CN115889647A - A Forging Method for Improving Carbon Segregation of Hot Work Die Steel H13 - Google Patents

Abstract

The invention discloses a forging method for improving carbon segregation of hot work die steel H13, which belongs to the technical field of metallurgy. It includes high-temperature diffusion and forging process before forging; high-temperature diffusion process before forging, the steel ingot is sent to the heating furnace and then heated to 1320±10°C, and the holding time is 1.5-2h/100mm; The first upsetting ratio is 1.5-1.8, the drawing-to-forging ratio is 1.8-2.0, and the drawing-down reduction is 10-15%; %~15%. The present invention adopts the high-temperature short-time high-temperature diffusion process before forging combined with the four-upsetting and four-drawing forging process. The hot work die steel H13 produced has a uniform band structure, greatly reduced segregation, and the flaw detection level meets the requirements of GB/T6402-2008 level 4. And the grain size is fine and uniform, and the low temperature impact toughness is good.

Description

A Forging Method for Improving Carbon Segregation of Hot Work Die Steel H13

technical field

The invention belongs to the technical field of metallurgy and relates to a forging method of hot work die steel, in particular to a forging method for improving carbon segregation of hot work die steel H13.

Background technique

H13 belongs to hot work die steel, grade 4Cr5MoSiV1; chemical composition: C: 0.32-0.45%; Si: 0.8-1.2%; Mn: 0.2-0.5%; Cr: 4.75-5.5%; Mo: 1.1-1.75%; V: 0.8-1.2%; it belongs to medium alloy chromium series hot work die steel. Because of its good thermal strength, red hardness, high toughness and thermal fatigue resistance, it is widely used in hot extrusion dies and die-casting dies for aluminum alloys; it can also be used to make hot forging dies and plastic dies.

Part of the carbon element in H13 steel enters the matrix to cause solid solution strengthening, and the other part combines with alloying elements to form carbides. In thermal processing and heat treatment processes, the type, distribution, and size of carbides in H13 steel will have a great impact on the thermal strength, thermal stability, impact toughness, and thermal fatigue properties of the steel when it is finally in service. Since the mold is non-directional during use, it requires the mold to have good mechanical isotropy, and the degree of carbide uniformity has a great influence on the performance.

In the large forging industry, high-temperature diffusion before forging is generally used to improve dendrite segregation and C segregation. The heating temperature adopted is generally 1240°C±10°C, and the holding time is 4h/100mm. It is relatively slow, often has uneven banded structure, and the impact value fluctuates in a relatively large range. The flaw detection level cannot meet the requirements of GB/T6402-2008 level 4, and this scheme greatly prolongs the time of the steel ingot in the furnace, which affects production efficiency. Conducive to production organization and cost optimization.

Contents of the invention

In order to solve the above-mentioned technical problems, the present invention provides a kind of forging method that improves hot work die steel H13 carbon segregation, and the technical scheme that the present invention takes is:

A forging method for improving carbon segregation of hot work die steel H13, which includes high-temperature diffusion before forging and forging processes.

In the high-temperature diffusion process before forging, when the steel ingot is ≥550°C, it is sent to the heating furnace, and the temperature is raised to 1320±10°C at a rate of 100-120°C/min, and the holding time is 1.5-2h/100mm.

The steel ingot is air-cooled to a surface temperature of 1160-1180°C for forging.

The forging process adopts the four-upsetting and four-drawing process, the first two upsetting ratios are 1.5-1.8, the drawing-length forging ratio is 1.8-2.0, and the drawing-length reduction is 10-15%; the last two upsetting ratios are 2.2-2.4, The elongation forging ratio is 2-2.2, the elongation reduction is 10%-15%, and the total forging ratio is 10-12.

The specification of hot work die steel H13 after forging is φ700～φ800mm.

The beneficial effects produced by adopting the above-mentioned technical scheme are:

1. The high-temperature diffusion process before forging of the present invention breaks the conventional heating concept, and the heating temperature of the steel ingot is 1320±10°C, which is about 800°C higher than the conventional process, which is more conducive to the dissolution and uniform distribution of carbides, and improves C segregation; the higher the heating temperature , The energy obtained by C atoms and alloy components is increased, and it is easy to migrate from places with high concentrations to places with low concentrations, so that the atoms can be fully diffused and a material with uniform composition can be obtained. The holding time is shortened by half compared with the conventional time, which improves production efficiency, saves energy consumption, reduces production costs, reduces carbon emissions, and improves product profits and competitiveness.

2. The heating temperature of the present invention is increased to 1320±10°C, which is easy to form coarse grains, which seriously affects the flaw detection and structure. The forging process of four upsetting and four pulling is used in the subsequent sequence to increase the upsetting ratio and the drawing ratio to ensure carbonization The material is fully broken, and the coarse grains are broken, which is beneficial to solve the uniform distribution of carbides and the refinement of grains, and is conducive to the improvement of the flaw detection level.

