CN112499640B

CN112499640B - Preparation of material with giant thermal hysteresis negative thermal expansion property and application of material in field of embedded pipe joint

Info

Publication number: CN112499640B
Application number: CN202010775909.XA
Authority: CN
Inventors: 孙莹; 崔进; 王聪; 袁秀良
Original assignee: Beihang University
Current assignee: Beihang University
Priority date: 2020-08-05
Filing date: 2020-08-05
Publication date: 2021-12-17
Anticipated expiration: 2040-08-05
Also published as: CN112499640A

Abstract

The connection of pipes is generally by welding, which, although convenient to handle, is relatively vulnerable to breakage due to the presence of microscopic stresses in the weld. Some negative thermal expansion materials with huge thermal hysteresis in temperature rise and fall cycles have the approximate effect of single-pass shrinkage effect due to the existence of the huge thermal hysteresis phenomenon, so that the negative thermal expansion materials can be applied to manufacturing thermal shrinkage and cold expansion embedded pipe joints. The invention provides a preparation method of a material with huge thermal hysteresis negative thermal expansion property and application thereof in the field of embedded pipe joints, and provides a new selection mode for pipeline connection. Compared with the traditional welding mode, the novel pipeline connecting mode provided by the invention has more remarkable advantages under the condition that the space is narrow and welding is inconvenient.

Description

Preparation of material with giant thermal hysteresis negative thermal expansion property and application of material in field of embedded pipe joint

Technical Field

The invention provides a giant thermal hysteresis negative thermal expansion material applicable to the field of pipe joints and a preparation method thereof. The material has obvious expansion characteristic in the temperature reduction process, and can be used as a raw material for manufacturing an embedded pipe joint. The connection principle of the pipe joint is mainly divided into two parts: firstly, stress can be generated between the pipe joint and the connected pipe by utilizing the expansion characteristic in the temperature reduction process, so that high-strength fastening connection is realized; secondly, when the temperature is increased and decreased within the range of the negative thermal expansion temperature zone in the temperature decreasing process, because of the huge thermal hysteresis, the pipe joint after assembly can not generate obvious contraction phenomenon, namely the connection state of the connection structure is maintained.

Background

At present, the traditional method adopted for connecting the pipelines is welding, and although the method has low production cost and convenient forming, the welding is carried out under open fire conditions, so that great potential safety hazards exist. In addition, the high temperature environment generated during welding can cause intergranular corrosion of the welding material, thereby destroying the mechanical properties of the material. Second, the welding process creates microscopic stresses in the weld, thereby creating a microscopic, invisible crack. Without the premonition, the cracks would be subject to corrosion cracking, i.e., damage to the pipe connections.

The memory alloy outer sleeve type pipe joint prepared by the one-way shape memory shrinkage effect of the wide thermal hysteresis shape memory alloy can realize pipeline connection, so that the welding process can be replaced under certain conditions. Compared with a welding mode, the memory alloy pipe joint requires a smaller operation space, and open fire is not generated in the connection process, so that the memory alloy pipe joint is suitable for connection of seabed, precise and dense pipelines. Besides the memory alloy, research finds that due to magnetic phase change, part of the manganese-based anti-perovskite compound also has obvious shrinkage phenomenon along with temperature reduction. However, the negative thermal expansion characteristic of the material has generally smaller thermal hysteresis in temperature rise and reduction cycle, so that the thermal shrinkage and cold expansion phenomena are alternately generated near a phase change temperature region in the thermal cycle process, and the stability of the connecting structure is further damaged to a certain extent. For a negative thermal expansion material with large thermal hysteresis, when the heat is circulated in a negative thermal expansion temperature region, the large thermal hysteresis can inhibit the generation of a thermal shrinkage and cold expansion alternating phenomenon, namely the thermal shrinkage and cold expansion phenomenon can be approximately considered as a one-way effect, so that the material has wider application prospect in the field of pipe joints.

Disclosure of Invention

The invention provides a preparation method of a giant thermal hysteresis negative thermal expansion material and provides a working principle of the material applied to the field of embedded pipe joints. The parent material related to the invention is Fe₃Ni alloy, which has a giant thermal hysteresis negative thermal expansion phenomenon caused by crystal structure phase transformation. The regulation and control of the negative thermal expansion temperature zone can be realized by doping boron (B) atoms into the alloy, and then the material can be used for manufacturing pipe joints applied to different temperature zone ranges.

The preparation method of the giant thermal hysteresis negative thermal expansion material comprises the following steps:

the method comprises the following steps: according to the stoichiometric ratio, respectively weighing iron powder, nickel powder and boron powder with the purity of 99.99 percent by using an electronic balance (0.0001g), and placing the weighed materials in a mortar for fully grinding for 1-2 hours;

step two: pressing the metal powder mixture fully ground in the step one into a blocky solid by using a tablet press and a corresponding die;

step three: sealing the blocky solid obtained in the step two into a vacuum quartz tube for later use by using a vacuum tube sealing system;

step four: and (3) placing the quartz tube with the sample in a muffle furnace, fully calcining for 80 hours at 1000 ℃, and cooling the furnace to room temperature to obtain the giant thermal hysteresis negative thermal expansion material.

