CN1745922A - Preparation method of micro/nanocrystalline industrial pure titanium block material by equal diameter angle extrusion - Google Patents

Abstract

An isometric angle squeezing technology for preparing micron/nano-crystal industrial-purity Ti block includes such steps as providing an industrial-purity Ti block, annealing, holding its temp, cutting it to become blanks, polishing the surface of blank, coating glass lubricant, coating graphite lubricant on the inner surface of an isometric angle squeezing die with a squeezing channel angle of 90-120 deg, heating said blank and die, and isometric angle squeezing. Its product has high strength, plasticity, biocompatibility and anticorrosion nature, the elastic modulus similar to that of bone, and low cost.

Description

Preparation method of micro/nanocrystalline industrial pure titanium block material by equal diameter angle extrusion

technical field

The invention relates to a preparation method in the technical field of metal materials, in particular to a preparation method for equal-diameter angular extrusion of micro/nano crystal industrial pure titanium blocks.

Background technique

Among all biomedical materials, metal materials are the earliest to be used, and are mainly used to repair bones, joints, teeth, and blood vessels. Currently used in biomedical materials are mainly stainless steel, titanium and titanium alloys. Metal titanium is extremely abundant in the earth's crust. It exists in ores in the form of compounds, and the main ores are ilmenite FeTiO ₃ . Titanium has certain strength and high plasticity. High-purity titanium has σb=300MPa, δ=40%, and can maintain high strength under high temperature conditions. It has both steel (high strength) and aluminum (light texture) Advantages, the melting point is (1663 ± 10) ° C, with excellent corrosion resistance and heat resistance. At the same time, titanium is a non-magnetic metal and will not be magnetized in a large magnetic field. Titanium and its alloys also have an elastic modulus very similar to bone, good biocompatibility and excellent corrosion resistance in biological environments. Therefore, it has been more and more widely used in clinical practice. However, compared with titanium alloys, pure titanium lacks sufficient strength and hardness, which limits its application in bearing parts in vivo. At the same time, although titanium and its alloys have the closest elastic modulus to bone (10-40GPa), they are still higher than the elastic modulus of bone, which easily causes the mismatch of mechanical properties on the interface.

Practice has proved that fine and equiaxed grains can improve the plastic deformation ability of metals, improve the strength and comprehensive mechanical properties of materials. Moreover, when the material grains are refined to the nanocrystalline scale, not only its comprehensive mechanical properties will be improved, but its physical and chemical properties will also undergo significant changes. Commonly used grain refinement processes are divided into four types: adding various grain refiners in the liquid state or breaking dendrites with the help of external energy, thereby refining the casting structure; semi-solid forming to refine grains; casting powder metallurgy forming; Strong plastic deformation, such as high pressure torsion (referred to as HPT) method, equal-diameter angular extrusion method (hereinafter referred to as ECAE), etc. The first three methods are casting molding, and the effect of grain refinement is not obvious. The high-pressure torsion method can only prepare very thin sheet-like materials, while the equal-diameter angular extrusion method can prepare relatively large bulk fine-grained materials.

After searching the literature of the prior art, it was found that S.L.Semiatin, D.P.Delo, etc. once published a paper on "ECAE process of difficult-to-deformable alloys" (Equal channel angular extrusion of difficult-to-work alloys) in "Materials and Design" , Materials and Design21 (2000) 311-322), this paper carried out ECAE process on hard-to-deform metals such as pure Ti, Ti-6Al-4V and 4340 steel, the author of this paper used a mold with a channel angle of 90°, selected The temperature range of 25°C to 325°C and the strain rate of 0.002/S to 2/S were used for the ECAE process on pure titanium. As a result, pure titanium is very sensitive to the shear localization in the ECAE process, and at room temperature (25°C) At the same time, choosing any strain rate between 0.002/S and 2/S will make pure titanium become fragments after the ECAE process; and the authors of this document try to treat pure titanium at other temperatures (125 ° C ~ 325 ° C). During the ECAE process, due to the influence of factors such as extrusion temperature, strain rate, and unsuitable lubrication conditions, the pure titanium after equal-diameter angle extrusion will also be fractured to varying degrees, so it is impossible to obtain large blocks of fine-grained materials. .

Contents of the invention

The purpose of the present invention is to address the deficiencies of the prior art, to provide a method for preparing micro/nanocrystalline industrial pure titanium blocks by equal diameter angle extrusion, so that it can improve the strength of metallic pure titanium at room temperature and its comprehensive mechanical properties. Performance, reduce processing cost, improve its finished product rate.

