阅读说明：本技术 一种提高双相不锈钢低温冲击性能的锻造方法 (Forging method for improving low-temperature impact property of duplex stainless steel ) 是由 叶强 栾吉哲 王守明 刘军凯 冯文静 曹路明 于 2021-08-27 设计创作，主要内容包括：本发明涉及合金材料锻造技术领域,尤其涉及一种提高双相不锈钢低温冲击性能的锻造方法,包括如下步骤：步骤一,将双相不锈钢冷锭升温至1200～1250℃,保温2～3小时后进行镦粗锻造,所述镦粗锻造的变形量为20％～35％,然后进行拔长锻造,得到经过预处理的双相不锈钢坯料；步骤二,将经过预处理的双相不锈钢坯料在1200～1250℃的条件下保温8～10小时后进行镦粗锻造,所述镦粗锻造的变形量为40％～52％,得到双相不锈钢坯料；步骤三,将双相不锈钢坯料在1050～1100℃的条件下保温2～3小时后进行拔长锻造。本发明提供的方法操作简单易于实现,采用本发明的锻造方法,可以达到提高双相不锈钢低温冲击性能的目的。(The invention relates to the technical field of alloy material forging, in particular to a forging method for improving the low-temperature impact property of duplex stainless steel, which comprises the following steps: step one, heating a duplex stainless steel cold ingot to 1200-1250 ℃, preserving heat for 2-3 hours, performing upsetting forging, wherein the deformation of the upsetting forging is 20% -35%, and then performing drawing forging to obtain a pretreated duplex stainless steel blank; step two, performing upsetting forging on the pretreated duplex stainless steel blank after the blank is subjected to heat preservation for 8-10 hours at 1200-1250 ℃, wherein the deformation of the upsetting forging is 40% -52%, and thus the duplex stainless steel blank is obtained; and step three, carrying out drawing forging on the duplex stainless steel blank after heat preservation for 2-3 hours at 1050-1100 ℃. The forging method provided by the invention is simple to operate and easy to realize, and the purpose of improving the low-temperature impact property of the duplex stainless steel can be achieved.)

1. A forging method for improving the low-temperature impact property of duplex stainless steel is characterized by comprising the following steps:

step one, heating a duplex stainless steel cold ingot to 1200-1250 ℃, preserving heat for 2-3 hours, performing upsetting forging, wherein the deformation of the upsetting forging is 20% -35%, and then performing drawing forging to obtain a pretreated duplex stainless steel blank;

step two, performing upsetting forging on the pretreated duplex stainless steel blank after the blank is subjected to heat preservation for 8-10 hours at 1200-1250 ℃, wherein the deformation of the upsetting forging is 40% -52%, and thus the duplex stainless steel blank is obtained;

and step three, preserving the heat of the duplex stainless steel blank at 1050-1100 ℃ for 2-3 hours, and then carrying out drawing forging.

2. The forging method for improving low-temperature impact properties of duplex stainless steel according to claim 1, wherein: the duplex stainless steel comprises the following chemical components in percentage by mass: less than or equal to 0.03 percent of C, less than or equal to 1.00 percent of Si, less than or equal to 1.00 percent of Mn, less than or equal to 0.020 percent of S, less than or equal to 0.030 percent of P, Ni: 5.0% -6.5%, Cr: 21.00% -23.00%, Mo: 3.0% -3.5%, N: 0.14 to 0.20 percent, and the balance of Fe and inevitable impurities.

3. The forging method for improving low-temperature impact properties of duplex stainless steel according to claim 1, wherein: in the first step, the temperature rising speed of the duplex stainless steel cold ingot is 50-90 ℃/h.

4. The forging method for improving low-temperature impact properties of duplex stainless steel according to claim 1, wherein: the deformation of the upsetting forging in the step one is 30-35%.

5. The forging method for improving low-temperature impact properties of duplex stainless steel according to claim 1, wherein: in the first step, the deformation amount of the drawing forging is 40-50%.

6. The forging method for improving low-temperature impact properties of duplex stainless steel according to claim 1, wherein: in the second step, the deformation of upsetting forging is 48-50%.

