CN103276302A - High-alumina 17-7 PH stainless steel and preparation method thereof - Google Patents

Abstract

The preparation method of high aluminum 17-7PH stainless steel, in terms of mass percentage, its composition is: Cr: 17%, Ni: 7%, Mn: 0.8%, Si: 0.8%, C: 0.08%, Al: 1.5%~3.5 %, the balance is Fe; the steps of the preparation method are: (1) Prepare the raw materials according to the above-mentioned ingredients, and carry out smelting. Furnace, billet opening at 1150°C, pressure 20MPa, deformation 55% to 58%, then air cooling, rolling at 1150°C, final rolling temperature greater than or equal to 900°C, pressing amount per pass 0.1mm, deformation 20% to 17%, and several times of intermediate annealing and air cooling, and finally a plate with a thickness of 3mm; (3) Heat treatment of the hot-rolled plate, solution treatment at 1050 ° C, water cooling after 30 minutes of heat preservation; Conditioned at 955°C, heat-preserved for 10 minutes, then air-cooled to room temperature; then placed in dry ice alcohol for cryogenic treatment within 24 hours, and held for 8 hours; then heated to 510°C for aging, held for 1 hour and then air-cooled.

Description

High aluminum 17-7PH stainless steel and preparation method thereof

the

technical field

The present invention relates to the preparation technology of 17-7PH stainless steel.

Background technique

17-7PH stainless steel alloy is widely used in the aviation industry as a high-strength stainless steel. However, it has poor corrosion resistance and is prone to stress corrosion cracking in an environment with high humidity. The corrosion resistance is between 18-8 steel and Martens body stainless steel. Its corrosion resistance mainly depends on the formation of a Cr ₂ O ₃ passivation film on the surface, but the thermal expansion coefficient difference between the Cr ₂ O ₃ film and the substrate is large, and it is easy to peel off under long-term cyclic thermal stress, and it is easy to form in a water-containing environment. The volatile Cr-containing hydroxide seriously deteriorates the stability of the Cr ₂ O ₃ passivation film. Compared with Cr ₂ O ₃ , Al ₂ O ₃ grows more slowly and more stably, and has a rate much lower than that of Cr ₂ O ₃ to form volatile hydroxides in a water vapor environment.

Contents of the invention

The purpose of this invention is to provide a kind of high aluminum 17-7PH stainless steel and its preparation method.

The present invention is high aluminum 17-7PH stainless steel and a preparation method thereof. The high aluminum 17-7PH stainless steel has the following components by mass percentage: Cr: 17%, Ni: 7%, Mn: 0.8%, Si: 0.8%, C: 0.08%, Al: 1.5%~3.5%, and the balance is Fe.

The preparation method of high aluminum 17-7PH stainless steel, its step is:

(1) Based on the composition of 17-7PH stainless steel, prepare raw materials containing 1.5%~3.5% Al according to the composition of claim 1, melt in a vacuum arc melting furnace with a current of 200A, and repeatedly pump 3 times before melting Vacuum, argon protection is used during the smelting process, and the workpiece is repeatedly turned and smelted 3 times to make it melt better and reduce defects;

(2) The smelted workpiece is subjected to billet hot rolling. The process is as follows: furnace is installed at 600°C, the billet is opened at 1150°C, the pressure is 20MPa, the deformation is 55% to 58%, and then air-cooled, and the rolling is started at 1150°C. The final rolling temperature is greater than or equal to 900°C, the amount of reduction per pass is 0.1mm, and the amount of deformation is 20% to 17%, and multiple intermediate annealing and air cooling are performed to finally obtain a plate with a thickness of 3mm;

(3) Heat-treat the hot-rolled plate. The process is as follows: solid solution treatment at 1050°C, water cooling after 30 minutes of heat preservation; then adjustment treatment at 955°C, 10 minutes of heat preservation and air cooling to room temperature; then within 24 hours Place in dry ice alcohol for cryogenic treatment and heat preservation for 8 hours; then heat to 510°C for aging, heat preservation for 1 hour and then air-cool.