3. The present invention adopts the four-upsetting and four-drawing process, and the upsetting ratio and the elongation ratio of the first two times and the last two times are different, distinguishing the difference between the welding ability in the cast state and the welding ability in the forged state, and solves the problem of welding of internal microscopic pores. Combined, it is beneficial to improve the impact capacity, effectively solve the problems of as-cast structure residue and grain refinement, and has a great effect on the improvement of banded structure and the improvement of flaw detection level.

The invention can effectively solve the problem of H13 hot work die steel composition and C segregation, avoid premature fatigue cracks caused by the hardness or uneven structure of the die during use or the quality of the produced product does not meet the requirements, and ensure that the quality of the die steel product can meet the requirements. Requirements. The banded structure of H13 hot work die steel after forging in the present invention is significantly improved, the degree of C segregation is significantly reduced, the flaw detection level reaches the highest level of GB/T6402-2008 4th grade, the normal temperature impact value reaches more than 280J, and the austenite grain size reaches fine Crystal level 5 and above.

Detailed ways

Example 1

In this embodiment, the cross-sectional size of the H13 steel after forging is φ700 mm, the cross-sectional size of the steel ingot is 900*930 mm, and the height is 1500 mm.

The forging method for improving the carbon segregation of hot work die steel H13 includes high temperature diffusion before forging and forging process. Concrete process steps are as follows:

(1) High-temperature diffusion process before forging. When the steel ingot is 600°C, it is sent to the heating furnace, and the temperature is raised to 1320°C at a speed of 100°C/min. The holding time is 17h. After holding the heat, it is air-cooled;

(2) The steel ingot is air-cooled to a surface temperature of 1160°C before forging;

(3) The forging process adopts four upsetting and four drawing processes. The first two upsetting ratios are 1.5, the drawing length forging ratio is 1.8, and the drawing length reduction is 10%; the last two upsetting ratios are 2.2, the drawing length forging ratio is 2.0, and the drawing The long reduction is 12%, and the total forging ratio is 10; after forging, superfine heat treatment is carried out according to the conventional process.

The H13 round steel obtained in this example was inspected under high magnification, and the banded structure reached SA1 level, and the degree of segregation was greatly reduced. Its flaw detection level reaches GB/T6402-2008 level 4, the austenite grain size reaches level 9, and the impact energy at 20 °C is 320J.

Example 2

In this embodiment, the cross-sectional size of the H13 steel after forging is φ750 mm, the cross-sectional size of the steel ingot is 1000*1030 mm, and the height is 1650 mm.

The forging method for improving the carbon segregation of hot work die steel H13 includes high temperature diffusion before forging and forging process. Concrete process steps are as follows:

(1) High-temperature diffusion process before forging. The steel ingot is sent to the heating furnace at 580 °C, and the temperature is raised to 1330 °C at a rate of 120 °C/min. The holding time is 20.6 hours. After holding, it is air-cooled;

(2) The steel ingot is air-cooled to a surface temperature of 1170°C before forging;

(3) The forging process adopts four upsetting and four drawing processes. The first two upsetting ratios are 1.6, the drawing length forging ratio is 1.9, and the drawing length reduction is 13.2%; the last two upsetting ratios are 2.3, the drawing length forging ratio is 2.2, and the drawing The long reduction is 15%, and the total forging ratio is 12; after forging, superfine heat treatment is carried out according to the conventional process.

The H13 round steel obtained in this example was inspected under high magnification, and the banded structure reached SA1 level, and the degree of segregation was greatly reduced. Its flaw detection level reaches GB/T6402-2008 level 4, the austenite grain size reaches level 8, and the impact energy at 20 °C is 325J.

Example 3

In this embodiment, the cross-sectional size of the H13 steel after forging is φ800 mm, the cross-sectional size of the steel ingot is 1180*1200 mm, and the height is 1700 mm.

The forging method for improving the carbon segregation of hot work die steel H13 includes high temperature diffusion before forging and forging process. Concrete process steps are as follows:

(1) High-temperature diffusion process before forging. When the steel ingot is 570°C, it is sent to the heating furnace, and the temperature is raised to 1310°C at a speed of 115°C/min. The holding time is 23.5h. After holding the heat, it is air-cooled;

(2) The steel ingot is air-cooled to a surface temperature of 1180°C before forging;

(3) The forging process adopts four upsetting and four drawing processes. The first two upsetting ratios are 1.8, the drawing length forging ratio is 2.0, and the drawing length reduction is 15%; the last two upsetting ratios are 2.2, the drawing length forging ratio is 2.1, and the drawing The long reduction is 15%, and the total forging ratio is 11.5; after forging, superfine heat treatment is carried out according to the conventional process.

The H13 round steel obtained in this example was inspected under high magnification, and the banded structure reached SA1 level, and the degree of segregation was greatly reduced. Its flaw detection level reaches GB/T6402-2008 level 4, the austenite grain size reaches level 8, and the impact energy at 20°C is 315J.

Example 4

In this embodiment, the cross-sectional size of the H13 steel after forging is φ780 mm, the cross-sectional size of the steel ingot is 1050*1120 mm, and the height is 1600 mm.

The forging method for improving the carbon segregation of hot work die steel H13 includes high temperature diffusion before forging and forging process. Concrete process steps are as follows:

(1) High-temperature diffusion process before forging, when the steel ingot is 560°C, it is sent to the heating furnace, and the temperature is raised to 1315°C at a speed of 105°C/min, and the holding time is 17h.