7. The forging method for improving low-temperature impact properties of duplex stainless steel according to claim 1, wherein: in the third step, the drawing forging comprises two to three times of heating.

8. The forging method for improving low-temperature impact properties of duplex stainless steel according to claim 7, wherein: the deformation of each hot forging of the drawing forging is 30-60%, and the single-hammer reduction of each pass is 80-120 mm.

Technical Field

The invention relates to the technical field of alloy material forging, in particular to a forging method for improving low-temperature impact property of duplex stainless steel.

Background

Duplex stainless steel, i.e., stainless steel having a solid solution structure in which both ferrite and austenite are present, contains ferrite and austenite in an amount of about 50% each in most cases, and generally contains a minor phase in an amount of not less than 40% at the minimum. The duplex stainless steel has been paid attention and advocated by technical personnel because of the excellent characteristics of both austenitic and ferritic stainless steels, and is widely applied to important fields of nuclear power, petroleum, chemical engineering, ocean engineering and the like.

However, since the ferrite phase in the duplex stainless steel has a body-centered cubic structure, ductile-brittle transition occurs in a low temperature environment, and when the temperature is lower than the ductile-brittle transition temperature, the toughness of the duplex stainless steel is rapidly reduced and embrittlement occurs. The production method of the traditional duplex stainless steel is that after a steel ingot is heated, the steel ingot is longitudinally drawn out and forged, the ferrite proportion of the obtained two-phase structure is high, the austenite proportion of the obtained two-phase structure is low, so the low-temperature impact performance of the duplex stainless steel is poor, the two-phase structure of the duplex stainless steel obtained by the traditional production method is approximately uniformly distributed in a strip shape, the tissue directionality is strong, the transverse low-temperature impact performance of the duplex stainless steel is low, and the use requirements of the materials in a low-temperature environment can not be met.

Disclosure of Invention

Based on the problems in the prior art, the forging method for improving the low-temperature impact property of the duplex stainless steel can obviously improve the low-temperature impact property of the duplex stainless steel and overcome the defects in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

the embodiment of the invention provides a forging method for improving the low-temperature impact property of duplex stainless steel, which comprises the following steps:

step one, heating a duplex stainless steel cold ingot to 1200-1250 ℃, preserving heat for 2-3 hours, performing upsetting forging, wherein the deformation of the upsetting forging is 20% -35%, and then performing drawing forging to obtain a pretreated duplex stainless steel blank;

step two, performing upsetting forging on the pretreated duplex stainless steel blank after the blank is subjected to heat preservation for 8-10 hours at 1200-1250 ℃, wherein the deformation of the upsetting forging is 40% -52%, and thus the duplex stainless steel blank is obtained;

and step three, preserving the heat of the duplex stainless steel blank at 1050-1100 ℃ for 2-3 hours, and then carrying out drawing forging.

The forging method for improving the low-temperature impact property of the duplex stainless steel comprises the steps of heating a duplex stainless steel cold ingot to 1200-1250 ℃, then carrying out upsetting and stretching forging pretreatment, primarily crushing an as-cast crystalline structure in the duplex stainless steel by controlling the temperature and time of heat treatment before upsetting forging and the deformation of upsetting forging after heat treatment, and then preserving the heat of a pretreated duplex stainless steel blank at 1200-1250 ℃ for 8-10 hours to fully homogenize the as-cast crystalline structure in the pretreated duplex stainless steel. Upsetting forging is carried out on the duplex stainless steel blank after the homogenized as-cast structure is carried out again, the directionality of the two-phase structure phase form and the distribution of the layered duplex structure of the duplex stainless steel can be changed by controlling the temperature and the time of heat treatment before upsetting forging and the deformation of upsetting forging after heat treatment, and finally the temperature of heat treatment before drawing forging is controlled to be 1050-1100 ℃, so that the multi-directional and multi-scale non-uniform layered duplex structure after high-temperature deformation can be reserved after cooling, the transformation from an austenite phase to high-temperature ferrite in the deformation process can be reduced, the two-phase structure with the largest possible austenite phase is obtained, and the ferrite phase is mainly used for influencing the low-temperature impact toughness, so that the increase of the austenite phase is beneficial to improving the duplex low-temperature impact toughness of the stainless steel. According to the forging method, by controlling the heating temperature and the forging deformation, a two-phase structure with a plurality of austenite phases can be obtained, the purpose of improving the low-temperature impact performance of the duplex stainless steel is achieved, a non-uniform layered two-phase structure with multi-direction and multi-scale grain distribution can be obtained, the purpose of improving the transverse low-temperature impact performance of the duplex stainless steel is achieved, and the defects in the prior art are overcome.

