A thermoforming process for a d2 material race

Abstract

The present application relates to the technical field of shield cutter, in particular to a hot forming process of D2 material cutter ring, comprising the following steps: D2 steel blank workpiece is put into furnace and heated in sections, primary forging, temperature compensation, secondary forging temperature compensation, model forging blank, after blank is reheated, D2 material cutter ring can be obtained after multi-pass ring rolling forming such as ring rolling + temperature compensation + ring rolling. The hot forming process of the D2 material cutter ring adopts the forging and ring rolling hot forming process of multi-pass heating and multi-pass forming, which avoids the poor heat conductivity of D2 steel, the large deformation temperature and the difficulty of rapid heat transfer of the core when deforming at a large rate and deformation amount, which may cause microburning or even melting of the core (the gathering place of alloy elements and low melting point inclusions), and easily cause cracks and cracking. The D2 material cutter ring prepared by the process has sufficient toughness, fatigue resistance, high strength, high hardness, high wear resistance and good red hardness.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of a shield cutter, in particular to a hot forming process of a D2 material cutter ring. BACKGROUND

[0002] Shield construction is a construction method for tunnel excavation in soil by a shield machine and simultaneous completion of tunnel permanent lining laying, and has the advantages of high mechanization degree, high construction speed and high safety, and has been widely applied to major projects such as subways, tunnels, water and electricity, and the shield machine is one of the most representative major key equipment for measuring the level and ability of equipment manufacturing industry of a country.

[0003] The shield cutter is a key matching tool for tunnel excavation of the shield machine, and the performance and service life of the shield cutter restrict the tunneling efficiency of the whole shield machine, at present, the shield cutter ring is made of H13 die steel and alloy steel inlaid with hard alloy, and in the use process, the shield cutter ring has common pain points such as poor wear resistance, broken blade and broken ring, and therefore the hot forming process of the D2 material cutter ring is provided to solve the above problems. SUMMARY

[0004] (I) Technical problems solved

[0005] In view of the defects of the prior art, the application provides a hot forming process of a D2 material cutter ring, which has the advantages of high strength, high hardness and high wear resistance, and solves the problems that the current shield cutter ring is made of H13 die steel and alloy steel inlaid with hard alloy, and in the use process, the shield cutter ring has problems such as poor wear resistance, broken blade and broken ring.

[0006] (II) Technical scheme

[0007] In order to achieve the purpose of high strength, high hardness and high wear resistance, the application provides the following technical scheme:

[0008] A hot forming process of a D2 material cutter ring comprises the following steps:

[0009] 1) The D2 steel blank workpiece is heated in the furnace in sections;

[0010] 2) The workpiece is subjected to initial forging;

[0011] 3) The workpiece after initial forging is transferred into the furnace body for temperature compensation;

[0012] 4) The workpiece is subjected to secondary forging, and then the temperature compensation operation of the above steps is repeated;

[0013] 5) The workpiece is subjected to model forging to obtain the blank;

[0014] 6) After ring rolling, the D2 material cutter ring is obtained.

[0015] Preferably, the segmented heating comprises the following steps:

[0016] 1) heating with gas furnace, cold billet preheated to 800 DEG C, holding for 0.5 hours;

[0017] 2) heating to 830 DEG C-850 DEG C with furnace, holding for 2-4 hours;

[0018] 3) heating to 940 DEG C±10 DEG C with furnace, holding for 0.5 hours after reaching temperature;

[0019] 4) heating to 990 DEG C with furnace, holding for 1.5 hours;

[0020] 5) setting temperature to 1050 DEG C, holding for 0.5 hours after reaching 1050 DEG C;

[0021] 6) setting temperature to 1100 DEG C, then heating to 1090 DEG C±10 DEG C with furnace, holding for 1 hour after reaching temperature.

[0022] Preferably, the initial forging adopts free forging light hammer forging, and the time of the initial forging is 3-4 minutes based on obvious rigid rebound of the forged piece until being immovable.

[0023] Preferably, the temperature compensation comprises the following steps:

[0024] 1) transferring the workpiece to the pit furnace for heating, holding for 3 hours after heating to 940 DEG C±10 DEG C;

[0025] 2) transferring to the gas furnace for heating, holding for 1 hour after heating to 1090 DEG C±10 DEG C.

[0026] Preferably, the die forging adopts die forging of the electric screw press, and the heavy hammer is forged for 3 times, the outer diameter is measured rapidly, and whether the second die forging needs temperature compensation is determined according to whether the measured outer diameter size meets the blank drawing requirement.

[0027] Preferably, the ring rolling comprises the following steps:

[0028] 1) after temperature compensation of the formed blank, open ring rolling machine is used for ring rolling until being immovable, and then the blank is sent to the heating furnace for temperature compensation again (1010 DEG C±10 DEG C, holding for 40 minutes);

[0029] 2) the open ring rolling machine is used for secondary ring rolling, and whether the third temperature compensation and ring rolling are needed is determined according to need until the product is rolled.

