Reaming die for bearing ring production and machining treatment technology of reaming die

Abstract

The invention discloses a broaching die for bearing ring production and a machining treatment process of the broaching die. And the reaming die is prepared by processing a 4CrMnSiMoVNi alloy bar with silicon distributed in a gradient manner. The 4CrMnSiMoVNi alloy rod with silicon in gradient distribution comprises the following chemical components in percentage by weight: 0.20%-0.50% of carbon, 1.00%-1.50% of chromium, 0.80%-1.50% of manganese, 0.20%-0.50% of molybdenum, 0.10%-0.30% of vanadium, 0.90%-1.50% of nickel, less than or equal to 0.030% of sulfur, less than or equal to 0.030% of phosphorus, and silicon with the content in gradient change from the surface to the center of the alloy rod, the silicon content in the center of the alloy rod is 0.20%-0.60%, the silicon content in the surface is 1.00%-1.30%, and the balance of iron and inevitable impurities.

Description

Technical Field

[0001] The present invention relates to the technical field of bearing processing equipment, and particularly relates to an alloy rod, a reaming die processed and prepared from the alloy rod, a processing technology of the reaming die, and an application of the reaming die in manufacturing a reaming die for a bearing ring forging processed by hot deformation. Background Art

[0002] The ring is a basic component of a bearing. The production of the ring generally includes processes such as blank induction heating, blanking, upsetting, forming, bottom cutting, reaming, and sizing. Reaming is generally carried out on a reaming machine. During reaming, the annular blank forging is sleeved on the reaming die, and the motor drives the rotating rolling wheel to roll the annular blank forging. Under the action of frictional force, the blank forging and the reaming die are driven to rotate together, so that the wall thickness of the blank forging is thinned, and the inner and outer diameters of the ring are increased. After rotary expansion, a forging finished product is made.

[0003] The inventor disclosed an alloy material in Patent CN114990447B. Its chemical composition by weight percentage is: carbon 1.06% - 1.20%, chromium 1.30% - 2.00%, manganese 0.30% - 0.49%, silicon 0.10% - 0.25%, rare earth cerium 0.106% - 0.120%, rare earth dysprosium 0.053% - 0.060%, rare earth terbium 0.053% - 0.060%, sulfur ≤ 0.005%, phosphorus ≤ 0.005%, and the rest is iron and inevitable impurities; and the mass ratio of carbon, rare earth cerium, rare earth dysprosium, and rare earth terbium is (16 - 24):(1.6 - 2.4):(0.8 - 1.2):(0.8 - 1.2). This patented technology also disclosed a reaming die prepared from the above alloy material and its processing technology. The above alloy material is spheroidized and annealed, and then processed and formed into a die with a target structure. The obtained die is quenched, cryogenically treated, tempered, and stress-relieved by aging treatment to obtain a reaming die. The reaming die of this patented technology has the characteristics of not being easily broken, not being easily worn on the surface, and having a long service life. Moreover, its processing technology is simple, and the requirements for heating equipment are low, which has important application value in the field of bearing processing. This patented technology is based on GCr15 steel for element blending, increasing the carbon content and introducing rare earth elements cerium, dysprosium, and terbium, among which the rare earth elements cerium, dysprosium, and terbium are relatively expensive. If an alloy material suitable for making a reaming die can be obtained without adding expensive elements such as rare earth elements, it is of great significance for reducing material costs.

[0004] 4CrMnSiMoV steel has high tempering resistance, good high-temperature strength, heat fatigue resistance and toughness, and has high hardenability, good cold and hot processing performance, and is suitable for manufacturing various types of hammer dies and press forging dies.

