CN115466914A

CN115466914A - Method for refining crystal grains on surface layer of welding seam of titanium plate

Info

Publication number: CN115466914A
Application number: CN202211260526.4A
Authority: CN
Inventors: 姜欢; 李名言; 王大月; 王佳佳; 胡静; 徐雁斌
Original assignee: China Steel Precision Materials Co ltd
Current assignee: China Steel Precision Materials Co ltd
Priority date: 2022-10-14
Filing date: 2022-10-14
Publication date: 2022-12-13

Abstract

The invention discloses a method for refining grains on the surface layer of a welding seam of a titanium plate, which comprises the steps of carrying out sand blasting treatment on a titanium plate sample after welding and heat treatment, refining the microstructure of each welded area to a certain extent after sand blasting, wherein the grain size of each welded area after sand blasting can be close to that of a base metal grain; the invention solves the problem that the surface layer crystal grains which are not fully eliminated by heat treatment exist at the welding seam of the titanium plate after welding.

Description

Method for refining surface crystal grains of titanium plate welding seam

Technical Field

The invention belongs to the technical field of metal metallurgy, and relates to a method for refining grains on the surface layer of a welding seam of a titanium plate.

Background

Titanium and titanium alloy have low density, high specific strength, good high temperature resistance, better toughness, excellent fatigue resistance and creep resistance, and thus are widely applied in the fields of aerospace, biomedical, chemical engineering, nuclear energy, power generation and the like, and particularly, titanium and titanium alloy are praised as one of spines in the aerospace industry because the titanium and titanium alloy can meet the design and use requirements of reducing quality, prolonging service life and the like in the field of aerospace, so that titanium and titanium alloy have great development potential and broad application prospects.

Commercially pure titanium has excellent corrosion resistance as the most widely used alloy in industry. The equipment manufactured by adopting the industrial pure titanium has longer service life and lower maintenance cost, thereby having extremely high economic benefit. The welding method of titanium and titanium alloy mainly comprises argon arc welding, electron beam welding, friction stir welding, laser welding and the like. The heat input is large in the welding process, the joint structure is thick, the phenomenon generally exists in each welding mode, the mechanics and the use performance of the joint are seriously influenced, the phenomenon that part of welded joint structures are uneven can be eliminated through postweld heat treatment, but the difference between the structure grains of a welding seam area and the structure of a base material is large after the postweld heat treatment, and the problem that the surface layer grains are too large cannot be completely eliminated only through the heat treatment.

Under the above circumstances, the titanium plate is likely to have coarsened grains after welding, which causes insufficient strength, and it is generally found that the strength of the weld bead is lower than that of the base metal in a tensile test across the weld bead, and therefore, the tensile fracture occurs at the weld bead.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a method for refining surface grains of a welding seam of a titanium plate, which aims to solve the problem that the surface grains which are not fully eliminated by heat treatment exist at the welding seam after the titanium plate is welded.

The invention relates to a method for refining grains on the surface layer of a welding seam of a titanium plate, which is characterized in that a welded and heat-treated titanium plate sample is subjected to sand blasting treatment, so that the microstructure of each welded area after sand blasting is refined to a certain degree, and the grain size of each welded area after sand blasting can be close to the grain size of a base metal.

On the basis of the technical scheme, the equipment used for sand blasting can be a BA600D standard type closed sand blasting machine or other commercial surface sand blasting equipment.

The titanium plate is TA1 (GR 1), TA2 (GR 2), TA3 (GR 3), TA18 (GR 9), TC4 (GR 5), or TA10 (GR 12).

The working distance of the sample from the nozzle is 40-70mm, preferably 55mm.

The effective thickness range of the sand blasting grain refinement is 100-500 mu m; the grain refinement degree can be improved by 2-3 grades, and the improvement range of the mechanical property is 10-30%.

The mechanism of the sand blasting grain refinement of the invention is as follows: the sand blasting provides a high strain condition for the surface layer of the pure titanium sample, so that a large amount of dislocation is generated on the surface layer. The dislocation density is continuously increased along with the increase of deformation, and high-density dislocation gradually forms a dislocation wall, namely a subgrain boundary; as the strain amount continues to increase, new subgrain boundaries composed of dislocations are continuously generated, and the subgrain boundaries formed earlier evolve into the grain boundaries, so that the grains are refined. The mechanical property of the weldment can be improved by grain refinement, for example, the titanium lantern ring can be applied to an electrolytic copper foil cathode roller, and the grain size of the produced copper foil can be improved by grain refinement.

According to the invention, through carrying out sand blasting treatment on the welded and heat-treated titanium plate sample, the microstructure of each welded area is refined to a certain extent after sand blasting, so that the difference between the weld joint area tissue and the base material tissue is further reduced.

