘条的拉拔性能。通过金相检验评估盘条组织中的马氏体/贝氏体严重程度来判定盘条的冷拉拔加工性能,比传统检验盘条拉伸性能的方法更为准确、可靠,本方法可用于钢厂产品出厂或金属制品厂购进原材料的验收标准,也可作为金属制品厂选择加工工艺的评判标准。(The invention provides a method for accurately evaluating the drawing processing performance of a steel wire rod for welding, which comprises the following steps: taking a gold sample bar at a representative position of the wire rod; carrying out thermal inlaying on the cross section of the metallographic specimen rod to prepare a metallographic specimen, and then carrying out mechanical grinding and polishing and corrosion; observing a metallographic sample under an optical microscope, finding out a martensite and/or bainite structure and taking a picture; and accurately judging the drawing performance of the wire rod according to the proportion of the martensite bainite structure in the microstructure picture. The cold drawing processing performance of the wire rod is judged by evaluating the severity of martensite/bainite in the wire rod structure through metallographic examination, and the method is more accurate and reliable than the traditional method for testing the tensile performance of the wire rod.)

1. The method for accurately evaluating the drawing processing performance of the steel wire rod for welding is characterized by sequentially comprising the following steps of:

s1, taking a gold sample bar at the representative position of the wire rod;

s2, carrying out thermal inlaying on the cross section of the metallographic specimen rod to prepare a metallographic specimen, and then carrying out mechanical polishing and corrosion;

s3, placing the metallographic sample under an optical microscope for observation, finding out a martensite and/or bainite structure and taking a picture;

and S4, accurately judging the drawing performance of the wire rod according to the proportion of the martensite bainite structure in the microstructure picture.

2. The method for accurately evaluating the drawing processing performance of the steel wire rod for welding according to claim 1, wherein in the step S1, after the wire rod sampling position is a part of a coil, which is completely sheared and does not penetrate water from head to tail, any circle of wire rod is taken, a metallographic sample rod is taken at intervals of not more than 30cm on the taken wire rod, the length of the sample rod is about 3cm, and the number of the sampled wire rods in one circle is not less than 6.

3. The method for accurately evaluating the drawing workability of a steel wire rod for welding according to claim 1, characterized in that: and step S2, the gold phase sample is corroded after being mechanically polished, and the corrosive agent is 3-4% of nital.

4. The method for accurately evaluating the drawing workability of a steel wire rod for welding according to claim 1, characterized in that: the optical microscope magnification in step S3 is 500 times.

5. The method for accurately evaluating the drawing workability of a steel wire rod for welding according to claim 1, characterized in that: in the step S4, the microstructure picture is compared with a reference standard map for judgment, and when the martensite is less than 1 grade and the bainite is less than 2 grade, the cold drawing performance is good and the wire breakage is not easy to occur.

6. The method for accurately evaluating the drawing workability of a steel wire rod for welding according to claim 5, characterized in that: the comparison standard atlas is a 0-4 grade standard metallographic atlas which is prepared according to the relation between the martensite/bainite structure content in the welding steel and the cold drawing processing performance counted in the repeated steps 1-4.

Technical Field

The invention relates to the technical field of high-speed wire rod production, in particular to a method for accurately evaluating the drawing processing performance of a steel wire rod for welding.

Background

Welding wire materials such as ER70S-6 are generally processed into filaments with the diameter of 1.2mm or even thinner from a wire rod with the diameter of 5.5mm through multi-pass cold drawing, so that the wire rod raw materials are required to have good cold drawing processing performance. According to the requirements of GB/T3429-2015 Steel wire rod for welding, 2 tensile samples are taken from each batch to test the tensile mechanical property of the steel wire rod. Because the steel for welding is generally low-carbon low-alloy steel, the microstructure of the wire rod produced by high-speed wire controlled rolling and controlled cooling is mainly ferrite and pearlite in the delivery state, and the actually measured reduction of area is as high as 80%. However, even if the wire rod has a reduction of area of 80% in the actual use process of the user, unexpected wire breakage phenomenon is often caused by the problem of raw materials in the fine drawing stage, and wire breakage does not occur in the whole drawing process although the reduction of area of the special welding steel is only 70%. It is seen that the reduction of tensile section does not allow accurate evaluation of the cold drawing mechanical properties of the wire rod.

Through analysis and summary of experience, data and summary of steel wire rods for years of production and use of tracking customers, the inventor finds that the raw material problem causing wire breakage in the fine drawing process of welding wire materials is mainly martensite/bainite abnormal structures in the microstructure of the welding wire materials. The cold drawing mechanical property of the wire rod can be accurately evaluated by detecting the content of the abnormal structure of the wire rod.

Disclosure of Invention

The invention aims to provide a method for accurately evaluating the drawing processing performance of a steel wire rod for welding, which can more accurately evaluate the cold drawing processing performance of the wire rod compared with the traditional method for testing the tensile mechanical performance, avoid the wire breakage risk caused by blindly throwing the wire rod and improve the production efficiency.

In order to achieve the purpose, the invention provides the following technical scheme: the method for accurately evaluating the drawing processing performance of the steel wire rod for welding comprises the following steps: the method comprises the following steps in sequence:

s1, taking a gold sample bar at the representative position of the wire rod;

s2, carrying out thermal inlaying on the cross section of the metallographic specimen rod to prepare a metallographic specimen, and then carrying out mechanical polishing and corrosion;

s3, placing the metallographic sample under an optical microscope for observation, finding out a martensite and/or bainite structure and taking a picture;

and S4, accurately judging the drawing performance of the wire rod according to the proportion of the martensite bainite structure in the microstructure picture.

