CN115852111A - Strengthening method of PH13-8Mo material - Google Patents

Abstract

The invention belongs to the technical field of stainless steel processing, and particularly relates to a strengthening method of a PH13-8Mo material. The method for strengthening the PH13-8Mo material comprises the following heat treatment steps: sequentially carrying out solid solution treatment, cooling and aging treatment on the blank; the blank is precipitation hardening stainless steel 0Cr13Ni8Mo2Al; the solid solution treatment is to keep the blank at 670-690 ℃ for 55-65 min, then heat the blank to 915-935 ℃ and keep the blank at the temperature for 55-65 min; and (3) performing cold treatment on the workpiece subjected to the solution treatment at a temperature of between 5 ℃ below zero and 5 ℃, and then performing aging treatment on the workpiece subjected to the solution treatment at a temperature of between 530 and 550 ℃ for 240 to 270min to obtain a heat-treated workpiece. The heat treatment process enables the PH13-8Mo material to have higher tensile strength, yield strength, impact toughness, fatigue resistance and corrosion resistance, and greatly improves the reliability of the material when the material is used for connection and fastening.

Description

A kind of strengthening method of PH13-8Mo material

technical field

The invention belongs to the technical field of stainless steel processing, and in particular relates to a strengthening method of PH13-8Mo material.

Background technique

At present, in fields such as aerospace, deep sea engineering, high-speed rail, ships, petrochemical ultra-high pressure vessel connectors, and shield machines, ultra-high-strength bolts are usually used due to the need for connection and fastening, and the reliability requirements for bolts are high; bolt materials are usually Alloy steel materials such as 30CrMnSiA are used. Although such materials can meet the strength requirements, electroplating is required to meet anti-corrosion requirements in practical applications. Because the electroplating solution contains a large amount of hydrogen, hydrogen will be absorbed during the electroplating process, and hydrogen will exist when the material is used. The risk of brittleness and chrome brittleness, the thread is prone to brittle fracture, causing accidents.

In order to solve the problem of hydrogen embrittlement in the application of 30CrMnSiA material, Chinese invention patent CN 111020424B discloses a high-strength aluminum alloy bolt. The strength requirement of tensile strength ≥ 630MPa, the relevant strength performance can meet the load-bearing requirements of aerospace fasteners, but it can be seen from the examples that the maximum tensile strength of this material is 726.8MPa. In practical applications, it is still necessary to find higher strength. , and good corrosion resistance materials.

PH13-8Mo material is precipitation hardening stainless steel, the domestic grade is 0Cr13Ni8Mo2Al, which has excellent mechanical properties and excellent corrosion resistance, but in order to obtain better mechanical properties of this type of alloy, appropriate strengthening processing must be carried out, and the current material There are fewer processing methods for ultra-high-strength bolts, and there are problems in batch processing.

Contents of the invention

The purpose of the present invention is to provide a strengthening method of PH13-8Mo material, so that the material has high strength and high corrosion resistance, and solve the problem of hydrogen embrittlement leading to fracture in the application of 30CrMnSiA material in the prior art.

In order to achieve the above object, the technical solution adopted in the present invention is:

A method for strengthening a PH13-8Mo material, comprising the following steps of heat treatment: performing solution treatment, cooling and aging treatment on a billet in sequence; the billet is precipitation hardening stainless steel 0Cr13Ni8Mo2Al; the solution treatment is to heat the billet at 670-690°C Keep warm for 55-65 minutes, then raise the temperature to 915-935°C and keep warm for 55-65 minutes; cold-treat the workpiece after solution treatment at -5-5°C, and then hold it at 530-550°C for 240-270 minutes for aging treatment to obtain heat-treated workpieces .

The present invention makes the PH13-8Mo material have higher tensile strength (1410-1560MPa), yield strength, impact toughness, fatigue resistance and corrosion resistance through the above-mentioned heat treatment process, which greatly improves the use of the material for connection and fastening Timely reliability and safety, while avoiding the problem of hydrogen embrittlement.

Preferably, the solution treatment is carried out under vacuum conditions.

In order to further improve the strength and toughness of the PH13-8Mo material, preferably, the cold treatment time is 60-120 min.

