A method for hot simulation of a plate production process

Abstract

The application discloses a hot simulation method of a medium plate production process, comprehensively utilizes a medium rolling mill and a Gleeble hot simulation testing machine to simulate the medium plate rolling process, and provides an effective method for researching the influence of the medium plate production process on material performance and structure, and finally achieves the purpose of optimizing product rolling parameters and improving product quality. The method has high flexibility, can select any stage in the rolling process to carry out local hot simulation testing, simulates and reproduces the structure evolution process in the rolling process, and provides technical support for process optimization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal simulation test, in particular to a thermal simulation method of plate production process. BACKGROUND

[0002] Thermal simulation test has complete simulation functions and wide application range. It can be used for dynamic process simulation test including rolling and forging process, continuous casting and smelting process, welding process, metal heat treatment process, mechanical thermal fatigue, etc., and can also be used for measuring metal high-temperature mechanical properties, metal thermal properties, CCT curve and stress-strain curve, etc. It provides reliable experimental basis for testers to develop and improve production process.

[0003] To simulate plate rolling production process, the simulation device needs to have basic capabilities such as heating, rolling or compression, temperature control, etc. The simulation device can use a pilot rolling mill or a Gleeble thermal simulation testing machine. The problem of using a pilot rolling mill for simulation rolling is that the temperature in the rolling process is greatly reduced and uncontrollable due to the relatively small sample, which cannot accurately simulate the temperature changes in the production site. The Gleeble thermal simulation testing machine produced by the United States DSI also has the basic conditions to simulate plate production process. The main problem is that the total engineering strain of the Gleeble thermal simulation testing machine for thermal compression test is generally not more than 0.8, which cannot meet the simulation of complete production rolling process. SUMMARY

[0004] The present application provides a thermal simulation method of plate production process to solve the problem that the existing pilot rolling mill and Gleeble thermal simulation testing machine cannot effectively simulate the plate rolling process, thereby providing an effective method for studying the influence of plate production process on performance and organization, and ultimately achieving the purpose of optimizing product rolling parameters and improving product quality.

[0005] The thermal simulation method of plate production process mainly adopts the following steps:

[0006] (1) Test preparation: select a plate production process parameter or collect temperature parameters, rolling passes, rolling interval time, reduction, rolling speed and roll diameter in the plate production process, and then select a plate cast blank sample and sample at one-fourth of its thickness.

[0007] (2) Hot simulation sample preparation: the sample taken in step 1) is heated in a pilot heating furnace, the heating temperature is the process temperature of the on-site heating furnace for producing the medium plate, and the sample is kept for 30-60 min; then the number of rolling passes that can be completed is calculated based on the maximum total engineering strain of the Gleeble thermal simulation machine, and the reduction of each pass is determined according to the on-site rolling process of the medium plate; then the initial breakdown pass rolling that cannot be completed by the Gleeble thermal simulation machine is completed using a pilot rolling mill, and after air cooling, the sample is cut along the thickness center line to prepare a 25mm long x 15mm wide x 10mm thick flat strain test sample required for the Gleeble thermal simulation test;

[0008] or the sample taken in step 1) is heated in a pilot heating furnace, the heating temperature is the austenite transformation temperature plus 100-200℃, and the sample is kept for 30-60 min; then the number of rolling passes that can be completed is calculated based on the maximum total engineering strain of the Gleeble thermal simulation machine, and the reduction of each pass is calculated and determined according to the single-pass strain of 0.1-0.3; then the initial breakdown pass rolling that cannot be completed by the Gleeble thermal simulation machine is completed using a pilot rolling mill, and after air cooling, the sample is cut along the thickness center line to prepare a 25mm long x 15mm wide x 10mm thick flat strain test sample required for the Gleeble thermal simulation test;

