Method for preparing rods from titanium-based alloys

Abstract

The invention relates to the pressure processing of metals, and specifically to methods for preparing rods and workpieces from titanium alloys, with applications as a structural material in nuclear reactor cores, in the chemical and petrochemical industries, and in medicine. The invention solves the problem of producing rods from high-quality titanium alloys while simultaneously ensuring the high efficiency of the process. A method for preparing rods or workpieces from titanium alloys includes the hot forging of an initial workpiece and subsequent hot deformation, the hot forging of an ingot is carried out following heating, with shear deformations primarily in the longitudinal direction and a reduction ratio of k=(1.22.5), and then performing hot rolling forging, without cooling, changing the direction of shear deformations to being primarily transverse and with a reduction ratio of up to 7.0, and conducting subsequent hot deformation by heating deformed workpieces.

Claims

1. A method of manufacturing a rod from a titanium alloy, the method including hot forging of a workpiece and the subsequent hot deformation, characterized in that: a) hot forging of an ingot is performed after heating the ingot to a temperature in the interval from (Tpt+20) to (Tpt+150) C. with shear deformations mainly in a longitudinal direction and a reduction ratio k=(1.22.5), thereby providing a forged piece; b) after step a), without cooling, hot rolling of the forged piece is performed in the temperature range of (Tpt+20)+(Tpt+150) C. with a change of shear deformations into a predominantly transverse direction and a reduction ratio of up to 7.0, the transverse direction being transverse relative to the longitudinal direction, and the hot rolling step providing a deformed workpiece; and c) the subsequent hot deformation is carried out by heating the deformed workpiece in the temperature range from (Tpt70) to (Tpt20) C., where Tpt is the temperature of polymorphic transformation of the ingot.

2. The method according to claim 1, wherein before hot rolling, the forged piece is heated to a temperature range from (Tpt+20) to (Tpt+150) C.

3. The method according to claim 1, wherein after hot forging and hot rolling, the deformed workpiece is cooled to the temperature of 350+500 C. followed by heating the deformed workpiece to a temperature in the range from (Tpt70) to (Tpt20) C. and the subsequent hot deformation of the deformed workpiece.

Description

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(1) Example 1. An ingot of titanium alloy IIT-7M (Cyrillic) (a alloy, averaged chemical composition 2.2 Al-2.5 Zr, GOST 19807-74 Wrought titanium and titanium alloys.) was heated to the temperature of Tpt+130 C. and hot forging was carried out on the forging press with a reduction ratio of 1.5. High single deformation due to high plasticity of the metal and deformation heating during forging led to the fact that, by the end of the forging, the forged piece temperature was in the range of (Tpt+20)+(Tpt+150) C. The forged piece was rolled on the screw rolling mill without heating with the reduction ratio of 3.80. Further, the rod was cut into parts, heated to the temperature of Tpt40 C. and hot rolled on the screw rolling mill with the reduction ratio of 2.45

(2) We obtained a rod of a given size with the required properties, Table 1, which can be used for the manufacture of pipe workpieces for subsequent hot extrusion, Table 1.

(3) TABLE-US-00001 TABLE 1 Physical and mechanical properties of heat-treated rods made from titanium alloy IIT-7M (Cyrillic), the longitudinal direction of samples cutting Test temperature 20 C. Test KCU, temperature 350 C. Properties .sub.B, MPa .sub.0.2, MPa , % , % kJ/m.sup.2 .sub.B, MPa .sub.0.2, MPa Actual 590-600 515-555 19-24 48-51 1280-1501 340-345 266-278 Requirements 480-650 380 18 36 1000 250 180 .sub.B - ultimate strength; .sub.0.2 - yield strength; - percentage elongation; - reduction of area; KCU - impact toughness

(4) As follows from Table 1, the rods fully meet the requirements.

(5) A similar result was obtained when manufacturing the rods from other alloys

(6) Example 2. An ingot of titanium alloy BTEC (Cyrillic) (+ alloy, averaged chemical composition 5Al-4V, GOST 19807-74 Wrought titanium and titanium alloys.) was heated to the temperature of Tpt+60 C. and hot forging was carried out on the forging press with the reduction ratio of 2.15. Further, without cooling, the forged piece was heated to the temperature of Tpt+60 C. and rolled on the screw rolling mill with the reduction ratio of 2.78 Then the rod was cooled to an ambient temperature and cut into three equal parts.