Preferably, it also includes using a passivation solution to passivate the heat-treated workpiece, and the passivation solution is a nitric acid passivation solution; the concentration of nitric acid in the nitric acid passivation solution is 400-500 g/L. Nitric acid passivation solution can form a chromium-rich passivation film on the surface of PH13-8Mo material, thereby improving the corrosion resistance of PH13-8Mo material.

In order to further improve the corrosion resistance of the PH13-8Mo material, preferably, the heat-treated workpiece is pickled with a pickling solution before the passivation; the pickling solution is a mixed acid solution of nitric acid, sulfuric acid, and hydrofluoric acid; The concentration of nitric acid in the pickling solution is 70-80g/L, the concentration of sulfuric acid is 80-100g/L, and the concentration of hydrofluoric acid is 40-50g/L. The scale formed after the heat treatment of the PH13-8Mo material can be removed by pickling, and the pickling time is strictly controlled to ensure complete removal of the scale; the pickling time is 20-40 minutes.

In order to further improve the corrosion resistance of the PH13-8Mo material, preferably, the heat-treated workpiece is also subjected to polishing treatment after pickling.

Preferably, the heat-treated workpiece is a fastener. PH13-8Mo material has high tensile strength, yield strength, impact toughness and corrosion resistance after heat treatment, which greatly improves the reliability and safety of the material when it is used for connection and fastening, and can avoid hydrogen embrittlement at the same time.

Preferably, the fasteners are bolts.

Preferably, the bolt includes the following processing steps: blanking, heading, heat treatment, pickling, preprocessing, thread rolling, rolling R, flaw detection, polishing, passivation; the preprocessing is to process the bolt polished rod size, cap thickness Dimensions and billet diameter. Among them, the rolling wire retains the metal flow line of the bolt, so that the bolt has higher strength; the rolling R increases the fatigue resistance of the PH13-8Mo bolt, and the average fatigue life is not less than 65,000 times; the flaw detection can eliminate crack defects Bolts are conducive to the mass production of ultra-high-strength bolts.

The PH13-8Mo bolt processed by the above method has a tensile strength of 1410-1560MPa, a fatigue resistance of 130,000 times, and a salt spray test of more than 192 hours. It can not only be used under ultra-high strength conditions, but also has high corrosion resistance. The reliability and safety of the threaded connection of key parts are greatly improved.

Preferably, the upsetting is hot upsetting at a temperature of 600-800°C; the nuts of the bolts are upset by the hot upsetting die, and the nuts can be hexagonal heads, hexagonal countersunk heads, dodecagonal heads, etc.

Preferably, sandblasting is performed after the hot heading. Sandblasting can remove the oxide scale produced by PH13-8Mo material during hot heading.

Detailed ways

The technical solution of the present invention will be further described below in combination with specific embodiments.

One, the concrete embodiment of the strengthening method of PH13-8Mo material of the present invention is as follows:

The sulfuric acid used in the embodiment of the present invention is a commercial product with a concentration of 93-98%.

The nitric acid used in the embodiments of the present invention is a commercially available product with a concentration of 65-68%.

The hydrofluoric acid used in the embodiment of the present invention is a commercial product with a concentration of 40-50%.

The electrochemical polishing liquid used in the embodiment of the present invention is Kaimeng Environmental Protection Electrochemical Polishing Liquid.

Example 1

The strengthening method of the PH13-8Mo material in this embodiment includes the following heat treatment steps: firstly, the PH13-8Mo material is subjected to solution treatment in a vacuum furnace, the solution temperature is 680°C, and the temperature is kept for 55 minutes, and then the temperature is raised to 925°C, and the heat preservation is carried out after 65 minutes. Oil cooling, cooling time 10min; after solid solution is completed, cold treatment is carried out, the temperature of cold treatment is 0°C, and the time is 60min. The temperature is 530°C, the temperature is kept for 270 minutes, and then air-cooled to obtain a heat-treated workpiece.

