RU2754541C1 - Deformable aluminium-based alloy and product made therefrom - Google Patents

Abstract

FIELD: non-ferrous metallurgy.

SUBSTANCE: invention relates to the field of non-ferrous metallurgy, in particular to head-hardened alloys based on the aluminium-magnesium-silicon system, intended for application in structural elements of the petroleum and gas industry, in particular, for manufacturing drill pipes and cylindrical hollow ingots. The deformable aluminium-based alloy comprises, wt.%: magnesium 1.45 to 1.85, copper 0.5 to 1.0, silicon 0.7 to 1.2, zinc 0.25 to 0.8, manganese 0.1 to 0.5, chromium 0.1 to 0.3, iron 0.1 to 0.3, nickel 0.25-0.6, no less than one element from the group containing: titanium 0.02 to 0.12, boron 0.001 to 0.02, carbon 0.001 to 0.01, aluminium and impurities the rest, wherein the Ni/Fe content ratio is no less than 1.

EFFECT: development of a deformable aluminium alloy with high corrosion resistance, exhibiting high strength at temperatures up to 150°C, yield strength of no lower than 330 MPa, and relatively high strength at room temperature, yield strength of no lower than 370 MPa.

5 cl, 1 dwg, 2 tbl, 1 ex

Description

Technology area

The invention relates to the field of non-ferrous metallurgy, in particular to heat-hardening alloys based on the aluminum-magnesium-silicon system, intended for use in structural elements for various purposes in the oil and gas industry.

State of the art

Under modern conditions and drilling technologies, a significant role is played by the total mass of the drill string, with an increase in its mass and dimensions, the frictional forces and working forces increase, and, consequently, its stress-strain state becomes more complicated. Taking into account the low weight and high corrosion resistance of aluminum materials, the most promising direction is the replacement of steel with aluminum alloys in the construction of drill pipes. Taking into account the operating temperatures of the drill strings (up to 150 ° C) associated with the depth of drilling, and the use of drilling fluids with a pH of 4 to 10 in field development, the aluminum alloy must provide a sufficient level of strength at these temperatures and be corrosion-resistant in the environment of these solutions. ...

Known wrought aluminum alloy D16 (Al-Cu-Mg system), widely used for the manufacture of drill pipes (GOST 4784-2019 "Aluminum and wrought aluminum alloys. Grades"), containing magnesium, copper, silicon, iron, chromium, manganese, zinc , titanium, with the following ratio of components (wt%):

Magnesium 1.2-1.8 Copper 3.8-4.9 Iron 0.5 Silicon 0.5 Chromium 0.1 Manganese 0.3-0.9 Zinc 0.25 Titanium 0.15 Aluminum Rest.

The alloy has strength at room temperature 420 MPa, ductility 10% (GOST 18482-79 Pipes extruded from aluminum and aluminum alloys.

Specifications), and also has an operating temperature of up to 160 ° C, which makes it possible to use pipes made of this alloy for ultra-deep drilling. However, due to the high copper content (up to 4.9 wt%), this alloy has a low rate of general corrosion, as well as exfoliation (and intergranular (ICC) corrosion. Therefore, the service life of such pipes is limited.

Known deformed aluminum alloy brand 1953, used for the manufacture of drill pipes (GOST 4784-2019 "Aluminum and wrought aluminum alloys. Grades"), containing magnesium, zinc, copper, manganese, chromium, and titanium in the following ratio, wt. %:

Magnesium 2.4-3.0 Zinc 5.6-6.2 Copper 0.4-0.8 Chromium 0.15-0.25 Manganese 0.1-0.3 Titanium 0.02-0.10 Aluminum Rest.

The alloy has a high strength index at room temperature (530 MPa) and has good corrosion resistance. The main disadvantage of this alloy is its low operating temperature (up to 120 ° C). An increase in the operating temperature above 120 ° C leads to a significant decrease in the strength properties, which does not allow it to be used when drilling superdeep wells. In addition, the alloy has a relatively low level of relative elongation of 7%, which is insufficient during the operation of drill pipes and can lead to their destruction during drilling.