The deformation amount of upset forging in the present invention means the deformation amount of cross sectional area of upset forging.

Preferably, the duplex stainless steel comprises the following chemical components in percentage by mass: less than or equal to 0.03 percent of C, less than or equal to 1.00 percent of Si, less than or equal to 1.00 percent of Mn, less than or equal to 0.020 percent of S, less than or equal to 0.030 percent of P, Ni: 5.0% -6.5%, Cr: 21.00% -23.00%, Mo: 3.0% -3.5%, N: 0.14 to 0.20 percent, and the balance of Fe and inevitable impurities.

Preferably, in the step one, the temperature rising speed of the duplex stainless steel cold ingot is 50-90 ℃/h. By limiting the temperature rise speed of the double-phase stainless steel cold ingot, the temperature of the double-phase stainless steel cold ingot can be uniformly raised inside and outside, and the thermal stress cracking of the double-phase stainless steel caused by too high temperature rise speed can be avoided.

Preferably, in the first step, the deformation amount of upsetting forging is 30% to 35%.

Preferably, in the first step, the deformation amount of the drawing forging is 40% to 50%.

The directionality of the two-phase structure phase morphology of the duplex stainless steel and the distribution of the layered duplex structure can be preliminarily changed by controlling the deformation of upsetting forging and drawing forging.

Preferably, in the second step, the deformation amount of upsetting forging is 48% to 50%.

The directionality of the two-phase structure phase morphology and the distribution of the layered two-phase structure of the duplex stainless steel can be greatly changed by controlling the deformation of upsetting forging.

Preferably, in step three, the elongation forging comprises two to three heats.

Preferably, the deformation of each hot forging of the drawing forging is 30-60%, and in each hot forging, the single-hammering reduction of each pass is 80-120 mm.

The directionality of the duplex structure of the duplex stainless steel and the distribution of the layered duplex structure can be further changed by limiting the deformation amount of drawing forging and the single hammer reduction, and the aim of improving the transverse low-temperature impact performance of the duplex stainless steel is fulfilled.

The forging method for improving the low-temperature impact property of the duplex stainless steel comprises the steps of heating a duplex stainless steel cold ingot to carry out upsetting and drawing forging, crushing an as-cast crystal structure of the duplex stainless steel, homogenizing the as-cast crystal structure of the duplex stainless steel through long-time high-temperature heating, then carrying out upsetting forging, changing the directionality of the two-phase structure phase form of the duplex stainless steel and the distribution of a layered duplex structure, improving the transverse low-temperature impact property of the duplex stainless steel, finally reducing the heating temperature to be below 1100 ℃ to carry out drawing forging, cooling the multi-direction and multi-scale heterogeneous layered duplex structure after high-temperature deformation to be reserved, reducing the transformation of an austenite phase to high-temperature ferrite in the deformation process, and improving the low-temperature impact toughness of the duplex stainless steel. The forging method for improving the low-temperature impact property of the duplex stainless steel is simple to operate and easy to realize, the production cost is not increased, and the duplex stainless steel with excellent low-temperature impact property, good forging plasticity and stable quality can be obtained by forging. The low-temperature impact performance of the duplex stainless steel obtained by the forging method is improved to 159-293J from the original 9-16J.

Drawings

FIG. 1 is a metallographic structure diagram of a duplex stainless steel forged in example 1 of the present invention;

FIG. 2 is a metallographic structure diagram of a duplex stainless steel forged in example 2 of the present invention;

FIG. 3 is a metallographic structure diagram of a duplex stainless steel forged in example 3 of the present invention;

FIG. 4 is a metallographic structure diagram of a duplex stainless steel forged in comparative example 1 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The duplex stainless steel in each embodiment comprises the following chemical components in percentage by mass: less than or equal to 0.03 percent of C, less than or equal to 1.00 percent of Si, less than or equal to 1.00 percent of Mn, less than or equal to 0.020 percent of S, less than or equal to 0.030 percent of P, Ni: 5.0% -6.5%, Cr: 21.00% -23.00%, Mo: 3.0% -3.5%, N: 0.14 to 0.20 percent, and the balance of Fe and inevitable impurities.

