阅读说明：本技术 一种超薄规格厚度钢板的连续冷却相变温度的测定方法 (Method for measuring continuous cooling phase transition temperature of ultrathin gauge thickness steel plate ) 是由 黄绪传 于 2018-06-27 设计创作，主要内容包括：本发明公开了一种超薄规格厚度钢板的连续冷却相变温度的测定方法,主要解决现有技术对于厚度≤0.6mm钢板的连续冷却相变温度无法测定的技术问题。本发明提供的厚度≤0.6mm钢板的连续冷却相变温度的测定方法,包括,1)制备直管试样；2)制备直管小试样；3)在直管小试样上安装测温热电偶；4)将安装有测温热电偶直管小试样置于DIL805A型淬火热膨胀仪的测量位；5)测量待测钢板的连续冷却相变温度。本发明实现了用DIL805A型淬火热膨胀仪测量厚度≤0.6mm钢板的相变温度,本发明方法操作简便,效率高、测量精度高,测量成本低。(The invention discloses a method for measuring the continuous cooling phase transition temperature of an ultrathin steel plate with specification and thickness, which mainly solves the technical problem that the continuous cooling phase transition temperature of the steel plate with the thickness less than or equal to 0.6mm cannot be measured in the prior art. The invention provides a method for measuring the continuous cooling phase transition temperature of a steel plate with the thickness less than or equal to 0.6mm, which comprises the following steps of 1) preparing a straight pipe sample; 2) preparing a straight tube small sample; 3) a temperature thermocouple is arranged on a small sample of the straight pipe; 4) placing a small sample provided with a temperature thermocouple straight tube at a measuring position of a DIL805A quenching thermal expansion instrument; 5) and measuring the continuous cooling phase change temperature of the steel plate to be measured. The invention realizes the measurement of the phase transition temperature of the steel plate with the thickness less than or equal to 0.6mm by using a DIL805A type quenching thermal expansion instrument, and the method has the advantages of simple and convenient operation, high efficiency, high measurement precision and low measurement cost.)

1. A method for measuring the continuous cooling phase transition temperature of a steel plate with the thickness less than or equal to 0.6mm is characterized by comprising the following steps:

1) preparing a straight pipe sample, cutting a steel plate to be detected with the size of 30mm multiplied by 60mm, rolling the steel plate into the straight pipe sample by adopting a pipe rolling device, and controlling the inner diameter of the straight pipe sample to be 2.8mm and the outer diameter of the straight pipe sample to be 3.4-4 mm;

2) preparing a straight pipe small sample, penetrating a steel bar with the outer diameter of 2.8mm into the straight pipe sample, cutting the straight pipe sample penetrated with the steel bar into the straight pipe small sample with the length of 8mm-12mm by using a precision cutting machine, and controlling the end surfaces of two sides of the straight pipe small sample to be vertical to the axis;

3) installing a temperature thermocouple on the small straight pipe sample, welding the temperature thermocouple on the outer surface of the small straight pipe sample, and taking out a steel bar in the small straight pipe sample;

4) placing a straight pipe small sample provided with a temperature thermocouple at a measuring position of a DIL805A type quenching thermal expansion instrument, installing the straight pipe small sample welded with the temperature thermocouple between two ejector rods of the DIL805A type quenching thermal expansion instrument, enabling the axis of the straight pipe small sample to coincide with the axis of the ejector rod, moving and fixing the straight pipe small sample in the middle of an induction coil of the DIL805A type quenching thermal expansion instrument, and controlling the clamping force of the straight pipe small sample to be 10-20 kgf;

5) measuring the continuous cooling phase transition temperature of the steel plate to be measured, operating a DIL805A type quenching thermal expansion instrument, and heating a straight pipe small sample to Ac₃At the above temperature, the straight tube small sample is Ac₃And (3) preserving the heat for 3-5 minutes at the temperature, then performing controlled cooling on the straight pipe small sample, collecting and obtaining a thermal expansion curve of the straight pipe small sample in the experimental cooling process, and determining the continuous cooling phase change temperature of the steel plate to be measured by adopting a tangent point method.

2. The method for measuring the phase transition temperature of a steel sheet having a thickness of 0.6mm or less according to claim 1, wherein the lift pins in step 4) are ceramic lift pins or quartz lift pins.

