CN110806472A - Quality evaluation method for preventing hot-rolled plain carbon steel from cracking at 90-degree bending - Google Patents
Quality evaluation method for preventing hot-rolled plain carbon steel from cracking at 90-degree bending Download PDFInfo
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Abstract
The invention discloses a quality evaluation method for monitoring quality and preventing hot-rolled plain carbon steel from cracking at 90-degree bending, which comprises the following steps: step S100: manufacturing a transverse blank; step S200: manufacturing a standard sample of mechanical property; step S300: testing the mechanical property; step S400: detecting chemical components of a finished product and detecting a metallographic phase; step S500: analyzing the unqualified reason of the quality product; step S600: according to unqualified reasons, the production process is combined for targeted improvement; the bending of the factory products at the user is ensured not to crack, quality objections are avoided, good reputation of the user is gained, and larger market share is obtained; the quality of iron and steel production enterprises is promoted to be comprehensively improved, the reasons and the working procedures of the iron and steel production enterprises which cause the quality to be unqualified are determined through metallographic microscopic analysis, the iron and steel production enterprises can be purposefully improved, and the quality is promoted to be comprehensively improved.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a quality evaluation method for preventing hot-rolled plain carbon steel from cracking at 90-degree bending.
Background
The hot-rolled plain carbon steel Q235B steel strip is a conventional product of steel companies, and is mainly applied to manufacturing spare parts such as mechanical structural parts, square tubes, round tubes, stamping parts and the like. However, when a user bends to a 90-degree angle in the production process of manufacturing mechanical structural parts, square pipes and the like, the bending angle is obviously cracked, so that the continuous production of the user is influenced, the yield is influenced, the quality and delivery period of the product are also influenced, and the normal settlement of both suppliers and demanders is directly influenced; sometimes, an upstream merchant can cut a steel strip into strips according to a certain specification, then the steel strip is sold to a downstream customer, and the bending cracking phenomenon is found at the downstream customer, so that quality dissimilarities among multiple supply and demand parties often occur, the smoothness of a supply channel is greatly influenced, the normal trade relation is influenced, and the normal operation of each company is restricted.
The factory test of hot rolled steel strip generally includes three items of chemical composition, tensile test and bending test. The technical requirements are given for product standards with corresponding materials in the three countries, but the countries have no clear standard requirements for metallographic examination, some steel companies with large scale have metallographic examination, and some companies with small scale do not take the metallographic examination as a necessary examination item for quality control.
The metallographic examination results of companies equipped with metallographic examination are generally used as a basis for quality monitoring and improvement, but there is no complete quality evaluation method for the risk of bending cracking of hot-rolled plain carbon steel.
At present, under the macroscopic background that the industrial foundation is comprehensively promoted, the traditional industry is promoted to be transformed and upgraded, the backward capacity is eliminated, the green development is realized, and the quality is the first, the quality promotion is urgently needed in the steel industry and the equipment manufacturing industry in China, the quality-improved products provided by the steel industry are imperative, and the quality evaluation method of the ordinary carbon steel for bending manufacturing is more important.
Disclosure of Invention
The invention provides a quality evaluation method for preventing hot-rolled plain carbon steel from cracking at 90-degree bending, which aims to solve the problem of cracking of hot-rolled plain carbon steel strips in bending of steel companies, stop the steel strips with cracking risks from leaving factories, promote the improvement of product quality, reduce waste in the production process and better provide high-quality products for downstream customers.
The invention is realized in such a way that a quality evaluation method for preventing hot-rolled plain carbon steel from cracking at 90 degrees comprises the following steps:
step S100: manufacturing a transverse blank;
step S200: manufacturing a standard sample of mechanical property;
step S300: testing the mechanical property;
step S400: detecting chemical components of a finished product and detecting a metallographic phase;
step S500: analyzing the unqualified reason of the quality product;
step S600: according to the unqualified reason, the targeted improvement is carried out in combination with the production process. .
Wherein, the step S100 includes the steps of:
a: hot cutting the hot rolled steel coil 7-10m away from the strip tail to be used as a detected blank;
b: secondly, cutting off 50-80mm of the hot cutting end of the blank, and cutting off the transverse blank with the length of 200-300mm along the rolling direction close to the cutting-off end;
c: preparing a sample blank with mechanical property and metallographic phase detection.
And C, preparing a sample blank with mechanical property and metallographic detection from one fourth of the width of the transverse blank.
Wherein, the step 400 requires the preparation of a spectrum sample, and the spectrum sample is prepared from a mechanical property sample after being stretched.
