A bearing ring production hole expanding die and its processing technology

Abstract

The application discloses a reaming die for bearing ring production and a processing technology thereof. The reaming die is prepared by processing a 4CrMnSiMoVNi alloy bar with gradient distribution of silicon. The chemical composition of the 4CrMnSiMoVNi alloy bar with gradient distribution of silicon is as follows in terms of percentage 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%, and silicon with a gradient change from the surface to the center of the alloy bar, wherein the silicon content at the center of the alloy bar is 0.20-0.60%, the silicon content on the surface is 1.00-1.30%, and the rest is iron and inevitable impurities.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of bearing machining equipment, in particular to an alloy bar, a reaming die prepared from the alloy bar, a machining process of the reaming die, and application of the reaming die in manufacturing a reaming die for a bearing ring forging processed through hot deformation. BACKGROUND

[0002] A ring is a basic component of a bearing. Ring production generally comprises the following procedures: blank induction heating, blanking, upsetting, forming, bottom cutting, reaming, and sizing. Reaming is generally performed on a reamer. During reaming, an annular blank forging is sleeved on a reaming die, a motor drives a rotating roller to roll the annular blank forging, the blank forging and the reaming die are driven to rotate under the action of friction, the wall thickness of the blank forging is reduced, and the inner and outer diameters of the ring are increased, so that the blank forging is formed into a forging product through rolling.

[0003] The inventor discloses an alloy material in patent CN114990447B, which comprises the following components in percentage by weight: 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). The patent also discloses a reaming die prepared from the alloy material and a machining process thereof. The alloy material is subjected to spheroidizing annealing, and then is processed into a die with a target structure. The obtained die is subjected to stress relief through quenching, cold treatment, tempering and aging treatment, and the reaming die is obtained. The reaming die has the characteristics of not being easy to break and not being easy to wear on the surface, has a long service life, and has a simple machining process and low requirement for heating equipment, and has important application value in the field of bearing machining. The patent technology is based on GCr15 steel and adjusts the elements, increases the carbon content and introduces rare earth elements cerium, dysprosium and terbium. The rare earth elements cerium, dysprosium and terbium are relatively expensive. If an alloy material suitable for manufacturing a reaming die can be obtained without adding expensive elements such as rare earth elements, it is of great significance to reduce the cost of materials.

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

[0005] The bearing ring forging enterprises often use 4CrMnSiMoV steel to manufacture the expanding die. Because the forming pressure of the blank forging is finally borne by the expanding die, the expanding die is prone to breakage. During the blank forging rolling expansion process, there is strong friction between the forging and the expanding die, which causes the surface of the expanding die to be prone to wear. The temperature of the blank forging during rolling expansion forming is above 800℃, and the heat is transferred to the expanding die, causing the expanding die to be passively heated, and after the forging is removed, the temperature of the expanding die will quickly drop, so the expanding die is in a high alternating stress working condition and is prone to fatigue. Due to breakage, surface wear and fatigue, the 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 the 4CrMnSiMoV steel to further manufacture the expanding die with the characteristics of not easy to break, slight surface wear, good oxidation resistance and fatigue resistance, long service life and the like under the premise of keeping low cost is an important and practical research direction. SUMMARY

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

[0007] The specific technical solutions are as follows:

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

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

[0010] In some embodiments, the silicon-gradient-distributed 4CrMnSiMoVNi alloy bar is prepared by casting: a layer of silicon powder is sprayed on the inner surface of the mold, the molten alloy liquid is filled into 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℃, for example, 300℃, etc. before pouring.

[0011] In order to melt the silicon powder sprayed on the inner surface of the mold and diffuse from the surface to the center of the alloy bar, the following strategies are adopted: 1) the pouring temperature is above the melting point of silicon, 250℃, to melt a small amount of low-melting-point silicon using the heat of the alloy liquid; 2) the mold is preheated to 200-500℃, for example, 300℃, etc. before pouring to reduce the cooling effect of the mold on the alloy liquid and prolong the solidification process and high-temperature cooling stage. If the pouring temperature and mold preheating are not coordinated, the melting and diffusion of the silicon powder cannot be fully carried out, and the piercing die made of this material is prone to breakage in 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, for example, 0.40%, 0.47%, etc.

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

[0015] In some preferred embodiments, the pouring temperature is above the melting point of silicon, 250℃, and is 1650-1750℃, for example, 1700℃, etc.

[0016] [2] A reaming die processed from the silicon-gradient-distributed 4CrMnSiMoVNi alloy bar of [1].

