CN108226210B - A thermal simulation method for preparing stainless steel/carbon steel composite ribbed steel bars - Google Patents

Abstract

The invention provides a thermal simulation method for preparing stainless steel/carbon steel composite ribbed steel bars. The method of the invention comprises the following steps: closely nesting and combining the stainless steel pipe and the carbon steel rod after surface treatment; welding a thermocouple on the outer surface of the stainless steel pipe; placing the bimetal sample between the chucks in the operation box of the thermal simulation experiment machine time; high temperature compression deformation and heat treatment experiments; microstructure and properties analysis of the samples after the experiment. The invention utilizes a thermal simulation experimental machine to complete the process simulation process of the rolling process of the stainless steel/carbon steel composite ribbed steel bar by changing the thermal simulation experimental process scheme; Ensure that the interface of stainless steel/carbon steel composite ribbed steel bars is well bonded, and the structure and properties meet the requirements. The invention has the advantages of simple preparation method, low cost, material saving, strong repeatability, easy achievement of experimental objectives, and quick and accurate finding of relevant laws.

Description

A thermal simulation method for preparing stainless steel/carbon steel composite ribbed steel bars

technical field

The invention belongs to the technical field of metal material technology research and thermal simulation, and in particular relates to a thermal simulation method for preparing stainless steel/carbon steel composite ribbed steel bars.

Background technique

The construction of infrastructure and major projects is inseparable from the extensive use of reinforced concrete structures, and the performance and quality of steel bars as concrete skeletons are increasingly concerned. Especially with the acceleration of the national urbanization construction and the vigorous proposal of the marine strategy, the demand for high-strength corrosion-resistant steel bars for construction will increase, while the commonly used traditional steel bars have poor corrosion resistance and are easy to rust and expand, resulting in reinforced concrete structures. It is easy to fail prematurely and cannot meet the requirements of building life, thereby causing huge economic losses to the society. In order to improve the corrosion problem of steel bars, the solid stainless steel bars developed due to the extensive use of precious metals such as chromium and nickel have greatly increased the production cost and greatly limited the scope of application. Comprehensive performance steel. As a result, the research ideas and processes of stainless steel/carbon steel composite steel bars came into being.

Stainless steel/carbon steel composite rebar is a new type of material. Stainless steel is used as the cladding material and carbon steel is used as the core material. Both are obtained through a certain forming process. This material combines the excellent corrosion resistance of stainless steel and the good carbon steel. Mechanical properties can greatly meet people's requirements for the safety and service life of infrastructure facilities. In addition, the stainless steel/carbon steel composite rebar reduces the consumption of precious metals such as chromium and nickel to a certain extent, greatly reduces the production cost, and realizes the perfect combination of low cost and high performance. As a resource-saving product, it will have Good social and economic benefits.

A key factor for the high performance of stainless steel/carbon steel clad rebar is interface bonding, which is also an important factor restricting the industrial production of stainless steel clad rebar. Therefore, it is crucial for the study of composite interfaces. At present, the research on stainless steel composite rebar is mainly limited to laboratory research. The relevant research group of Yanshan University obtained stainless steel clad steel bars and compacted carbon steel scraps in the stainless steel pipe by using the stainless steel pipe inner sleeve carbon steel rod to be drawn, and then welded and sealed at both ends and rolled, and then heated and rolled into stainless steel clad steel. Finally, the microstructure and properties of steel bars were analyzed, and it was found that there were generally the shortcomings of uneven distribution of cladding and easy fluctuation of bonding strength. By continuously adjusting process parameters and repeating hot rolling experiments, the microstructure properties were controlled. This method not only has a complicated preparation process, but also wastes experimental materials, and it is not easy to achieve the experimental purpose; researchers from the National Engineering Research Center for High Efficiency Rolling, University of Science and Technology Beijing, used stainless steel strips to weld into tubes, inner sleeves of carbon steel rods, and welded both ends of the tubes. After rolling, the stainless steel clad steel bar is obtained, and then the microstructure and properties are analyzed. There are also the shortcomings of the above-mentioned fluctuations in the interface properties; other reports of stainless steel clad steel bars also generally have performance defects such as uneven distribution of cladding thickness and low bonding interface strength. The objective problem is that the preparation process is complicated. It can be seen that there are certain problems in the research of composite steel bars. The rolling process is still in the theoretical stage, and there is a lack of a simple and low-cost experimental research method. As a result, there is still no mature industrial production process for this new material.