The present invention is realized through the following technical scheme. The present invention selects industrial pure titanium (TA2) blocks as raw materials. After annealing and heat preservation, the industrial pure titanium blocks are then cut into blanks, subjected to surface finish treatment, and coated with glass lubricant . The mold adopts an equal-diameter curved angle extrusion mold with an extrusion channel angle of 90° to 120°, and the surface of the mold cavity is coated with graphite lubricant. The billet and the mold are heated and kept together, and taken out from the heating furnace at the same time for equal-diameter angle extrusion, and finally a micro/nanocrystalline industrial pure titanium block with good strength and plasticity is obtained.

The present invention is described further below, and concrete steps are as follows:

(1) Using commercially pure titanium (TA2) blocks as raw materials, annealing the commercially pure titanium blocks at 700°C to 750°C and keeping them warm for 1 to 2 hours;

(2) Cut the industrially pure titanium TA2 blocks after annealing and heat preservation into blanks (10×10×120mm ³ ), and carry out surface treatment on the blanks to achieve a surface precision above grade 4, and the surface roughness of the blanks should not be lower than Ra= 1.25μm;

(3) Clean the surface of the blank with acetone, preheat it at a temperature of 60°C to 100°C for 20 to 60 minutes, and then apply glass lubricant on the surface of the blank by dip coating. The coating should be uniform and the coating should be uniform. The thickness is 0.2-0.4mm. After coating, the blank should be dried at a temperature of 60°C to 100°C for 20 to 60 minutes. If there are defects such as falling coating, scratches, and peeling, it should be recoated or washed off for recoating.

(4) Equal diameter and angle extrusion dies are adopted, and the extrusion channel angle of the die is 90°-120°. Clean the surface and cavity of the mold with acetone, preheat at a temperature of 100°C to 150°C for 60 to 90 minutes, then apply graphite lubricant, the coating thickness should be uniform, and then place the mold at a temperature of 100°C to 150°C Dry at low temperature for 60-90 minutes.

(5) Put the billet coated with glass lubricant into the extrusion channel of the mold coated with graphite lubricant, and then heat it together in a heating furnace at 400°C to 500°C for a holding time of 40 to 60 minutes.

(6) Take out the heated billet and mold at the same time, and then quickly squeeze the billet on a 300KN hydraulic universal testing machine. Repeat the surface treatment and coating of glass lubricant on the extruded billet, coating the mold cavity with graphite lubricant, and then extruding for 2 to 8 times to obtain micro/nanocrystalline industrial pure titanium blocks. The average grain size is 0.2-0.6 μm.

The invention adopts an equal-diameter bending angle extrusion process, which is characterized in that the size of the sample remains unchanged before and after deformation, the processing is simple, the yield is high, and the processing of large workpieces can be realized. Different lubrication treatments are carried out on the mold cavity and the billet to be extruded before extrusion, which can effectively prevent the sharp temperature drop of the high-temperature billet, and at the same time significantly reduce the sliding friction resistance between the billet and the working surface of the die, thus effectively Improve the flow uniformity of pure titanium metal materials to ensure the smooth progress of the extrusion process; the lubrication treatment process is simple and low in cost. After the actual operation, the billet and the mold will fall off by themselves without being bonded to each other, and the processability is good. The radian of the end of the billet and the smoothness of the billet surface are determined, which is conducive to reducing friction during the extrusion process of the billet and improving the uniformity of the plastic flow of the billet. The determination of the heating time and holding time of the billet and mold, as well as taking the heated billet and mold out of the heating furnace at the same time for equal-diameter angle extrusion can prevent grain growth and facilitate the formation of fine pure titanium micro/nano crystals , and finally obtain industrial pure titanium blocks with good properties such as strength and plasticity. The invention can improve the strength and comprehensive mechanical properties of metallic pure titanium at room temperature, reduce processing cost and increase yield.

Detailed ways

The technical solution of the present invention will be further described below through specific examples.

