A new type of corrosion-resistant plastic mold steel 2Cr16MoWVN and its preparation method

Abstract

The present invention discloses a new type of corrosion-resistant plastic mold steel 2Cr16MoWVN and a preparation method thereof. The addition of high content of chromium, molybdenum, tungsten, vanadium, and especially nitrogen in this steel makes the new type of plastic mold steel have the characteristics of high hardness, high wear resistance, high corrosion resistance and high polishability; the preparation method provides a solution for the manufacture of the new type of plastic mold steel, and nitrogen is blown into the molten steel in the refining furnace in the later stage of smelting, and chromium nitride and silicon nitride are added in the remelting process to make the nitrogen reach the expected design value; the steel ingot is upset three times to reduce band segregation and make the internal structure of the steel more uniform and refined; the steel is subjected to a special spheroidizing annealing process for 2Cr16MoWN, so that the carbides inside the steel are dispersed and evenly distributed. The advantages of the present invention: 2Cr16MoWVN plastic mold steel has the advantages of high hardness, high wear resistance, high corrosion resistance and high polishability by virtue of its unique composition design and advanced preparation method. This new type of mold steel can meet the demand for high-quality molds in modern plastic mold manufacturing.

Description

Technical Field

[0001] The invention belongs to the field of mold steel, and in particular relates to a novel corrosion-resistant plastic mold steel 2Cr16MoWVN and a preparation method thereof. Background Art

[0002] With the rapid development of the plastics industry, the performance requirements for plastic mold steel are increasing. The chemical composition of traditional plastic mold steel generally contains 12.00% to 17.00% chromium (Cr), 0% to 1.00% molybdenum (Mo), 0% to 1.00% nickel (Ni), and 0% to 0.50% vanadium (V); heat treatment hardness (HRC): 32 to 52, wear resistance: wear rate 0.10 to 0.50 mg / N·m, corrosion resistance: 50g / l concentration of NaCl neutral salt spray test for 24h to 72h without rust and polishing performance: 8000# to 12000#. It is difficult to meet the needs of some high-precision, long-term molds. Summary of the invention

[0003] The invention discloses a novel corrosion-resistant plastic mold steel 2Cr16MoWVN and a preparation method thereof. The novel plastic mold steel has the properties of high hardness, high wear resistance, high corrosion resistance and high polishability, and the preparation method provides a solution for the manufacture of the novel plastic mold steel.

[0004] 1. New corrosion-resistant plastic mold steel 2Cr16MoWVN

[0005] ⑴Chemical composition

[0006] The chemical composition of the new corrosion-resistant plastic mold steel 2Cr16MoWVN should comply with the requirements of Table 1.

[0007] Table 1

[0008]

[0009] ⑵Performance

[0010] Hardness (HRC): not less than 58;

[0011] Wear resistance: wear rate is no more than 0.08mg / N·m;

[0012] Corrosion resistance: No rust after 50g / l NaCl neutral salt spray test for no less than 120h; Polishing performance: no less than 14000#.

[0013] 2. Preparation method of 2Cr16MoWVN

[0014] ⑴ Melting

[0015] ①Raw material selection

[0016] We select high-purity ferroalloy raw materials, strictly control the precise addition of high chromium, low chromium, ferromolybdenum, ferrotungsten, ferrovanadium, ferrosilicon and ferromanganese according to the target values ​​of chemical composition to ensure the accuracy of the composition; at the same time, we strictly screen the initial scrap steel raw materials.

[0017] ②Smelting process

[0018] The UHP+LF+VD smelting process is adopted to accurately control the smelting temperature and time. In the later stage of smelting, nitrogen is blown into the molten steel in the refining furnace until the nitrogen content in the steel reaches 0.10% to 0.11%. The electrode is remelted for the second time in a 15t pressurized electroslag furnace, and chromium nitride and silicon nitride are added during the remelting process to make the nitrogen reach the expected design value of 0.35% to 0.45%.

[0019] ⑵Forging

[0020] ①Heating

[0021] The steel ingots are heated in stages at 1050°C and 1190°C.

[0022] ②Forging

[0023] The steel ingot is upset three times with a suitable forging ratio. During the forging process, the direction and degree of forging deformation are well controlled.

[0024] ③Heat treatment:

[0025] After forging, the finished product is air-cooled to 300℃ and loaded into the furnace for 2Cr16MoWN special spheroidizing annealing process. The first stage temperature is 860℃, the holding time is 3h, the second stage temperature is 730℃, the holding time is 6h, the third stage temperature is 880℃, the holding time is 3h, and the fourth stage temperature is 650℃, the holding time is 8h.

