DE1300302B - Process for the heat treatment of objects made of an aluminum-copper wrought alloy - Google Patents

Description

The invention relates to a further advantageous embodiment of the patent application P 1276334.7-24 described procedure.

The present invention relates to a method for the heat treatment of objects made of an aluminum-copper wrought alloy with 4 to 7 percent by weight copper, optionally lead and / or Bismuth of 0.1 to 0.75% each and / or at least one hardening element made of 0.15 to 1.5% manganese, 0.05 to 0.15% vanadium, 0.05 to 0.3% zirconium and 0.05 to 0.25% titanium, molybdenum, tungsten, Chromium, boron, nickel, cobalt, tantalum and / or niobium, the total amount of these elements, with the exception of manganese, vanadium and zirconium, does not exceed 0.25% and the alloy is free of magnesium and zinc except that these elements may be present as impurities where a Vr solution heat treatment for up to 12 hours of the object at a temperature of 482 to 566 ° C, but below the temperature of a beginning Melting of any alloy phase takes place, the object is quenched, work-hardened and then is stored warm at a temperature of 149 to 204 ° C for 1 to 48 hours, according to patent application P 1276334.7-24. The method according to the invention is characterized in that that the work-hardened object is precipitation hardened according to the following equation:

B-I -0.25CW

t =

(JL) ⁸

\ 350j BI- 0.25 CW

f—

where t is the minimum time required to achieve the maximum yield point, T is the precipitation hardening temperature, CW is the cold deformation in% and

B = antilog

(0.01 Tf [1 + 0.01

According to a preferred embodiment of the method according to the invention, the work-hardened Item precipitation hardened according to the following equation:

log (i + 1) =

(0.01 T) ³ [0.75 + 0, (H)

where t is the minimum time required to achieve a solution potential of 800 mV, T is the precipitation hardening temperature and CW is the percentage cold deformation.

The type of alloy that is improved by the method of the invention should be at least 4% copper to achieve high strength, while on the other hand with a copper content of more than 7% difficulties arise in machining the alloy and the higher copper content also does not lead to a significant increase in strength. Other elements that are in solid Aluminum are practically insoluble, can be present in the small amounts indicated above. If the suitability of the alloy for machining is to be improved, lead and / or bismuth in the specified amounts of 0.1 to 0.75% each and a total amount of no more added as 1.5%. None of the above-mentioned elements affect the specified Amount - as far as known - the physical properties of the alloy in a disadvantageous way. This one Elements in solid aluminum are practically insoluble, they interfere with the dissolution and excretion of the Not copper. In order to avoid such disturbances, the alloys of magnesium and zinc are the Soluble in solid aluminum are practically free, except when these elements are considered impurities are present, whereby the magnesium content should not exceed 0.02% and the zinc content 0.25%. The usual impurities iron and silicon can be tolerated, but it is advisable to use the To limit iron content to a maximum of 0.5%, while the 'silicon content should not exceed 0.3%.

45 The first stage of the process according to the invention consists in the solution treatment at 482 to 566 ° C. for about ¹ I ₄ . up to 12 hours to achieve practically complete dissolution of the copper. After this heating time has elapsed, the alloy must be rapidly quenched to a much lower temperature, generally room temperature. The cooling or quenching can be carried out by conventional methods, such as. B. in water, by spraying with water or with the help of a fan, if the object is not too thick. When the alloy article room temperature or a temperature has reached near the same, it will be cold worked, what either (a curved workpiece straightening) by a reduction in cross section by rolling, pressing or drawing or ^Λ by other known MetalÜbearbeitungsverfahren or simply by smoothing and stretching of the article obtained will. To achieve a significant increase in strength, it is necessary to reduce the area, which should generally be at least about 1%. A cross-section reduction of more than 20% offers no advantage. The extent of cold deformation depends on the type of object. In the case of extruded products, in contrast to sheet metal, only a relatively small reduction in cross section can be achieved by stretching. Generally, 1 to 10 percent cold deformation is preferred. The special relationships specified above using a formula were determined [cf. Equation (I)], which concern the yield strength and the maximum corrosion resistance. Exceeding the minimum duration t z. B. by 2 hours the stretching

55

6o

limit generally less than 2.1 kp / mm ² . The corrosion resistance of a product treated in this way is adequate for many purposes.