Example 1:

Using industrial pure titanium (TA2) as raw material, anneal the industrial pure titanium block at 700°C, keep it warm for 2 hours, and use an electric spark cutting machine to cut the pure titanium metal block into sections with a size of 10mm×10mm and a length of 120mm. The blank, and the surface treatment of the blank, reaches the surface precision above grade 4, and the surface roughness of the blank should not be lower than Ra=1.25μm. Clean the surface of the blank with acetone, place the blank on a clean stainless steel tray, preheat it at a temperature of 60°C for 60 minutes, and then apply a glass lubricant on the surface of the blank by dip coating. The coating should be uniform. The thickness of the coating is about 0.2mm. After coating, the blank is dried at 60°C for 60 minutes. If there are defects such as falling coating, scratches, and peeling, it should be re-coated or washed off and re-coated. Use acetone to clean the surface and cavity of the mold with an extrusion angle of 90°, preheat it at 100°C for 90 minutes, and then apply graphite lubricant. The coating should be uniform. Put the mold coated with graphite lubricant on the Dry in a heating oven at 100°C for 90 minutes.

Put the blank coated with glass lubricant into the extrusion channel of the mold coated with graphite lubricant, and heat it together in a heating furnace at 500 ° C for 40 minutes. Then take out the heated billet and the mold at the same time, and quickly extrude it on the hydraulic universal testing machine. After the extruded billet is subjected to surface treatment for the second extrusion, the microcrystalline industrial pure titanium block can be obtained. . When the grains of industrial pure titanium TA2 block are refined to the micron level, σ _0.2 increases from 600MPa in the initial annealed state to 750MPa, and σ _b increases from 670MPa to 810MPa.

Example 2:

Using industrial pure titanium (TA2) as the raw material, anneal the industrial pure titanium block at 750°C and keep it warm for 1 hour. Use an electric spark cutting machine to cut the pure titanium metal block into pieces with a cross-sectional size of 10mm×10mm and a length of 120mm. The blank, and the surface treatment of the blank, reaches the surface precision above grade 4, and the surface roughness of the blank should not be lower than Ra=1.25μm. Clean the surface of the blank with acetone, place the blank on a clean stainless steel tray, preheat it at a temperature of 80°C for 40 minutes, and then apply a glass lubricant on the surface of the blank by dipping. The coating should be uniform. The thickness of the coating is about 0.3mm. After coating, the blank is dried at a temperature of 80°C for 40 minutes. If there are defects such as falling coating, scratches, and peeling, it should be recoated or washed off and recoated. Use acetone to clean the surface and cavity of the mold with an extrusion angle of 120°, preheat it at 120°C for 80 minutes, and then apply graphite lubricant. The coating should be uniform. Put the mold coated with graphite lubricant on the Dry in a heating oven at 120°C for 80 minutes.

Put the blank coated with glass lubricant into the extrusion channel of the mold coated with graphite lubricant, and heat it together in a heating furnace at 450 ° C for 50 minutes. Then take out the heated billet and the mold at the same time, and quickly extrude it on the hydraulic universal testing machine. After the extruded billet is surface treated and extruded 4 times, the submicron crystal industrial pure titanium block can be obtained. . When the grains of commercially pure titanium TA2 block are refined to the submicron level, σ _0.2 increases from 600MPa in the initial annealed state to 820MPa, and σ _b increases from 670MPa to 890MPa.

Example 3:

Commercially pure titanium (TA2) blocks are used as raw materials, and the commercially pure titanium blocks are annealed at 750° C. and kept for 1.5 hours. Use electric spark cutting machine to cut pure titanium block into blanks with cross-sectional size of 10mm×10mm and length of 120mm, and carry out surface treatment on the blanks to achieve a surface precision above grade 4, and the surface roughness of the blanks should not be lower than Ra = 1.25 μm. Clean the surface of the blank with acetone, place the blank on a clean stainless steel tray, preheat it at a temperature of 100°C for 20 minutes, and then apply a glass lubricant on the surface of the blank by dipping. The coating should be uniform. The thickness of the coating is about 0.4mm. After coating, the blank is dried at 100°C for 20 minutes. If there are defects such as falling coating, scratches, and peeling, it should be re-coated or washed off and re-coated. Use acetone to clean the surface and cavity of the mold with an extrusion angle of 90°, preheat it at 150°C for 60 minutes, and then apply graphite lubricant. The coating should be uniform. Put the mold coated with graphite lubricant on the Dry in a heating oven at 150° C. for 60 minutes.

Put the blank coated with glass lubricant into the extrusion channel of the mold coated with graphite lubricant, and heat it together in a heating furnace at 400 ° C for 60 minutes. Then take out the heated billet and the mold at the same time, and quickly extrude it on the hydraulic universal testing machine, and then carry out surface treatment on the extruded billet for 8 times of extrusion, and you can obtain micron/nanocrystalline industrial pure titanium block material. When the grains of industrial pure titanium TA2 block are refined to the micron/nano scale, σ _0.2 increases from 600MPa in the initial annealed state to 910MPa, and _σb increases from 670MPa to 970MPa.