[0005] Bearing ring forging enterprises often use 4CrMnSiMoV steel to manufacture hole expanding dies. Since the forming pressure of the rough forging ring rolling is ultimately borne by the hole expanding die, the hole expanding die is prone to fracture. During the ring rolling process of the rough forging, there is a strong frictional force between the forging and the hole expanding die, resulting in easy wear on the surface of the hole expanding die. When the rough forging is formed by ring rolling, the temperature is above 800 °C, and the heat is transferred to the hole expanding die, causing the hole expanding die to be heated passively. After the forging is removed, the temperature of the hole expanding die will drop rapidly. Therefore, the hole expanding die is in a high alternating stress condition and is prone to fatigue. Due to fracture, surface wear and fatigue, the hole expanding die needs to be replaced frequently, which reduces the production efficiency and brings huge economic losses to the enterprise production. How to improve and optimize on the basis of 4CrMnSiMoV steel, so that the further prepared hole expanding die has more excellent characteristics such as not easy to fracture, slight wear, oxidation and fatigue resistance, and long service life while maintaining a relatively low cost, is an important and practical research direction. Summary of the Invention

[0006] In view of the above technical problems and the deficiencies in the art, the present invention provides an alloy rod, a hole expanding die processed and prepared from the alloy rod, and a processing technology for the hole expanding die. The hole expanding die prepared using the alloy rod is not easy to fracture, has small surface wear, good oxidation and fatigue resistance, and a long service life. Using the alloy rod to manufacture the hole expanding die has important application value in the bearing processing field.

[0007] The specific technical solutions are as follows:

[0008] [1] A 4CrMnSiMoVNi alloy rod with a silicon gradient distribution, the chemical composition is calculated by weight percentage as follows: carbon 0.20% - 0.50% (such as 0.40% etc.), chromium 1.00% - 1.50% (such as 1.20% etc.), manganese 0.80% - 1.50% (such as 1.20% etc.), molybdenum 0.20% - 0.50% (such as 0.40% etc.), vanadium 0.10% - 0.30% (such as 0.20% etc.), nickel 0.90% - 1.50% (such as 1.00% etc.), sulfur ≤ 0.030%, phosphorus ≤ 0.030%, and silicon with a gradient change from the surface to the center of the alloy rod, and the silicon content at the center of the alloy rod is 0.20% - 0.60% (such as 0.30%, 0.40% etc.), the silicon content on the surface is 1.00% - 1.30% (such as 1.10%, 1.20% etc.), and the rest is iron and inevitable impurities.

[0009] The diameter of the 4CrMnSiMoVNi alloy rod with a silicon gradient distribution can be 30 - 100 mm, such as 45 mm etc.

[0010] In some embodiments, a 4CrMnSiMoVNi alloy rod with a silicon gradient distribution is prepared by casting: a layer of silicon powder is sprayed on the inner surface of the mold, and the molten alloy liquid fills the mold from bottom to top through a stepped gating system to avoid turbulence of the alloy liquid in the mold; the mold is preheated to 200 - 500 °C before pouring, such as 300 °C etc.

[0011] In order to dissolve the silicon powder sprayed on the inner surface of the mold and diffuse it from the surface of the alloy rod to the center, the following strategies are adopted: 1) The pouring temperature is above the melting point of silicon, 250 °C, and the self-heat of the alloy liquid is used to melt a small amount of low-melting-point silicon; 2) The mold is preheated to 200 - 500 °C before pouring, such as 300 °C etc., to reduce the cooling effect of the mold on the alloy liquid and extend the solidification process and the high-temperature cooling stage. If the pouring temperature and mold preheating are not coordinated, the dissolution and diffusion of the silicon powder cannot be fully carried out, and the punching die made of this material is prone to fracture during actual use.

[0012] In some embodiments, zircon sand can be used for molding.

[0013] In some embodiments, the mass of the sprayed silicon powder is 0.05% - 1.50% of the mass of the poured alloy liquid, such as 0.40%, 0.47% etc.

[0014] In some embodiments, the chemical components in the alloy liquid are by weight percentage: carbon 0.20% - 0.50% (such as 0.40% etc.), chromium 1.00% - 1.50% (such as 1.20% etc.), manganese 0.80% - 1.50% (such as 1.20% etc.), molybdenum 0.20% - 0.50% (such as 0.40% etc.), vanadium 0.10% - 0.30% (such as 0.20% etc.), nickel 0.90% - 1.50% (such as 1.00% etc.), sulfur ≤ 0.030%, phosphorus ≤ 0.030%, silicon 0.20% - 0.60% (such as 0.30%, 0.40% etc.), and the rest is iron and inevitable impurities.

[0015] In some preferred examples, the pouring temperature is above the melting point of silicon, 250 °C, and is 1650 - 1750 °C, such as 1700 °C etc.

