Thin sheet manufacturing method

FIELD: metallurgy.

SUBSTANCE: manufacturing method of thin sheets from pseudo-alpha titanium alloys involves deformation of an ingot into a slab, mechanical processing of a slab, multipass rolling of a slab for a semi-finished rolled stock, cutting of the semi-finished rolled stock into sheet workpieces, their assembly into a pack and its rolling and finishing operations. Multipass slab rolling is performed at several stages. After the semi-finished rolled stock is cut into sheet workpieces, their finishing operations are performed. Assembly of sheet workpieces into a pack is performed by laying so that direction of sheets of the previous rolling is perpendicular to direction of sheets of the next rolling. Rolling of the pack is performed till a final size, and then, obtained sheets are removed from it and finishing operations are performed.

EFFECT: obtaining a microstructure of sheets, which provides high and uniform level of strength and plastic properties.

1 dwg, 2 tbl

 

The invention relates to the processing of metals by pressure, and in particular to methods of manufacturing thin sheets of pseudo-alpha titanium alloys for the manufacture of parts of aircraft.

A known method of manufacturing parts of the pseudo-alpha titanium alloys, including heat in the beta region above the temperature of polymorphic transformation (hereinafter CCI), cooling, re-heating in the two-phase region, repeated deformation in this region during the cooling process, re-cooling, the final heating in the two-phase region, the shutter speed and cooling (A.S. USSR №1740487, publ. 15.06.1992). The known method is intended for manufacturing of forged and stamped products and not optimized for a sheet of semi-finished products.

A known method of manufacturing sheets of low-alloy titanium alloys, including heat flat ingot, hot rolling the strips, cut strips on the billet, heating the billet in a two-phase region, rolling them on the sheets, heat treatment, etching, editing, cutting sheets to finished size (patent RF №2198237, publ. 10.02.2003). The known method does not take into account technological features pseudo-alpha titanium alloys.

A known method of manufacturing a particularly thin sheets of high-strength titanium alloys, including the production of the original sheet, the collection is a package of sheet blanks with obmazyvaem coating using case hot rolling and heat treatment batch, split and finish of the obtained sheets (Patent RF №2381297, publ. 10.02.2010) prototype. However, in the known method are not regulated modes of thermomechanical processing, which does not allow for a given level of mechanical properties and structure.

The problem to which the invention is directed, is the development of a method for manufacturing thin sheets of pseudo-alpha titanium alloys having a homogeneous structure and mechanical properties, and high surface quality and geometrical parameters.

The technical result achieved in the implementation of the invention is to obtain the microstructure of sheets, providing a high and uniform level of strength and plastic properties.

This object is achieved in that in the method of manufacturing thin sheets of pseudo-alpha titanium alloys, including deformation of the ingot into a slab, machining slab, rolling slab on steel, cutting steel into billets, rolling blanks on worksheets and adjusting operations according to the invention for the manufacture of sheets use the slab obtained from the deformed ingot after heating to a temperature of 150÷250°C higher CCI with a total degree of deformation of 30÷60% and after heating at 100÷200°C above the CCI with a total degree of deformat and 40÷70%, perform multi-pass rolling slab on steel by heating to a temperature of 90÷150° above the chamber of Commerce with the degree of deformation per pass 10÷20% and additional heating after reaching the degree of deformation 25÷35% when the total deformation at this temperature, 50÷80%, heating to a temperature of 30-60°With the lower chamber of Commerce with the degree of deformation per pass 5÷10%, when the total deformation at this temperature, 15÷25%, heating to a temperature of 80÷120°C above the chamber of Commerce with the degree of deformation per pass 10÷20% and more the heating after reaching the degree of deformation 25÷35% when the total deformation at this temperature, 50÷80%, heating to a temperature of 50÷70°C lower chamber of Commerce with the degree of deformation per pass 5÷10% and an additional heating after reaching the degree of deformation 15÷25% of the total deformation at this temperature, 40÷65%, then perform the cutting of rolled sheet metal workpiece and adjusting the operation, Assembly, sheet blanks in the package so that the direction of the leaves of the previous rolling was perpendicular to the direction of the sheets subsequent rolling, rolling package the finished size with heating to a temperature of 70÷100°C lower chamber of Commerce with the degree of deformation of the package for the passage 10÷20% and additional heating of the package after reaching the degree of deformation 25÷35% when the total deformation of the package 55÷70%.

The method is implemented the trail the way.