Claims (10)

1. A method for preparing micro/nanocrystalline industrial pure titanium blocks by equal diameter angle extrusion, characterized in that industrial pure titanium TA2 blocks are selected as raw materials, and after annealing and heat preservation, the industrial pure titanium TA2 blocks are cut into billets , surface finish treatment, and coated with glass lubricant; the mold adopts equal-diameter angle extrusion mold, and the surface of the mold cavity is coated with graphite lubricant. By bending and angle extrusion, the micro/nanocrystalline industrial pure titanium block is finally obtained. 2. The method for preparing micro/nanocrystalline industrial pure titanium blocks by equal-diameter angular extrusion according to claim 1, characterized in that it comprises the following steps: (1) Select industrial pure titanium blocks as raw materials, and anneal the industrial pure titanium blocks for heat preservation; (2) Cut the industrially pure titanium block after annealing and heat preservation into blanks, and carry out surface treatment on the blanks to achieve a surface precision above grade 4, and the surface roughness of the blanks is Ra≤1.25μm; (3) Clean the surface of the blank with acetone. After preheating, apply a glass lubricant on the surface of the blank by dip coating, and dry the blank after coating; (4) Adopt an equal-diameter bending angle extrusion mold, clean the surface and cavity of the mold with acetone, after preheating, apply graphite lubricant, and then dry the mold; (5) Put the blank coated with glass lubricant into the extrusion channel of the mold coated with graphite lubricant, and then heat it together in a heating furnace to keep it warm; (6) Take out the heated billet and the mold at the same time, then quickly extrude the billet, repeat the surface treatment and coating of the extruded billet with glass lubricant, apply graphite lubricant to the mold cavity, and then extrude Press 2 to 8 times to obtain micro/nano crystal industrial pure titanium block. 3. The method for preparing micro/nanocrystalline industrial pure titanium blocks by equal-diameter angular extrusion according to claim 1, characterized in that, in step (1), the industrial pure titanium blocks are annealed at 700°C to 750°C, Keep warm for 1-2 hours. 4. The method for preparing micro/nanocrystalline industrial pure titanium blocks by equal-diameter angle extrusion according to claim 1, characterized in that, in step (2), the industrial pure titanium blocks are cut into blanks of 10×10×120mm ³ . 5. The method for preparing micro/nanocrystalline industrial pure titanium blocks by equal diameter angle extrusion according to claim 1, characterized in that, in step (3), the surface of the blank is cleaned with acetone, and the surface is cleaned at 60°C to Preheat at 100°C for 20-60 minutes, and evenly coat the glass lubricant with a coating thickness of 0.2-0.4mm. 6. The method for preparing micro/nanocrystalline industrial pure titanium blocks by equal-diameter angular extrusion according to claim 1 or 5, characterized in that, in step (3), the blank after coating is heated at a temperature of 60°C to 100°C. Dry at high temperature for 20-60 minutes. If there is a defect, it should be re-coated or washed off and re-coated. 7. The method for preparing micro/nanocrystalline industrial pure titanium blocks by equal-diameter angular extrusion according to claim 1, characterized in that, in step (4), the extrusion channel angle of the die is 90°-120°. 8. The method for preparing micro/nanocrystalline industrial pure titanium blocks by equal-diameter angular extrusion according to claim 1 or 7, characterized in that in step (4), the surface and cavity of the mold are cleaned with acetone, Preheat at a temperature of 100°C to 150°C for 60 to 90 minutes, apply graphite lubricant evenly, and then dry the mold at a temperature of 100°C to 150°C for 60 to 90 minutes. 9. The method for preparing micro/nanocrystalline industrial pure titanium blocks by equal-diameter angular extrusion according to claim 1, characterized in that, in step (5), the blank and the mold are placed in a heating furnace at 400°C to 500°C Heating together, the holding time is 40-60 minutes. 10. The method for preparing micro/nanocrystalline industrial pure titanium blocks by equal-diameter angle extrusion according to claim 1, characterized in that in step (6), the billet is extruded on a 300KN hydraulic universal testing machine to obtain The micro/nanocrystalline industrial pure titanium bulk material has an average microscopic grain size of 0.2-0.6 μm.