Wherein, the metallographic phase detection must satisfy the following 4 conditions: c-type inclusions are less than or equal to 1.5 grade; the tissue is F + P, and abnormal tissues generated by rapid cooling such as grains B and tempered S cannot exist; the band-shaped tissue is less than or equal to grade 2; the grain size is 8.5-10 grade.
Wherein the step S600 includes: the bending requirement of 90-degree bending which cannot be met but the common technical requirement of the Q235B steel strip can be changed into common use but cannot be used for bending; meanwhile, the problems of the steel-making process and the steel rolling process are mainly improved, so that the quality is comprehensively improved.
Wherein, the chemical composition detection in the step S400 comprises carbon, silicon, manganese, phosphorus, sulfur and total aluminum content.
Compared with the prior art, the invention has the beneficial effects that: the quality evaluation method for preventing hot-rolled plain carbon steel from cracking at 90-degree bending has the following advantages:
quality monitoring is carried out, bending of products leaving factories at users is guaranteed not to crack, quality objections are avoided, good reputation of users is gained, and larger market share is obtained;
the quality of iron and steel production enterprises is promoted to be comprehensively improved, the reasons and the working procedures of the iron and steel production enterprises which cause the quality to be unqualified are determined through metallographic microscopic analysis, the iron and steel production enterprises can be purposefully improved, and the quality is promoted to be comprehensively improved.
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FIG. 1 is a flow chart of the present invention;
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the description of the present invention, it is to be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention. Further, in the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
Referring to fig. 1, the present invention provides a technical solution: a quality evaluation method for preventing hot-rolled plain carbon steel from cracking at 90-degree bending comprises the following steps:
step S100: manufacturing a transverse blank;
step S200: manufacturing a standard sample of mechanical property;
step S300: testing the mechanical property;
step S400: detecting chemical components of a finished product and detecting a metallographic phase;
step S500: analyzing the unqualified reason of the quality product;
step S600: according to the unqualified reason, the targeted improvement is carried out in combination with the production process.
In the embodiment, firstly, cutting is carried out on a hot rolled steel coil, a transverse blank is manufactured, then, a mechanical property standard sample is manufactured according to the manufactured transverse blank, then, a mechanical property test is carried out on the standard sample with the changed mechanical property, then, the sample is subjected to chemical component detection, when the detection results of the sample are qualified, metallographic detection is carried out, then, the unqualified reason of the product is analyzed according to various detected data, and the pertinence is improved according to the unqualified reason and the production process.
Further, step S100 includes the steps of:
a: hot cutting the hot rolled steel coil 7-10m away from the strip tail to be used as a detected blank;
b: secondly, cutting off 50-80mm of the hot cutting end of the blank, and cutting off the transverse blank with the length of 200-300mm along the rolling direction close to the cutting-off end;
c: preparing a sample blank with mechanical property and metallographic phase detection;
step C, preparing a sample blank with mechanical property and metallographic detection from one fourth of the width of the transverse blank
In the embodiment, the corresponding hot rolled steel coil is cut according to the limited size, so that the mechanical property test, the chemical component test and the metallographic detection of the sample blank can be more convenient, the size error occurs in the detection process, and the unnecessary time waste and the unnecessary economic expense loss are avoided.
Further, step 400 requires the preparation of a spectral sample, which is prepared from the stretched mechanical property sample.
In the embodiment, the spectrum sample is prepared on the stretched mechanical property sample, the components of the finished product are measured, the components meet the component requirements of corresponding materials, the uniformity of the detected sample can be ensured by preparing the spectrum sample from the stretched mechanical property sample, the product corresponding to the sample is prevented from being different due to the re-preparation, and the wrong experimental detection is avoided.
Further, the metallographic detection should satisfy the following 4 conditions: c-type inclusions are less than or equal to 1.5 grade; the tissue is F + P, and abnormal tissues generated by rapid cooling such as grains B and tempered S cannot exist; the band-shaped tissue is less than or equal to grade 2; the grain size is 8.5-10 grade.
