阅读说明：本技术 一种减少桥梁支座用耐腐蚀钢裂纹的方法 (Method for reducing corrosion-resistant steel cracks for bridge support ) 是由 郭勇 赵红图 陈振 张洪涛 吉杏斗 韩年 王亚宁 周占宇 安晓意 于 2021-01-18 设计创作，主要内容包括：本发明提供了一种减少桥梁支座用耐腐蚀钢裂纹的方法,该方法通过在原料中添加Nb、Ti、稀土合金和采用硅钙钡作为脱氧剂等方法,配合工艺的改进与优化,解决了现有技术中耐腐蚀钢材易出现裂纹的问题,在提高材料耐腐蚀性能和力学性能的同时,有效减少了耐腐蚀钢的裂纹敏感性,提高了桥梁支座的成品率,降低了桥梁支座用钢出现裂纹的概率,具有很高的经济效益。(The invention provides a method for reducing the cracks of corrosion-resistant steel for a bridge bearing, which solves the problem that the corrosion-resistant steel is easy to crack in the prior art by adding Nb, Ti and rare earth alloy into raw materials, adopting silicon, calcium and barium as deoxidizers and the like and matching with the improvement and optimization of the process, effectively reduces the crack sensitivity of the corrosion-resistant steel while improving the corrosion resistance and the mechanical property of the material, improves the yield of the bridge bearing, reduces the crack probability of the steel for the bridge bearing and has high economic benefit.)

1. The method for reducing the cracks of the corrosion-resistant steel for the bridge bearing is characterized by comprising the following steps of:

1) selecting low-phosphorus low-sulfur scrap steel and required alloy materials, and smelting molten steel by adopting an alkaline arc furnace, wherein the molten steel comprises the following elements in parts by weight:

0.08 to 0.15 percent of C; si 0.16-1.0%; 0.5 to 1.6 percent of Mn; 0.60 to 11.0 percent of Cr; ni 0.30-2.0%; 0.01 to 0.5 percent of Al; 0.02 to 0.05 percent of Nb; 0.01 to 0.03 percent of Ti; p is less than or equal to 0.015 percent; s is less than or equal to 0.015 percent; cu is less than or equal to 0.80 percent; v is less than or equal to 0.06 percent; mo is less than or equal to 0.35 percent; the balance of Fe and inevitable impurities;

2) adding a deoxidizing agent and a rare earth alloy into the steel ladle, and then tapping;

3) pouring molten steel into a casting mould, hammering by using an air impact hammer to remove a riser after a casting is solidified and cooled, wherein the casting mould is a sand casting process model, the riser is set as a necking exothermic riser, and the root of the riser is provided with an easily-cut piece;

4) carrying out heat treatment on the casting: firstly, carrying out normalizing pretreatment, then carrying out quenching and tempering heat treatment, and finally carrying out tempering heat treatment;

5) and (4) performing finished product machining on the casting after the heat treatment is finished, and then assembling the casting into the bridge support.

2. The method for reducing cracks of the corrosion-resistant steel for bridge supports according to claim 1, wherein the deoxidizer in the step 2) is silicon calcium barium, and the addition amount is 2-3 kg/ton of molten steel.

3. The method for reducing the cracks of the corrosion-resistant steel for bridge supports according to claim 1, wherein the addition amount of the rare earth alloy in the step 2) is 0.5-1.5 kg/ton of molten steel.

4. The method for reducing the cracks of the corrosion-resistant steel for bridge supports as claimed in claim 1, wherein the tapping temperature in the step 2) is 1620-1650 ℃.

5. The method for reducing the cracks of the corrosion-resistant steel for bridge supports as claimed in claim 1, wherein the casting temperature in the step 3) is 1540-1580 ℃.

6. The method for reducing the cracks of the corrosion-resistant steel for bridge supports according to claim 1, wherein the temperature rise rate in the step 4) is 60-80 ℃/h.

7. The method for reducing the corrosion-resistant steel cracks for the bridge bearing according to claim 1, wherein the normalizing pretreatment in the step 4) is performed by the following steps: the furnace temperature is kept for 2-4h from normal temperature to 650 ℃, then the furnace is heated to 900-950 ℃ and kept for 4-6h, and then the furnace is cooled to below 500 ℃ and cooled to room temperature.

8. The method for reducing the cracks of the corrosion-resistant steel for bridge supports according to claim 1, wherein the treatment method of the quenching and tempering heat treatment in the step 4) is as follows: the furnace temperature is raised to 900-950 ℃, the temperature is kept for 4-6h, the furnace is quenched in NaCl solution with the concentration of 5-10 percent and the temperature of 15-35 ℃, and the water outlet temperature of the workpiece is 100-150 ℃.

9. The method for reducing the cracks of the corrosion-resistant steel for bridge supports according to claim 1, wherein the tempering heat treatment in the step 4) is as follows: the temperature of the furnace is raised to 650-700 ℃, the temperature is kept for 4-7h, and the furnace is cooled to the room temperature by air.

Technical Field

The invention relates to the technical field of metal materials, in particular to a method for reducing corrosion-resistant steel cracks for a bridge bearing.