[0009] For example: taking the production of a 20mm thick medium plate as an example, the sample thickness of the casting blank is 64mm (the original thickness of the casting blank is 220mm), and the finished product thickness reaches 5.82mm (the finished product thickness is 20mm) according to the medium plate production process. The total engineering strain is (64-5.82) / 64=0.91, which exceeds the strain of 0.8, and the Gleeble thermal simulation tester cannot complete the whole process of rolling simulation test, so the 64mm casting blank sample needs to be rolled by a pilot rolling mill first for 6 passes (the strain of each pass is 0.1-0.2) to 26.2mm; the total strain of the 26.2mm sample to 5.82mm is (26.2-5.82) / 26.2=0.78, which meets the requirement of not exceeding 0.8, and then the 26.2mm blank is cut along the thickness center line to prepare a standard thermal simulation sample for subsequent pass thermal simulation test according to the medium plate production process (see the examples for details).

[0010] (3) Calculation of thermal simulation test parameters: the rolling strain rate parameter is calculated according to the rolling strain rate precise calculation formula (1) or the Selezov formula, and the rolling diameter D, the strain of each rolling pass and the rolling speed are collected to calculate;

[0011] (1)

[0012] Wherein: θ - maximum contact angle, v - rolling piece exit roller speed, D - roller diameter, h1 - post-rolling height, h0 - pre-rolling height, ε - strain amount

[0013] The specific derivation process of the above formula is shown in the paper "Precise Calculation Method of Rolling Strain Rate Parameter ε" by Zhao Dewen and Tie Weilin, Applied Science Journal, 1995, No. 1.

[0014] (4) Hot simulation test: the plane strain test sample is placed in the Gleeble hydraulic wedge unit test chamber, and the rolling pass, temperature, rolling interval time, strain, strain rate reduction parameters required for the multi-pass plane strain hot compression test are input into the QuikSim control software of the Gleeble hot simulation machine, the temperature rising, holding and related rolling process parameters are set according to the predetermined process requirements, and the thermocouple temperature control mode is used in the whole test process.

[0015] In summary, the present application uses the pilot rolling mill and the hot simulation testing machine to cooperate with each other to simulate the plate production process according to the same rolling process, reproduce the on-site rolling process, help researchers understand the material performance and organizational morphology changes in the rolling process, and have great significance for improving the rolling process level.

[0016] The method has the following beneficial effects:

[0017] 1. The method can simulate the plate production process with high simulation degree, provides a technical reference for the design and optimization of hot-rolled plate rolling process, and also provides a possibility for studying the influence of plate production process on material performance and organization;

[0018] 2. The method has high flexibility, can select any stage in the rolling process for local hot simulation test, and also can perform quenching treatment at the end of the test to study the high-temperature organization at this stage; based on this, the method can completely simulate and reproduce the organizational evolution process in the rolling process, and provide technical support for process optimization. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a multi-pass hot compression process schematic diagram of the embodiment of the present application;

[0020] Figure 2 It is a stress-strain curve diagram of the embodiment of the present application;

[0021] Figure 3 It is a metallographic structure photo of the hot simulation sample of the embodiment of the present application;

[0022] Figure 4 It is a metallographic structure photo of the on-site product. DETAILED DESCRIPTION

[0023] The method of the present application will be further described in detail below with reference to the accompanying drawings and specific examples. Examples

[0024] 1. On-site production of thick plates: the production process parameters of finished thickness 20 mm Q235B, including rolling passes, temperature, rolling speed, roll diameter, rolling interval time and reduction parameters.

[0025] 2. A 120 mm long x 120 mm wide x 64 mm thick test blank was taken from the Q235B cast blank at the quarter thickness.

[0026] 3. Referring to the on-site rolling parameters (as shown in Table 1), the heating temperature was set to 1160°C for 30 minutes, and a pilot rolling mill with a roll diameter of Φ450 mm was used to roll the 120 mm long x 120 mm wide x 64 mm thick test blank for 6 passes of blooming, and after 6 passes of rolling, a line cutting was used to process a 25 mm long x 15 mm wide x 10 mm thick flat strain test sample. (Note: Because the standard sample required by the Gleeble testing machine hydraulic wedge unit is 25 mm x 15 mm x 10 mm, the same size sample was taken and the same rolling process and compression ratio was continued to simulate the test)