(7) The rolled rods were heated in the furnace to the temperature of Tpt40 C., then the second stage of screw rolling with the reduction ratio of 2.25 was performed.

(8) The deformation of the metal was stable without macro- and microdefects.

(9) After the second stage of rolling, the rods were cooled to ambient temperature and cut into specified lengths.

(10) The rods were divided into two groups. The first group of rods as ready-made large-size rods was sent for the check of compliance with the requirements. At the request of the customer, they were additionally machined.

(11) The second group of rods was heated in the induction furnace to the temperature of Tpt40 C. and rolled on the screw rolling mill with the reduction ratio of 3.62, then cooled to ambient temperature. The rods were also checked for compliance. At the request of the customer, they were additionally machined.

(12) The obtained rods were characterized by high accuracy of geometrical dimensions and absence of defects. In addition to the basic research (mechanical properties, hardness, macro- and microstructure), the ultrasonic continuity check was carried out on the rods.

(13) The results of properties check are given in Table 2.

(14) TABLE-US-00002 TABLE 2 Physical and mechanical properties of the rods made from titanium alloy BT6C (Cyrillic), the direction of samples cuttinglongitudinal, test temperature 20 C. KCU, Diameter/side of the rod, tested samples state .sub.B, MPa , % , % kJ/m.sup.2 Annealed 10-12 mm Actual 951-964 14.4-16.8 37.8-41.1 (1st group) Requirements 835-980 10 30 12-60 mm Actual 948-961 15.1-16.9 37.7-41.2 630-890 (1st group) Requirements 835-980 10 30 400 60-100 mm Actual 946-963 15.0-17.0 36.2-39.9 640-910 (2nd group) Requirements 835-980 10 25 400 100-150 mm Actual 940-960 15.2-16.9 37.0-40.5 620-870 (2nd group) Requirements 755-980 7 22 400 Hardened and aged 10-12 mm Actual 1104-1107 8.7-11.9 30.2-31.4 (1st group) Requirements 1030 6 20 12-100 mm Actual 1139-1140 12.3-12.5 43.8-48.2 560-600 (2nd group) Requirements 1030 6 20 300 Note. Requirements - according to GOST 26492-85 Titanium and titanium alloys rolled bars to the high-quality bars. .sub.B - ultimate strength; .sub.0.2 - yield strength; - percentage elongation; - reduction of area; KCU - impact toughness The grade of the rod grains - 1 to 3 points, if required - no more than 4 to 8 points (depending on the nomenclature). Microstructure - of 1 to 5 type, if required of 1 to 7 type. The side of the rod - for rods of square or rectangular cross-section.

(15) Rods made of alloy BTEC (Cyrillic) of the first group correspond to the requirements to the large-sized rolled rods made from titanium alloys, that of the second groupto the requirements for rolled rods made from titanium alloys.

(16) A similar result was obtained when manufacturing the rods from other + alloys.

(17) Example 3 illustrates the manufacture of rods made of pseudo alloy IIT-3B (Cyrillic) which has a significantly worse plasticity than the alloys in examples 1-2. The ingot of titanium alloy IIT-3B (Cyrillic) (averaged chemical composition 4Al-2V, GOST 19807-74 Wrought titanium and titanium alloys.) was heated to the temperature of Tpt+125 C. and hot forging was carried out on the forging press with the reduction ratio of 1.25. Further, this forged piece was heated to the temperature of Tpt+125 C. and rolled on the screw rolling mill with the reduction ratio of 2.64 Further, the rod was cut into parts, heated to the temperature of Tpt25 C. and hot forged on the forging press with the reduction ratio of 4.14 to a rod of circular cross-section of the finished size.

(18) At the customer's request, additional heat or mechanical treatment was performed.

(19) For rods with a rectangular cross-section, the rod after cutting was heated to the temperature of Tpt25 C. and hot forging was carried out on the forging press with the reduction ratio of 3.16 to a rod of rectangular cross-section of the finished size.

(20) At the customer's request, heat or mechanical treatment was performed.

(21) The properties of the obtained rods of circular and rectangular cross-section of IIT-3B (Cyrillic) alloy are shown in Table 3.