[0016] [2] A reaming die processed and prepared from the 4CrMnSiMoVNi alloy rod with a silicon gradient distribution described in [1].

[0017] [3] The processing technology of the reaming die according to [2], including:

[0018] Preparation of 4CrMnSiMoVNi alloy rod with gradient silicon distribution by casting: Spray a layer of silicon powder on the inner surface of the mold. Through a stepped gating system, the molten alloy liquid fills the mold from bottom to top to avoid turbulence of the alloy liquid in the mold. Before pouring, the mold is preheated to 200 - 500 °C, such as 300 °C, etc.

[0019] The 4CrMnSiMoVNi alloy rod with gradient silicon distribution is first subjected to isothermal annealing treatment, then machined into the target structure and size, then quenched, and then tempered, and cooled to obtain the reaming die.

[0020] In some embodiments, zircon sand molding can be used.

[0021] In some embodiments, the mass of the sprayed silicon powder is 0.05% - 1.50% of the mass of the poured alloy liquid, such as 0.40%, 0.47%, etc.

[0022] In some embodiments, the chemical components in the alloy liquid are by weight percentage: carbon 0.20% - 0.50% (such as 0.40%, etc.), chromium 1.00% - 1.50% (such as 1.20%, etc.), manganese 0.80% - 1.50% (such as 1.20%, etc.), molybdenum 0.20% - 0.50% (such as 0.40%, etc.), vanadium 0.10% - 0.30% (such as 0.20%, etc.), nickel 0.90% - 1.50% (such as 1.00%, etc.), sulfur ≤ 0.030%, phosphorus ≤ 0.030%, silicon 0.20% - 0.60% (such as 0.30%, 0.40%, etc.), and the rest is iron and inevitable impurities.

[0023] In some preferred examples, the pouring temperature is above the melting point of silicon, 250 °C, and is 1650 - 1750 °C, such as 1700 °C, etc.

[0024] In some embodiments, the isothermal annealing treatment specifically includes: heating to 850 - 950 °C, such as 880 ± 10 °C, etc., holding for 20 - 300 min, such as 120 - 130 min, etc., cooling to 700 - 750 °C, such as 720 ± 10 °C, etc., holding for 60 - 300 min, such as 120 - 130 min, etc., furnace cooling to 480 - 500 °C, and taking out of the furnace for air cooling.

[0025] In some embodiments, the quenching specifically includes: quenching temperature 850 - 950 °C, such as 900 ± 10 °C, etc., holding for 20 - 60 min, such as 30 - 35 min, etc., and oil cooling.

[0026] In some embodiments, the tempering treatment specifically includes: tempering temperature 500 - 650 °C, such as 580 ± 10 °C, etc., holding for 20 - 300 min, such as 120 - 125 min, etc., and oil cooling.

[0027] [4] Application of the 4CrMnSiMoVNi alloy rod with silicon gradient distribution according to [1] or the reaming die according to [2] in manufacturing a reaming die for bearing ring forgings processed by hot deformation.

[0028] Exemplarily, the alloy rod of the present invention can be used to manufacture a reaming die for bearing ring forgings, heat-treat it according to the designed process, install the manufactured reaming die on a D51 type ring rolling mill, produce bearing rings (such as with an outer diameter of 90 mm), and record the service life of the reaming die.

[0029] The present invention can obtain a reaming die that is not easily broken, has slight wear, is resistant to oxidation and fatigue, and has a long service life.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] Compared with traditional 4CrMnSiMoV, 4CrMnSiMoVNi steel has an increased nickel content. Nickel improves the toughness of the material, enabling the reaming die to withstand the impact load when the rolling wheel hits the blank without breaking, and extending the service life of the reaming die. In particular, the simultaneous use of nickel and silicon can significantly improve the toughness of the material, with a unique synergistic effect, far superior to the limited effects of using nickel or silicon alone.