Example 1

The embodiment provides a forging method for improving the low-temperature impact performance of duplex stainless steel, which comprises the following steps:

(1) and (3) heating a single duplex stainless steel cold ingot with the weight of 1.69 tons and the height of 1.4 meters to 1250 ℃ at the speed of 50 ℃/h, keeping the temperature for 2 hours, discharging the ingot out of the furnace, upsetting and forging, wherein the deformation of upsetting and forging is 35%, then drawing and forging, and the deformation of drawing and forging is 40%, thus obtaining the pretreated duplex stainless steel blank.

(2) And returning the pretreated duplex stainless steel blank back to the furnace, continuing to heat at 1200 ℃ for 10 hours, discharging the blank out of the furnace for upsetting forging, wherein the deformation of the upsetting forging is 40%, and obtaining the duplex stainless steel blank after upsetting is finished.

(3) And (3) returning the obtained duplex stainless steel blank to the furnace, reducing the temperature to 1100 ℃, preserving the heat for 2h, discharging the blank from the furnace, performing first-time hot drawing forging, wherein the deformation of the forging is 40%, the single-hammer reduction is 120mm, and preserving the heat for 2h at 1050 ℃.

(4) And discharging the duplex stainless steel blank out of the furnace, carrying out secondary fire drawing forging, wherein the deformation of the forging is 40%, the single hammer rolling reduction is 120mm, and returning to the furnace for 1050 ℃ and keeping the temperature for 2 hours.

(5) And discharging the duplex stainless steel blank out of the furnace, carrying out third-time drawing forging, wherein the deformation of the forging is 40%, the single-hammer reduction is 120mm, and after air cooling to room temperature, polishing to obtain a finished product.

Example 2

The embodiment provides a forging method for improving the low-temperature impact performance of duplex stainless steel, which comprises the following steps:

(1) and (3) heating a single duplex stainless steel cold ingot with the weight of 2.45 tons and the height of 1.46 meters to 1200 ℃ at the speed of 90 ℃/h, keeping the temperature for 3 hours, discharging the ingot out of the furnace, performing upsetting forging, wherein the deformation of the upsetting forging is 20%, then performing drawing forging, and the deformation of the drawing forging is 50%, thus obtaining the pretreated duplex stainless steel blank.

(2) Returning the pretreated duplex stainless steel blank to the furnace, continuing to heat at 1200 ℃ for 10 hours, discharging the blank out of the furnace for upsetting forging, wherein the deformation of the upsetting forging is 52 percent, and obtaining the duplex stainless steel blank after the upsetting is finished

(3) And returning the obtained duplex stainless steel blank to the furnace, reducing the temperature to 1050 ℃, preserving the heat for 3 hours, discharging the blank from the furnace, performing first-time hot drawing forging, wherein the deformation of the forging is 30 percent, the single-hammer reduction is 100mm, and preserving the heat for 3 hours at 1100 ℃.

(4) Discharging the duplex stainless steel blank out of the furnace, carrying out secondary fire drawing forging, wherein the deformation of the forging is 30%, the single hammer rolling reduction is 100mm, and the temperature is maintained for 3 hours at 1100 ℃ after the duplex stainless steel blank is re-melted.

(5) And discharging the duplex stainless steel blank out of the furnace, carrying out third-time drawing forging, wherein the deformation of the forging is 30%, the single-hammer rolling reduction is 100mm, and after air cooling to room temperature, polishing to obtain a finished product.

Example 3

The embodiment provides a forging method for improving the low-temperature impact performance of duplex stainless steel, which comprises the following steps:

(1) heating a single duplex stainless steel cold ingot with the weight of 3 tons and the height of 1.42 meters to 1225 ℃ at the speed of 60 ℃/h, keeping the temperature for 2.5 hours, discharging the ingot out of a furnace, upsetting and forging, wherein the deformation of upsetting and forging is 30%, then drawing and forging, and the deformation of drawing and forging is 45%, thus obtaining the pretreated duplex stainless steel blank.