Known aluminum alloy for the production of drill pipes, related to the alloys of the Al-Mg-Si system (RF patent No. 2385359, C22C 21/18, publ. 03/27/2010), containing the following ratio of components, wt. %:

Magnesium 0.9-1.3 Copper 0.8-1.7 Silicon 0.7-1.1 Manganese 0.2-0.6 Zinc 0.4-0.8 Titanium 0.01-0.03 Chromium 0.18-0.3 Molybdenum 0.0007-0.012 Calcium 0.05-0.15 Beryllium 0.00005-0.00015 Aluminum Rest.

The alloy has a high ultimate strength at a temperature of 150 ° C (440 MPa) due to the formation of finely dispersed phases that are resistant to coagulation at high temperatures. The main disadvantage of this alloy is the high copper content, which leads to a decrease in corrosion resistance (the alloy has a score of 5 exfoliating corrosion).

Known wrought aluminum-based alloy (RF patent No. 2215055, C22C 21/08, publ. 27.10.2003), related to alloys of the Al-Mg-Si system. The alloy has high mechanical properties, satisfactory corrosion resistance and is suitable for use as a structural material in transport engineering, including for drill pipes. The proposed aluminum-based alloy contains, wt. %:

Magnesium 0.7-1.4 Zinc 0.01-0.8 Silicon 0.6-1.2 Nickel 0.005-0.5 Copper 0.6-1.4

at least one element from the group, mass. %:

Scandium 0.005-0.4 Cerium 0.005-0.2

and at least one element from the group, mass. %:

Chromium 0.01-0.3 Manganese 0.01-0.5 Titanium 0.01-0.3 Zirconium 0.005-0.2 Aluminum Rest.

The main disadvantage of this aluminum alloy is the presence of a large number of transition and rare earth elements, such as scandium, nickel, cerium, copper, chromium, zirconium and their high total concentration, which leads to a significant increase in the cost of the alloy, as well as a decrease in its manufacturability and plasticity. Low manufacturability will lead to difficulties in the production of semi-finished products from this alloy, and insufficient plasticity can lead to the destruction of the drill pipe during operation.

The closest, taken as a prototype, in technical essence to the claimed invention is a wrought alloy based on aluminum (patent EP 3214191, C22C 21/02; C22F 1/05, publ. 09/06/2017), intended for the production of pressed semifinished products. The alloy contains the following ratio of components, wt. %:

Magnesium 0.85-1.1 Copper no more than 0.75 Silicon 1.3-1.7 Manganese 0.7-0.8 Titanium no more than 0.1 Chromium 0.15-0.25 Iron 0.14-0.25 Zinc no more than 0.2 Zirconium 0.15-0.25 Aluminum Rest.

The alloy has high tensile strength MPa and yield strength. However, the alloy has a low corrosion resistance (MCC reaches 200 microns), which is also caused by a high silicon content. In addition, the declared amount of copper in combination with other elements in the alloy may be insufficient to achieve the required level of strength of semi-finished products at high temperatures.

Disclosure of the invention The objective of this invention is to develop a new technological wrought aluminum alloy with high corrosion resistance, which has high strength at temperatures up to 150 ° C (yield point not lower than 330 MPa) and high strength at room temperature (yield point not lower than 370 MPa).

The technical result of the claimed invention is the creation of an aluminum alloy with the achievement of the above characteristics.

The technical result is achieved due to the fact that in the proposed wrought aluminum-based alloy containing magnesium, zinc, silicon, copper, manganese, chromium, iron, it is new that the composition contains nickel and at least one element from the group: titanium, boron, carbon, with the following ratio of components, wt. %:

Magnesium 1.45-1.85 Copper 0.5-1.0 Silicon 0.7-1.2 Zinc 0.25-0.8 Manganese 0.1-0.5 Chromium 0.1-0.3 Iron 0.1-0.3 Nickel 0.25-0.6

at least one element from a group containing:

Titanium 0.02-0.12 Boron 0.001-0.02 Carbon 0.001-0.01

Aluminum and other impurities, while the following condition for the content of elements in the alloy must be met: Ni / Fe not less than 1.

The proposed invention also relates to an article made of the aforementioned wrought aluminum-based alloy.

The invention is supplemented by particular cases of execution. So, nickel is in the form of phases of eutectic origin, no more than 15 microns in size.