[0017] [3] A processing process of the reaming die of [2], comprising:

[0018] The silicon-gradient 4CrMnSiMoVNi alloy rod is prepared by casting: a layer of silicon powder is sprayed on the inner surface of the mold, the molten alloy liquid is filled into 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, for example, 300°C, etc. before pouring;

[0019] The silicon-gradient 4CrMnSiMoVNi alloy rod is first subjected to isothermal annealing, then machined into a target structure and size, then quenched, and then tempered to obtain the said hole-expanding 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, for example, 0.40%, 0.47%, etc.

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

[0023] In some preferred embodiments, the pouring temperature is above the melting point of silicon, i.e., 250°C, and is 1650-1750°C, for example, 1700°C, etc.

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

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

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

[0027] [4] The application of the silicon gradient distribution 4CrMnSiMoVNi alloy bar according to [1] or the reaming die according to [2] in the production of bearing ring forging reaming die by hot deformation processing.

[0028] Example, the alloy bar of the application can be used to produce bearing ring forging reaming die, which is heat treated according to the designed process, installed on the D51 type rolling and expanding machine, and used for the production of bearing ring (such as outer diameter 90mm), and the service life of the reaming die is recorded.

[0029] The application can obtain a reaming die which is not easy to break, has slight wear, is resistant to oxidation and fatigue, and has long service life.

[0030] Compared with the prior art, the application has the following beneficial effects:

[0031] Compared with the traditional 4CrMnSiMoV, the 4CrMnSiMoVNi steel increases nickel, which improves the toughness of the material, so that the reaming die can withstand the impact load when the rolling wheel hits the blank and is not broken, thereby prolonging the service life of the reaming die. In particular, the use of nickel and silicon together can significantly improve the toughness of the material, and has a unique synergistic effect, which is much better than the limited effect of using nickel or silicon alone.

[0032] The silicon gradient distribution 4CrMnSiMoVNi alloy bar 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℃, which is much higher than the melting point of silicon, so that the silicon powder adhering to the inner wall of the mold can be melted, thereby increasing the silicon content on the surface of the alloy bar. A stepped pouring system is adopted, so that the alloy liquid fills the mold slowly and smoothly from bottom to top, avoiding turbulence of the alloy liquid inside the mold, and the melted silicon can be concentrated and distributed on the surface layer of the alloy bar. The mold is preheated before pouring, which reduces the chilling effect of the mold, prolongs the solidification time and high-temperature residence time of the alloy bar, and ensures the sufficient diffusion of silicon to the center, forming a gradient distribution.

[0033] The silicon gradient distribution has three beneficial effects on the 4CrMnSiMoVNi alloy bar. Effect 1: In the center of the bar, the silicon content is low, which ensures high overall toughness of the material and resistance to impact load, so that the reaming die made of it is not easy to break; Effect 2: On the surface of the bar, the silicon content is high, and the solid solution strengthening effect of silicon can improve the surface hardness, so that the surface wear of the reaming die made of it is more slight; Effect 3: High silicon content can improve the oxidation resistance of the steel, especially in high temperature environment, so that the reaming die made of it can be used for a long time and the surface is stable without oxidation.

[0034] In the center of the bar, the silicon content is controlled at 0.20% to 0.60%, which can ensure a good balance between toughness and strength, and is suitable for the working condition of the hole expanding die. Too low silicon content will result in insufficient strength of the hole expanding die core, and too high silicon content will reduce the toughness of the die core.

[0035] On the surface of the bar, the silicon content is controlled at 1.00% to 1.30%, which can ensure that the die surface has high enough hardness, and is suitable for the working condition of the hole expanding die. Too low silicon content will reduce the die surface hardness, resulting in poor wear resistance of the die. Silicon content exceeding 1.30% will increase the brittleness of the die surface layer, affecting the comprehensive mechanical properties of the die surface layer after high temperature tempering.

[0036] The moderately high silicon content on the surface can improve the tempering stability of the hole expanding die, delay the tempering softening process, and enable the hole expanding die to maintain high hardness after high temperature tempering, thereby improving the wear resistance of the hole expanding die.

[0037] The moderately high silicon content on the surface can improve the strength and hardness of the die surface layer, improve the fatigue performance of the hole expanding die, and significantly improve the service life of the hole expanding die. DETAILED DESCRIPTION

[0038] The application will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not to limit the scope of the application. The operation methods not specified in the following examples are usually performed under conventional conditions or under the conditions recommended by the manufacturer.

[0039] Example 1:

[0040] A 4CrMnSiMoVNi alloy bar for a bearing ring forging hole expanding die includes 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 0.40%, the surface silicon content is 1.10%, and the silicon content is gradiently distributed from the surface to the center; the rest is iron and unavoidable impurities.

