Processing technology for inhibiting weld coarse grains of magnesium alloy profiles

Abstract

Disclosed is a processing technology for inhibiting weld coarse grains of magnesium alloy profiles, including the following steps: preparation of a magnesium alloy ingot, homogenization, scalping, extrusion, pre-stretching at room temperature, solution treatment, quenching, stretching correction, artificial aging, etc. The processing technology can effectively control the production of weld coarse grains in extrusion and heat treatment processes of magnesium alloy profiles, and all property indexes of final products are higher than standard requirements.

Claims

1. A processing technology for inhibiting weld coarse grains of magnesium alloy profiles, comprising the following steps: (1) preparing a magnesium alloy ingot, wherein a size of the ingot needs to be selected according to an extruder used; (2) homogenizing the magnesium alloy ingot; (3) scalping the magnesium alloy ingot obtained in step (2); (4) extruding the magnesium alloy ingot obtained in step (3) to obtain a magnesium alloy extruded profile, and at the same time, cooling an extrusion die by using liquid nitrogen during extrusion; (5) pre-stretching the extruded profile obtained in step (4) at room temperature; (6) performing solution treatment on the magnesium alloy profile pre-stretched in step (5), and quenching the magnesium alloy profile after the solution treatment is completed; (7) performing stretching correction on the magnesium alloy profile after the solution treatment in step (6); and (8) artificially aging the profile obtained in step (7), wherein in step (5), a pre-stretching deformation at room temperature is 10-20%, in step (4), a temperature of the magnesium alloy ingot is 250-350° C., a temperature of the die is 280-380° C., a temperature of an extrusion cylinder is 260-360° C., an extrusion speed is 0.5-5 mm/s, and an outlet pressure of the liquid nitrogen is 0.5-0.6 MPa, in step (6), a solution treatment temperature is 380-420° C., and a solution treatment time is 1-3 h, in step (7), a stretching deformation of the stretching correction is 0.5-1.5%, in step (8), an aging temperature is 98-225° C., and an aging time is 12-144 h.

2. The processing technology for inhibiting weld coarse grains of magnesium alloy profiles according to claim 1, wherein the size of the ingot is Φ120×400 mm.

3. The processing technology for inhibiting weld coarse grains of magnesium alloy profiles according to claim 1, wherein the temperature of the homogenization is 380-410° C., and a holding time is 10-24 h.

4. The processing technology for inhibiting weld coarse grains of magnesium alloy profiles according to claim 1, wherein during the scalping, a processing amount of a surface layer is 1-6 mm, and a surface roughness Ra is less than or equal to 23 μm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings that form a part of the present invention are used to provide further understanding of the present invention, and the exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute improper limitations on the present invention.

(2) FIG. 1 is a flow chart of a technological method of the present invention.

(3) FIG. 2 is a photograph of part of the grain structure in a weld zone of a magnesium alloy profile when no pre-stretching treatment is performed.

(4) FIG. 3 is a photograph of part of the grain structure in a weld zone of a magnesium alloy profile when 5% pre-stretching treatment is performed.

(5) FIG. 4 is a photograph of part of the grain structure in a weld zone of a magnesium alloy profile when 10% pre-stretching treatment is performed.

(6) FIG. 5 is a photograph of part of the grain structure in a weld zone of a magnesium alloy profile when 20% pre-stretching treatment is performed.

DESCRIPTION OF THE EMBODIMENTS

(7) The present invention is described in detail below with reference to specific embodiments.

(8) The present invention provides a processing technology for inhibiting weld coarse grains of magnesium alloy profiles. Specific technological processes are shown in FIG. 1. Specific implementations are as follows:

Embodiment 1

(9) A processing technology for inhibiting weld coarse grains of magnesium alloy profiles included the following specific steps:

(10) (1) An ordinary commercial ZK60 magnesium alloy ingot was prepared, wherein the size of the ingot was Φ120×400 mm.

(11) (2) The magnesium alloy ingot was homogenized at 410° C., wherein a holding time was 24 h.

(12) (3) The magnesium alloy ingot obtained in step (2) was scalped. During the scalping, a processing amount of a surface layer was 1 mm, and a surface roughness Ra was less than or equal to 23 μm.

(13) (4) The magnesium alloy ingot obtained in step (3) was extruded to obtain a magnesium alloy extruded profile, wherein a temperature of a cast rod was 350° C., a temperature of a die was 380° C., a temperature of an extrusion cylinder was 360° C., and an extrusion speed was 5 mm/s. In addition, during the extrusion, an extrusion die was cooled by using liquid nitrogen, and an outlet pressure of the liquid nitrogen was 0.5 MPa.

(14) (5) The extruded profile obtained in step (4) was pre-stretched at room temperature, wherein a stretching deformation rate was 10%.

(15) (6) Solution treatment was performed on the magnesium alloy profile pre-stretched in step (5) at 420° C. for 1 h. Quenching was performed after the solution treatment was completed.

(16) (7) Stretching correction was performed on the magnesium alloy profile after the solution treatment in step (6), wherein a stretching deformation rate was 1.5%.

(17) (8) The profile obtained in step (7) was artificially aged at 225° C. for 12 h.

(18) The tensile strength, yield strength, elongation at break and weld zone hardness of the magnesium alloy profile obtained in Embodiment 1 were 278 MPa, 224 MPa, 0.13 and 59 HV respectively.