(2) And returning the pretreated duplex stainless steel blank back to the furnace, continuing to heat at 1210 ℃ for 9 hours, discharging the blank out of the furnace for upsetting forging, wherein the deformation of the upsetting forging is 50%, and obtaining the duplex stainless steel blank after upsetting is finished.

(3) And returning the obtained duplex stainless steel blank to the furnace, reducing the temperature to 1060 ℃, preserving the heat for 2 hours, discharging the blank from the furnace, performing first-time hot drawing forging, wherein the deformation of the forging is 50 percent, the single-hammer reduction is 80mm, and preserving the heat for 2.5 hours at 1060 ℃.

(4) Discharging the duplex stainless steel blank out of the furnace, carrying out secondary fire drawing forging, wherein the deformation of the forging is 50%, the single hammer rolling reduction is 80mm, and carrying out heat preservation for 2.5 hours at 1060 ℃ after remelting.

(5) And discharging the duplex stainless steel blank out of the furnace, carrying out third-time drawing forging, wherein the deformation of the forging is 50%, the single-hammer reduction is 80mm, and after air cooling to room temperature, polishing to obtain a finished product.

Example 4

The embodiment provides a forging method for improving the low-temperature impact performance of duplex stainless steel, which comprises the following steps:

(1) and (3) heating a duplex stainless steel cold ingot with a single support weight of 3.5 tons and a height of 1.46 meters to 1220 ℃ at a speed of 70 ℃/h, preserving heat for 2 hours, discharging from a furnace, carrying out upsetting forging, wherein the deformation of the upsetting forging is 25%, then carrying out drawing forging, and the deformation of the drawing forging is 42%, thus obtaining the pretreated duplex stainless steel blank.

(2) And returning the pretreated duplex stainless steel blank to the furnace, continuously heating at 1240 ℃ for 10 hours, keeping the temperature, discharging the blank out of the furnace for upsetting forging, wherein the deformation of the upsetting forging is 48 percent, and obtaining the duplex stainless steel blank after the upsetting is finished.

(3) And (3) returning the obtained duplex stainless steel blank to the furnace, reducing the temperature to 1070 ℃, keeping the temperature for 3h, discharging the blank from the furnace, carrying out first-time hot drawing forging, wherein the deformation of the forging is 50%, the single-hammer reduction is 80mm, and keeping the temperature at 1070 ℃ for 2 h.

(4) And discharging the duplex stainless steel blank out of the furnace, carrying out secondary fire drawing forging, wherein the deformation of the forging is 50%, the single hammer rolling reduction is 80mm, and returning to the furnace at 1070 ℃ for heat preservation for 2 hours.

(5) And discharging the duplex stainless steel blank out of the furnace, carrying out third-time drawing forging, wherein the deformation of the forging is 50%, the single-hammer reduction is 80mm, and after air cooling to room temperature, polishing to obtain a finished product.

Example 5

The embodiment provides a forging method for improving the low-temperature impact performance of duplex stainless steel, which comprises the following steps:

(1) and (3) heating a single duplex stainless steel cold ingot with the weight of 4.5 tons and the height of 1.6 meters to 1230 ℃ at the speed of 100 ℃/h, keeping the temperature for 3 hours, discharging the ingot out of the furnace, performing upsetting forging, wherein the deformation of the upsetting forging is 32%, then performing drawing forging, and the deformation of the drawing forging is 48%, thus obtaining the pretreated duplex stainless steel blank.

(2) And returning the pretreated duplex stainless steel blank back to the furnace, continuously heating at 1220 ℃, keeping the temperature for 9 hours, discharging the blank out of the furnace for upsetting forging, wherein the deformation of the upsetting forging is 50%, and obtaining the duplex stainless steel blank after upsetting is finished.

(3) And (3) returning the obtained duplex stainless steel blank to reduce the temperature to 1080 ℃ and preserving the heat for 2 hours, discharging the blank from the furnace and carrying out first-time hot drawing forging, wherein the deformation of the forging is 60 percent, the single-hammer reduction is 120mm, and the blank is returned to the furnace and preserved the heat for 3 hours at 1080 ℃.