[0041] The 4CrMnSiMoVNi alloy bar with the above-mentioned silicon gradient distribution was prepared by casting. Zircon sand was used for molding, and a layer of silicon powder was sprayed on the inner surface of the mold. The mass of the sprayed silicon powder was 0.47% of the mass of the alloy liquid. The chemical composition in the alloy liquid was as follows in terms of percentage by mass: 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 balance being iron and inevitable impurities. The alloy liquid was filled into the mold from bottom to top smoothly and slowly through a stepped gating system to avoid turbulence of the alloy liquid inside the mold. The pouring temperature was 1700°C, and the mold was preheated to 300°C before pouring. The diameter of the alloy bar was 45mm.

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

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

[0044] The reaming die was quenched at a heating temperature of 900±10°C for 30min and oil-cooled. Then, the reaming die was high-temperature tempered at a tempering temperature of 580±10°C for 120min and oil-cooled.

[0045] The reaming die was installed on a D51-type reaming machine to produce bearing rings (outer diameter 90mm), and fractured after 257h of continuous production.

[0046] Comparative Example 1:

[0047] The difference from Example 1 was only that a commercial 4CrMnSiMoV steel was used. The chemical composition of the commercial 4CrMnSiMoV steel was as follows in terms of percentage by mass: 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 balance being iron and inevitable impurities.

[0048] A reaming die was made using a commercial 4CrMnSiMoV steel alloy bar, and a reaming die with the same specifications was manufactured using the same process as in Example 1, and the production was carried out under the same conditions. The reaming die fractured after 52h of continuous production.

[0049] Comparative Example 2:

[0050] The difference from Example 1 is only that no silicon powder is sprayed on the inner surface of the mold during pouring, and the prepared 4CrMnSiMoV alloy bar has no silicon gradient distribution but uniform silicon distribution, and the silicon content at the surface and center of the alloy bar is 0.40% by weight.

[0051] The same specification of the reaming die is manufactured by using the same process as in Example 1, and the production is carried out under the same conditions. The reaming die is broken after 89 hours of continuous production.

[0052] Comparative Example 3:

[0053] The difference from Example 1 is that the 4CrMnSiMoV steel without nickel is used after smelting and pouring, i.e. the chemical composition in the alloy liquid is as follows by weight percentage: 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 inevitable impurities. The prepared 4CrMnSiMoV alloy bar has a silicon gradient distribution, the silicon content at the center is 0.40% by weight, and the silicon content at the surface is 1.10% by weight.

[0054] The same specification of the reaming die is manufactured by using the same process as in Example 1, and the production is carried out under the same conditions. The reaming die is broken after 81 hours of continuous production.

[0055] Comparing Example 1 with Comparative Examples 1-3, it can be seen that the present application introduces silicon in addition to Ni and makes the silicon gradiently distributed in the cross section of the material, and the two improvement methods work together to significantly prolong the service life of the reaming die from not more than 89 hours to 257 hours.

[0056] Example 2:

[0057] A 4CrMnSiMoVNi alloy bar for a bearing ring forging reaming die, 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 at the center of the alloy bar is 0.30% by weight, the silicon content at the surface is 1.00% by weight, and the silicon content is gradiently distributed from the surface to the center; and the rest is iron and inevitable impurities.

[0058] The above-mentioned 4CrMnSiMoVNi alloy bar with silicon gradient distribution is prepared by using the same casting process as in Example 1, the amount of sprayed silicon powder is 0.47% of the mass of the poured alloy liquid, and the chemical composition in the alloy liquid is as follows 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 0.30%, and the rest is iron and inevitable impurities.

[0059] A reaming die of the same specification was manufactured using the same process as Example 1, and production was carried out under the same conditions. The die fractured after 201 h of continuous production.

[0060] Example 3:

[0061] A 4CrMnSiMoVNi alloy bar for a bearing ring forging reaming die comprises 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 is distributed in a gradient from the surface to the center; the rest is iron and unavoidable impurities.

[0062] The 4CrMnSiMoVNi alloy bar with the above-mentioned silicon gradient distribution was prepared using the same casting process as Example 1, but the amount of sprayed silicon powder was 0.40% of the mass of the alloy liquid, and the chemical composition of the alloy liquid was as follows 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 0.60%, and the rest was iron and unavoidable impurities.

[0063] A reaming die of the same specification was manufactured using the same process as Example 1, and production was carried out under the same conditions. The die fractured after 231 h of continuous production.