[0030] (Three) beneficial effects

[0031] Compared with the prior art, the application provides a hot forming process of a D2 material knife ring, and has the following beneficial effects:

[0032] The hot forming process of the D2 material cutter ring avoids the poor thermal conductivity of the D2 steel, the large deformation temperature and the difficulty of rapid heat transfer of the core when deforming at a large rate and deformation, which can cause micro-burning and even melting of the core (the gathering place of alloying elements and low-melting-point inclusions), and is prone to cause cracks and cracking. Furthermore, the D2 material needs to be heated and cooled slowly and in stages during thermal deformation and heat treatment to avoid the risk of stress cracking due to rapid heating and cooling. The D2 material cutter ring prepared by the process has sufficient toughness, fatigue resistance, high strength, high hardness, high wear resistance and good red hardness, solving the problems of the current shield cutter cutter ring made of H13 die steel and alloy steel with hard alloy cutter ring, such as poor wear resistance, edge collapse and ring breakage. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A D2 material cutter ring hot forming process flow chart is provided for the present application;

[0034] Figure 2 A D2 material cutter ring hot forming process flow chart is provided for the present application;

[0035] Figure 3 A D2 material cutter ring hot forming process flow chart is provided for the present application;

[0036] Figure 4 A D2 material cutter ring hot forming process flow chart is provided for the present application;

[0037] Figure 5 A D2 material cutter ring hot forming process flow chart is provided for the present application;

[0038] Figure 6 A D2 material cutter ring hot forming process flow chart is provided for the present application; DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described in detail below, obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0040] A D2 material cutter ring hot forming process, comprising the following steps:

[0041] 1) The D2 steel blank workpiece is heated in stages;

[0042] 2) initial forging of the workpiece;

[0043] 3) transferring the initial forged workpiece into the furnace for temperature compensation;

[0044] 4) secondary forging of the workpiece, followed by repeating the temperature compensation operation of the above steps;

[0045] 5) model forging of the workpiece to obtain a blank;

[0046] 6) the D2 material ring is obtained after ring rolling.

[0047] It should be noted that the D2 material is a high-carbon high-chromium ledeburite steel with appropriate increase of Mo and V content based on Cr12MoV cold work abrasive tool steel. In addition to the network carbide, the original structure of the blank also contains coarse fishbone-shaped eutectic carbide (see Figure 2 ). These carbides are hard and brittle, and are usually not completely dissolved during heating, which affects the continuity of metal deformation during hot deformation and cuts the matrix, making the hot plasticity of the steel very poor, especially under the action of tensile and shear stress, which is prone to crack or crack. Due to the high carbon content and high chromium content, the austenite region temperature range (i.e. hot deformation temperature range) of the D2 material is narrow, making it difficult to perform continuous deformation during hot working, and it is difficult to control the initial forging temperature and the final forging temperature. In addition, the D2 steel not only has poor thermal conductivity, but also has relatively slow dissolution and diffusion of Cr, Mo and V carbides in the steel. During heating and hot deformation, there is a different degree of micro-segregation of Cr, Mo, V and C, which may cause micro-burn or even melting of the core (aggregation of alloying elements and low-melting-point inclusions) (see Figure 3 ) when deformed at a large rate and deformation amount, which is prone to cause cracks and cracks. Furthermore, during the heating of the hot deformation of the D2 material and the heating and cooling of the heat treatment, it needs to be slow and segmented to avoid the risk of stress cracking due to rapid heating and cooling (see Figure 4 ).

[0048] In this embodiment, the segmented heating includes the following steps:

[0049] 1) using a gas furnace to heat, the cold blank is preheated to 800°C, and the temperature is maintained for 0.5 hours;

[0050] 2) heating to 830°C-850°C with the furnace, and maintaining the temperature for 2-4 hours;

[0051] 3) heating to 940°C±10°C with the furnace, and maintaining the temperature for 0.5 hours;

[0052] 4) heating to 990°C with the furnace, and maintaining the temperature for 1.5 hours;

[0053] 5) Set temperature to 1050 °C, to 1050 °C warm after 0.5 hours;

[0054] 6) Set temperature to 1100 °C, then with furnace heating to 1090 °C + 10 °C warm after 1 hour.

[0055] In this embodiment, the initial forging is free forging light hammer forging. Before forging, all preparations are in place, personnel are on duty, semi-open door discharging, the action should be as fast as possible when discharging, and the furnace door is closed quickly after discharging. The initial forging time is 3-4 minutes, based on the obvious rigid bounce of the forged piece, until it cannot be hit. The carbonides in the steel are broken as much as possible to ensure sufficient toughness and fatigue resistance. The outer diameter and surface temperature are measured quickly, and the forged piece is transferred quickly after completing the measurement to enter the next temperature compensation process.

[0056] In this embodiment, the temperature compensation includes the following steps:

[0057] 1) The workpiece is transferred to the pit furnace for heating, heated to 940 °C + 10 °C, and kept for 3 hours;

[0058] 2) Transfer to the gas furnace for heating, heating temperature 1090 °C + 10 °C, keep for 1 hour.