Produced and machined cylindrical ingot is heated to a temperature of 150÷250°C higher chamber and subjected to forging, with a total degree of deformation of 30÷60%, which destroys the cast structure, averages the chemical composition of the alloy, compacting the workpiece, eliminating such casting defects such as voids, sinks and other Temperature below the specified limit leads to the reduction of plastic characteristics, the difficulty of deformation and the appearance of surface cracking, the heating temperature is above the specified limit causes a significant increase in gas-saturated layer, which leads to superficial lacerations during deformation, deterioration of the metal surface and consequently to increased metal removal with the billet surface. The following strain with a total degree 40÷70% after heating at 100÷200°C above the CCI allows multiple grind the grain size relative to the initial state. For complete removal of surface defects resulting slab mechanical process from all sides. Further multi-pass rolling of the slab to tackle with the total degree of deformation of 50÷80% after heating to a temperature of 90÷150°C above the CCI increases the ductility of the metal and limits the formation of defects during subsequent deformation in the (α+β)region. The slab is rolled with the degree of deformation is then for the passage 10÷20%, and after reaching the degree of deformation 25÷35%, produce additional heating, which improves the ductility of the metal, to keep the process rolling satisfactory surface quality and to avoid the formation of cracks. After deformation β is effected by heating to a temperature of 30÷60°C lower chamber of Commerce and carry out multi-pass rolling with a total deformation 15÷25% for the destruction of large angle grain boundaries, increasing the density of dislocations, i.e. they perform the deformation hardening. The degree of deformation per pass 5÷10% is determined by technological properties of alloys at this temperature deformation. The resulting metal has a higher internal energy and subsequent heating to a temperature of 80÷120°C above the CCI with the total deformation 50÷80% is accompanied by recrystallization from grinding grain, allowing you to get in the workpiece being machined equiaxial macasero. Then take further rolling with level 40÷65% after heating at 50÷70°C lower chamber of Commerce to prepare a given microstructure to obtain the mechanical properties in the transverse direction, to the further batch rolling to produce the preparation of the microstructure to obtain the mechanical properties mainly in the longitudinal direction. The degree of deformation per pass 5÷10% is determined by the technology the properties and conditions of achievement of the minimum thickness variation of the sheet workpiece before the batch rolling. At this stage, after reaching the degree of deformation 15÷25% produce additional hot rolled, allowing you to maintain a satisfactory surface quality.

In the absence of the possibility of applying cold rolling to obtain thin sheets because of the low ductility of the alloys and high loads on the mill because of the high deformation resistance of the final deformation of the sheets on the finished size is carried out by the batch method, for which the rolled cut-to-length sheet, while the sheet stack in the direction of rolling so that the direction of the subsequent rolling was perpendicular to the previous direction of rolling. Changing the direction of rolling of the package allows to obtain optimal crystallographic texture in the leaves and reduce the anisotropy of mechanical properties. Temperature range heating (heating at 70÷100°C higher CCI) and the degree of deformation at this stage 55÷70% can increase the level grinding and coagulation of primary α-phase, which contributes to obtaining equiaxial fine micrograins, providing uniform mechanical properties in all directions. After the batch rolling the sheets removed from the package and carry adjusting processing, test sheets and in which akuku.

Industrial applicability is confirmed by specific example of carrying out the invention.

To obtain sheets of thickness 2 mm were smelted ingots of pseudo-alpha titanium alloy with a diameter of 540 mm weight 740 kg

The chemical composition of the alloy is given in table 1. The temperature of polymorphic transformation alloy 1008°C.

Table 1
The sampling location sampleMass fraction of elements, %
AlMoZrSnFeSiNbGdAboutNH
Top6,400,513,962,120,0340,151,390,250,1160,0120,0010,002
Bottom 6,690,563,482,240,0350,151,350,190,1190,0040,002<0,002