[0064] Comparative Example 4:

[0065] A 4CrMnSiMoVNi alloy bar for a bearing ring forging reaming die comprises 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 is distributed in a gradient from the surface to the center; the rest is iron and unavoidable impurities.

[0066] The 4CrMnSiMoVNi alloy bar with the above-mentioned silicon gradient distribution was prepared using the same casting process as Example 1, but the amount of sprayed silicon powder was 0.33% of the mass of the alloy liquid, and the chemical composition of the alloy liquid was as follows 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 0.10%, and the rest was iron and unavoidable impurities.

[0067] A reaming die of the same specification was manufactured using the same process as Example 1, and production was carried out under the same conditions. The die fractured after 102 h of continuous production.

[0068] Comparative Example 5:

[0069] A 4CrMnSiMoVNi alloy bar for a bearing ring forging reaming die, 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 surface silicon content is 1.40%, and the silicon content is distributed in a gradient from the surface to the center; the rest is iron and inevitable impurities.

[0070] The 4CrMnSiMoVNi alloy bar with the above-mentioned silicon gradient distribution is prepared by the same casting process as Example 1, but the amount of sprayed silicon powder is 0.33% of the mass of the alloy liquid, and the chemical composition in the alloy liquid is as follows 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 0.90%, and the rest is iron and inevitable impurities.

[0071] The same specification reaming die is manufactured by the same process as Example 1, and production is carried out under the same conditions. The die breaks after 129 hours of continuous production.

[0072] Comparative Example 6:

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

[0074] The same specification reaming die is manufactured by the same process as Example 1, and production is carried out under the same conditions. The die breaks after 91 hours of continuous production. Inspection finds that the silicon distribution on the surface of the die is uneven, with serious segregation, 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 Example 3, but the pouring temperature is 1500°C.

[0077] The same specification reaming die is manufactured by the same process as Example 1, and production is carried out under the same conditions. The die breaks after 117 hours of continuous production. Inspection finds that most of the silicon has not melted into the alloy, the silicon content on the surface of the alloy is low, and the gradient is not obvious.

[0078] From the comparison of Example 3 and Comparative Examples 6 and 7, it can be seen that the silicon powder is melted into the surface layer of the alloy bar and diffuses to the center to form a gradient structure, which requires precise coordination of the pouring temperature and the preheating temperature.

[0079] It is to be understood that even though numerous characteristics and embodiments of the application have been set forth in the foregoing disclosure, the details can be varied without departing from the application, which is defined by the claims.

Claims

1. A machining process for a reaming die, characterized in that, The reaming die is made of a 4CrMnSiMoVNi alloy bar with gradient distribution of silicon; The 4CrMnSiMoVNi alloy bar with gradient distribution of silicon has the following chemical components in percentage 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%, and silicon with gradient distribution from the surface to the center of the alloy bar, wherein the silicon content at the center of the alloy bar is 0.20-0.60%, the silicon content at the surface is 1.00-1.30%, and the rest is iron and inevitable impurities. The processing technology of the reaming die comprises the following steps: The 4CrMnSiMoVNi alloy bar with gradient distribution of silicon is prepared by casting: a layer of silicon powder is sprayed on the inner surface of a casting mold, and the molten alloy liquid is filled into the casting mold from bottom to top through a stepped pouring system to avoid turbulent flow of the alloy liquid in the casting mold; the pouring temperature is 1650-1750℃; and the casting mold is preheated to 200-500℃ before pouring; The 4CrMnSiMoVNi alloy bar with gradient distribution of silicon is first subjected to isothermal annealing treatment, then machined into a target structure and size, and then subjected to quenching and tempering treatment, and finally cooled to obtain the reaming die.

2. The process according to claim 1, characterized in that, The 4CrMnSiMoVNi alloy bar with gradient distribution of silicon has a diameter of 30-100 mm.

3. The process of claim 1 wherein, The mass of the sprayed silicon powder is 0.05-1.50% of the mass of the alloy liquid.

4. The process of claim 1 wherein, The chemical components of the alloy liquid are as follows in percentage 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 is iron and inevitable impurities.

5. The process of claim 1 wherein, The isothermal annealing treatment specifically comprises the following steps: heating to 850-950℃, holding for 20-300 min, cooling to 700-750℃, holding for 60-300 min, furnace cooling to 480-500℃, and furnace cooling to 480-500℃.

6. The process of claim 1 wherein, The quenching specifically comprises the following steps: quenching temperature 850-950℃, holding for 20-60 min, and oil cooling.

7. The process of claim 1 wherein, The tempering treatment specifically comprises the following steps: tempering temperature 500-650℃, holding for 20-300 min, and oil cooling.