The strengthening method of the PH13-8Mo material in this embodiment also includes using a passivation solution to passivate the above-mentioned heat-treated workpiece, which specifically includes: first pickling the heat-treated workpiece with a pickling solution to remove the scale on the surface of the heat-treated workpiece, acid The washing solution is a mixed acid solution of nitric acid, sulfuric acid and hydrofluoric acid. The concentration of nitric acid in the pickling solution is 70g/L, the concentration of sulfuric acid is 100g/L, the concentration of hydrofluoric acid is 40g/L, and the pickling time is 30min; Finally, the PH13-8Mo material is electropolished with an electrochemical polishing solution; finally, the PH13-8Mo material is passivated with a nitric acid passivation solution. The concentration of nitric acid in the nitric acid passivation solution is 400g/L, which can be A layer of chromium-rich passivation film is formed on the surface of 8Mo material to improve the corrosion resistance of PH13-8Mo material.

The PH13-8Mo material of this embodiment is an ultra-high-strength bolt with a specification of M8, including the following processing steps:

(1) Material preparation: choose PH13-8Mo round bar material with a diameter of φ8.5mm;

(2) Ordinary car: process the bar before heading according to the single-piece quantity required by the bolt;

(3) Hot upsetting: heating the PH13-8Mo round bar to 600°C with a heating coil, and then upsetting the hexagonal head nut of the bolt through the hot upsetting die;

(4) Sand blasting: remove the scale produced by the hot heading process;

(5) Heat treatment: use the above heat treatment process to heat treat the PH13-8Mo round bar;

(6) Pickling: Use nitric acid, sulfuric acid, hydrofluoric acid mixed acid solution to pickle the PH13-8Mo round bar. The concentration of nitric acid in the pickling solution is 70g/L, the concentration of sulfuric acid is 100g/L, and the concentration of hydrofluoric acid 40g/L, pickling time is 30min;

(7) Numerical control car: use the numerical control car to process the size of the polished rod of the bolt, the thickness of the cap and the diameter of the rolling blank;

(8) Thread rolling: use the thread rolling machine to roll the thread of the bolt;

(9) Rolling R: use the rolling R machine to roll the transition R angle of the nut and the polished rod of the bolt;

(10) Flaw detection: Use non-destructive testing to eliminate bolts that may have crack defects;

(11) Electropolishing: use electrochemical polishing solution to electropolish PH13-8Mo bolts;

(12) Passivation: Use nitric acid passivation solution to passivate PH13-8Mo bolts. The concentration of nitric acid in the nitric acid passivation solution is 400g/L.

In other embodiments, in step (3), the hot heading temperature can be adjusted to 650°C, 680°C, 700°C, 750°C, 800°C; the nut can be a hexagonal countersunk head or a dodecagonal head.

Example 2

The strengthening method of the PH13-8Mo material in this embodiment includes the following heat treatment steps: first, the PH13-8Mo material is subjected to solution treatment in a vacuum furnace, the solution temperature is 670°C, and the temperature is kept for 60 minutes, and then the temperature is raised to 915°C, and the heat preservation is carried out after 60 minutes. Oil cooling, the cooling time is 10min; cold treatment is carried out after the solution is completed, the temperature of the cold treatment is -5°C, the time is 90min, the interval between solution treatment and cold treatment is not more than 1h, and then the PH13-8Mo material is subjected to aging treatment in an air furnace , the aging temperature was 540°C, and the temperature was kept at 250 minutes for air cooling to obtain heat-treated workpieces.

The strengthening method of the PH13-8Mo material in this embodiment also includes using a passivation solution to passivate the above-mentioned heat-treated workpiece, which specifically includes: first pickling the heat-treated workpiece with a pickling solution to remove the scale on the surface of the heat-treated workpiece, acid The washing solution is a mixed acid solution of nitric acid, sulfuric acid and hydrofluoric acid. The concentration of nitric acid in the pickling solution is 70g/L, the concentration of sulfuric acid is 80g/L, the concentration of hydrofluoric acid is 50g/L, and the pickling time is 30min; Finally, the PH13-8Mo material is electropolished with an electrochemical polishing solution; finally, the PH13-8Mo material is passivated with a nitric acid passivation solution. The concentration of nitric acid in the nitric acid passivation solution is 450g/L, which can be A layer of chromium-rich passivation film is formed on the surface of 8Mo material to improve the corrosion resistance of PH13-8Mo material.