Technical Field

The invention relates to a method for measuring the solid phase transition temperature of a steel material, in particular to a method for measuring the continuous cooling phase transition temperature of an ultrathin steel plate with specification and thickness, specifically to a method for measuring the continuous cooling phase transition temperature of the steel plate with the thickness of less than or equal to 0.6mm by adopting a thermal expansion method, and belongs to the technical field of physical detection of metal materials.

Background

At present, the main methods for measuring the continuous cooling phase transition temperature of the steel material at home and abroad comprise a metallographic method, a thermal analysis method, a calculation method, a thermal expansion method and the like, and the methods have the advantages but also have some defects. For example, the metallography method has large sampling workload, the thermal analysis method and the calculation method have low precision, and the thermal expansion method needs to be assisted by a specific expansion device and has complex operation. However, with the popularization of various thermal expansion devices and the improvement of control technologies thereof in recent times, the thermal expansion method can more intuitively reflect the phase change law of the steel material in the continuous thermal change process, and the experimental determination result is more favorable for the application of practical production, so that the thermal expansion method gradually becomes the most common physical determination method for determining the solid-state phase change temperature of the steel material in the field of the current metal materials. However, due to the limitations of the structure and controllability of the thermal expansion device, there are certain requirements for the shape and size of the sample required for measuring the transformation temperature of the steel material by the expansion method.

For steel plates meeting a certain thickness range, a thermal expansion instrument is adopted to measure a thermal expansion curve of the strip steel sample in the width or length direction; currently, strip steel with the thickness of more than or equal to 3mm can be processed into a cylindrical sample with the outer diameter of more than 3mm, and the phase change temperature is accurately measured by a thermal expansion instrument; in the measurement of the transformation temperature of a steel sheet having a thickness of 3mm or less, since the clamping and fixing of the dilatometer are difficult and a thin steel sheet having a thickness of 3mm or less tends to buckle during the thermal change, the dilatometer cannot accurately measure the expansion curve in either the longitudinal or width direction, and a thin steel sheet having a thickness of 1mm or less cannot be measured.

Disclosure of Invention

The invention aims to provide a method for measuring the continuous cooling phase transition temperature of a steel plate with the thickness of less than or equal to 0.6mm, and mainly solves the technical problem that the continuous cooling phase transition temperature of the steel plate with the thickness of less than or equal to 0.6mm cannot be measured in the prior art.

The technical idea of the invention is as follows: a sample suitable for phase change measurement of a DIL805A quenching thermal expansion instrument is designed, because a mandril of the sample of the DIL805A quenching thermal expansion instrument is a hollow rod with the outer diameter of 4mm and the inner diameter of 2.8mm, a steel plate sample needs to be horizontally clamped between the two hollow rods, a steel plate with the thickness of less than or equal to 0.6mm is coiled to be made into a hollow tubular sample, and in order to ensure the circulation of cooling gas between the inside of the sample and the middle part of the mandril and ensure that the tubular sample can be stably and horizontally clamped between the two hollow rods, the inner diameter of the tubular sample is controlled to be 2.8mm, and the outer diameter of; and measuring an axial thermal expansion curve of the tubular sample in the temperature change process by using a DIL805A type quenching thermal expansion instrument, and analyzing to obtain the phase change temperature of the steel plate with the thickness of less than or equal to 0.6 mm.

The invention has the technical scheme that the method for measuring the continuous cooling phase transition temperature of the steel plate with the thickness less than or equal to 0.6mm comprises the following steps:

1) preparing a straight pipe sample, cutting a steel plate to be detected with the size of 30mm multiplied by 60mm, rolling the steel plate into the straight pipe sample by adopting a pipe rolling device, and controlling the inner diameter of the straight pipe sample to be 2.8mm and the outer diameter of the straight pipe sample to be 3.4-4 mm;

2) preparing a straight pipe small sample, penetrating a steel bar with the outer diameter of 2.8mm into the straight pipe sample, cutting the straight pipe sample penetrated with the steel bar into the straight pipe small sample with the length of 8mm-12mm by using a precision cutting machine, and controlling the end surfaces of two sides of the straight pipe small sample to be vertical to the axis;

3) installing a temperature thermocouple on the small straight pipe sample, welding the temperature thermocouple on the outer surface of the small straight pipe sample, and taking out a steel bar in the small straight pipe sample;