SUMMARY OF THE INVENTION

According to the above-mentioned technical problems of complex preparation process, long cycle and high cost of stainless steel composite steel bars, a thermal simulation method for preparing stainless steel/carbon steel composite ribbed steel bars is provided. The present invention mainly utilizes the MMS series thermal simulation experimental machine (patent name: multifunctional thermal simulation experimental machine, patent number: ZL 201110100302.2) independently developed by the State Key Laboratory of Rolling Technology and Continuous Rolling Automation of Northeastern University, with the help of specially processed threaded steel bars The special chuck of the rib groove performs high temperature deformation and heat treatment on the bimetal composite billets of different sizes, and simulates the deformation process of the stainless steel/carbon steel composite ribbed steel bar. The purpose of the experiment is to optimize the thermal processing process and adjust the size of the sample, so as to determine the most suitable process plan.

The technical means adopted in the present invention are as follows:

A thermal simulation method for preparing stainless steel/carbon steel composite ribbed steel bar, characterized in that it comprises the following steps:

S1. Raw material preparation: prepare stainless steel pipes and carbon steel rods of preset sizes; the above-mentioned raw materials are all ordinary stainless steel or carbon steel materials, which can be obtained without special processing;

S2. Raw material treatment and billet assembly: Clean the inner wall of the selected stainless steel pipe and the outer surface of the carbon steel rod to ensure that clean metal is exposed on the surface to be joined. After drying, the carbon steel rod is tightly nested in the stainless steel pipe to form a double Metal composite billets;

S3. Thermocouple setting: welding a thermocouple at the center of the outer surface of the stainless steel pipe; preferably, welding a pair of thermocouples for experiment use;

S4. Clamping the sample: Clamp the bimetal composite billet welded with the thermocouple on the clamps of the left and right clamps in the operation box of the thermal simulation experiment machine, to be tested;

S5. Carry out a single-pass compression experiment: after the sample is loaded, the operation box of the thermal simulation experiment machine is evacuated and filled with protective gas, such as nitrogen and argon; the bimetal composite blank is kept in a certain vacuum state, and then a high temperature is carried out. Compression deformation and heat treatment experiments;

S6. Microstructure and performance analysis: After the experiment, the composite steel bar samples are subjected to wire cutting and sampling along the circumferential and axial directions. After pretreatment, metallographic, hardness and scanning detection are carried out to finally obtain the required experimental data of microstructure and properties. analysis. In order to achieve the purpose of good metallurgical bonding of the composite interface and ensure the good comprehensive mechanical properties of the composite steel bar, it is necessary to continuously optimize the sample specifications and the thermal processing route, and finally successfully prepare the stainless steel composite ribbed steel bar.

Further, the surface treatment methods of the raw materials in the step S2 are ultrasonic cleaning, mechanical grinding and pickling to remove rust and oil stains on the surface, as well as high-pressure cleaning and drying.

Further, in the step S4, the chuck is provided with a rib groove for simulating the deformation of the threaded steel bar, and the depth of the rib groove is changed according to the deformation requirement of the bimetal composite blank.

Further, each process parameter in the high temperature compression deformation and heat treatment experiment in the step S5 can be adjusted according to the specific experimental purpose, and relevant data can be obtained through the data acquisition system for analysis.

The invention also discloses the stainless steel/carbon steel composite ribbed steel bar prepared by the above thermal simulation method.