The PH13-8Mo material of this embodiment is an ultra-high-strength bolt with a specification of M8, including the following processing steps:

(1) Material preparation: choose PH13-8Mo round bar material with a diameter of φ8.5mm;

(2) Ordinary car: process the bar before heading according to the single-piece quantity required by the bolt;

(3) Hot upsetting: Heating the PH13-8Mo round bar to 600°C with a heating coil, and then upsetting the dodecagonal head nuts of the bolts through the hot upsetting die;

(4) Sand blasting: remove the scale produced by the hot heading process;

(5) Heat treatment: use the above heat treatment process to heat treat the PH13-8Mo round bar;

(6) Pickling: The PH13-8Mo round bar is pickled with nitric acid, sulfuric acid and hydrofluoric acid mixed acid solution. The concentration of nitric acid in the pickling solution is 70g/L, the concentration of sulfuric acid is 80g/L, and the concentration of hydrofluoric acid 50g/L, pickling time is 30min;

(7) Numerical control car: use the numerical control car to process the size of the polished rod of the bolt, the thickness of the cap and the diameter of the rolling blank;

(8) Thread rolling: use the thread rolling machine to roll the thread of the bolt;

(9) Rolling R: use the rolling R machine to roll the transition R angle of the nut and the polished rod of the bolt;

(10) Flaw detection: Use non-destructive testing to eliminate bolts that may have crack defects;

(11) Electropolishing: use electrochemical polishing solution to electropolish PH13-8Mo bolts;

(12) Passivation: Use nitric acid passivation solution to passivate PH13-8Mo bolts. The concentration of nitric acid in the nitric acid passivation solution is 450g/L.

Example 3

The strengthening method of the PH13-8Mo material in this embodiment The strengthening method includes the following heat treatment steps: first, use a vacuum furnace to perform solution treatment on the PH13-8Mo material. After 55 minutes, carry out oil cooling, and the cooling time is 10 minutes; after solid solution is completed, carry out cold treatment, the temperature of cold treatment is 5 ° C, and the time is 60 minutes. Carry out aging treatment, aging temperature is 550 ℃, keep warm for 240min and carry out air cooling, obtain heat treatment workpiece.

The strengthening method of the PH13-8Mo material in this embodiment also includes using a passivation solution to passivate the above-mentioned heat-treated workpiece, which specifically includes: first pickling the heat-treated workpiece with a pickling solution to remove the scale on the surface of the heat-treated workpiece, acid The washing solution is a mixed acid solution of nitric acid, sulfuric acid and hydrofluoric acid. The concentration of nitric acid in the pickling solution is 80g/L, the concentration of sulfuric acid is 90g/L, the concentration of hydrofluoric acid is 40g/L, and the pickling time is 30min; Finally, the PH13-8Mo material is electropolished with an electrochemical polishing solution; finally, the PH13-8Mo material is passivated with a nitric acid passivation solution. The concentration of nitric acid in the nitric acid passivation solution is 500g/L, which can be A layer of chromium-rich passivation film is formed on the surface of 8Mo material to improve the corrosion resistance of PH13-8Mo material.

The PH13-8Mo material of this embodiment is an ultra-high-strength bolt with a specification of M8, including the following processing steps:

(1) Material preparation: choose PH13-8Mo round bar material with a diameter of φ8.5mm;

(2) Ordinary car: process the bar before heading according to the single-piece quantity required by the bolt;

(3) Hot upsetting: use heating coil to heat PH13-8Mo round bar to 600°C, and then make hexagonal countersunk nuts of bolts through hot upsetting die;

(4) Sand blasting: remove the scale produced by the hot heading process;

(5) Heat treatment: use the above heat treatment process to heat treat the PH13-8Mo round bar;

(6) Pickling: Use nitric acid, sulfuric acid, hydrofluoric acid mixed acid solution to pickle the PH13-8Mo round bar. The concentration of nitric acid in the pickling solution is 80g/L, the concentration of sulfuric acid is 90g/L, and the concentration of hydrofluoric acid 40g/L, pickling time is 30min;