[0026] Invention point and mechanism analysis:

[0027] 1. Main chemical components

[0028] ⑴ The high chromium (Cr) content is about 16%, which forms a stable chromium oxide film to prevent the steel from further oxidation and corrosion, greatly improving the steel's oxidation resistance and corrosion resistance. The high chromium content in this steel is the basis for its good corrosion resistance.

[0029] ⑵ The addition of molybdenum (Mo) can refine the grains and improve the strength and toughness of the steel; at the same time, molybdenum combines with chromium to play a synergistic role in improving the hardness of the mold steel. In this type of steel, the presence of molybdenum is beneficial to improving the wear resistance of the steel.

[0030] ⑶ Tungsten (W) is an effective strengthening element that can form extremely hard carbides in steel. These carbides are dispersed in the matrix, significantly improving the hardness of the mold steel. Moreover, the addition of tungsten helps to improve the red hardness of the steel, allowing the mold to maintain good mechanical properties in a high temperature environment.

[0031] ⑷ Vanadium (V) forms carbides in steel with high hardness and high stability. These carbides can prevent grain growth and improve the fine grain strengthening effect of steel. In this steel, one of the functions of vanadium is to improve the wear resistance of steel.

[0032] ⑸ Nitrogen (N) 0.40% addition is a feature of this steel. Nitrogen can partially replace the role of carbon in steel, and the nitride formed has a positive effect on improving the hardness, strength, wear resistance and corrosion resistance of steel, and the presence of nitrogen can improve the cutting performance of steel; different from carbides, nitrides are evenly distributed in steel and have lighter segregation, which greatly improves the polishing performance of steel.

[0033] 2. Preparation method

[0034] ②Smelting process

[0035] During the smelting process, the smelting temperature and time are precisely controlled, and inclusions in the molten steel are removed through multiple refining to improve the purity of the molten steel. In the later stage of smelting, nitrogen is blown into the molten steel in the refining furnace until the nitrogen content in the steel reaches 0.10% to 0.11%, providing the basic nitrogen content for the subsequent remelting in a pressurized electric slag furnace. At the same time, nitrogen is used to increase nitrogen and reduce production costs. The electrode is remelted twice in a 15t pressurized electric slag furnace for secondary purification, and chromium nitride and silicon nitride are added during the remelting process to make the nitrogen reach the expected design value.

[0036] ⑵Forging

[0037] Due to the addition of nitrogen, the heating speed and temperature must be strictly controlled during the heating process before forging to avoid cracks in the steel due to over-rapid heating.

[0038] The steel ingot is upset three times to reduce band segregation. Through repeated upsetting and stretching processes, the internal structure of the steel is made more uniform and refined. During the forging process, the direction and degree of forging deformation are controlled to avoid forging defects.

[0039] ③Heat treatment:

[0040] The steel adopts the special spheroidizing annealing process of 2Cr16MoWN to make the carbides inside the steel dispersed and evenly distributed. The carbide particle size is controlled by the holding time, which is beneficial to the subsequent processing and heat treatment. At the same time, the forging internal stress is eliminated and the toughness of the steel is improved.

[0041] 3. Achieve high hardness, high wear resistance, high corrosion resistance and high polishing performance

[0042] ⑴High hardness

[0043] Alloy elements such as chromium, tungsten, molybdenum, and vanadium form carbides and nitrides in steel. These hard phases are dispersed in the steel matrix and improve the hardness of the steel through the dispersion strengthening mechanism. The carbides formed by tungsten and molybdenum have higher hardness, while the nitrides formed by vanadium and nitrogen further supplement the strengthening effect, making 2Cr16MoWVN steel have high hardness, so that the plastic molds made of this steel can better resist deformation and ensure the accuracy of the shape of the mold during long-term use, thereby ensuring the stability of the dimensional accuracy of plastic products.

[0044] ⑵High wear resistance

[0045] Hard phases such as carbides and nitrides in steel not only increase the hardness, but also have good wear resistance. During the use of the mold, it can resist the wear of the mold surface by the current special new plastic materials, extend the service life of the mold, reduce the frequency of mold replacement, thereby improving the production efficiency of plastic production enterprises and reducing production costs.