(22) TABLE-US-00003 TABLE 3 Physical and mechanical properties of heat-treated rods made from titanium alloy IIT-3B (Cyrillic), the direction of samples cutting - longitudinal Test temperature Test temperature 20 C. 350 C. .sub.0.2 KCU, .sub.B .sub.0.2 H, Diameter/side of rod .sub.B, MPa MPa , % , % kJ/m.sup.2 MPa MPa % of mass 100 mm Actual 755-805 683-734 14.8-18.5 35.7-50.0. 1162-1537 489-511 356-420 <0.001 Requirements 638 589 10 25 687 343 294 0.008 100-200 mm Actual 772-788 718-755 14.2-17.8 31.8-42.3 1364-1403 445-471 392-398 <0.001 Requirements 638 589 9 22 589 343 294 0.008 200-400 mm Actual 764-790 712-745 13.9-17.1 29.2-41.8 1420-1501 439-465 401-412 <0.001 Requirements 638 589 8 22 589 343 294 0.008 .sub.B - ultimate strength; .sub.0.2 - yield strength; - percentage elongation; - reduction of area; KCU - impact toughness; H - hydrogen content. The side of the rod - for rods of square or rectangular cross-section.

(23) As follows from Table 3, the rods fully meet the presented requirements.

(24) A similar result was obtained when manufacturing the rods from other pseudo alloys.

(25) The main parameters of the invention Preferred Embodiment within and beyond the claimed limits and the obtained results are shown in Table 4.

(26) TABLE-US-00004 TABLE 4 Forging Rolling Hot deformation No. t.sub.1, C. .sub.1 Heating t.sub.2, C. .sub.2 type t.sub.3, C. .sub.3 Obtained result 1 Tpt + 60 2.15 Yes Tpt + 60 2.78 R Tpt 40 3.63 Meets the requirements, high 2 Tpt + 125 1.27 Yes Tpt + 125 2.64 F Tpt 25 4.14 performance Yes F Tpt 25 3.16 3 Tpt + 130 1.50 No Tpt + 130 3.80 R Tpt 30 2.46 4 Tpt + 130 1.10 No Tpt + 70 4.20 R Tpt 40 4.18 Small deformation on the forging has led to a shrinkage depression on the rolling - low yield ratio and low productivity 5 Tpt + 10 1.31 Yes Tpt + 60 3.10 F Tpt 40 2.91 Cracking at the forging stage, high 6 Tpt + 100 2.85 Yes Tpt + 60 3.10 F Tpt 40 2.91 metal losses at the intermediate turning - low yield ratio and low productivity 7 Tpt + 80 2.31 Yes Tpt + 10 2.78 F Tpt 40 3.63 Defects of continuity in the axial 8 Tpt + 80 2.31 Yes Tpt + 80 8.00 F Tpt 40 3.63 zone occurred during rolling - low yield ratio and low productivity 9 Tpt + 90 2.30 Yes Tpt + 90 4.68 R Tpt 10 2.41 Non-compliance by the structural condition, overheating during hot deformation (R) - defective products 10 Tpt + 90 2.30 Yes Tpt + 90 4.68 R Tpt 80 2.08 Defects of continuity in the axial zone occurred during hot deformation (R) - non-compliance with the requirements 11 Tpt + 90 2.30 Yes Tpt + 90 4.68 F Tpt 80 2.08 Low plasticity of the metal at the stage of hot deformation (F) requires additional heating - increased production cycle, low productivity Note: Rrolling; Fforging.

INDUSTRIAL APPLICABILITY

(27) The proposed invention was tested in the production of JSC CHMZ when manufacturing the rods from alloys IIT-7M, IIT-1M (Cyrillic) (-alloys), BTEC, IIT-3B, 2B (Cyrillic) (pseudo alloys), BT6, BT3-1, BT9 (Cyrillic) (+ alloys) and other titanium alloys.

(28) The results of the invention embodiment showed that the rods with a cross section size from 10 to 180 mm with specified macro- and microstructures and mechanical properties were obtained.

(29) Rods made by the method according to the invention meet the requirements to workpieces or products made from titanium alloys in the form of rods used for the nuclear reactor cores, as well as in the chemical, oil and gas industry, and medicine.

(30) At the same time, the method provides a lower cost by reducing the manufacturing cycle, increasing the yield ratio, significant reduction in the number of defective products.