Description of the drawings:

FIG. 1 shows a pure titanium TA1 plate base metal phase of 100x (20 μm);

FIG. 2 is a metallographic phase of a weld zone microstructure of 100x (58 μm) after welding of a pure titanium TA1 plate and annealing at 650 ℃/2 h;

FIG. 3 is a metallographic phase of a microstructure of a weld zone of 100x (15 μm) after welding a pure titanium TA1 plate, annealing at 650 ℃/2h and blasting sand for 55 mm;

FIG. 4 is a metallographic phase of a weld zone microstructure of 100x (22 μm) after welding a pure titanium TA1 plate, annealing at 650 ℃/2h and blasting sand for 65 mm;

FIG. 5 shows the tensile failure location of the weldment (comparative example a on the left, example b in the middle, and example c on the right).

The specific implementation mode is as follows:

the invention is further illustrated by the following examples, which are intended to be illustrative and not limiting of the scope of the invention.

Taking a common pure titanium TA1 plate with the thickness of 4.5mm as an example, welding wires are adopted for welding, the welding parameters are shown in Table 1, and the microstructure of the base material of the titanium plate is shown in figure 1.

TABLE 1 pure titanium TA1 sheet weld parameters

Welding current

Welding voltage

Welding speed

Main nozzle

Support cover

Back side of the panel

Number of layers

120A

25V

0.5cm/s

20L/min

12L/min

10L/min

3 layers of

The titanium plate sample which is welded by the former welding wire and subjected to heat treatment is subjected to sand blasting treatment, the used equipment is a BA600D standard closed sand blasting machine, the working distance from the sample to the nozzle in the embodiment b is 55mm, the working distance from the sample to the nozzle in the embodiment c is 65mm, and the sprayed material is 120-mesh Al ₂ O ₃ Ceramic beads with a blasting pressure of 0.6MPa and a blasting time of 25min, the total deformation layer thickness after blasting of example b being about 110 μm and after blasting of example c being about 95 μm.

Comparative example a: and (3) welding by using a TA1 titanium plate and annealing heat treatment at 650 ℃/2h, wherein the microstructure of a welding seam area is shown in figure 2.

Example b: welding a TA1 titanium plate, annealing heat treatment at 650 ℃/2h and sand blasting treatment of 55mm, wherein the microstructure of a welding seam area is shown in figure 3.

Example c: welding by using a TA1 titanium plate, annealing heat treatment at 650 ℃/2h and sand blasting treatment at 65mm, wherein the microstructure of a welding seam area is shown in figure 4.

TABLE 2 titanium sheet working methods and Performance comparisons of comparative examples and examples

The grain size of the titanium plate base metal adopted in the welding test is 8 grade, the grain size of the welding seam area after tailor welding is 5 grade, the grain size of the welding seam area is 5.5 grade after annealing at 650 ℃ for 2h, the grain size of the welding seam area is 8.5 grade after sand blasting treatment of example b, and the grain size of the welding seam area is 8 grade after sand blasting treatment of example c. The comparison of the tensile property TS/YS/EL% of the weldment before and after sand blasting is shown in the table 2, and the tensile property is obviously improved after sand blasting; meanwhile, after sand blasting, the tensile fracture position of the weldment is changed from a welding bead to a base metal, as shown in figure 5, the strength of the welding bead is obviously improved.

This creation adopts the sandblast surface treatment mode to enable the regional microstructure of pure titanium plate welding seam to obtain a certain degree and refine to further reduce the difference of welding seam district tissue and substrate tissue, promote weldment tensile properties and welding bead intensity simultaneously.

While the present disclosure has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the disclosure, and therefore, the scope of the disclosure should be limited only by the appended claims.

Claims

1. A method for refining surface grains of a titanium plate welding seam is characterized by comprising the following steps: and carrying out sand blasting treatment on the welded and heat-treated titanium plate sample, so that the microstructure of each welded area after sand blasting is refined to a certain degree, and the grain size of each welded area after sand blasting can be close to that of the base metal.

2. The method for refining surface grains of a welding seam of a titanium plate as claimed in claim 1, wherein the equipment used for sand blasting can be a BA600D standard type closed sand blasting machine or other commercial surface sand blasting equipment.

3. The method for refining the surface grains of the welding seam of the titanium plate as claimed in claim 1, wherein the titanium plate is TA1 (GR 1), TA2 (GR 2), TA3 (GR 3), TA18 (GR 9), TC4 (GR 5) or TA10 (GR 12).

4. The method for refining surface grains of a titanium plate weld according to claim 1, wherein the working distance of the test sample from the nozzle is 40-70mm.

5. The method for refining the grains of the surface layer of the welding seam of the titanium plate as claimed in claim 4, wherein the working distance of the test sample from the nozzle is 55mm.

6. The method for refining the grains on the surface layer of the welding seam of the titanium plate as recited in claim 1, wherein the effective thickness of the sand blasting grain refining is 100-500 μm.

7. The method for refining the surface grains of the welding seam of the titanium plate as recited in claim 1, wherein the degree of grain refinement is improved by about 2-3 levels, and the improvement of the mechanical property is improved by 10-30%.