阅读说明：本技术 提高棒材强韧性和力学性能均匀性的热处理方法 (Heat treatment method for improving strength, toughness and mechanical property uniformity of bar ) 是由 张帅 于 2019-10-29 设计创作，主要内容包括：本发明涉及金属材料热处理技术领域,具体涉及提高棒材强韧性和力学性能均匀性的热处理方法,包括升温、保温、固溶、降温、冷处理、回复、时效硬化步骤,本发明提供PH13-8Mo棒材在批量制造时,提高材料强韧性和力学性能均匀性的简单易操作热处理工艺方法。(The invention relates to the technical field of metal material heat treatment, in particular to a heat treatment method for improving the strength and toughness and the mechanical property uniformity of a bar, which comprises the steps of heating, heat preservation, solid solution, cooling, cold treatment, recovery and age hardening, and provides a simple and easy-to-operate heat treatment process method for improving the strength and toughness and the mechanical property uniformity of a material when a PH13-8Mo bar is manufactured in batches.)

1. The heat treatment method for improving the strength, toughness and mechanical property uniformity of the bar is characterized in that a cold treatment step is added in the processes of solid solution and age hardening.

2. The heat treatment method for improving the strength and toughness and the uniformity of mechanical properties of the bar according to claim 1, wherein the cold treatment is to place the PH13-8Mo bar in an ice-water mixed medium at 0-1 ℃ for protection for more than or equal to 6 hours.

3. The heat treatment method for improving the strength and toughness and the uniformity of mechanical properties of the bar according to claim 1, wherein the solid solution is to perform solid solution heat preservation on the PH13-8Mo bar at the temperature of 910-940 ℃ for 2-3 h.

4. The heat treatment method for improving the strength and toughness and the uniformity of mechanical properties of the bar according to claim 1, which comprises the steps of heating, heat preservation, solid solution, cooling, cold treatment, recovery and age hardening.

5. The heat treatment method for improving the strength and toughness and the uniformity of mechanical properties of the bar according to claim 4, wherein the temperature rise rate is less than or equal to 180 ℃/h.

6. The heat treatment process of claim 4 for raising the strength and toughness and mechanical performance homogeneity of bar material, and features that the temperature lowering is air cooling of PH13-8Mo bar material to room temperature.

7. The heat treatment method for improving the strength and toughness and the uniformity of mechanical properties of the bar according to claim 4, wherein the recovery is carried out by heating the PH13-8Mo bar to 510-550 ℃ at a speed of 120 ℃/h or less, preserving the temperature for 4h, and then cooling in air.

8. The heat treatment method for improving the strength and toughness and the uniformity of mechanical properties of the bar according to claim 1, wherein the diameter of the PH13-8Mo bar is less than 70 mm.

9. The heat treatment method for improving the strength and toughness and the uniformity of mechanical properties of the bar material according to claim 1, wherein the chemical compositions of the PH13-8Mo bar material are, by mass, 0.03-0.05% of C, 0.01-0.02% of Mn, 0.02-0.06% of Si, 0.002-0.004% of P, 0.001-0.002% of S, 12.0-12.7% of Cr12, 8.3-8.4% of Ni0, 2.0-2.5% of Mo2, and 1.0-1.1% of Al.

Technical Field

The invention relates to the technical field of metal material heat treatment, in particular to a heat treatment method for improving the strength, toughness and mechanical property uniformity of a bar.

Background

PH13-8Mo steel (domestic brand is 0Cr13Ni8Mo2Al) is martensite precipitation hardening stainless steel with excellent performance, can reach the ultrahigh strength level through alloying and phase change control, has the advantages of excellent strength and toughness, particularly excellent medium temperature resistance, corrosion resistance, formability and the like, and has been widely applied to the fields of aerospace, nuclear reactors, petrochemical industry and the like. For example, the medium-temperature corrosion-resistant important bearing fasteners, structural parts and the like are used for large solid rocket engines, air passenger A380 large airplanes and fourth-generation advanced fighters.

With the rapid development of the national aerospace industry, the requirements on the performance and the stability of the ultrahigh-strength stainless steel fastener for the key parts of large solid rockets and aviation aircrafts are higher and higher, particularly in the aspect of high toughness, although domestic and foreign scholars have fully researched the structure performance control of PH13-8Mo martensite precipitation hardening stainless steel, the problems that the high strength and the high toughness are difficult to match and the uniformity of mechanical properties is poor still exist in the actual industrial mass production.