The beneficial effect of the present invention is that based on 17-7PH steel, when aluminum is added to the alloy, since Al is an easy passivation element, the passivation ability is stronger than that of Cr element, and the formed Al ₂ O ₃ oxide film has good stability and corrosion rate, it can be applied in acidic oxidizing medium. Both chromium and aluminum are contained in the alloy, and under the synergistic effect of the two, the corrosion resistance will be improved.

Alloy of the present invention and 17-7PH performance contrast table as follows:

The following tensile experiments were carried out on a microcomputer-controlled electronic universal material testing machine with a maximum load of 100KN and a tensile rate of 0.2 mm/min; the corrosion resistance of the material was tested by the weight loss method, and the concentration of the sample placed in boiling was 65%. The uniform corrosion experiment was carried out in the HNO ₃ , and the corrosion time was 8 hours.

the

It can be seen from the table that under the premise of maintaining the mechanical properties of the alloy at room temperature, the corrosion resistance of the present invention is significantly improved.

Detailed ways

Example 1:

In terms of mass percentage, Ni: 7%, Cr: 17%, Al: 1.5%, Mn: 0.8%, Si: 0.8%, C: 0.08%, the balance is Fe, and the corresponding components are weighed, and the raw material powder Put it into a planetary ball mill and mix it for 8 hours, press the mixed powder into a cylinder of Φ20×50, and melt it in a WS-4 non-consumable vacuum arc melting furnace with a current of 200A. Protected with argon gas. The sample was turned and melted repeatedly 3 times to make it melt better and reduce defects. After melting, the sample was cooled to room temperature in a water-cooled copper crucible. The smelted alloy is subjected to billet hot rolling, and the process is as follows: furnace loading at 600°C → billet billeting at 1150°C, pressure at 20 MPa, deformation of 55% to 58% → air cooling → rolling at 1150°C, final rolling ≥ 900°C, every The pressing amount of each pass is 0.1mm, the deformation amount is 20% to 17%, and the intermediate annealing → air cooling is carried out several times. After blanking and hot rolling, a plate sample with a thickness of 3mm is finally obtained. Then heat-treat the hot-rolled plate, the process is as follows: solution treatment at 1050°C, heat preservation for 30 minutes and then water cooling; then adjustment treatment at 955°C, heat preservation for 10 minutes and air cooling to room temperature; then place in dry ice alcohol within 24 hours Carry out cryogenic treatment and heat preservation in the medium for 8h; then heat to 510°C for aging, hold heat for 1h and then air cool. The alloy structure is martensite + ferrite + a small amount of retained austenite. Performance data: tensile strength σ _b =1382MPa, yield strength σ _0.2 =1109MPa, elongation A=14%, corrosion rate 1.16 g/ m ² ·h.

Example 2:

In terms of mass percentage, Ni: 7%, Cr: 17%, Al: 2%, Mn: 0.8%, Si: 0.8%, C: 0.08%, the balance is Fe, and the corresponding components are weighed, and the raw material powder Put it into a planetary ball mill and mix it for 8 hours, press the mixed powder into a cylinder of Φ20×50, and melt it in a WS-4 non-consumable vacuum arc melting furnace with a current of 200A. Protected with argon gas. The sample was turned and melted repeatedly 3 times to make it melt better and reduce defects. After melting, the sample was cooled to room temperature in a water-cooled copper crucible. The smelted alloy is subjected to billet hot rolling, and the process is as follows: furnace loading at 600°C → billet billeting at 1150°C, pressure at 20 MPa, deformation of 55% to 58% → air cooling → rolling at 1150°C, final rolling ≥ 900°C, every The pressing amount of each pass is 0.1mm, the deformation amount is 20% to 17%, and the intermediate annealing → air cooling is carried out several times. After blanking and hot rolling, a plate sample with a thickness of 3mm is finally obtained. Then heat-treat the hot-rolled plate, the process is as follows: solution treatment at 1050°C, heat preservation for 30 minutes and then water cooling; then adjustment treatment at 955°C, heat preservation for 10 minutes and air cooling to room temperature; then place in dry ice alcohol within 24 hours Carry out cryogenic treatment and heat preservation in the medium for 8h; then heat to 510°C for aging, hold heat for 1h and then air cool. The alloy structure is martensite + ferrite + a small amount of retained austenite. Performance data: tensile strength σ _b =1351MPa, yield strength σ _0.2 =1037MPa, elongation A=15%, corrosion rate 0.98 g/ m ² ·h.