[0059] In this embodiment, the secondary forging is air hammer or electric screw press heavy hammer forging (pause 2-3 seconds between each hammer), further breaking the carbonides in the steel as much as possible (see Figure 5 ) to ensure sufficient toughness and fatigue resistance, and to provide original organization preparation for the subsequent model forging and ring rolling. Before forging, all preparations are in place, personnel are on duty, semi-open door discharging, the action should be as fast as possible when discharging, and the furnace door is closed quickly after discharging. The secondary forging is hit until it cannot be hit (based on the obvious rigid bounce of the forged piece). The outer diameter and surface temperature are measured quickly, and the forged piece is transferred quickly after completing the measurement to enter the next temperature compensation process (temperature compensation heating specification is the same as above).

[0060] Preferably, the model forging is electric screw press model forging, heavy hammer 600-750 continuous forging 3 times, quickly measure the outer diameter, and decide whether it needs to be temperature compensated again for the second model forging according to whether the measured outer diameter size meets the blank drawing requirements. After the workpiece size meets the requirements after completing the measurement, the forged piece is quickly transferred to enter the next process of punching, and after punching is completed, it is sent to the heating furnace for temperature compensation (1010 °C + 10 °C, 40 minutes) to prepare for ring rolling.

[0061] In this embodiment, the ring rolling includes the following steps:

[0062] 1) After the formed blank is temperature compensated, it is used for ring rolling operation using an open ring rolling machine, until it cannot be rolled, and then it is sent to the heating furnace for temperature compensation again (1010 °C + 10 °C, 40 minutes);

[0063] 2) using open ring rolling machine for secondary ring rolling, according to whether the third time needs to be heated and ring rolling, until the finished product (see Figure 6 ).

[0064] The beneficial effects of the present application are: the hot forming process of the D2 material cutter ring, through the multi-pass heating and multi-pass forming forging ring hot forming process, avoids the poor thermal conductivity of D2 steel, when deformed at a larger rate and deformation, the deformation temperature is larger and the core heat is not easy to be quickly transmitted out, which will cause the micro-burning of the core (the gathering place of alloy elements and low melting point inclusions) even melting, which is easy to cause cracks and cracking. Furthermore, the D2 material needs to be heated and cooled slowly and segmented during thermal deformation and heat treatment, in order to avoid the risk of stress cracking due to rapid heating and cooling. The D2 material cutter ring prepared by the process has sufficient toughness, fatigue resistance, high strength, high hardness, high wear resistance, good red hardness, solves the problem that the current shield cutter cutter ring is made of H13 die steel cutter ring and alloy steel hard alloy cutter ring, and the cutter ring has the problems of not wear-resistant, broken blade, broken ring and the like in the use process.

[0065] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A thermoforming process for a D2 material blade ring, characterized in that, Includes the following steps: 1) The D2 steel billet workpiece is heated in sections in the furnace; 2) Perform initial forging of the workpiece; 3) Transfer the forged workpiece into the furnace for reheating; 4) Perform secondary forging of the workpiece, and then repeat the above steps for reheating. 5) Forge the workpiece into a blank using a mold; 6) After rolling, a D2 material cutting ring can be obtained; The segmented heating includes the following steps: 1) A gas-fired furnace is used for heating. The cold billets are preheated to 800℃ and held for 0.5 hours. 2) Heat the furnace to 830℃-850℃ and hold for 2-4 hours; 3) Heat the furnace to 940℃±10℃ and hold for 0.5 hours; 4) Heat to 990℃ in the furnace and hold for 1.5 hours; 5) Set the temperature to 1050℃, and maintain the temperature for 0.5 hours after reaching 1050℃; 6) Set the temperature to 1100℃, then heat it to 1090℃±10℃ and hold it for 1 hour.

2. The thermoforming process for a D2 material blade ring according to claim 1, characterized in that, The initial forging is carried out by free forging with a light hammer. The initial forging time is 3-4 minutes, based on the obvious rigidity and bounce of the forging, until it can no longer be forged.

3. The thermoforming process for a D2 material blade ring according to claim 1, characterized in that, The temperature replenishment includes the following steps: 1) The workpiece is transferred to a pit furnace for heating. After heating to 940℃±10℃, it is held at that temperature for 3 hours. 2) Transfer to a gas furnace for heating at 1090℃±10℃ and keep warm for 1 hour.

4. The thermoforming process for a D2 material blade ring according to claim 1, characterized in that, The secondary forging is carried out using an air hammer or an electric screw press with a heavy hammer, pausing for 2-3 seconds between each hammer strike, until the forging exhibits obvious rigidity and bounce.

5. The thermoforming process for a D2 material blade ring according to claim 1, characterized in that, The rolling process includes the following steps: 1) After the formed billet is reheated, it is rolled into a ring using an open ring rolling mill until it can no longer be rolled. Then it is sent to a heating furnace for reheating again. The reheating temperature is 1010℃±10℃ and the temperature is held for 40 minutes. 2) Use an open ring rolling mill for secondary ring rolling, and perform a third rolling and heating as needed until the finished product is obtained.

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