[0032] The 4CrMnSiMoVNi alloy rod with silicon gradient distribution is prepared by casting. Silicon powder is sprayed on the inner surface of the mold as an additional silicon source. The pouring temperature of 4CrMnSiMoVNi is 1650 - 1750 °C, which is much higher than the melting point of silicon, and can melt the silicon powder attached to the inner wall of the mold, thereby increasing the silicon content on the surface of the alloy rod. A stepped gating system is adopted to enable the alloy liquid to fill the mold smoothly and slowly from bottom to top, avoiding turbulence of the alloy liquid inside the mold, and allowing the melted silicon to be concentrated on the surface layer of the alloy rod. The mold is preheated before pouring to reduce the chilling effect of the mold, extend the solidification time and high-temperature residence time of the alloy rod, and ensure the full diffusion of silicon towards the center to form a gradient distribution.

[0033] The silicon gradient distribution brings three beneficial effects to the 4CrMnSiMoVNi alloy rod. Effect 1: In the center of the rod, the silicon content is low, ensuring high overall toughness of the material, resistance to impact load, and the reaming die made of it is not easily broken; Effect 2: On the surface of the rod, the silicon content is high, and the solution strengthening effect of silicon can increase the surface hardness, and the surface of the reaming die made of it wears more slightly; Effect 3: The high silicon content can improve the oxidation resistance of the steel, especially in a high-temperature environment, and the reaming die made of it can be used for a long time with a stable surface without oxidation.

[0034] At the center of the bar, the silicon content is controlled within 0.20% - 0.60%, which can ensure a good balance between toughness and strength and is suitable for the working conditions of the hole-expanding die. If the silicon content is too low, it will lead to insufficient strength at the core of the hole-expanding die; if the silicon content is too high, it will reduce the toughness of the die core.

[0035] On the surface of the bar, the silicon content is controlled within 1.00% - 1.30%, which can ensure that the surface of the die has a sufficiently high hardness and is suitable for the working conditions of the hole-expanding die. If the silicon content is too low, it will reduce the surface hardness of the die, resulting in the die being not wear-resistant. If the silicon content exceeds 1.30%, it will increase the brittleness of the die surface layer and affect the comprehensive mechanical properties of the die surface layer after high-temperature tempering.

[0036] A moderately high silicon content on the surface can improve the tempering stability of the hole-expanding die, delay the tempering softening process, enable the hole-expanding die to still maintain a relatively high hardness after high-temperature tempering, and thus improve the wear resistance of the hole-expanding die.

[0037] A moderately high silicon content on the surface can improve the strength and hardness of the surface layer of the die, improve the fatigue performance of the hole-expanding die, and significantly increase the service life of the hole-expanding die. Specific embodiments

[0038] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The operating methods without specific conditions noted in the following embodiments are usually in accordance with conventional conditions or in accordance with the conditions recommended by the manufacturer.

[0039] Example 1:

[0040] A 4CrMnSiMoVNi alloy bar for a hole-expanding die of a bearing ring forging, comprising the following substances in weight percentages: carbon 0.40%, chromium 1.20%, manganese 1.20%, molybdenum 0.40%, vanadium 0.20%, nickel 1.00%, sulfur ≤0.030%, phosphorus ≤0.030%; the silicon content at the center of the alloy bar is 0.40%, the silicon content on the surface is 1.10%, and the silicon content from the surface to the center shows a gradient distribution; the rest is iron and inevitable impurities.

[0041] The above 4CrMnSiMoVNi alloy rod with silicon gradient distribution is prepared by casting. Zircon sand is used for molding, and a layer of silicon powder is sprayed on the inner surface of the mold. The mass of the sprayed silicon powder is 0.47% of the mass of the poured alloy liquid. The chemical components in the alloy liquid are by weight percentage: carbon 0.40%, chromium 1.20%, manganese 1.20%, molybdenum 0.40%, vanadium 0.20%, nickel 1.00%, sulfur ≤ 0.030%, phosphorus ≤ 0.030%, silicon 0.40%, and the rest is iron and inevitable impurities. Through a stepped gating system, the alloy liquid fills the mold smoothly and slowly from bottom to top to avoid turbulence of the alloy liquid inside the mold. The pouring temperature is 1700 °C, and the mold is preheated to 300 °C before pouring. The diameter of the alloy rod is 45 mm.

