CN105149369A - New preparing method for high-strength nanocrystalline titanium alloy pipe - Google Patents

Abstract

The invention discloses a new method for preparing high-strength nanocrystalline titanium alloy tubes. The feature of the invention is that high-strength thin-walled tubes can be prepared at low cost instead of thick-walled tubes, and the titanium alloy tube can be drawn once by using a circular mold channel. Finally, the severe plastic deformation of the titanium alloy tube can be realized, and finally the large deformation can be accumulated to obtain a high-strength nanocrystalline titanium alloy tube. The circular channel drawing die designed by the invention adopts the double-layer prestressed ferrule structure, which can greatly improve the strength of the circular channel die and improve the service life of the die. The tin melt used to enrich the titanium alloy tube avoids the cross-sectional distortion of the tube during the drawing process of the circular mold channel. At the same time, the material of the tube is better refined under the two-dimensional stress, so that the mechanical properties of the titanium alloy tube are further improved. Under the premise of ensuring high density, it has both high strength and good toughness.

Description

A new method for preparing high-strength nanocrystalline titanium alloy tube

technical field

The invention relates to the field of forming metal pipes, in particular to realizing nanometerization of titanium alloy pipe materials through a "self" channel mold and drawing process, and relates to a method and mold for preparing high-strength nanocrystalline titanium alloy pipes .

Background technique

At present, titanium alloys are mainly used in aerospace, nuclear power and medical applications. Among them, titanium alloy metal pipes are strong, corrosion-resistant, have high mechanical properties, excellent stamping properties, and can be used in various forms. Welding, the strength of the welded joint can reach 90% of the strength of the base metal, and the cutting performance is good. Titanium tubes have high corrosion resistance to chlorides, sulfides and ammonia. The corrosion resistance of titanium in seawater is higher than that of aluminum alloy, stainless steel, and nickel-based alloys. Titanium is also more resistant to water shock. Therefore, titanium alloy tubes have been widely used in aerospace and nuclear power fields. Extrusion technology can be used to prepare small-diameter thick-walled pipes. This method uses bar casting-bar heating and hot extrusion-rolling and stretching. The process is complicated and the energy consumption is high. The welding method can be used to prepare large-diameter thick-walled pipes. This method is energy-efficient and reduces the number of procedures. However, the welding process itself has a weld zone and a heat-affected zone, and the aerospace and nuclear power fields have extremely high safety requirements. Therefore, the current titanium The forming technology of alloy tubes restricts the further application of titanium alloy tubes in aerospace and nuclear power fields.

The invention whose application publication number is CN102626724A adopts two-roll cold rolling, three-roll cold rolling and vacuum annealing process to obtain titanium alloy tubes, and the invention whose application publication number is CN102974645A obtains titanium alloy tubes by upsetting, rough rolling and finishing rolling. Both are traditional rolling forming processes, which cannot obtain nanometerization of titanium alloy tube materials. The inventions with application numbers 20110347299.4 and 201110374700.3 propose a method for equal-channel variable-section extrusion and drawing of pipes. By changing from circle-ellipse-circle and ellipse torsion, the material can be accumulated and deformed, which can improve the material’s durability. strength and improve pipe performance, but the cross-section of the mold channel is changed by this method, and the obtained pipe fittings cannot keep the original cross-sectional geometry of the pipe well.

The present invention proposes a "self"-shaped curved channel mold drawing method, which can theoretically obtain infinitely long high-strength nanocrystalline titanium alloy tubes, and at the same time, because it is a channel with equal cross-section deformation, the tube can be maintained The original cross-sectional geometry can not only meet the low processing cost of preparing thin-walled pipes, but also obtain high-strength pipes, partially replacing the use of thick-walled pipes. Therefore, the present invention proposes a "self"-shaped curved channel die drawing method to improve the mechanical properties of titanium alloy tubes to obtain nanocrystalline high-strength titanium alloy tubes.

Contents of the invention

The purpose of the present invention is: to overcome the strength problem of thin-walled titanium alloy tubes, to provide a new method for preparing high-strength nanocrystalline titanium alloy tubes, to provide a method of drawing through a "self"-shaped curved channel mold, which can be used at low cost Obtain a longer size high-strength nanocrystalline titanium alloy tube.

A method for preparing long-sized titanium alloy tubes and nanocrystalline titanium alloy tubes by a "self"-shaped curved channel die drawing method proposed by the present invention comprises the following steps:

Step 1, tube blank preparation: divide the tube blank to be drawn into two parts, the first part is the pipe drawing end part: this part is sealed by welding, and a titanium alloy rope clamp is set at the port part; the second part is The main drawing part of the pipe: this part will obtain large strain, nanostructure, and finally obtain excellent mechanical properties; inject tin melt into the titanium alloy pipe sealed at one end for cooling, and a solid titanium alloy pipe can be obtained by this method. Avoid the distortion of the cross-section of the pipe in the deformation of the second step.

Step 2, drawing preparation: After the tube blank is phosphated and saponified, the outer surface of the tube blank is coated with a mixture of molybdenum disulfide and paraffin wax, and the titanium alloy rope chuck of the first part of the prepared tube blank is connected to the drawing device. The steel wire rope is connected, and then the tube blank is put into the "self"-shaped curved channel mold under the traction of the titanium alloy wire rope.

Step 3, drawing deformation: the drawing device pulls the tube blank through the "self"-shaped curved channel mold at a pulling speed of 5mm/s-20mm/s, and can accumulate enough strain through one drawing to obtain high-strength nano Crystal titanium alloy tube.