Implementation of the invention

The main phase-hardener in the considered Al-Mg-Si system is β'-Mg ₂ Si. In the proposed invention, the content of Mg and Si is controlled in the range of 1.45-1.85 and 0.7-1.2 wt. %, respectively. At this ratio of components in the alloy, the maximum precipitation of β'-Mg ₂ Si phases after quenching and aging is provided, which provides the required level of strength properties at room temperature. At component concentrations below the specified limits, the required density of precipitates of the β'-Mg ₂ Si phase is not ensured, which will reduce the strength of the alloy, and exceeding will lead to a drop in the processability of the material.

Cu content at a concentration of 0.5-1.0 wt. % provides an additional increase in strength at room and high temperatures, due to secondary precipitation of phases with copper, for example, Q'-AlMgSiCu. Also at the indicated concentration, copper provides solid solution hardening. However, the Cu content should not be higher than 1.0 wt. %, otherwise the corrosion resistance of the material will be significantly reduced.

The presence of Mn in the alloy at the level of 0.1-0.5 wt. % promotes the formation of the α-AlFeSiMn phase instead of the β-AlFeSi and Al ₃ Fe phases, which increases the corrosion resistance of the material and the manufacturability of the material. In addition, the addition of manganese provides an additional increase in strength without reducing corrosion resistance and ductility due to the precipitation of Al ₆ Mn dispersoids during technological heating.

Fe content 0.1-0.3 wt. % together with manganese, chromium, copper and nickel increases strength at room and elevated temperatures due to the release of intermetallics, for example, α-AlFeSiMn, (Fe, Mn) Al ₆ , AlFeSi (Mn, Cr), Al ₉ FeNi and others, and also improves casting properties through the formation of eutectic. At the same time, the addition of iron has a negative effect on the corrosion resistance of aluminum alloys, and an excess of phases with iron can lead to a deterioration in the processability of the material, therefore, its content must be limited. The introduction of iron at a concentration of less than 0.1 wt. % does not allow to provide the required increase in the level of strength, including at elevated temperatures.

Zn in the amount of 0.25-0.8 wt. % provides solid solution hardening of the alloy without reducing ductility and corrosion resistance. In addition, the upper limit of alloying is selected taking into account the level of the limiting solubility of the element in aluminum to prevent the formation of diffusion mobile phases.

The presence of Cr in an amount of 0.1-0.3 wt. %. provides grain modification during casting, as well as obtaining a non-recrystallized structure after deformation and subsequent heat treatment due to the formation of secondary precipitates of Al ₇ Cr less than 200 nm in size, which contributes to obtaining high strength properties at room and elevated temperatures. When this limit is exceeded during crystallization, there is a tendency to the formation of coarse brittle intermetallic compounds, which can lead to a decrease in corrosion resistance, manufacturability of the alloy, and the appearance of hot cracks.

Ni content in the amount of 0.25-0.6 wt. % provides the required level of strength at elevated temperatures due to the formation of thermally stable compact intermetallic compounds Al ₃ Ni and Al ₉ FeNi with a size of no more than 15 microns. Nickel also provides an increase in casting properties due to the formation of a eutectic with nickel. In addition, nickel contributes to the elimination of coarse precipitates of the iron phase in the structure, especially when the content exceeds the iron content in the alloy, thereby increasing manufacturability. Exceeding the nickel concentration of 0.6 wt. % can lead to the appearance of primary coarse precipitates of Al ₃ Ni, which will contribute to the formation of defects during casting and a decrease in workability during deformation. Additive less than 0.25 wt. % will not ensure the formation of the required density of the precipitated phases of eutectic origin, such as Al ₃ Ni and Al ₉ FeNi.

The addition of at least one element from the group Ti, B, and C provides a fine grain, which reduces the likelihood of hot cracks during casting and increases the workability of the alloy during deformation.

A prerequisite for achieving the technical result is the fulfillment of the ratio: Ni / Fe not less than 1, which provides an optimal combination of mechanical properties at elevated temperatures without a significant decrease in corrosion resistance and manufacturability. When the ratio of elements is less than 1, the required density of precipitates of eutectic phases containing nickel is not provided, which reduces the strength at elevated temperatures.

Zirconium is not used in the alloy, since it weakens the modifying effect of titanium and boron, which necessitates the introduction of titanium and boron in large quantities.