Compared with the prior art, in order to determine the appropriate thermal processing process system and process parameters, this application adopts the MMS series thermal simulation experimental machine, which has a comprehensive thermal simulation function and can simulate parameters such as temperature, displacement, force, speed, stress and strain. , which can realize various functions such as tensile experiment, single/multi-pass compression experiment, plane strain compression experiment, etc., and analyze the temperature-time curve, displacement-time curve, stress-strain curve, etc. obtained by the data acquisition system of the experimental machine. At the same time, the structure and performance of the experimental samples are tested and analyzed; and the related experiments are concentrated on one device, which is flexible and convenient; it is now widely used in the study of the thermal-mechanical coupling deformation behavior of metal materials. The deformation heat treatment method of the stainless steel/carbon steel composite billet is exactly in line with the single-pass compression experimental process of the thermal simulation test machine, that is, with the help of a special chuck with threaded steel rib grooves, the single-pass compression process can achieve double-pass compression. Deformation and heat treatment of metal billets, and finally prepare stainless steel/carbon steel composite ribbed steel bars by optimizing thermal processing parameters.

Compared with the hot rolling experiment, the thermal simulation method of stainless steel/carbon steel composite ribbed steel bar rolling can well solve the problems of many preparation links, long cycle, unstable control, and poor experimental repeatability in the hot rolling experiment. It can provide a convenient research method for the hot rolling process of stainless steel/carbon steel composite ribbed steel bar, and it is feasible.

The present invention has the following advantages:

1. The use of MMS series thermal simulation testing machine and its vacuum system can minimize the oxidation problem of the bimetallic interface during the experiment, so as to ensure that the prepared stainless steel/carbon steel composite ribbed steel bar structure and performance meet the requirements.

2. By designing a special chuck, the thermal simulation experiment of stainless steel/carbon steel composite ribbed steel bars (including transverse and longitudinal ribs) can be successfully completed.

3. The specially designed chuck is processed with rib grooves to simulate the deformation of threaded steel bars. The form and style of the rib grooves can be flexibly designed according to the purpose of the experiment, and the depth of the rib grooves can be changed according to the deformation requirements of the bimetallic composite.

4. Through the analysis of the data of the acquisition system and the testing of the structure and performance of the experimental samples, a large amount of comparative research data can be provided for the hot-rolled stainless steel/carbon steel composite ribbed steel bar, and it can be used for the rolling process of the stainless steel/carbon steel composite ribbed steel bar. Industrial applications provide theoretical basis and convenient research methods.

5. Compared with actual production and other simulation experiments, the thermal simulation test sample size is small and the deformation is relatively uniform. The accuracy of the research results can be ensured by accurate simulation control of parameters such as temperature and deformation.

6. In the whole experimental process, the material preparation is simple, the operation process is convenient, the cost is low, the material is saved, the experimental period is short, the repeatability is strong, and the relevant laws can be found in a quick calibration.

Based on the above reasons, the present invention can be extended beyond the laboratory hot rolling experimental research of stainless steel/carbon steel composite ribbed steel bar, and provides theoretical guidance for the industrial production of stainless steel/carbon steel composite steel bar.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

Fig. 1 is a chuck (simulating a longitudinal rib of a ribbed steel bar) processed by the present invention.

Fig. 2 is a chuck (simulating a transverse rib of a ribbed steel bar) processed by the present invention.

Fig. 3 is a schematic diagram of the combination of the blank (stainless steel pipe and carbon steel rod) of the present invention.

Fig. 4 is a schematic diagram of a sample of the present invention welded with a thermocouple (stainless steel pipe and carbon steel rod).

Fig. 5 is a photo of the ribbed steel bar after the thermal simulation experiment of the present invention-single-pass compression experiment is completed.

Fig. 6 is the metallographic photographs of the finished ribbed steel bar in the thermal simulation experiment of the present invention in the axial and circumferential directions.