Step 4, obtaining the pipe material: place the drawn end part of the obtained high-strength nanocrystalline titanium alloy pipe vertically upwards in a heating tank and bake it to 230° for one hour. The tin metal filling material is completely melted and flows out when heated, and the outflowed tin material can be used repeatedly. At the same time, the titanium alloy tube is subjected to stress relief annealing to obtain a high-strength nanocrystalline titanium alloy tube with excellent mechanical properties.

The present invention realizes the "self"-shaped curved channel mold for drawing and deforming titanium alloy tubes, including a circular channel die, a first layer of prestressed compression sleeve, a second layer of prestressed compression sleeve, and corresponding accessories such as steel wire rope clips and wire rope.

The beneficial effects of the present invention are: adopting this scheme, the titanium alloy tube is drawn by two deformation methods of "self"-shaped curved channel die drawing, and at the same time, the interior is filled with tin metal material, and the compressive stress applied to the inner wall of the titanium alloy tube can ensure that the titanium alloy tube The shape and size of the cross-section of the alloy tube do not change during the drawing process, and the method can realize the nanostructure of the titanium alloy tube, thereby obtaining a high-strength nanocrystalline titanium alloy tube with excellent performance. The continuous drawing deformation of titanium alloy tubes is realized on the basis of the "ji"-shaped curved channel mold, which not only realizes the nanometerization of the tube wall metal, but also reduces the labor intensity of the operators, and broadens the application range of thin-walled titanium alloy tubes .

Description of drawings

The following is a detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings and examples.

Fig. 1 is a simplified schematic diagram of the processing technology of the present invention;

Fig. 2 is a drawing process device diagram of a "self" type curved channel mold of the present invention;

The transmission electron microscope micrograph of the extruded sample obtained in Fig. 3;

Figure 4 is the stress-strain curve of the drawn pipe sample.

The labels in the above figure are:

Fig. 1 is 1. circular passage die of the present invention schematic diagram of processing technology, 2. extruded part tube blank;

Fig. 2 is the 1. circular passage die of the present invention's " self " type curve channel mold drawing process device figure, 2. extruded part tube blank, 3. the first layer of die prestressed ferrule, 4. the second Layer die prestressed ferrule, 5. Chuck, 6. Steel wire rope, 7. Prestressed mold base.

Detailed ways

Embodiment, a new method for preparing high-strength nanocrystalline titanium alloy tube

Weld and seal the drawn end of the tube billet to be drawn, and at the same time set a wire rope chuck at the end; inject tin melt into the titanium alloy tube sealed at one end for cooling, and a solid titanium alloy tube can be obtained by this method. After phosphating and saponifying the tube blank, coat the molybdenum disulfide and paraffin wax mixture on the outer surface of the tube blank, connect the steel wire rope chuck of the first part of the prepared tube blank with the steel wire rope of the drawing device, and then draw the tube under the wire rope The billet is put into the "J"-shaped curved channel mold, and the drawing device pulls the tube blank through the "J"-shaped curved channel mold at a pulling speed of 8mm/s to accumulate enough strain once to accumulate enough strain, and then obtain high-strength nanocrystalline titanium The drawn end of the alloy tube is placed vertically upwards in a heating tank, roasted to 230°, and then kept warm for one hour. The tin metal filling material is completely melted and flowed out. At the same time, the titanium alloy tube is also subjected to a stress-relief annealing process to obtain a product with excellent mechanical properties. High-strength nanocrystalline titanium alloy tube.

It can be seen from the transmission electron microscope microscopic photo of the nanocrystalline titanium alloy drawn tube sample shown in Figure 3 that the average grain structure of the titanium alloy tube is a nanomaterial smaller than 400nm. From the tensile true stress-strain curve of the nanocrystalline copper drawn pipe sample shown in Figure 4, it can be seen that the strength is 119% higher than that of the traditional sample. According to the Hall-Pech formula, the smaller the grain size of the material, Its external macroscopic mechanical properties are higher.

It can be seen that the average grain structure of the nanocrystalline titanium alloy drawn pipe sample is a nanomaterial less than 400nm, and the strength of the nanocrystalline copper drawn pipe sample is 119% higher than that of the traditional sample.

The high-strength nanocrystalline titanium alloy tube provided by the invention can adopt simple wire drawing processing equipment, and the obtained material has high hardness and strength while maintaining good toughness. Therefore, the material of the invention has potential application value, especially in the fields of aviation, spaceflight and nuclear power.

The "self" type curved channel mold structure adopted in the present invention can adopt the prior art, and the present invention is not limited to the specific implementation forms listed above, and all those skilled in the art can obtain improvements without creative work. All belong to the protection scope of the present invention.

Claims (3)

1. the novel preparation method of the brilliant titanium alloy tube of high-strength nano, low cost can prepare the use of high-strength thin-walled tubing replacement thick-wall tube, it is characterized in that: by the severe plastic deformation adopting " own " type channel die drawing titanium alloy tube once can realize titanium alloy tube, final accumulation large deformation, obtains the brilliant titanium alloy tube of high-strength nano.

2. the novel preparation method of the brilliant titanium alloy tube of a kind of high-strength nano according to claim 1, it is characterized in that: the steel wire clamp of pipe Part I is connected with the steel wire rope of draw-off gear, then under rope traction, pipe is put into " own " type curved channel mould, pipe once can be accumulated enough strains by " own " type curved channel mould drawing deformation with the hauling speed of 8mm/s by draw-off gear.

3. the novel preparation method of the brilliant titanium alloy tube of a kind of high-strength nano according to claim 1, it is characterized in that: the average crystal grain tissue of nanocrystalline titanium alloy drawing pipes sample is the nano material being less than 400nm, its nanocrystalline copper drawing pipes probe intensity comparatively conventional specimen improves 119%.