Brief Description of the Drawings FIG. 1 shows a typical structure of a material depicting a phase of the type Mg ₂ Si and (Al, Fe, Ni) of eutectic origin.

Examples of implementation of the invention

Example 1

Cylindrical hollow ingots with an outer diameter of 275 mm and an inner diameter of 90 mm were produced by the method of semi-continuous casting. The chemical composition of the proposed alloys is shown in Table 1.

The ingots were homogenized at a temperature of 530-540 ° C and holding at which the degree of transformation of the ferrous phases and the grain size were optimal. A decrease in the homogenization temperature requires longer exposures in the oven to obtain an optimal result, which is economically inexpedient, and an increase in temperature above the upper limit of the specified temperature range can lead to overburning (irreparable rejects).

Then, on a horizontal press using a needle, the ingots were pressed into pipes with an outer diameter of 100 mm and a wall thickness of 10 mm. Then the pipes were subjected to heat treatment according to the T6 regime. Quenching was carried out at a temperature at which the maximum enrichment of the solid solution occurred. After holding, the pipes were cooled in water, followed by artificial aging at a temperature of 165-175 ° C. Heat-treated pipes according to the T6 mode were examined in a Tescan Mira 3 LM scanning electron microscope, tensile tests at a temperature of 20 ° C in accordance with GOST 10006-80 and at 150 ° C in accordance with GOST 19040-81 with the determination of the main mechanical properties, in addition, the corrosion resistance was determined pipes for intergranular (MCC) corrosion in accordance with GOST 9.021 (solution No. 2). The test results are shown in Table 2.

From the analysis of table 2, it follows that alloy No. 1, which does not satisfy the condition of the content of iron and nickel, due to the appearance of coarse primary precipitates of ferrous phases that do not contain nickel, showed low mechanical properties at room and elevated temperatures. In addition, the corrosion resistance of the alloy was also reduced. The mechanical properties, as well as the corrosion resistance of the rest of the considered alloys, satisfying all the conditions of the formula, correspond to the technical result. Compared to the prototype, the mechanical properties at room temperature of alloys No. 2-5 were slightly lower. However, at elevated temperatures, the alloys under consideration exceed the prototype by more than 5%. A high value of strength at elevated temperatures is achieved by the optimal ratio of Ni and Fe, which ensures the formation in the structure of a sufficient number of strengthening phases of eutectic origin, containing nickel, which are not prone to coagulation under these conditions. In this case, the size of the phases of eutectic origin, containing nickel, does not exceed 15 μm. At the same time, the low Cu content provides additional solid solution hardening without significantly affecting the corrosion resistance. In accordance with the results obtained (see table 2), there was a decrease in the tendency to intergranular corrosion of the considered alloys in relation to the prototype by a factor of 2. Thus, the presence of high mechanical properties at room and elevated temperatures, as well as the presence of high corrosion resistance, make it possible to consider this alloy for the production of products for the oil and gas industry, in particular for the production of drill pipes.

Claims (9)

1. Wrought aluminum-based alloy containing magnesium, zinc, silicon, copper, manganese, chromium, iron, characterized in that the alloy contains nickel and at least one element from the group: titanium, boron, carbon, in the following ratio of components , wt. %: Magnesium 1.45-1.85 Copper 0.5-1.0 Silicon 0.7-1.2 Zinc 0.25-0.8 Manganese 0.1-0.5 Chromium 0.1-0.3 Iron 0.1-0.3 Nickel 0.25-0.6 at least one element from a group containing: Titanium 0.02-0.12 Boron 0.001-0.02 Carbon 0.001-0.01 Aluminum and impurities Rest, in this case, the condition for the content of elements in the Ni / Fe alloy must be at least 1. 2. A wrought aluminum-based alloy according to claim 1, characterized in that nickel is present in it in the form of phases of eutectic origin with a size of not more than 15 microns. 3. A product for the oil and gas industry from a wrought aluminum-based alloy, characterized in that it is made of an alloy according to claim 1. 4. A product according to claim 3, characterized in that it is made in the form of a drill pipe. 5. Product according to claim 3, characterized in that it is made in the form of a cylindrical hollow ingot.

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