[0027] Table 1

[0028]

[0029] 4. The rolling passes, temperature, rolling interval time and reduction parameters required for the multi-pass plane strain hot compression experiment can be directly input into the test program, and the strain rate parameters are calculated according to the strain rate accurate calculation formula (1), and the rolling strain rate parameters in the plane strain process are calculated according to the on-site roll diameter D=940 mm, rolling passes and rolling speed, as shown in Table 2:

[0030] Table 2

[0031]

[0032] 5. The plane strain sample was placed in the Gleeble testing machine, and the 7-pass plane strain test parameters were set, and the test was performed according to the strain rate curve and the test parameters in Table 2, and after the test was completed, the stress-strain curve shown in Figure 1 Figure 2

[0033] 6. Analysis of test results

[0034] After coarse grinding, fine grinding, coarse polishing and fine polishing, the hot simulation sample and the same batch of on-site rolled 20 mm Q235B plate product were etched with nitric acid alcohol, and the microstructure was observed under a metallographic microscope, and the microstructure morphology is shown in Figure 3 ,​​Figure 4 .

[0035] Comparative analysis of heat extraction simulation samples and field rolling product samples shows that the microstructure content and grain size of the two are relatively close (as shown in Table 3), and the overall difference in microstructure content and grain size is within 7%, indicating that the heat simulation test has good process reproducibility in simulating medium plate production process.

[0036] Table 3

[0037]

Claims

1. A thermal simulation method for medium-thick plate production process, characterized in that, Includes the following steps: 1) Select a medium-thick plate for the test and collect the production process parameters of this type of medium-thick plate. Then, take a sample at one-quarter of the thickness direction of the medium-thick plate billet. 2) Place the billet sample taken in step 1) into a pilot heating furnace and heat it at the process temperature of the on-site heating furnace for producing this type of medium-thick plate, and hold it for 30-60 minutes. Then, based on the maximum total engineering strain of the Gleeble thermal simulator, calculate the number of rolling passes that can be completed from the finished product passes. The reduction amount of each pass is determined by the on-site rolling process of this type of medium-thick plate. Then, use a pilot rolling mill to complete the initial billet rolling passes that the Gleeble thermal simulator cannot complete. After rolling and air cooling, cut the sample symmetrically along its thickness centerline to prepare the plane strain test specimen required for the Gleeble thermal simulation test. Alternatively, the billet sample taken in step 1) can be placed in a pilot-scale heating furnace and heated to a temperature of 100-200°C above the austenitic transformation temperature, and held for 30-60 minutes. Then, based on the maximum total engineering strain of the Gleeble thermal simulator, the number of rolling passes that can be completed can be calculated by working backward from the finished product passes. The reduction per pass is calculated based on a single pass strain of 0.1-0.

3. Next, the initial billet passes that cannot be completed by the Gleeble thermal simulator can be rolled using a pilot-scale rolling mill. After rolling and air cooling, the billet is symmetrically cut along its thickness centerline to prepare the plane strain test specimen required for the Gleeble thermal simulation test. 3) Calculate the rolling strain rate parameters. The rolling strain rate parameters are calculated based on the accurate calculation formula (1) or the Tserkov formula, by collecting the on-site roll diameter D, the strain of each rolling pass and the rolling speed. （1） Where: θ - maximum contact angle, v - roll exit speed, D - roll diameter, h1 - height after rolling, h0 - height before rolling, ε - strain; 4) Place the plane strain test specimen into the hydraulic wedge unit test chamber of the Gleeble thermal simulator, and input the rolling pass, temperature, rolling interval time, strain, and rolling strain rate parameters required for the multi-pass plane strain thermal compression test. The thermocouple temperature control mode is used throughout the test.

2. The thermal simulation method for medium-thick plate production process according to claim 1, characterized in that: The specimen used for the plane strain test in step 2) is 25mm long × 15mm wide × 10mm thick.

3. The thermal simulation method for medium-thick plate production process according to claim 1, characterized in that: In step 2), the maximum total engineering strain of the Gleeble thermal simulator is 0.8.

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