(2) The steel ingot is air-cooled to a surface temperature of 1175°C before forging;

(3) The forging process adopts four upsetting and four drawing processes. The first two upsetting ratios are 1.7, the drawing length forging ratio is 1.85, and the drawing length reduction is 14%. The reduction is 14%, and the total forging ratio is 10.5; after forging, superfine heat treatment is carried out according to the conventional process.

The H13 round steel obtained in this example was inspected under high magnification, and the banded structure reached SA2 level, and the degree of segregation was greatly reduced. Its flaw detection level reaches GB/T6402-2008 level 4, the austenite grain size reaches level 8.5, and the impact energy at 20 °C is 315 J.

Example 5

In this embodiment, the cross-sectional size of the H13 steel after forging is φ740 mm, the cross-sectional size of the steel ingot is 1100*1150 mm, and the height is 1650 mm.

The forging method for improving the carbon segregation of hot work die steel H13 includes high temperature diffusion before forging and forging process. Concrete process steps are as follows:

(1) High-temperature diffusion process before forging. The steel ingot is sent to the heating furnace at 590 °C, and the temperature is raised to 1312 °C at a rate of 120 °C/min. The holding time is 18.7 hours.

(2) The steel ingot is air-cooled to a surface temperature of 1165°C before forging;

(3) The forging process adopts four upsetting and four drawing processes. The first two upsetting ratios are 1.65, the drawing length forging ratio is 2.0, and the drawing length reduction is 12.5%; the last two upsetting ratios are 2.25, the drawing length forging ratio is 2.15, and the drawing The long reduction is 12.5%, and the total forging ratio is 11.2; after forging, superfine heat treatment is carried out according to the conventional process.

The obtained H13 round steel of the present embodiment is inspected under high magnification, and the banded structure reaches SA 1 level, and the degree of segregation is greatly reduced. Its flaw detection level reaches GB/T6402-2008 level 4, the austenite grain size reaches level 9, and the impact energy at 20°C is 330J.

Example 6

In this embodiment, the cross-sectional size of the H13 steel after forging is φ710 mm, the cross-sectional size of the steel ingot is 1120*1200 mm, and the height is 1700 mm.

The forging method for improving the carbon segregation of hot work die steel H13 includes high temperature diffusion before forging and forging process. Concrete process steps are as follows:

(1) High-temperature diffusion process before forging. When the steel ingot is 600°C, it is sent to the heating furnace, and the temperature is raised to 1325°C at a speed of 120°C/min. The holding time is 20.2h.

(2) The steel ingot is air-cooled to a surface temperature of 1168°C before forging;

(3) The forging process adopts four upsetting and four drawing processes. The first two upsetting ratios are 1.72, the drawing length forging ratio is 1.95, and the drawing length reduction is 11.5%; the last two upsetting ratios are 2.25, the drawing length forging ratio is 2.05, and the drawing The long reduction is 11.5%, and the total forging ratio is 11.8; after forging, superfine heat treatment is carried out according to the conventional process.

The H13 round steel obtained in this example was inspected under high magnification, and the banded structure reached SA1 level, and the degree of segregation was greatly reduced. Its flaw detection level reaches GB/T6402-2008 level 4, the austenite grain size reaches level 7, and the impact energy at 20°C is 315J.

Claims (7)

1. A forging method for improving carbon segregation of hot work die steel H13, characterized in that it comprises high-temperature diffusion and forging procedures before forging; In the high-temperature diffusion process before forging, the steel ingot is sent to the heating furnace and then heated to 1320±10°C, and the holding time is 1.5-2h/100mm; The forging process adopts the four-upsetting and four-drawing process, the first two upsetting ratios are 1.5-1.8, the drawing-length forging ratio is 1.8-2.0, and the drawing-length reduction is 10-15%; the last two upsetting ratios are 2.2-2.4, The elongation and forging ratio is 2 to 2.2, and the elongation reduction is 10% to 15%. 2. The forging method for improving carbon segregation of hot work die steel H13 according to claim 1, characterized in that in the high-temperature diffusion process before forging, the hot delivery temperature of the steel ingot is ≥550°C. 3. The forging method for improving carbon segregation of hot work die steel H13 according to claim 2, characterized in that, in the high-temperature diffusion process before forging, the heating rate is 100-120° C./min. 4. The forging method for improving carbon segregation of hot work die steel H13 according to claim 3, characterized in that, in the high-temperature diffusion process before forging, the steel ingot is kept warm and then released from the furnace for air cooling. 5. The forging method for improving carbon segregation of hot work die steel H13 according to claim 4, characterized in that the steel ingot is air-cooled to a surface temperature of 1160-1180°C for forging. 6. The forging method for improving carbon segregation of hot work die steel H13 according to claim 5, characterized in that, in the forging process, the total forging ratio is 10-12. 7. The forging method for improving carbon segregation of hot work die steel H13 according to any one of claims 1-6, characterized in that the specification of the hot work die steel H13 after forging is φ700-φ800 mm.