Embodiment 3:

In terms of mass percentage, Ni: 7%, Cr: 17%, Al: 2.5%, Mn: 0.8%, Si: 0.8%, C: 0.08%, the balance is Fe, and the corresponding components are weighed, and the raw material powder Put it into a planetary ball mill and mix it for 8 hours, press the mixed powder into a cylinder of Φ20×50, and melt it in a WS-4 non-consumable vacuum arc melting furnace with a current of 200A. Protected with argon gas. The sample was turned and melted repeatedly 3 times to make it melt better and reduce defects. After melting, the sample was cooled to room temperature in a water-cooled copper crucible. The smelted alloy is subjected to billet hot rolling, and the process is as follows: furnace loading at 600°C → billet billeting at 1150°C, pressure at 20 MPa, deformation of 55% to 58% → air cooling → rolling at 1150°C, final rolling ≥ 900°C, every The pressing amount of each pass is 0.1mm, the deformation amount is 20% to 17%, and the intermediate annealing → air cooling is carried out several times. After blanking and hot rolling, a plate sample with a thickness of 3mm is finally obtained. Then heat-treat the hot-rolled plate, the process is as follows: solution treatment at 1050°C, heat preservation for 30 minutes and then water cooling; then adjustment treatment at 955°C, heat preservation for 10 minutes and air cooling to room temperature; then place in dry ice alcohol within 24 hours Carry out cryogenic treatment and heat preservation in the medium for 8h; then heat to 510°C for aging, hold heat for 1h and then air cool. The alloy structure is austenite + ferrite. Performance data: tensile strength σ _b =962MPa, yield strength σ _0.2 =559MPa, elongation A=20%, corrosion rate 0.37 g/ m ² ·h.

Claims (2)

1. high alumina 17-7PH stainless steel, by mass percentage, its composition is: Cr:17%, Ni:7%, Mn:0.8%, Si:0.8%, C:0.08%, Al:1.5% ~ 3.5%, surplus is Fe.

2. the stainless preparation method of high alumina 17-7PH the steps include:

(1) based on the stainless composition of 17-7PH, containing Al by the described one-tenth assignment system of claim 1 is 1.5% ~ 3.5% raw material, melting in vacuum arc melting furnace, electric current is 200A, take out vacuum before the melting repeatedly 3 times, adopt argon shield in the fusion process, with the workpiece melting 3 times of overturning repeatedly, make its better fusing to reduce defective;

(2) workpiece with melting carries out the cogging hot rolling, its technology is as follows: 600 ℃ of shove charges, 1150 ℃ of coggings, pressure is 20MPa, deflection 55%～58%, air cooling then, 1150 ℃ of open rollings, finishing temperature is more than or equal to 900 ℃, every time volume under pressure is 0.1mm, deflection 20%～17%, and carry out repeatedly process annealing and air cooling, finally obtain the sheet material that thickness is 3mm;

(3) sheet material after the hot rolling is heat-treated, technological process is as follows: carry out solution treatment at 1050 ℃, water-cooled behind the insulation 30min; Adjust processing subsequently under 955 ℃ of conditions, air cooling is to room temperature behind the insulation 10min; Carry out sub-zero treatment at 24h in the dry ice alcohol to be built in then, insulation 8h; Reheat to 510 ℃ carries out timeliness, air cooling behind the insulation 1h.