The ingot was subjected to forging by flattening by forming a thickness of 250 mm after heating to 1200°C (190°C higher CCI) with deformation rate of 53%. Then the billet was heated to a temperature of 1150°C (140°C above CCI) and has been forging a billet of rectangular cross section with dimensions of 130×680×1700 mm with a total degree of deformation of 55%. Further forged slab struck at the size 117×680×1100 mm Slab was heated to the set temperature of 1130°C (120°C higher CCI) and rolled for 2 passes with the degree of deformation in each pass, respectively 16.3% and 10.6% of mm, then when reaching the total deformation for heating 30% tackle was heated at the same installation temperature. Further rolling was carried out as previously described for a thickness of 30 mm, the total degree of deformation at the stage of 74.4%. To improve the surface quality of the rolled subjected to mechanical treatment (solid abrasive cleaning) with the removal of 0.30 mm on the side. Next, the strips were heated to a temperature of 970°C (40°C below CCI) and p is oizvodil rolling in 2 passes for 25 mm thick with degrees of deformation in each pass, respectively, 10% and 7.5%, with a total deformation of 15%. Further rolling was carried out at a temperature of 1100°C (80°C higher CCI) at a thickness of 12 mm Rolling was carried out in 2 passes with degrees of deformation in each pass, respectively, 10 and 20% and, after reaching the accumulated strain of 30% was carried out by heating at the same temperature. The total deformation rate was 58%. Further rolling was carried out at a temperature of 950°C (60°C below CCI), rolled for 2 passes to a thickness of 10 mm with a degree of deformation of 5÷10% in each pass with total degree of deformation of 15%. Further, the rolling was carried out at a temperature of 950°C (60°C below CCI), rolled for 2 passes to the thickness of 8.5 mm with a degree of deformation of 5÷10% in each pass with total degree of deformation of 15%. Further, the rolling was carried out at a temperature of 950°C (60°C below CCI), rolled for 2 passes to the thickness of 7.3 mm, with a deformation rate of 5÷10% in each pass with total degree of deformation of 15%. Further, the rolling was carried out at a temperature of 950°C (60°C below CCI), rolled for 2 passes to the thickness of 6.2 mm with a degree of deformation of 5÷10% in each pass. The total degree of deformation at a temperature of 950°C was 49%. Then the rolled cut-to-length sheet, spent adjusting operation and collecting the bags, when this sheet was placed in the package so that the direction of the subsequent use of the TCI was perpendicular to the previous direction of rolling. In the package was placed on sheet 3 of the workpiece, taking into account the upper and lower steel plates of a thickness of the package accounted for 50.9 mm Then perform the final stage of rolling the batch method, for which the package was heated to a temperature of 920°C (90°C below CCI) and rolled for 2 passes to the thickness of 38.5 mm (degree of deformation 16% and 10% in the aisles). Then was carried out by heating and rolling for 2 passes on the thickness of the package 29 mm (degree of deformation of the passages 16% and 10%, the total degree of deformation of 24.7%), followed by manufactured heating and rolling of the package for 2 passes on the thickness of the package 22 mm (degree of deformation of the passages 16% and 10%), the overall degree of deformation 24.0%), and then carried out the heating and rolling for 2 passes on the thickness of the package 16 mm (degree of deformation of the passages 16% and 13%, the total deformation of 27.2%). The total degree of deformation of the package was 61%. Then carried out the disassembly of packets, resulting in the obtained sheet sizes 2,3÷2,4×900÷910×2900÷2950 mm

The obtained sheets were produced by adjusting the processing, cutting to final size, sampling and testing of mechanical properties and study patterns. The results of testing the mechanical properties of the sheets are given in table 2, images of the microstructure of the sheets is presented in figure 1. The surface quality of sheet met all the requirements of normative documents, cracks and race is of loani not recorded.

Table 2
The condition of the test sampleMechanical properties
The yield strength, σof 0.2, MPaTensile strength, σin, MPaElongation, δ,%
Longitudinal directionTransverse directionLongitudinal directionTransverse directionLongitudinal directionTransverse direction
After the heat treatment regime: 930°C - exposure 60 minutes air cooling927903100198315,814,8
After the heat treatment regime: 950°C - exposure 60 minutes air cooling92290899198915,2/td> 14,3
Required level-≥950≥14

Thus, the present invention compared to the known methods, can be obtained from pseudo-alpha titanium alloy thin sheets with a high level of mechanical properties with minimal anisotropy and a homogeneous structure and a satisfactory surface quality.

A method of manufacturing thin sheets of pseudo-alpha titanium alloys, including deformation of the ingot into a slab, machining slab, multi-pass rolling slab on steel, cutting steel sheet billets, their Assembly into the package and its rolling and adjusting operation, characterized in that the deformation of the ingot in the slab is carried out by heating it to a temperature of 150÷250°C higher than the temperature of polymorphic transformation (CCI) and deformation from the total deformation rate 30÷60%, subsequent heating to a temperature of 100÷200°C higher CCI and deformation from the total deformation rate 40÷70%, multi-pass rolling of the slab is carried out in several stages, in which the slab is heated to a temperature of 90÷150°C higher CCI and rolled with a total degree of deformation at this temperature, 50÷80%, statutorily for passage 10÷20% and additional heating after reaching the degree of deformation 25÷35%, the strips are heated to a temperature of 30÷60°C lower chamber of Commerce and rolled with a total degree of deformation at this temperature, 15÷25% and the degree of deformation per pass 5÷10%, steel is heated to a temperature of 80÷120°C higher CCI and rolled with a total degree of deformation at this temperature, 50÷80%, degree of deformation per pass 10÷20% and additional heating after reaching the degree of deformation 25÷35%, steel is heated to a temperature of 50÷70°C lower chamber of Commerce and rolled with the total deformation at this 40 ° ÷65%, degree of deformation per pass 5÷10% and an additional heating after reaching the degree of deformation 15÷25%, after cutting the strips on the sheet hold their auxiliary operations, Assembly, sheet blanks in the package is done by laying so that the direction of the leaves of the previous rolling was perpendicular to the direction of the sheets subsequent rolling, rolling package the finished size lead by heating to a temperature of 70÷100°C lower chamber of Commerce and rolling with a total degree of deformation 55÷70%, the degree of deformation per pass 10÷20% and additional heatings package after reaching the degree of deformation 25÷35%, then from the package, remove the sheets and carry out auxiliary operations.



 

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