CN-122012892-A - Heat treatment process of corrosion-resistant bolt

Abstract

The application relates to the technical field of bolt processing, and particularly discloses a heat treatment process of a corrosion-resistant bolt. The heat treatment process of the corrosion-resistant bolt comprises the following steps of cleaning a bolt blank, blow-drying to obtain a pretreated bolt blank, heating, preserving heat, immersing in quenching oil for cooling, taking out, washing, blow-drying to obtain a semi-finished bolt product, heating, preserving heat, immersing in a post-treatment working solution, standing for 5-10min, stirring for 10-30min, taking out, washing, and carrying out heat preservation at 100-120 ℃ for 40-60min to obtain the corrosion-resistant bolt, wherein the post-treatment working solution is mainly prepared from water, sodium nitrite, molybdate, aminated nano silica aerogel and a dispersing agent. The corrosion-resistant bolt obtained by the heat treatment process has the advantages of high tensile strength and high corrosion resistance, and meets the market demand.

Inventors

• HUANG TIANJIAO
• GAO CHANGKUI
• ZHONG CHONGGEN
• CHEN JINHUA
• Yin Fukuan
• DING JIE

Assignees

• 济南实达紧固件股份有限公司

Dates

Publication Date

20260512

Application Date

20260224

Claims (10)

1. 1. A heat treatment process of a corrosion-resistant bolt is characterized by comprising the following steps: S1, cleaning a bolt blank, removing oil stains on the surface of the bolt blank, and drying the bolt blank to obtain a pretreated bolt blank; S2, under the condition of methanol and liquefied gas, heating the pretreated bolt blank to 840-850 ℃, carrying out heat preservation treatment for 70-90min, continuously heating to 850-860 ℃, carrying out heat preservation treatment for 90-110min, immersing in quenching oil with the temperature of 40-80 ℃ for cooling, taking out, washing with water, and drying to obtain a semi-finished bolt product; s3, heating the semi-finished bolt to 470-490 ℃, carrying out heat preservation treatment for 110-130min, immersing in a post-treatment working solution with the temperature of 10-30 ℃, standing for 5-10min, stirring for 10-30min, taking out, washing with water, and carrying out heat preservation treatment for 40-60min at the temperature of 100-120 ℃ to obtain the corrosion-resistant bolt; The post-treatment working solution is mainly prepared from the following raw materials, by weight, 1000 parts of water, 30-50 parts of sodium nitrite, 10-20 parts of molybdate, 2-4 parts of amino nano silicon dioxide aerogel and 1-3 parts of dispersing agent.
2. 2. The heat treatment process of the corrosion-resistant bolt, as set forth in claim 1, is characterized in that the aminated nano silica aerogel is prepared by mixing an ethanol aqueous solution and 3-aminopropyl triethoxysilane at a temperature of 50-70 ℃, adding the hydrophobic nano silica aerogel, stirring for 4-6 hours, filtering, washing with water, and drying to obtain the aminated nano silica aerogel.
3. 3. The heat treatment process of the corrosion-resistant bolt, which is characterized in that the weight ratio of the hydrophobic nano silicon dioxide aerogel to the 3-aminopropyl triethoxysilane is 100 (7-13).
4. 4. The heat treatment process of the corrosion-resistant bolt according to claim 2, wherein the average particle size of the hydrophobic nano silica aerogel is 10-50nm, and the specific surface area is 200-500m 2 /g.
5. 5. The heat treatment process of a corrosion-resistant bolt according to claim 1, wherein the molybdate is one or more selected from the group consisting of sodium molybdate, potassium molybdate, ammonium molybdate and ammonium dodecamolybdate, and the dispersant is one or more selected from the group consisting of polyvinylpyrrolidone, sodium polyacrylate, ammonium polyacrylate and sodium hexametaphosphate.
6. 6. The heat treatment process of the corrosion-resistant bolt, as set forth in claim 1, wherein the weight ratio of the semi-finished bolt product to the post-treatment working fluid is 1 (15-25).
7. 7. The heat treatment process of the corrosion-resistant bolt, which is characterized in that the post-treatment working solution is prepared by uniformly mixing water, sodium nitrite, molybdate, amino nano silica aerogel and a dispersing agent.
8. 8. The heat treatment process of the corrosion-resistant bolt of claim 1, wherein the bolt blank is made of one of 42CrMo steel, 35CrMo steel, SCM440 steel and 10B33 steel.
9. 9. A heat treatment process for a corrosion resistant bolt according to claim 1, wherein the nominal diameter of the bolt blank is 5-27mm and the nominal length is 10-200mm.
10. 10. The heat treatment process of the corrosion-resistant bolt according to claim 1, wherein in the step S2, the flow rate of the methanol is 8-12L/h, and the flow rate of the liquefied gas is 0.4-0.6m 3 /h.