[0046] ⑶High corrosion resistance

[0047] Since plastic products may come into contact with different chemicals during the production process, such as plastic additives, release agents, etc., the highly corrosion-resistant 2Cr16MoWN can effectively resist the corrosion of these chemicals, prevent rust or other corrosion damage on the mold surface, maintain the mold surface quality, and thus ensure the quality stability of plastic products.

[0048] ⑷High polishability

[0049] During the preparation process, inclusions are removed through secondary smelting to reduce the impurity content. Low-impurity steel can obtain a smoother surface during the polishing process to prevent impurities from interfering with the polishing effect. At the same time, the uniform organizational structure is conducive to the polishing process. Whether it is martensitic structure or dispersed carbides, nitrides, etc., the uniformity can ensure that the material removal rate of each part during the polishing process is relatively consistent, thereby obtaining a high-polished surface. When manufacturing plastic products with high appearance requirements, such as plastic products with a smooth mirror effect, the good polishing property of 2Cr16MoWN can easily achieve a high-roughness mold surface, meeting the appearance requirements of high-end plastic products.

[0050] Advantages of the present invention:

[0051] 2Cr16MoWVN plastic mold steel has the advantages of high hardness, high wear resistance, high corrosion resistance and high polishing due to its unique composition design and advanced preparation method. This new mold steel can meet the demand for high-quality molds in modern plastic mold manufacturing. DETAILED DESCRIPTION

[0052] According to the above technical solution, the following three preferred embodiments are provided.

[0053] Example 1

[0054] Corrosion-resistant plastic mold steel 2Cr16MoWN forged flat steel, finished product size is 210mm×600mm.

[0055] 1. Consumable electrode smelting: UHP+LF+VD process is used for smelting. The raw materials include scrap steel, high chromium, low chromium, ferromolybdenum, ferrotungsten, ferrovanadium, ferrosilicon and ferromanganese, which are added precisely according to the target value of chemical composition. Nitrogen is blown into the refining furnace until the nitrogen content in the steel reaches 0.10%.

[0056] 2. Electroslag remelting: The electrode is remelted twice in a 15t pressurized electroslag furnace and nitrogen is added to 0.405%.

[0057] 3. Forging: The steel ingot is heated in sections at 1050℃ and 1190℃. The steel ingot is upset three times to reduce band segregation. During the forging process, the direction and degree of forging deformation are well controlled.

[0058] 4. Heat treatment: After forging, the finished material is air-cooled to 300℃ and loaded into the furnace for 2Cr16MoWN special spheroidizing annealing process. The first stage temperature is 860℃, the holding time is 3h, the second stage temperature is 730℃, the holding time is 6h, the third stage temperature is 880℃, the holding time is 3h, and the fourth stage temperature is 650℃, the holding time is 8h.

[0059] 5. Physical and chemical test results:

[0060] (1) The chemical composition analysis results of corrosion-resistant plastic mold steel 2Cr16MoWN forged flat steel are shown in Table 2;

[0061] Table 2

[0062]

[0063] ⑵Hardness: Through quenching + tempering heat treatment, the hardness (HRC) reaches 58.4;

[0064] ⑶ Wear resistance: wear rate 0.066mg / N·m;

[0065] ⑷ Corrosion resistance: No rust after 130h of 50g / l NaCl neutral salt spray test;

[0066] ⑸Polishing performance: Polishing 14000#.

[0067] Example 2

[0068] Corrosion-resistant plastic mold steel 2Cr16MoWN forged round steel, finished product size is Φ225mm.

[0069] 1. Consumable electrode smelting: UHP+LF+VD process is used for smelting. The raw materials include scrap steel, high chromium, low chromium, ferromolybdenum, ferrotungsten, ferrovanadium, ferrosilicon and ferromanganese, which are added precisely according to the target value of chemical composition. Nitrogen is blown into the refining furnace until the nitrogen content in the steel reaches 0.11%.

[0070] 2. Electroslag remelting: The electrode is remelted twice in a 15t pressurized electroslag furnace and nitrogen is added to 0.405%.

[0071] 3. Forging: The steel ingot is heated in sections at 1050℃ and 1190℃. The steel ingot is upset three times to reduce band segregation. During the forging process, the direction and degree of forging deformation are well controlled.

[0072] 4. Heat treatment: After forging, the finished material is air-cooled to 300℃ and loaded into the furnace for 2Cr16MoWN special spheroidizing annealing process. The first stage temperature is 860℃, the holding time is 3h, the second stage temperature is 730℃, the holding time is 6h, the third stage temperature is 880℃, the holding time is 3h, and the fourth stage temperature is 650℃, the holding time is 8h.

