阅读说明：本技术 7Cr7Mo2V2Si高温镦锻模具的表面处理方法 (Surface treatment method of 7Cr7Mo2V2Si high-temperature upsetting die ) 是由 罗勇 付又桥 于 2020-05-25 设计创作，主要内容包括：本发明公开了一种7Cr7Mo2V2Si高温镦锻模具的表面处理方法,具体步骤如下：1)高温氧化：由7Cr7Mo2V2Si模具钢制作的模具放入箱式炉中进行保温,模具型腔表面上的氧化膜是由模具本体内的Fe元素与空气中的氧元素形成细腻的四氧化三铁；2)低温油浴：模具高温氧化后冷却至室温,然后浸入至油脂中,油脂渗入至氧化膜内,油脂在零件成型过程中起润滑、隔离作用；模具通过高温表面氧化、浸油处理后的高温热镦锻模具,使用时粘连现象消失,零件表面粗糙度大幅提升,同时高温热镦锻模具寿命大幅提高。(The invention discloses a surface treatment method of a 7Cr7Mo2V2Si high-temperature upsetting die, which comprises the following specific steps: 1) high-temperature oxidation: placing a mould made of 7Cr7Mo2V2Si mould steel into a box-type furnace for heat preservation, wherein an oxidation film on the surface of a mould cavity is fine ferroferric oxide formed by Fe element in a mould body and oxygen element in air; 2) low-temperature oil bath: cooling the mold to room temperature after high-temperature oxidation, then immersing the mold into grease, and enabling the grease to penetrate into an oxidation film, wherein the grease plays a role in lubrication and isolation in the part forming process; the high-temperature hot heading forging die after the die is subjected to high-temperature surface oxidation and oil immersion treatment has the advantages that the adhesion phenomenon disappears during use, the surface roughness of parts is greatly improved, and meanwhile, the service life of the high-temperature hot heading forging die is greatly prolonged.)

The surface treatment method of the 1.7Cr7Mo2V2Si high-temperature upsetting die comprises the following specific steps:

first-step high-temperature oxidation: placing a mold made of 7Cr7Mo2V2Si mold steel into a box furnace at the temperature of 750 +/-10 ℃, and preserving heat for 13-17 min, wherein an oxidation film on the surface of a mold cavity is fine ferroferric oxide formed by Fe element in a mold body and oxygen element in air;

and a second step of low-temperature oil bath: cooling the mold to 250-200 ℃ at room temperature after high-temperature oxidation, immersing the mold into grease for 10-12 min, and taking out the mold after cooling the mold to room temperature in the grease; the grease is formed by mixing sulfur-containing lubricating oil and thin-layer anti-rust oil, the sulfur-containing grease permeates into an oxidation film and plays a lubricating role in the part forming process, the thin-layer anti-rust oil forms an oil film layer on the oxidation film, the thickness of the oil film layer is 6-10 microns, and the thin-layer anti-rust oil plays an isolating role in the part forming process.

2. The surface treatment method of a 7Cr7Mo2V2Si high-temperature upsetting die as claimed in claim 1, wherein: the temperature of the box furnace is 750 ℃.

3. The surface treatment method of 7Cr7Mo2V2Si high-temperature upsetting die as claimed in claim 1 or 2, wherein: the sulfur-containing lubricating oil accounts for 18-22%, and the thin-layer anti-rust oil accounts for 75-85% by mass.

Technical Field

The invention belongs to the field of high-temperature upsetting dies, and particularly relates to a surface treatment method of a 7Cr7Mo2V2Si high-temperature upsetting die.

Background

The method of the invention is close to the related technology that: PVD, CVD, PCVD, TD, ceramic nanocoating. Through the application test of the surface coating technologies listed above, the surface coating technologies cannot improve the part forming galling phenomenon due to the influence of high-temperature and high-speed working environments, and the die service life improving effect is not obvious.

With the internationalization of the automobile industry in China, the large-size and high-strength nut 1 (shown in figure 1) continuously appears in the fastener industry, and the hot forming processing becomes an indispensable development trend. The high-temperature thermal forming (workpiece heating temperature 1060 ℃ -1150 ℃) process can greatly improve the production efficiency and the material utilization rate. However, the large-sized high-strength nut is generally made of 45 # steel, 40Cr and other materials, a die used for part forming works in a working environment of 1060-1150 ℃ and a production beat of 110-150 pieces/min, and the forming female die used in hot forming processing is required to be capable of well meeting the requirements of the working environment for high-temperature and high-speed forming.

Due to the working environment of the die at high temperature of 1060-1150 ℃ and the production rhythm of 110-150 pieces/min at high speed, the die needs to bear repeated impact load and cold-heat alternation. The die is easy to generate fatigue fracture under the action of thermal stress, the surface of the die cavity generates friction effect under the action of high-temperature metal flow, and particularly under the condition that oxide scales on the surface of a blank are not cleaned, the friction effect is stronger, so that the abrasion of the surface of the die cavity is accelerated, and the peeling phenomenon is generated. After 3Cr2W8V, H13, DAC and other hot die steel are optimized (the service life is less than 5000 pieces), dies (shown in figure 2) made of 7Cr7Mo2V2Si are adopted, the service life is the highest, the service life of each die is only 10000 pieces, and when 40Cr is used as a raw material of a part, the part is adhered to the die (shown as a right-angled part 3 in a die forming cavity in figure 2) only in about 100 pieces of formed parts, and galling is generated at six corners of the part.

In conclusion, when the female die used by the hot forming machine manufactured by 7Cr7Mo2V2Si is processed, the anti-oxidation and hot corrosion performances of the female die and the forming working surface of the part are improved through the improvement of the working surface treatment process of the die, the working environment of forming and demoulding of the part is improved, and the purposes of prolonging the service life of the die and improving the forming quality of the high-strength nut are achieved.