In order to achieve maximum corrosion resistance, although a certain deterioration in the yield strength must be accepted, the minimum duration of precipitation hardening should be determined according to equation (II) above. Equation (II) assumes that the maximum corrosion resistance is achieved when the solution potential of the alloy has a value of not less than 800 mV, determined in an aqueous 3.5% NaCl standard solution containing 0.3% H by volume _{Contains 2} O ₂ , measured against a standard calomel half-cell.

As for the relationship between the amount of cold working and the temperature of precipitation hardening, e.g. For example, a sheet having a l, 5% thickness reduction experienced by cold rolling can be precipitation hardened at a temperature of 117 ° C while a 10% abgewalztes sheet at 163 ° C can be precipitation hardened.

The maximum yield strength given above varies with the copper content of the alloy and the cold working. The yield strength will generally be within the range of 28.1 to 45.7 kgf / mm ² . A minimum yield strength is often required for special workpieces. The conditions of cold working and precipitation hardening must then be chosen so that this minimum yield point is reached or exceeded.

Precipitation hardening is carried out in such a way that the cold-worked workpiece is aged for 1 to 48 hours at a temperature of 149 to 204 ^° C. The choice of special conditions is based on the equations given above. At temperatures below 149 ° C the time required to achieve the desired values for practical purposes is too long, while above the present opposite conditions of 204 ⁰ C, that is, the time is so short that a system becomes difficult.

Although the above description of the method according to the invention deals with the treatment of an entire object, parts of an object can also advantageously be treated according to the method according to the invention. This applies both to welded joints of objects made of this Al-Cu alloy with a welding material of a similar composition and to weld beads made of a material of this type. The mechanical properties of the weld bead and the adjacent workpiece area are improved.

Claims (5)

Patent claims: 1. Process for the heat treatment of objects made of an aluminum-copper wrought alloy with 4 to 7 percent by weight copper, optionally lead and / or bismuth at 0.1 to 0.75% each and / or at least one hardening element from 0.15 to 1, 5% manganese, 0.05 to 0.15% vanadium, 0.05 to 0.3% zirconium and 0.05 to 0.25% titanium, molybdenum, tungsten, chromium, boron, nickel, cobalt, tantalum and / or Niobium, the total amount of these elements, with the exception of manganese, vanadium and zirconium, not exceeding 0.25% and the alloy being free of magnesium and zinc with the exception that these elements may be present as impurities, with a ¹ J ₄ - to 12stündiges solution heat treating the article at a temperature of 482-566 ° C, however, any alloy phases takes place below the temperature of incipient melting, the object quenched, cold worked and then swapped out hot at a temperature of 149-204 ⁰ C during 1 to 48 hours is, according to Patenta registration P 1276334.7-24, characterized in that the potash-hardened object is precipitation hardened according to the following equation: B - 1 - 0.25 CW + 4S where t is the minimum time required to achieve the maximum yield strength, T is the precipitation hardening temperature, CW is the cold deformation in% and 51 B - Antilog (0.01 Tf [1 is. 2. The method according to claim 1, characterized in that the cold-hardened object after following equation is precipitation hardened: log (i (0.0ΓΓ) ³ [0.75 + 0.35 (CW ²⁵ ] ' where t is the minimum time required to achieve a solution potential of 800 mV, T is the precipitation hardening temperature and CW is the percentage cold deformation. 3. The method according to claim 1 or 2, characterized in that the work hardening by a cold deformation is carried out, by means of which the cross-sectional area of the object is changed 1 to 20%, preferably by 1 to 10%. is decreased. 4. The method according to claim 1 or 2, characterized in that the work hardening by a cold deformation of the object is carried out without increasing its cross-sectional area change, 5. Application of the method according to one of claims 1 to 4 to welds made of alloys of the composition mentioned in claim 1.