In the figure: 1. Longitudinal rib groove; 2. Transverse rib groove; 3. Stainless steel pipe; 4. Carbon steel rod; 5. Thermocouple wire; 6. Sample welded with thermocouple wire; 7. Ribbed steel bar sample.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

As shown in Figures 1-6, a thermal simulation method for preparing stainless steel/carbon steel composite ribbed steel bars includes the following steps:

S1. Raw material preparation: prepare stainless steel pipe 3 and carbon steel rod 4 of preset size;

S2. Raw material treatment and billet assembly: Due to the small size of the selected stainless steel pipe 3 and carbon steel rod 4, first immerse in alcohol and then ultrasonically clean for a period of time. After drying, use sandpaper to polish the inner wall and carbon steel rod of stainless steel pipe 3. The outer surface of 4 is wiped with acetone for cleaning to ensure that clean metal is exposed on the surface to be bonded. After drying, the carbon steel rod 4 is tightly nested in the stainless steel pipe 3 to form a bimetallic composite billet.

S3. Thermocouple setting: Use a thermocouple welding machine at the center of the outer surface of the stainless steel pipe 3 nested with the carbon steel rod 4 to firmly weld a pair of thermocouple wires 5 on the surface of the sample by impact welding. During welding, the root of the thermocouple wire 5 is required to be perpendicular to the surface of the sample, and the spacing between the thermocouple wires 5 should be appropriate.

S4. Clamping the sample: Clamp the sample 6 welded with the thermocouple wire on the chucks of the left and right side fixtures in the operation box of the thermal simulation experiment machine, to be tested; the chuck is provided with The rib grooves (ie longitudinal rib grooves 1 or/and transverse rib grooves 2) that simulate the deformation of threaded steel bars, the depth of the rib grooves is changed according to the deformation requirements of the bimetal composite blank. Then, a pair of thermocouple wires 5 on the sample 6 welded with the thermocouple wires were connected to the positive and negative electrodes of the terminals in the operation box, respectively.

S5. Carry out a single-pass compression experiment: after the sample is loaded, the operation box of the thermal simulation experiment machine is evacuated and filled with protective gas to keep the sample in a certain vacuum state, and then a single-pass compression experiment is carried out according to the thermal processing process route. . After the sample 6 is kept warm above the austenitizing temperature, the hammer head of the main hydraulic cylinder of the thermal simulation experiment machine compresses and deforms the sample according to the given deformation amount and strain rate in the position control mode. The actual deformation amount can be measured by The distance between the two chucks is compared with the initial distance. The ribbed steel bar sample 7 after compression can be ensured by various methods such as adjusting the current size and changing the cooling medium (water, gas, heat conduction, etc.) according to the given cooling process to ensure the cooling process, temperature change and cooling process setting curve. Consistent.

S6. Analysis of microstructure and properties: The ribbed steel bar sample 7 after single-pass compression is subjected to line cutting sampling along the circumferential and axial directions, rough grinding with sandpaper, and polishing after fine grinding, until the surface is free of scratches After the marks are clean and bright, the corrosion treatment is carried out, and finally the tissue properties are analyzed according to the experimental purpose.

Example

(外径×壁厚×长度，mm)和

(外径×长度，mm)，二者之间紧密结合，用此坯料在MMS-300热力模拟实验机上进行单道次压缩实验，变形量为75％。In this embodiment, the seamless 304 austenitic stainless steel pipe 3 is used as the clad material, and the 20MnSi carbon steel rod 4 is used as the core material.

(outer diameter × wall thickness × length, mm) and

(outer diameter×length, mm), the two are closely combined, and the single-pass compression experiment was carried out on the MMS-300 thermal simulation experiment machine with this blank, and the deformation amount was 75%.

The above-mentioned seamless 304 austenitic stainless steel pipe 3 and 20MnSi carbon steel rod 4 were immersed in alcohol and then ultrasonically cleaned for 30 minutes. After drying, the inner wall of the stainless steel pipe 3 and the outer surface of the carbon steel rod 4 were polished with sandpaper. Wipe with acetone for cleaning to ensure that clean metal is exposed on the surface to be bonded. After drying, the carbon steel rod 4 is tightly nested in the stainless steel pipe 3;

Then use a thermocouple welding machine at a certain position in the middle of the sample of stainless steel pipe 3 covered with carbon steel rod 4 to firmly weld a pair of thermocouple wires 5 on the surface of the sample by impact welding;