[0042] The 4CrMnSiMoVNi alloy rod with silicon gradient distribution is first subjected to isothermal annealing treatment, heated to 880 ± 10 °C, held for 120 min; cooled to 720 ± 10 °C, held for 120 min; furnace cooled to 500 °C, taken out of the furnace, and then air cooled to room temperature.

[0043] The alloy rod is machined into a reaming die with a conventional structure and size.

[0044] The reaming die is quenched, the heating temperature is 900 ± 10 °C, held for 30 min, and oil cooled. Then high-temperature tempering is carried out, the tempering temperature is 580 ± 10 °C, the tempering time is 120 min, and oil cooled.

[0045] The reaming die is installed on a D51 type ring rolling machine to produce bearing rings (outer diameter 90 mm), and it breaks after continuous production for 257 h.

[0046] Comparative Example 1:

[0047] The difference from Example 1 is only that commercial 4CrMnSiMoV steel is used. The chemical components of commercial 4CrMnSiMoV steel are by weight percentage: carbon 0.35% - 0.45%, chromium 1.30% - 1.60%, manganese 0.80% - 1.10%, molybdenum 0.20% - 0.40%, vanadium 0.20% - 0.30%, sulfur ≤ 0.030%, phosphorus ≤ 0.030%, silicon 0.80% - 1.00%, and the rest is iron and inevitable impurities.

[0048] A reaming die is made of commercial 4CrMnSiMoV steel alloy rod, and a reaming die with the same specifications is manufactured by the same process as in Example 1 and produced under the same conditions. It breaks after continuous production for 52 h.

[0049] Comparative Example 2:

[0050] The difference from Example 1 is only that during casting, a layer of silicon powder was not sprayed on the inner surface of the mold. The prepared 4CrMnSiMoVNi alloy bar has a uniform silicon distribution instead of a silicon gradient distribution, and the weight content of silicon on the surface and in the center of the alloy bar is both 0.40%.

[0051] An expansion die of the same specification was manufactured using the same process as in Example 1, and production was carried out under the same conditions. It fractured after continuous production for 89 hours.

[0052] Comparative Example 3:

[0053] The difference from Example 1 is that it was melted and cast using 4CrMnSiMoV steel without nickel. That is, the chemical composition in the alloy liquid by weight percentage is: carbon 0.40%, chromium 1.20%, manganese 1.20%, molybdenum 0.40%, vanadium 0.20%, sulfur ≤0.030%, phosphorus ≤0.030%, silicon 0.40%, and the rest is iron and unavoidable impurities. A 4CrMnSiMoV alloy bar with a silicon gradient distribution was prepared. The weight content of silicon in the center is 0.40%, and the weight content of silicon on the surface is 1.10%.

[0054] An expansion die of the same specification was manufactured using the same process as in Example 1, and production was carried out under the same conditions. It fractured after continuous production for 81 hours.

[0055] From the comparison between Example 1 and Comparative Examples 1 - 3, it can be seen that in the present invention, while introducing Ni, silicon is additionally introduced and the silicon shows a gradient distribution across the material cross-section. These two improvement methods work synergistically, significantly extending the service life of the expansion die from no more than 89 hours to 257 hours.

[0056] Example 2:

[0057] A 4CrMnSiMoVNi alloy bar for an expansion die of a bearing raceway forging, comprising the following substances by weight percentage: carbon 0.40%, chromium 1.20%, manganese 1.20%, molybdenum 0.40%, vanadium 0.20%, nickel 1.00%, sulfur ≤0.030%, phosphorus ≤0.030%; the silicon content in the center of the alloy bar is 0.30%, the silicon content on the surface is 1.00%, and the silicon content shows a gradient distribution from the surface to the center; the rest is iron and unavoidable impurities.

[0058] The above 4CrMnSiMoVNi alloy bar with a silicon gradient distribution was prepared using the same casting process as in Example 1. The amount of sprayed silicon powder is 0.47% of the mass of the cast alloy liquid, and the chemical composition in the alloy liquid by weight percentage is: carbon 0.40%, chromium 1.20%, manganese 1.20%, molybdenum 0.40%, vanadium 0.20%, nickel 1.00%, sulfur ≤0.030%, phosphorus ≤0.030%, silicon 0.30%, and the rest is iron and unavoidable impurities.