(7) Numerical control car: use the numerical control car to process the size of the polished rod of the bolt, the thickness of the cap and the diameter of the rolling blank;

(8) Thread rolling: use the thread rolling machine to roll the thread of the bolt;

(9) Rolling R: use the rolling R machine to roll the transition R angle of the nut and the polished rod of the bolt;

(10) Flaw detection: Use non-destructive testing to eliminate bolts that may have crack defects;

(11) Electropolishing: use electrochemical polishing solution to electropolish PH13-8Mo bolts;

(12) Passivation: Use nitric acid passivation solution to passivate PH13-8Mo bolts. The concentration of nitric acid in the nitric acid passivation solution is 500g/L.

2. Comparison ratio

Comparative example 1

The strengthening method of the PH13-8Mo material of this comparative example is different from that of Example 1 in that: the solution heat treatment of Example 1 adopts a vacuum furnace, and the solution heat treatment of the PH13-8Mo material of this comparative example adopts an air furnace.

3. Experimental example

Experimental example 1

This experimental example detects the mechanical properties and corrosion resistance of the bolts processed by the PH13-8Mo material in Examples 1-3 and Comparative Example 1. The specific results are shown in Table 1:

The performance of the bolt processed by PH13-8Mo material in Table 1 embodiment 1-3 and comparative example 1

Compared with Comparative Example 1, the bolts processed with PH13-8Mo material in Examples 1-3 of the present invention have higher tensile strength and yield strength, and excellent corrosion resistance, which greatly improves the reliability of the material when used for connection and fastening. sex and safety.

Claims (10)

1. A strengthening method of a PH13-8Mo material is characterized by comprising the following heat treatment steps: sequentially carrying out solid solution treatment, cooling and aging treatment on the blank; the blank is precipitation hardening stainless steel 0Cr13Ni8Mo2Al;

the solid solution treatment is to keep the blank at 670-690 ℃ for 55-65 min, then heat the blank to 915-935 ℃ and keep the blank at the temperature for 55-65 min; and (3) performing cold treatment on the workpiece subjected to the solution treatment at a temperature of between 5 ℃ below zero and 5 ℃, and then performing aging treatment on the workpiece subjected to the solution treatment at a temperature of between 530 and 550 ℃ for 240 to 270min to obtain a heat-treated workpiece.

2. The method for strengthening a PH13-8Mo material of claim 1, wherein the solution treatment is performed under vacuum condition.

3. The method for strengthening a PH13-8Mo material of claim 1, wherein the cold treatment time is 60-120 min.

4. The method for strengthening the PH13-8Mo material according to claim 1, further comprising passivating the heat-treated workpiece with a passivating solution, wherein the passivating solution is a nitric acid passivating solution; the concentration of nitric acid in the nitric acid passivation solution is 400-500 g/L.

5. The method for strengthening the PH13-8Mo material according to claim 4, wherein the heat-treated workpiece is pickled with pickling solution before passivation; the pickling solution is a mixed acid solution of nitric acid, sulfuric acid and hydrofluoric acid; the concentration of nitric acid in the pickling solution is 70-80 g/L, the concentration of sulfuric acid is 80-100 g/L, and the concentration of hydrofluoric acid is 40-50 g/L.

6. The method for strengthening PH13-8Mo material according to claim 5, wherein the heat-treated workpiece is further subjected to polishing treatment after acid pickling.

7. The method for strengthening a PH13-8Mo material according to any one of claims 1-6, wherein the heat-treated workpiece is a fastener.

8. The method for strengthening PH13-8Mo material of claim 7, wherein said fastening member is a bolt.

9. The method for strengthening PH13-8Mo material according to claim 8, wherein the bolt comprises the following processing steps: blanking, upsetting, heat treatment, acid washing, preprocessing, thread rolling, R rolling, flaw detection, polishing and passivation; the preprocessing comprises the steps of processing the size of a bolt polish rod, the size of a cap thickness and the diameter of a thread rolling blank.

10. The method for strengthening a PH13-8Mo material of claim 9, wherein the upsetting is hot upsetting and the temperature is 600-800 ℃.