Then fix a pair of chucks with rib grooves (longitudinal rib groove 1 or/and transverse rib groove 2, the depth of the rib groove is 0.8mm) on the left and right sides of the operation box of the thermal simulation experimental machine, respectively. On the side fixture; then fix the sample 6 welded with the thermocouple wire between a pair of clamps on the fixture in the operation box of the thermal simulation experiment machine, and then separate the pair of thermocouple wires 5 on the sample. Connect to the positive and negative poles of the terminal in the operation box;

After the sample loading, the operation box of the thermal simulation experiment machine was evacuated and filled with protective gas to keep the sample in a certain vacuum state, and then a single-pass compression experiment was carried out according to the thermal processing process route: the sample was heated at a temperature of 10°C/s. The speed was heated from room temperature to 1200 °C, followed by holding for 5 minutes, and then cooled to 1050 °C at a cooling rate of 10 °C/s. After holding for 30 s, a single-pass compression experiment with a deformation of 75% was carried out, and then air-cooled. Finally, stainless steel was obtained. / Carbon steel composite ribbed bar sample 7;

After the experiment, the ribbed steel bar sample 7 is subjected to line cutting and sampling along the circumferential and axial directions, smoothed with coarse sandpaper, polished with fine sandpaper, and then polished. After the surface has no scratches and is clean and bright, use 4% The carbon steel of the core is corroded with nitric acid alcohol solution, and finally metallographic analysis, electronic probe analysis and hardness measurement are carried out.

As shown in Figure 5 and Figure 6, through the analysis of the experimental phenomena and conclusions, it is obtained that the bonding interface of the stainless steel/carbon steel composite ribbed steel bar prepared by the above thermal simulation method has achieved a good metallurgical bond, and the microstructure and properties meet certain requirements. requirements, and provide theoretical guidance for hot rolling experiments.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention. scope.

Claims (3)

1. A thermal simulation method for preparing stainless steel/carbon steel composite ribbed steel bars is characterized in that an MMS series thermal simulation experiment machine is adopted, and the method comprises the following steps:

s1, preparing raw materials: preparing a stainless steel pipe and a carbon steel rod with preset sizes;

s2, raw material treatment and assembly: cleaning the inner wall of the selected stainless steel pipe and the outer surface of the carbon steel rod, drying, and tightly embedding the carbon steel rod in the stainless steel pipe to form a bimetal composite blank;

s3, setting a thermocouple: welding a thermocouple at the center of the outer surface of the stainless steel pipe;

s4, clamping a sample: clamping the bimetal composite blank welded with the thermocouple on clamping heads of clamping devices on the left side and the right side in an operation box of the thermal simulation experiment machine, and detecting; the clamping head is provided with a rib groove simulating the deformation of the twisted steel, and the depth of the rib groove is changed according to the deformation requirement of the bimetal composite blank;

s5, carrying out single-pass compression experiment: after the sample loading is finished, vacuumizing and filling protective gas into an operation box of the thermal simulation experiment machine to keep the bimetal composite blank in a certain vacuum state, and then performing high-temperature compression deformation and heat treatment experiments;

s6, analyzing organization performance: and performing linear cutting sampling on the tested composite steel bar sample along the circumferential direction and the axial direction, preprocessing the sample, and performing metallographic phase, hardness and scanning detection to finally obtain experimental data of required tissues and properties for analysis.

2. The thermal simulation method for preparing the stainless steel/carbon steel composite ribbed steel bar according to claim 1, wherein the raw material is subjected to surface treatment in step S2 by ultrasonic cleaning, mechanical grinding and pickling to remove rust and oil stains on the surface, and high-pressure cleaning and drying.

3. The thermal simulation method for preparing the stainless steel/carbon steel composite ribbed steel bar according to claim 1, wherein each process parameter in the high-temperature compression deformation and heat treatment experiment in the step S5 can be adjusted according to a specific experiment purpose, and related data can be obtained through a data acquisition system for analysis.

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