(4) And discharging the duplex stainless steel blank out of the furnace, carrying out secondary fire drawing forging, wherein the deformation of the forging is 60%, the single-hammer reduction is 120mm, and after air cooling to room temperature, polishing to obtain a finished product.

Comparative example 1

The comparative example provides a forging method for duplex stainless steel low temperature impact properties tested in the research process, comprising the following steps:

(1) heating a duplex stainless steel cold ingot with the single branch weight of 3 tons and the height of 1.4 meters to 1200 ℃ at the speed of 100 ℃/h, preserving heat for 2 hours, discharging the ingot out of the furnace, performing first fire drawing forging, wherein the deformation of the forging is 40 percent, the single hammer rolling reduction is 100mm, and returning the ingot to the furnace for 1200 ℃ and preserving heat for 2 hours.

(2) And (4) second fire drawing and forging, wherein the deformation of forging is 40%, the single-hammer rolling reduction is 100mm, and the temperature is maintained for 2 hours at 1200 ℃ after remelting.

(3) And (3) drawing and forging for the third fire time, wherein the deformation of the forging is 40%, the single-hammer rolling reduction is 100mm, and the temperature is maintained for 2 hours at 1200 ℃ after the furnace is returned.

(4) And fourthly, drawing out and forging for the fourth time, wherein the deformation of forging is 40%, the single-hammer reduction is 100mm, and the finished product is obtained by polishing after air cooling to room temperature.

Comparative example 2

The comparative example provides a forging method for duplex stainless steel low temperature impact properties tested in the research process, comprising the following steps:

(1) heating a duplex stainless steel cold ingot with the single branch weight of 4.5 tons and the height of 1.6 meters to 1180 ℃ at the speed of 90 ℃/h, preserving heat for 3 hours, discharging the ingot out of the furnace, performing first fire drawing forging, wherein the deformation of the forging is 30 percent, the single hammer reduction is 80mm, and returning the ingot to the furnace 1180 ℃ for preserving heat for 3 hours.

(2) And (4) drawing and forging for the second fire time, wherein the deformation of the forging is 30%, the single hammer reduction is 80mm, and the temperature is maintained for 3 hours at 1180 ℃ in a furnace.

(3) And (3) drawing and forging for the third fire time, wherein the deformation of the forging is 30%, the single hammer reduction is 80mm, and the temperature is maintained for 3 hours at 1180 ℃ in a furnace.

(4) And fourthly, drawing out and forging for the fourth time, wherein the deformation of forging is 30%, the single-hammer reduction is 80mm, and the finished product is obtained by polishing after air cooling to room temperature.

Comparative example 3

The comparative example provides a forging method for duplex stainless steel low temperature impact properties tested in the research process, comprising the following steps:

(1) heating a duplex stainless steel cold ingot with the single branch weight of 4.5 tons and the height of 1.6 meters to 1200 ℃ at the speed of 60 ℃/h, preserving heat for 2.5 hours, discharging the ingot out of the furnace, performing first fire drawing forging, wherein the deformation of the forging is 45 percent, the single hammer reduction is 120mm, and returning the ingot to the furnace for 1200 ℃ and preserving heat for 2.5 hours.

(2) And (4) second-time drawing and forging, wherein the deformation of forging is 45%, the single-hammer reduction is 120mm, and the temperature is maintained for 2.5 hours at 1200 ℃ after remelting.

(3) And (3) drawing and forging for the third fire time, wherein the deformation of the forging is 45%, the single-hammer reduction is 120mm, and the finished product is obtained by polishing after the air cooling is carried out to the room temperature.

Experimental example 1

The duplex stainless steel bars forged in examples 1 to 5 and comparative examples 1 to 3 were subjected to a low temperature impact performance test at-46 ℃ according to the charpy impact test method for GB/T229-2007 metal materials, and the test results are shown in table 1:

TABLE 1 Low temperature impact test results

The data in the table show that the forging method for improving the low-temperature impact property of the duplex stainless steel can obviously improve the low-temperature impact property of the duplex stainless steel.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents or improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.