Disclosure of Invention

The invention provides a surface treatment method of a 7Cr7Mo2V2Si high-temperature upsetting and forging die, which aims to improve the oxidation resistance and hot corrosion resistance of a female die and a part forming working surface, and by developing and applying a surface treatment technology, the purposes of improving the part forming and demolding working environment, eliminating the adhesion and galling phenomena of parts and prolonging the service life of the die are achieved.

In order to solve the technical problems, the technical scheme of the invention is as follows: the surface treatment method of the 7Cr7Mo2V2Si high-temperature upsetting die comprises the following specific steps:

first-step high-temperature oxidation: placing a mold made of 7Cr7Mo2V2Si mold steel into a box furnace at the temperature of 750 +/-10 ℃, and preserving heat for 13-17 min, wherein an oxidation film on the surface of a mold cavity is fine ferroferric oxide formed by Fe element in a mold body and oxygen element in air;

and a second step of low-temperature oil bath: cooling the mold to 250-200 ℃ at room temperature after high-temperature oxidation, immersing the mold into grease for 10-12 min, and taking out the mold after cooling the mold to room temperature in the grease; the grease is formed by mixing sulfur-containing lubricating oil and thin-layer anti-rust oil, the sulfur-containing grease permeates into an oxidation film and plays a lubricating role in the part forming process, the thin-layer anti-rust oil forms an oil film layer on the oxidation film, the thickness of the oil film layer is 6-10 microns, and the thin-layer anti-rust oil plays an isolating role in the part forming process.

The technical scheme is further limited, and the temperature of the box type furnace is 750 ℃.

The technical scheme is further limited, wherein the sulfur-containing lubricating oil accounts for 18-22%, and the thin-layer anti-rust oil accounts for 75-85% by mass.

The invention has the beneficial effects that: the high-temperature hot-heading forging die treated by high-temperature surface oxidation and oil immersion disappears adhesion phenomenon in use, the surface roughness of parts is greatly improved, and meanwhile, the service life of the high-temperature hot-heading forging die is greatly prolonged from 1.0 ten thousand per part to 3 ten thousand per part.

Drawings

Fig. 1 is a schematic view of a nut in the background art.

Fig. 2 is a schematic diagram illustrating a galling phenomenon in a nut of the related art.

Detailed Description

The surface treatment method of the 7Cr7Mo2V2Si high-temperature upsetting die comprises the following specific steps:

first-step high-temperature oxidation: placing a mold made of 7Cr7Mo2V2Si mold steel into a box furnace at 750 ℃, preserving heat for 15min, wherein an oxidation film on the surface of a mold cavity is fine ferroferric oxide formed by Fe element in a mold body and oxygen element in air; through multiple tests, the oxide film formed by insulating the oxide film for 15 minutes at 750 ℃ of the die is the smallest and greasy, if the temperature exceeds 750 ℃, the hardness of the die can be rapidly reduced, the working surface of the die is excessively oxidized, the uniform and fine oxide film cannot be formed, but the oxide layer which is easy to peel off is formed, and the surface roughness is damaged; when the temperature is lower than 740 ℃, the oxidation time is increased, the oxidation reaction between oxygen in the air and Fe in the matrix of the mold can not be rapidly and sufficiently generated, the oxidation time is increased, the roughness of the working surface of the mold is damaged, and the aim of forming a uniform and fine oxide film can not be achieved; before the die works at high temperature, an oxide film is formed on the working surface of the die in advance, the oxide film increases the surface hardness of the die, eliminates the high-temperature action of the die during working, increases the surface roughness of the die for keeping time, ensures smooth demoulding of parts during forming, and eliminates the adhesion tendency of the parts during high-temperature forming;

and a second step of low-temperature oil bath: cooling the mold to 230 ℃ at room temperature after high-temperature oxidation, immersing the mold into grease for 11min, and taking out the mold after cooling to room temperature; oil temperature can be too high when the oil bath is higher than 250 ℃, which causes safety problems; the oil temperature is lower than 150 ℃, so that the quality of grease penetrating into the oxidation film is reduced; the grease is formed by mixing sulfur-containing lubricating oil and thin-layer anti-rust oil, the sulfur-containing grease permeates into an oxidation film (namely sulfur elements in the sulfur-containing lubricating oil are distributed in gaps of the oxidation film of the die), and the sulfur-containing grease has a lubricating effect in the part forming process; the thin-layer anti-rust oil has excellent lubricity and film-forming property, can quickly permeate into metal, can form an oil film layer on an oxidation film, has the thickness of 8 mu m, has a separation effect in the part forming process, and solves the problem that parts made of 40Cr materials are adhered to the surface of a mould; the sulfur-containing lubricating oil accounts for 20 percent, and the thin-layer anti-rust oil accounts for 80 percent by mass;

the sulfur-containing lubricating oil is prepared by blending high-quality mineral base oil, high-performance vulcanized lard oil and vulcanized fatty acid ester serving as main agents; produced by FRANCOOL corporation of Jiangsu, China, and the brand number: FRANCOOL 9006D;

the thin-layer rust preventive oil: the rust preventive oil is mainly prepared from a plurality of oil-soluble corrosion inhibitors, a stabilizer, a dehydrating agent and refined base oil; manufactured by Shi Wei Shuangqi technology Limited, and having the brand number: and S2018.

After the surface treatment of the 7Cr7Mo2V2Si die: 1) the hardness of the die is improved: increasing the HRC from 58-59 to 61-62; 2) surface roughness of a mold cavity: ra0.2.