[0059] The same - sized reaming die as that in Example 1 was manufactured by the same process, and production was carried out under the same conditions. It fractured after continuous production for 201 h.

[0060] Example 3:

[0061] A 4CrMnSiMoVNi alloy bar for a reaming die of a bearing ring forging, comprising the following substances by weight percentage: carbon 0.40%, chromium 1.20%, manganese 1.20%, molybdenum 0.40%, vanadium 0.20%, nickel 1.00%, sulfur ≤ 0.030%, phosphorus ≤ 0.030%; the silicon content in the center of the alloy bar is 0.60%, the silicon content on the surface is 1.20%, and the silicon content from the surface to the center shows a gradient distribution; the rest is iron and inevitable impurities.

[0062] The above 4CrMnSiMoVNi alloy bar with silicon gradient distribution was prepared by the same casting process as that in Example 1, but the amount of sprayed silicon powder is 0.40% of the mass of the poured alloy liquid, and the chemical composition in the alloy liquid by weight percentage is: carbon 0.40%, chromium 1.20%, manganese 1.20%, molybdenum 0.40%, vanadium 0.20%, nickel 1.00%, sulfur ≤ 0.030%, phosphorus ≤ 0.030%, silicon 0.60%, and the rest is iron and inevitable impurities.

[0063] The same - sized reaming die as that in Example 1 was manufactured by the same process, and production was carried out under the same conditions. It fractured after continuous production for 231 h.

[0064] Comparative Example 4:

[0065] A 4CrMnSiMoVNi alloy bar for a reaming die of a bearing ring forging, comprising the following substances by weight percentage: carbon 0.40%, chromium 1.20%, manganese 1.20%, molybdenum 0.40%, vanadium 0.20%, nickel 1.00%, sulfur ≤ 0.030%, phosphorus ≤ 0.030%; the silicon content in the center of the alloy bar is 0.10%, the silicon content on the surface is 0.60%, and the silicon content from the surface to the center shows a gradient distribution; the rest is iron and inevitable impurities.

[0066] The above 4CrMnSiMoVNi alloy bar with silicon gradient distribution was prepared by the same casting process as that in Example 1, but the amount of sprayed silicon powder is 0.33% of the mass of the poured alloy liquid, and the chemical composition in the alloy liquid by weight percentage is: carbon 0.40%, chromium 1.20%, manganese 1.20%, molybdenum 0.40%, vanadium 0.20%, nickel 1.00%, sulfur ≤ 0.030%, phosphorus ≤ 0.030%, silicon 0.10%, and the rest is iron and inevitable impurities.

[0067] The same - sized reaming die as that in Example 1 was manufactured by the same process, and production was carried out under the same conditions. It fractured after continuous production for 102 h.

[0068] Comparative Example 5:

[0069] A 4CrMnSiMoVNi alloy bar for an expanding hole die of a bearing ring forging, comprising the following substances by weight percentage: carbon 0.40%, chromium 1.20%, manganese 1.20%, molybdenum 0.40%, vanadium 0.20%, nickel 1.00%, sulfur ≤ 0.030%, phosphorus ≤ 0.030%; the silicon content in the center of the alloy bar is 0.90%, the silicon content on the surface is 1.40%, and the silicon content from the surface to the center shows a gradient distribution; the rest is iron and inevitable impurities.

[0070] The above 4CrMnSiMoVNi alloy bar with silicon gradient distribution is prepared by the same casting process as in Example 1, but the amount of sprayed silicon powder is 0.33% of the mass of the poured alloy liquid, and the chemical composition in the alloy liquid by weight percentage is: carbon 0.40%, chromium 1.20%, manganese 1.20%, molybdenum 0.40%, vanadium 0.20%, nickel 1.00%, sulfur ≤ 0.030%, phosphorus ≤ 0.030%, silicon 0.90%, and the rest is iron and inevitable impurities.

[0071] An expanding hole die of the same specification is manufactured by the same process as in Example 1, and production is carried out under the same conditions. It fractures after continuous production for 129 h.

[0072] Comparative Example 6:

[0073] The 4CrMnSiMoVNi alloy bar is prepared by the same casting process as in Example 3, but the mold is not preheated before pouring.