Embodiment 2

(19) A processing technology for inhibiting weld coarse grains of magnesium alloy profiles included the following specific steps:

(20) (1) An ordinary commercial ZK60 magnesium alloy ingot was prepared, wherein the size of the ingot was Φ120×400 mm.

(21) (2) The magnesium alloy ingot was homogenized at 380° C., wherein a holding time was 24 h.

(22) (3) The magnesium alloy ingot obtained in step (2) was scalped. During the scalping, a processing amount of a surface layer was 6 mm, and a surface roughness Ra was less than or equal to 23 μm.

(23) (4) The magnesium alloy ingot obtained in step (3) was extruded to obtain a magnesium alloy extruded profile, wherein a temperature of a cast rod was 250° C., a temperature of a die was 280° C., a temperature of an extrusion cylinder was 260° C., and an extrusion speed was 0.5 mm/s. In addition, during the extrusion, an extrusion die is cooled by using liquid nitrogen, and an outlet pressure of the liquid nitrogen was 0.6 MPa.

(24) (5) The extruded profile obtained in step (4) was pre-stretched at room temperature, wherein a stretching deformation rate was 20%.

(25) (6) Solution treatment was performed on the magnesium alloy profile pre-stretched in step (5) at 380° C. for 3 h. Quenching was performed after the solution treatment was completed.

(26) (7) Stretching correction was performed on the magnesium alloy profile after the solution treatment in step (6), wherein a stretching deformation rate was 0.5%.

(27) (8) The profile obtained in step (7) was artificially aged at 98° C. for 144 h.

(28) The tensile strength, yield strength, elongation at break and weld zone hardness of the magnesium alloy profile obtained in Embodiment 2 were 335 MPa, 276 MPa, 0.18 and 72 HV respectively.

Embodiment 3

(29) A processing technology for inhibiting weld coarse grains of magnesium alloy profiles included the following specific steps:

(30) (1) An ordinary commercial ZK60 magnesium alloy ingot was prepared, wherein the size of the ingot was Φ120×400 mm.

(31) (2) The magnesium alloy ingot was homogenized at 400° C., wherein a holding time was 20 h.

(32) (3) The magnesium alloy ingot obtained in step (2) was scalped. During the scalping, a processing amount of a surface layer was 4 mm, and a surface roughness Ra was less than or equal to 23 μm.

(33) (4) The magnesium alloy ingot obtained in step (3) was extruded to obtain a magnesium alloy extruded profile, wherein a temperature of a cast rod was 300° C., a temperature of a die was 320° C., a temperature of an extrusion cylinder was 300° C., and an extrusion speed was 2 mm/s. In addition, during the extrusion, an extrusion die is cooled by using liquid nitrogen, and an outlet pressure of the liquid nitrogen was 0.6 MPa.

(34) (5) The extruded profile obtained in step (4) was pre-stretched at room temperature, wherein a stretching deformation rate was 15%.

(35) (6) Solution treatment was performed on the magnesium alloy profile pre-stretched in step (5) at 380° C. for 3 h. Quenching was performed after the solution treatment was completed.

(36) (7) Stretching correction was performed on the magnesium alloy profile after the solution treatment in step (6), wherein a stretching deformation rate was 1.0%.

(37) (8) The profile obtained in step (7) was artificially aged at 200° C. for 20 h.

(38) The tensile strength, yield strength, elongation at break and weld zone hardness of the magnesium alloy profile obtained in Embodiment 3 were 308 MPa, 241 MPa, 0.15 and 65 HV respectively.

(39) Magnesium alloy profiles treated according to the above processing technology for inhibiting weld coarse grains of magnesium alloy profiles are different in that no pre-stretching treatment is performed on the magnesium alloy profile (1), 5% pre-stretching treatment is performed on the magnesium alloy profile (2), 10% pre-stretching treatment is performed on the magnesium alloy profile (3), and 20% pre-stretching treatment is performed on the magnesium alloy profile (4). After solution treatment (temperature: 400° C., time: 1 h) is performed on the above four magnesium alloy profiles, photographs of part of the grain structure in weld zones of the magnesium alloy profiles are studied. As shown in FIG. 2, FIG. 3, FIG. 4 and FIG. 5, the grain size of a weld zone of the magnesium alloy profile (1) is about 250 μm, and a matrix zone is also composed of recrystallized grains with a grain size of about 20 μm and elongated deformed grains; the grain size of a weld zone of the magnesium alloy profile (2) is about 200 μm, and a matrix zone is also composed of recrystallized grains with a grain size of about 80 μm; the grain size of a weld zone of the magnesium alloy profile (3) is about 30 μm, and a matrix zone is also composed of recrystallized grains with a grain size of about 20 μm; and the grain size of a weld zone of the magnesium alloy profile (4) is about 9 μm, and a matrix zone is also composed of recrystallized grains with a grain size of about 10 μm. It can be seen that the pre-stretching treatment has a great influence on the coarse grains in the weld zone of the magnesium alloy profile. By the pre-stretching treatment at room temperature, the deformation stored energy distribution, texture type and strength of the grains in the weld zone of the magnesium alloy profile are adjusted. Through comparative experiments, it can be seen that when the pre-stretching deformation rate is 10%-20%, the refining degree of the grains in the weld zone after the solution treatment is obvious. With the increase of the pre-stretching deformation rate, the refining degree of the grains in the weld zone after the solution treatment is gradually increased.