Description

Heat treatment process of corrosion-resistant bolt Technical Field The application relates to the technical field of bolt processing, in particular to a heat treatment process of a corrosion-resistant bolt. Background Bolts are used as indispensable fasteners in the fields of machine manufacturing, automobile industry, engineering machinery, construction and the like, and the performance of the bolts directly determines the assembly stability, the operation safety and the service life of equipment. Particularly in humid, salt mist and other environments, the bolt not only needs to meet the requirement that the tensile strength is more than or equal to 1040MPa, but also needs to have excellent corrosion resistance so as to avoid assembly failure, structure loosening and the like caused by surface corrosion. The heat treatment process of the corrosion-resistant bolt in the prior art generally comprises the steps of preprocessing a bolt blank, and then quenching and tempering to obtain the corrosion-resistant bolt. In order to increase corrosion resistance, some researchers use sodium nitrite aqueous solution for treatment in tempering and cooling stages, and form a protective film on the surface by using sodium nitrite, so that the neutral salt fog resistance time is improved. However, the neutral salt spray resistance time is about 600h, the corrosion resistance is limited to be improved further. Disclosure of Invention In order to improve the neutral salt spray time and increase the corrosion resistance of the corrosion-resistant bolt, the application provides a heat treatment process of the corrosion-resistant bolt, which adopts the following technical scheme: a heat treatment process of a corrosion-resistant bolt comprises the following steps: S1, cleaning a bolt blank, removing oil stains on the surface of the bolt blank, and drying the bolt blank to obtain a pretreated bolt blank; S2, under the condition of methanol and liquefied gas, heating the pretreated bolt blank to 840-850 ℃, carrying out heat preservation treatment for 70-90min, continuously heating to 850-860 ℃, carrying out heat preservation treatment for 90-110min, immersing in quenching oil with the temperature of 40-80 ℃ for cooling, taking out, washing with water, and drying to obtain a semi-finished bolt product; s3, heating the semi-finished bolt to 470-490 ℃, carrying out heat preservation treatment for 110-130min, immersing in a post-treatment working solution with the temperature of 10-30 ℃, standing for 5-10min, stirring for 10-30min, taking out, washing with water, and carrying out heat preservation treatment for 40-60min at the temperature of 100-120 ℃ to obtain the corrosion-resistant bolt; The post-treatment working solution is mainly prepared from the following raw materials, by weight, 1000 parts of water, 30-50 parts of sodium nitrite, 10-20 parts of molybdate, 2-4 parts of amino nano silicon dioxide aerogel and 1-3 parts of dispersing agent. According to the heat treatment process of the corrosion-resistant bolt, firstly, a bolt blank is cleaned, quenched and tempered, and a post-treatment working solution is cooled and forms a protective film, so that the corrosion-resistant bolt is obtained. The synergistic effect of quenching and tempering is utilized to improve the tissue structure and the tensile strength. The post-treatment working solution is utilized to cool the semi-finished bolt product, and a compact organic-inorganic hybrid protective film is formed on the surface of the semi-finished bolt product through the mutual matching of the raw materials, so that the corrosion resistance is improved. The corrosion-resistant bolt obtained by the heat treatment process has the advantages of high tensile strength and high corrosion resistance, has the advantages of neutral salt spray resistance time of more than 1000h and tensile strength of more than 1150MPa, has good comprehensive performance, and meets market demands. In the post-treatment working solution, sodium nitrite and molybdate are added into the raw materials simultaneously. Sodium nitrite can quickly form a protective film, molybdate ions are enriched and adsorbed on the surface of the protective film, molybdenum-containing oxide is formed, microscopic defects are improved, and the compactness and stability of the protective film are improved by utilizing the synergy between sodium nitrite and molybdate. The amino nano silica aerogel is added into the raw materials of the aftertreatment treatment solution, can perform coordination bonding or hydrogen bonding with the protective film to form a framework support, wherein amino groups are coordinated with molybdate to guide the protective film to grow on the amino nano silica aerogel network to form a chemically bonded organic-inorganic hybrid protective film, so that the physical barrier property is improved, and the corrosion resistance is improved. Optionally, the amination nanometer silicon dioxide aerogel is pre