Patent No. CN201410649189.7 discloses a heat treatment process method of 0Cr13Ni8Mo2Al steel, which discloses that a cold treatment step is added between solution treatment and aging treatment,

the patent No. CN201811381851.X discloses a high-toughness and high-strength aluminum alloy wheel hub for automobiles and a manufacturing method thereof, wherein the manufacturing method comprises the steps of smelting, refining, casting, solution treatment, cryogenic treatment, aging treatment and the like.

However, the prior art still has the defects of difficult matching of high strength and high toughness and poor uniformity of mechanical properties when the PH13-8Mo material used for the aerospace super-strength fastener is manufactured in batches by using bars (the diameter is less than 70 mm).

Disclosure of Invention

The invention provides a heat treatment method for improving the strength, toughness and mechanical property uniformity of a bar in order to solve the technical problems.

The method is realized by the following technical scheme:

the heat treatment method for improving the strength, toughness and mechanical property uniformity of the bar adds a cold treatment step in the processes of solid solution and age hardening.

The cold treatment is to place the PH13-8Mo bar in an ice-water mixed medium at the temperature of 0-1 ℃ for protection for more than or equal to 6 hours.

The solid solution is to perform solid solution and heat preservation on a PH13-8Mo bar at the temperature of 910-940 ℃ for 2-3 h.

Further, the heat treatment method for improving the strength and toughness and the mechanical property uniformity of the bar comprises the steps of heating, heat preservation, solid solution, cooling, cold treatment, recovery and age hardening.

The heating rate is less than or equal to 180 ℃/h.

And the temperature reduction is to cool the PH13-8Mo bar to room temperature in air.

The temperature at room temperature was 23. + -. 10 ℃.

And the recovery is that the PH13-8Mo bar is heated to 510-550 ℃ at the speed of less than or equal to 120 ℃/h, heat preservation is carried out for 4h, and then air cooling is carried out.

The diameter of the PH13-8Mo bar is less than 70 mm.

Preferably, the chemical components of the PH13-8Mo bar are 0.03-0.05 wt% of C, 0.01-0.02 wt% of Mn, 0.02-0.06 wt% of Si, 0.002-0.004 wt% of P, 0.001-0.002 wt% of S, 12.0-12.7 wt% of Cr12.3-8.4 wt% of Ni8.0-2.5 wt% of Mo2.0-1.1 wt% of Al in mass fraction.

Has the advantages that:

according to the invention, one-time cold treatment is added between the steps of solid solution and age hardening, so that the residual austenite structure in the material is reduced, the full transformation of martensite is promoted, the lath structure of the martensite is refined, and the toughness is improved while the ultrahigh strength of the material is maintained after the aging temperature is increased; on the other hand, because the indoor air temperature during solid solution cooling is difficult to control in actual production, the volume fraction of martensite in the material of the same batch of bars during aging treatment is basically the same by adding a 0 ℃ cold treatment by utilizing the principle that the volume fraction of the martensite of the PH13-8Mo material after solid solution is related to the final cooling temperature, and the uniformity of the structure and the mechanical property is improved; finally, the invention is simple and easy to operate, and can be implemented under the conditions that the indoor air temperature is unstable and uncontrollable during solution cooling and no large-scale low-temperature refrigeration equipment is provided.

The invention provides a simple and easy-to-operate heat treatment process method for improving the strength, toughness and mechanical property uniformity of a material during batch production of a PH13-8Mo bar.

Drawings

FIG. 1 is a schematic diagram of the heat treatment process flow and time temperature of a PH13-8Mo material bar (diameter less than 70mm) according to the invention;

FIG. 2 is a schematic diagram of the process flow and time-temperature diagram of this example 1.

Detailed Description

The following is a detailed description of the embodiments of the present invention, but the present invention is not limited to these embodiments, and any modifications or substitutions in the basic spirit of the embodiments are included in the scope of the present invention as claimed in the claims.

The following examples used forged PH13-8Mo bars of the specification: φ 65 × 670, quantity: 36 pieces, chemical composition as shown in the following table one:

table one: chemical composition of forging (Wt/%)

Element(s)	C	Mn	Si	P	S	Cr	Ni	Mo	Al
										Content (wt.)	0.037	0.01	0.04	0.003	0.001	12.40	8.35	2.25	1.04