4) placing a straight pipe small sample provided with a temperature thermocouple at a measuring position of a DIL805A type quenching thermal expansion instrument, installing the straight pipe small sample welded with the temperature thermocouple between two ejector rods of the DIL805A type quenching thermal expansion instrument, enabling the axis of the straight pipe small sample to coincide with the axis of the ejector rod, moving and fixing the straight pipe small sample in the middle of an induction coil of the DIL805A type quenching thermal expansion instrument, and controlling the clamping force of the straight pipe small sample to be 10-20 kgf;

5) measuring the continuous cooling phase transition temperature of the steel plate to be measured, operating a DIL805A type quenching thermal expansion instrument, and heating a straight pipe small sample to Ac₃At the above temperature, the straight tube small sample is Ac₃And (3) preserving the heat for 3-5 minutes at the temperature, then performing controlled cooling on the straight pipe small sample, collecting and obtaining a thermal expansion curve of the straight pipe small sample in the experimental cooling process, and determining the continuous cooling phase change temperature of the steel plate to be measured by adopting a tangent point method.

Further, the ejector rod in the step 4) is a ceramic ejector rod or a quartz ejector rod, so that the ejector rod is ensured not to be physically deformed at high temperature.

The number of coiled layers of the straight pipe sample is determined according to the thickness of the steel plate to be measured, and the number of coiled layers of the straight pipe sample can be 2 or more.

According to the method, the thickness of the steel plate to be measured is less than or equal to 0.6mm, the steel plate to be measured is prepared into a straight pipe sample, the pipe wall of the straight pipe sample is thin, and the steel plate is very easy to flatten and deform in the processes of preparing the straight pipe small sample by cutting and welding the temperature thermocouple on the straight pipe small sample, so that a steel bar support penetrates into the straight pipe sample pipe in the process of preparing the straight pipe small sample by cutting, a steel bar support penetrates into the straight pipe small sample in the process of welding the temperature thermocouple on the straight pipe small sample, and the steel bar is taken out of the straight pipe small sample after the temperature thermocouple is welded and installed on the straight pipe small sample.

The method realizes the accurate measurement of the continuous cooling phase transition temperature of the steel plate with the thickness of less than or equal to 0.6mm, and the method adopts a thermal expansion method to realize the accurate measurement of the continuous cooling phase transition temperature of the steel plate with the thickness of less than or equal to 0.6 mm. Through the phase change measurement and inspection of the same-grade steel standard sample, under the same process conditions, the phase change temperature measured by the experimental method is basically consistent with the measurement result of the standard sample, and the error is less than 2%.

Compared with the prior art, the invention has the following positive effects: 1. the invention realizes that the DIL805A type quenching thermal expansion instrument is used for measuring the phase change temperature of the steel plate with the thickness less than or equal to 0.6mm, has no special requirements on the structure of the experimental instrument and the fixture of the sample, has no influence on other experimental functions and safety of the experimental instrument, and expands the experimental functions of the experimental instrument; the method has the advantages of simple operation, high efficiency, high measurement precision and low measurement cost. 2. The method not only realizes the measurement of the phase transition temperature of the steel plate with the thickness less than or equal to 0.6mm, but also is matched with the change of the structure of the ejector rod, and the method can be popularized to the measurement of the phase transition temperature of tubular finished steel samples or other special-shaped steel samples.

Drawings

FIG. 1 is a longitudinal cross-sectional view of a straight tube sample according to an embodiment of the present invention.

FIG. 2 is a schematic transverse cross-sectional view of a straight tube sample according to an embodiment of the present invention.

FIG. 3 is a 5 ℃/s continuous cooling phase transition temperature of 0.6mm thick SPHE steel plate measured in example 1 of the present invention.

FIG. 4 is a 5 ℃/s continuous cooling transformation temperature of SPHE steel measured in example 1 using a phi 5mm x 10mm standard cylinder.

FIG. 5 shows the phase transition temperature of 0.35mm thick SPHC steel sheet during 10 ℃/s continuous cooling, measured in example 2 of the present invention.

FIG. 6 is a 10 ℃/s continuous cooling phase transition temperature of SPHC steel measured using a standard cylinder sample of φ 5mm × 10mm in example 2.

FIG. 7 shows the phase transition temperature of 0.25mm thick SPHC steel sheet measured in example 3 of the present invention during 20 ℃/s continuous cooling.

FIG. 8 is a 20 ℃/s continuous cooling phase transition temperature of SPHC steel measured using a standard cylinder sample of φ 5mm × 10mm in example 3.

Detailed Description

The invention is further described with reference to the following figures and specific embodiments.