Preferably, in the step S1, after the coil rod sampling position is a part of a coil, which is completely sheared and does not penetrate water from head to tail, any coil rod is taken, a metallographic sample rod is taken at an interval of not more than 30cm from the taken coil rod, the length of the sample rod is about 3cm, and the number of the sampled coil rods is not less than 6.

Preferably, the gold phase sample in step S2 is mechanically polished and then etched, and the etchant is 3-4% nital.

Preferably, the optical microscope magnification in step S3 is 500 times.

Preferably, in step S4, the microstructure picture is compared with a reference standard map for determination, and when the martensite is less than 1 grade and the bainite is less than 2 grade, the cold-drawing performance is good and the wire is not easy to break.

Preferably, the reference standard map is a 0-4 grade standard metallographic map prepared according to the relation between the martensite/bainite structure content in the welding steel and the cold drawing processing performance counted in the repeated steps 1-4.

The invention has the beneficial effects that:

the cold drawing processing performance of the wire rod is judged by evaluating the severity of martensite/bainite in the wire rod structure through metallographic examination, which is more accurate and reliable than the traditional method for testing the tensile performance of the wire rod, and the method can be used for the acceptance criteria of the steel mill products leaving the factory or the raw materials purchased by the metal product factory, and can also be used as the judgment criteria of the metal product factory for selecting the processing technology; the inventor adopts the patent method, and 50 ten thousand tons of steel wire rods for welding are produced and sold since the martensite/bainite grade is used as the judgment standard for the qualification of the drawing performance of the product, and the quality objection of fine drawing broken wires caused by the wire rod problem is not generated.

Drawings

FIG. 1 is a standard metallographic atlas level 0 sample;

FIG. 2 is a standard metallographic atlas level 1 sample;

FIG. 3 is a standard metallographic atlas level 2 sample;

FIG. 4 is a standard metallographic atlas grade 3 sample;

FIG. 5 is a standard metallographic atlas level 4 sample;

FIG. 6 is a standard metallographic atlas grade 5 sample;

FIG. 7 is a gold phase diagram of the wire rod tested in example 2.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

This example illustrates in detail a method for accurately evaluating the drawing workability of a steel wire rod for welding, which comprises the following steps in order:

s1, taking hot-rolled wire rods produced by high-speed wire production, taking one circle after the head and tail parts without water penetration are completely sheared, taking 6 metallographic sample rods on the sampling coil at intervals of 30cm, and ensuring that the sampling positions cover the middle part and the edge part of the coil on a stelmor roller way;

s2, carrying out thermal inlaying on the cross section of the metallographic specimen rod to prepare a metallographic specimen, and then mechanically polishing, wherein the polishing is carried out and then is corroded by 3-4% nitric acid alcohol solution;

s3, placing the metallographic sample under an optical microscope for observation, finding out the region with the most serious martensite and/or bainite tissues, and taking and storing a picture under the condition of 500-fold magnification of the optical microscope;

s4, repeating the steps 1-4 until the corresponding relation between the martensite/bainite content and cold drawing processing is counted, and making a standard metallographic graph according to the number of the martensite and bainite contents by 5 grades, wherein the standard metallographic graph specifically comprises the following steps:

level 0: no martensite or bainite structure, all ferrite and pearlite (see fig. 1);

level 1: martensite and/or bainite are concentrated in the core of the metallographic sample, and the number of the martensite and/or bainite is less than or equal to 10;

and 2, stage: the core parts of the martensite and/or bainite concentrated metallographic samples are 10-20; or martensite and/or bainite are distributed at the center and the edge of the metallographic sample simultaneously;

and 3, level: the core parts of the martensite and/or bainite concentrated metallographic samples are 20-30; or martensite and/or bainite are distributed at the center and the edge of the metallographic sample simultaneously, and the number of the martensite and/or bainite is more than 10;

4, level: the structure is mainly martensite or bainite, and only a small amount or no ferrite and pearlite exist.

When the martensite of the wire rod is less than grade 1 and the bainite is less than grade 2, the cold drawing performance is better, and the wire breakage is not easy to occur.

Example 2

S1, taking hot-rolled wire rods produced by high-speed wire production, taking one circle after the head and tail parts without water penetration are completely sheared, taking 6 metallographic sample rods on the sampling coil at intervals of 30cm, and ensuring that the sampling positions cover the middle part and the edge part of the coil on a stelmor roller way;

s2, carrying out thermal inlaying on the cross section of the metallographic specimen rod to prepare a metallographic specimen, and then mechanically polishing, wherein the polishing is carried out and then is corroded by 3-4% nitric acid alcohol solution;

s3, placing the metallographic sample under an optical microscope for observation, finding out the region with the most serious martensite and/or bainite tissues, and taking and storing a picture under the condition of 500-fold magnification of the optical microscope;

s4, comparing with a standard metallographic atlas, judging that the drawing performance of the wire rod of a certain batch is martensite grade 3 and bainite grade 2 according to the proportion of martensite and bainite structures in the microstructure picture, and recommending to process after annealing, wherein the cold drawing performance is poor.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.