In the embodiment, the uniform plastic deformation of the steel is realized by controlling more detailed and more specific indexes of a microscopic metallography, the phenomenon that micro cracks caused by microscopic unevenness of the steel due to the existence of inclusions, strips, grains or abnormal structures are expanded to finally generate macroscopic cracks or even cracks is avoided, the cracking effect of the inclusions on base metal can be further verified through an electronic image, wherein C-type silicate inclusions are larger than A-type sulfide inclusions in the cracking effect, gaps between the C-type silicate inclusions and the A-type sulfide inclusions are obviously larger, each A-type inclusion has gaps basically, only a single serious A-type inclusion has gaps basically, and in addition, the grades and types of the inclusions are observed and analyzed to reflect whether the deoxidation operation of steelmaking is abnormal or not and whether the steelmaking operation reaches the standard or not; analyzing whether segregation exists in the steel-making process and whether secondary condensation cooling is abnormal or not from the strip shape and the sulfide strip shape; whether the heating temperature is normal or not, and whether the finishing temperature and the cooling mode are abnormal or not are analyzed from the grain size grade, whether the fast cooling structure exists or not, the depth of the fast cooling structure, and which surface the fast cooling structure is located on.
Furthermore, the steel strip can be changed into common use but cannot be used for bending, wherein the bending requirement of 90-degree bending cannot be met, but the common technical requirement of the Q235B steel strip is met; meanwhile, the problems of the steel-making process and the steel rolling process are mainly improved, so that the quality is comprehensively improved.
In the embodiment, the quality problem under the complex process is exposed by a scientific microstructure detection method, so that the problem is clearly determined and the problem is improved, the quality evaluation of the outgoing hot-rolled product is based on the fact, the implementation is more specific, quantification and visualization can be realized, convenience and feasibility are realized, and the limitation of the mechanical property detection from the macro aspect is avoided: firstly, the mechanical property ignores the defect of local microstructure; secondly, the abnormality occurring in the process operation can not be diagnosed accurately, and the production improvement can not be guided accurately in a targeted way.
Further, the chemical composition detection in step S400 includes carbon, silicon, manganese, phosphorus, sulfur, and total aluminum content.
In the present embodiment, the chemical component detection can completely detect the components of the hot-rolled steel coil, and determine whether the hardness and the curvature of the hot-rolled steel coil are affected by excessive components.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (7)
1. A quality evaluation method for preventing hot-rolled plain carbon steel from cracking at 90-degree bending is characterized by comprising the following steps:
step S100: manufacturing a transverse blank;
step S200: manufacturing a standard sample of mechanical property;
step S300: testing the mechanical property;
step S400: detecting chemical components of a finished product and detecting a metallographic phase;
step S500: analyzing the unqualified reason of the quality product;
step S600: according to the unqualified reason, the targeted improvement is carried out in combination with the production process.
2. The quality evaluation method for preventing cracking of hot-rolled plain carbon steel at 90-degree bending as claimed in claim 1, wherein the step S100 comprises the steps of:
a: hot cutting the hot rolled steel coil 7-10m away from the strip tail to be used as a detected blank;
b: secondly, cutting off 50-80mm of the hot cutting end of the blank, and cutting off the transverse blank with the length of 200-300mm along the rolling direction close to the cutting-off end;
c: preparing a sample blank with mechanical property and metallographic phase detection.
3. The method for evaluating the quality of preventing the 90-degree bending cracking of the hot-rolled plain carbon steel according to claim 2, wherein the step C is to prepare a sample blank with mechanical properties and metallographic detection from one quarter of the width direction of the transverse blank.
4. The method for evaluating the quality of hot-rolled plain carbon steel for preventing 90-degree bending cracking as claimed in claim 1, wherein the step 400 requires the preparation of a spectrum sample, and the spectrum sample is prepared from a mechanical property sample after being stretched.
5. The quality evaluation method for preventing 90-degree bending cracking of hot-rolled plain carbon steel according to claim 1, wherein the metallographic phase detection needs to satisfy the following 4 conditions: c-type inclusions are less than or equal to 1.5 grade; the tissue is F + P, and abnormal tissues generated by rapid cooling such as grains B and tempered S cannot exist; the band-shaped tissue is less than or equal to grade 2; the grain size is 8.5-10 grade.
6. The quality evaluation method for preventing cracking of hot-rolled plain carbon steel at 90-degree bending as claimed in claim 1, wherein the step S600 comprises: the bending requirement of 90-degree bending which cannot be met but the common technical requirement of the Q235B steel strip can be changed into common use but cannot be used for bending; meanwhile, the problems of the steel-making process and the steel rolling process are mainly improved, so that the quality is comprehensively improved.
7. The quality evaluation method for preventing 90-degree bend cracking of hot-rolled plain carbon steel according to claim 1, wherein the chemical composition detection in the step S400 comprises contents of carbon, silicon, manganese, phosphorus, sulfur and total aluminum.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112816277A (en) * | 2020-11-30 | 2021-05-18 | 中国第一汽车股份有限公司 | Method for evaluating internal quality of core region of hot-rolled round bar steel |
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