[0073] 5. Physical and chemical test results:

[0074] (1) The chemical composition analysis results of corrosion-resistant plastic mold steel 2Cr16MoWN forged flat steel are shown in Table 3;

[0075] Table 3

[0076]

[0077] ⑵Hardness: Through quenching + tempering heat treatment, the hardness (HRC) reaches 58.3;

[0078] ⑶ Wear resistance: wear rate 0.071mg / N·m;

[0079] ⑷ Corrosion resistance: No rust after 125h of 50g / l NaCl neutral salt spray test;

[0080] ⑸Polishing performance: Polishing 14000#.

[0081] Example 3

[0082] Corrosion-resistant plastic mold steel 2Cr16MoWN forged flat steel, finished product size is 170mm×610mm.

[0083] 1. Consumable electrode smelting: UHP+LF+VD process is used for smelting. The raw materials include scrap steel, high chromium, low chromium, ferromolybdenum, ferrotungsten, ferrovanadium, ferrosilicon and ferromanganese, which are added precisely according to the target value of chemical composition. Nitrogen is blown into the refining furnace until the nitrogen content in the steel reaches 0.105%.

[0084] 2. Electroslag remelting: The electrode is remelted twice in a 15t pressurized electroslag furnace and nitrogen is added to 0.412%.

[0085] 3. Forging: The steel ingot is heated in sections at 1050℃ and 1190℃. The steel ingot is upset three times to reduce band segregation. During the forging process, the direction and degree of forging deformation are well controlled.

[0086] 4. Heat treatment: After forging, the finished material is air-cooled to 300℃ and loaded into the furnace for 2Cr16MoWN special spheroidizing annealing process. The first stage temperature is 860℃, the holding time is 3h, the second stage temperature is 730℃, the holding time is 6h, the third stage temperature is 880℃, the holding time is 3h, and the fourth stage temperature is 650℃, the holding time is 8h.

[0087] 5. Physical and chemical test results:

[0088] (1) The chemical composition analysis results of corrosion-resistant plastic mold steel 2Cr16MoWN forged flat steel are shown in Table 4;

[0089] Table 4

[0090]

[0091] ⑵Hardness: Through quenching + tempering heat treatment, the hardness (HRC) reaches 58.6;

[0092] ⑶ Wear resistance: wear rate 0.068mg / N·m;

[0093] ⑷ Corrosion resistance: No rust after 128h of 50g / l NaCl neutral salt spray test;

[0094] ⑸Polishing performance: Polishing 14000#.

Claims

1. A new type of corrosion-resistant plastic mold steel 2Cr16MoWVN, characterized by: ⑴The chemical composition shall comply with the requirements of Table 1; Table 1 ⑵Performance Hardness (HRC): not less than 58; Wear resistance: wear rate is no more than 0.08mg / N·m; Corrosion resistance: No rust after 50g / l NaCl neutral salt spray test for no less than 120h; Polishing performance: not less than 14000#.

2. The method for preparing the novel corrosion-resistant plastic mold steel 2Cr16MoWVN according to claim 1, characterized in that: ⑴ Melting ①Raw material selection We select high-purity ferroalloy raw materials, strictly control the precise addition of high chromium, low chromium, ferromolybdenum, ferrotungsten, ferrovanadium, ferrosilicon and ferromanganese according to the target values ​​of chemical composition to ensure the accuracy of the composition; at the same time, we strictly screen the initial scrap steel raw materials. ②Smelting process The UHP+LF+VD smelting process is adopted to accurately control the smelting temperature and time. In the later stage of smelting, nitrogen is blown into the molten steel in the refining furnace until the nitrogen content in the steel reaches 0.10% to 0.11%. The electrode is remelted for the second time in a 15t pressurized electroslag furnace, and chromium nitride and silicon nitride are added during the remelting process to make the nitrogen reach the expected design value of 0.35% to 0.45%. ⑵Forging ①Heating The steel ingots are heated in stages at 1050°C and 1190°C. ②Forging The steel ingot is upset three times with a suitable forging ratio. During the forging process, the direction and degree of forging deformation are well controlled. ③Heat treatment: After forging, the finished product is air-cooled to 300℃ and loaded into the furnace for 2Cr16MoWN special spheroidizing annealing process. The first stage temperature is 860℃, the holding time is 3h, the second stage temperature is 730℃, the holding time is 6h, the third stage temperature is 880℃, the holding time is 3h, and the fourth stage temperature is 650℃, the holding time is 8h.

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