[0074] An expanding hole die of the same specification is manufactured by the same process as in Example 1, and production is carried out under the same conditions. It fractures after continuous production for 91 h. Inspection finds that the silicon distribution on the surface layer of the die is uneven and seriously segregated, causing stress concentration and becoming the source of crack initiation.

[0075] Comparative Example 7:

[0076] The 4CrMnSiMoVNi alloy bar is prepared by the same casting process as in Example 3, but the pouring temperature is 1500 °C.

[0077] An expanding hole die of the same specification is manufactured by the same process as in Example 1, and production is carried out under the same conditions. It fractures after continuous production for 117 h. Inspection finds that most of the silicon does not melt into the alloy, the silicon content on the alloy surface is low, and the gradient is not obvious.

[0078] It can be seen from the comparison between Example 3 and Comparative Examples 6 and 7 that the melting of silicon powder into the surface layer of the alloy bar and the diffusion towards the center to form a gradient structure require precise coordination of the pouring temperature and the preheating temperature.

[0079] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A 4CrMnSiMoVNi alloy rod with silicon gradient distribution, characterized in that: The chemical composition is calculated by weight as follows: carbon 0.20% to 0.50%, chromium 1.00% to 1.50%, manganese 0.80% to 1.50%, molybdenum 0.20% to 0.50%, vanadium 0.10% to 0.30%, nickel 0.90% to 1.50%, sulfur ≤0.030%, phosphorus ≤0.030%, and silicon whose content changes gradually from the surface to the center of the alloy rod, and the silicon content in the center of the alloy rod is 0.20% to 0.60%, and the silicon content on the surface is 1.00% to 1.30%, and the rest is iron and unavoidable impurities.

2. The 4CrMnSiMoVNi alloy rod with silicon gradient distribution according to claim 1, characterized in that: The diameter of the 4CrMnSiMoVNi alloy rod with silicon gradient distribution is 30-100 mm.

3. A hole expansion die made by processing the 4CrMnSiMoVNi alloy rod with silicon gradient distribution as claimed in claim 1 or 2.

4. The processing technology of the hole expansion die according to claim 3 is characterized in that: include: Preparation of 4CrMnSiMoVNi alloy rods with silicon gradient distribution by casting: spraying a layer of silicon powder on the inner surface of the mold, and using a stepped pouring system to allow the molten alloy liquid to fill the mold from bottom to top to avoid turbulence of the alloy liquid in the mold; the pouring temperature is 1650-1750°C; the mold is preheated to 200-500°C before pouring; The 4CrMnSiMoVNi alloy rod with silicon gradient distribution is firstly subjected to isothermal annealing treatment, then machined into a target structure and size, then quenched, then tempered, and cooled to obtain the hole expansion die.

5. The processing process according to claim 4, characterized in that: The mass of the sprayed silicon powder is 0.05% to 1.50% of the mass of the cast alloy liquid.

6. The processing technology according to claim 4, characterized in that: The chemical components in the alloy liquid are as follows by weight: carbon 0.20%-0.50%, chromium 1.00%-1.50%, manganese 0.80%-1.50%, molybdenum 0.20%-0.50%, vanadium 0.10%-0.30%, nickel 0.90%-1.50%, sulfur ≤0.030%, phosphorus ≤0.030%, silicon 0.20%-0.60%, and the rest are iron and unavoidable impurities.

7. The processing process according to claim 4, characterized in that: The isothermal annealing treatment specifically includes: heating to 850-950° C., keeping the temperature for 20-300 minutes, cooling to 700-750° C., keeping the temperature for 60-300 minutes, furnace cooling to 480-500° C., and air cooling after exiting the furnace.

8. The processing technology according to claim 4, characterized in that: The quenching specifically includes: quenching temperature of 850-950° C., heat preservation for 20-60 minutes, and oil cooling.

9. The processing process according to claim 4, characterized in that: The tempering treatment specifically includes: tempering temperature of 500-650° C., heat preservation for 20-300 minutes, and oil cooling.

10. Use of the 4CrMnSiMoVNi alloy rod with silicon gradient distribution according to claim 1 or 2 or the hole expansion die according to claim 3 in manufacturing a hole expansion die for a bearing ring forging processed by hot deformation.