In the process of preparing the pipe joint by using the giant thermal hysteresis negative thermal expansion material, the material is supposed to be prepared into an embedded type pipe joint. The principle of operation of this concept is shown in fig. 1, i.e. the outer diameter of the pipe connection is made slightly smaller than the inner diameter of the pipe to be connected. During assembly, the pipe joint is firstly sleeved between the pipes to be connected, and then the expansion characteristic of the negative thermal expansion material in the cooling process is utilized to generate stress between the pipe joint and the pipes to be connected so as to realize pipeline connection. Due to the existence of the huge thermal hysteresis phenomenon, the abnormal thermal expansion phenomenon of the assembled pipe joint does not occur in the range of the negative thermal expansion temperature region, thereby avoiding the failure of the connection effect.

Drawings

FIG. 1 is a schematic view of the working principle of a joint with huge thermal hysteresis and negative thermal expansion.

FIG. 2 Fe obtained by variable temperature X-ray diffraction pattern₃NiB_0.5Volume versus temperature curve (thermal expansion curve).

Detailed Description

The invention relates to a negative thermal expansion material with huge thermal hysteresis, which is prepared by adopting a solid-phase reaction sintering method. In order to more clearly illustrate the manufacturing method and the design principle of the pipe joint, Fe is used below₃NiB_0.5For example, specific methods thereof are described. The method is only for illustrating the invention and not for limiting the invention.

The method comprises the following steps: according to the chemical molar ratio of Fe, Ni and B being 3:1:0.5, iron powder, nickel powder and boron powder with the purity of 99.99 percent are respectively divided by electron space, and are placed in an agate mortar to be fully ground for 1.5 hours, so that the powder is uniformly mixed;

step two: pressing the uniformly mixed metal powder into a long block with the mass of about 1g by using a tablet press and a common long strip-shaped die with the length of 10 mm;

step three: sealing the bulk material obtained in the second step into a quartz tube by using a vacuum tube sealing system, wherein the vacuum degree in the quartz tube is kept at 10^-3The magnitude of Pa;

step four: putting the quartz tube packaged in the step two into a muffle furnace, and setting the temperature rise process as follows: heating from room temperature to 350 deg.C for 1.5 hr, heating to 1000 deg.C for 2 hr, heat treating at 1000 deg.C for 80 hr, and naturally cooling to room temperature.

Thus, the preparation of the giant thermal hysteresis negative thermal expansion material is finished.

Step five: the sample prepared in step four was taken out and tested for thermal expansion properties using a DIL402C thermal expansion instrument manufactured by sanchi germany and an X-ray diffractometer manufactured by panacea netherlands. The X-ray map reveals that the phase change of the crystal structure causes the generation of the phenomenon of huge thermal hysteresis negative thermal expansion. With Fe₃NiB_0.5For example, we observed a large thermal hysteresis of about 500 ℃ in their thermal expansion curve (see fig. 2), and the relative change in unit cell volume in the negative thermal expansion temperature region during cooling was up to 1.46%. Based on the above abnormal physical properties, we considered that this material could be used as a raw material for an inline type pipe joint.

Step six: based on the giant thermal hysteresis negative thermal expansion material obtained in the fifth step, a design scheme shown in fig. 1 is given, namely the outer diameter of the pipe joint is slightly smaller than the inner diameter of the pipe to be connected, the pipe joint is sleeved between the pipe to be connected in an inner mode during assembly, and the expansion phenomenon in the temperature reduction process is utilized to achieve connection of pipelines.

Claims

1. A huge thermal hysteresis negative thermal expansion material used as a raw material of an embedded pipe joint is characterized in that:

(1) the matrix of the giant thermal hysteresis negative thermal expansion material is Fe₃The Ni alloy material realizes the regulation and control of a negative thermal expansion temperature zone of the alloy by doping boron (B) atoms into the alloy, so that the material system can be utilized to prepare thermal shrinkage and cold expansion embedded pipe joints applied in different temperature zone ranges;

(2) the material can generate obvious negative thermal expansion phenomenon caused by crystal structure phase change in temperature rise and drop circulation, and Fe is tested by an X-ray diffractometer₃NiB_0.5The relative change of the unit cell volume is 1.46 percent in the temperature reduction process of-50 ℃ to-150 ℃;

(3) the negative thermal expansion phenomenon has huge thermal hysteresis in temperature rise and fall circulation, wherein Fe₃NiB_0.5The existence of a huge thermal hysteresis at 500 ℃;

wherein Fe₃NiB_0.5The preparation method of (A) is as follows,

the preparation method is characterized by comprising the following steps:

the method comprises the following steps: respectively weighing iron powder, nickel powder and boron powder with the purity of 99.99 percent by using an electronic balance according to the stoichiometric ratio, and placing the materials in a mortar for fully grinding for 1-2 hours;

step two: pressing the powder mixture fully ground in the first step into a block solid by using a tablet press and a corresponding die;

2. The use of the giant thermal hysteresis negative thermal expansion material as claimed in claim 1, wherein the working method of the thermal shrinkage and cold expansion embedded pipe joint is as follows:

preparing the huge thermal hysteresis negative thermal expansion material into a pipe joint of which the outer diameter is slightly smaller than the inner diameter of a pipe to be connected, and sleeving the pipe joint between the pipes to be connected in an assembling process; due to the abnormal expansion characteristic of the material in the cooling process, stress is generated between the outer wall of the pipe joint and the inner wall of the pipe to be connected, and finally the connection of the pipeline is realized; when the assembled connecting structure is subjected to heat circulation in a negative thermal expansion temperature area in the cooling process, due to the existence of huge thermal hysteresis, the thermal shrinkage and cold expansion phenomena cannot be alternately generated, so that the stability of the connecting structure is maintained.