Background

The bridge support is an important material for bridge construction, is positioned above pier abutments, and plays a role in supporting and buffering between a bridge deck and the pier abutments. With the wider construction of bridge buildings, the service environment of the bridge bearing is more severe, and ordinary carbon steel cannot meet the requirements of special environments, particularly the marine environment in coastal areas, so that the corrosion-resistant steel for the bridge bearing is developed. The corrosion-resistant steel is required to have higher strength, impact toughness and atmospheric corrosion resistance.

The Chinese patent with the publication number of CN105624586A and the name of 'a corrosion-resistant bridge bearing steel suitable for marine environment' discloses a corrosion-resistant bridge bearing steel suitable for marine environment, and the disclosed corrosion-resistant bridge bearing steel improves the corrosion resistance and mechanical property of materials and can meet the requirements of engineering on different corrosion resistance grades and strength grades. However, the material has high alloy element content, so that the steel has high crack sensitivity and is easy to crack in the using process, thereby causing certain potential safety hazard. The bridge engineering requires very high safety factor, so the steel for the bridge bearing is forbidden to have crack defects. In the prior art, the production process or the manufacturing method of the corrosion-resistant steel cannot reduce the crack sensitivity, so that the rejection rate is high. Therefore, the invention provides a new production method, which can remarkably reduce the crack sensitivity of the corrosion-resistant steel and reduce the crack defects of the bridge bearing steel casting.

Disclosure of Invention

In order to solve the problems, the invention provides a method for reducing the cracks of corrosion-resistant steel for a bridge bearing, which comprises the following steps:

1. the method for reducing the cracks of the corrosion-resistant steel for the bridge bearing is characterized by comprising the following steps of:

1) selecting low-phosphorus low-sulfur scrap steel and required alloy materials, and smelting molten steel by adopting an alkaline arc furnace, wherein the molten steel comprises the following elements in parts by weight:

0.08 to 0.15 percent of C; 0.16 to 1.0 percent of Si; 0.5 to 1.6 percent of Mn0; 0.60 to 11.0 percent of Cr0; ni0.30-2.0%; 0.01 to 0.5 percent of Al0; nb0.02-0.05%; 0.01 to 0.03 percent of Ti0.01 percent; p is less than or equal to 0.015 percent; s is less than or equal to 0.015 percent; cu is less than or equal to 0.80 percent; v is less than or equal to 0.06 percent; mo is less than or equal to 0.35 percent; the balance of Fe and inevitable impurities;

2) adding a deoxidizing agent and a rare earth alloy into the steel ladle, and then tapping;

3) pouring molten steel into a casting mould, hammering by using an air impact hammer to remove a riser after a casting is solidified and cooled, wherein the casting mould is a sand casting process model, the riser is set as a necking exothermic riser, and the root of the riser is provided with an easily-cut piece;

4) carrying out heat treatment on the casting: firstly, carrying out normalizing pretreatment, then carrying out quenching and tempering heat treatment, and finally carrying out tempering heat treatment;

5) and (4) performing finished product machining on the casting after the heat treatment is finished, and then assembling the casting into the bridge support.

Further, the deoxidizer in the step 2) is silicon-calcium-barium, and the addition amount is 2-3 kg/ton of molten steel.

Further, the addition amount of the rare earth alloy in the step 2) is 0.5-1.5 kg/ton of molten steel.

Further, the tapping temperature in the step 2) is 1620-.

Further, the pouring temperature in the step 3) is 1540-1580 DEG C

Further, the temperature rise speed in the step 4) is 60-80 ℃/h;

further, the treatment method of the normalizing pretreatment in the step 4) is as follows: the furnace temperature is kept for 2-4h from normal temperature to 650 ℃, then the furnace is heated to 900-950 ℃ and kept for 4-6h, and then the furnace is cooled to below 500 ℃ and cooled to room temperature.

Further, the method for quenching and tempering heat treatment in the step 4) is as follows: the furnace temperature is raised to 900-950 ℃, the temperature is kept for 4-6h, the furnace is quenched in NaCl solution with the concentration of 5-10 percent and the temperature of 15-35 ℃, and the water outlet temperature of the workpiece is 100-150 ℃.

Further, the tempering heat treatment in the step 4) comprises the following steps: the temperature of the furnace is raised to 650-700 ℃, the temperature is kept for 4-7h, and the furnace is cooled to the room temperature by air.

The invention controls the content of P, S element in the raw material to be less than 0.012 percent by adding Nb and Ti in the raw material and combining the processing method of smelting molten steel by an electric arc furnace.

The invention adopts silicon-calcium-barium as a deoxidizer, effectively controls the Al content in the raw materials within 0.05 percent, and simultaneously achieves the effect of obviously purifying molten steel.

During tapping, a certain amount of rare earth alloy is added into the steel ladle to modify the inclusions in the molten steel, so that the intergranular crack tendency is eliminated.

When the bridge support steel casting is produced by pouring, the necking riser is used as a feeding riser on the steel casting, and after the casting is cooled, the gas impact hammering falling riser is used for replacing the traditional hot cutting riser, so that the defect of cracks caused by thermal stress is eliminated.

Compared with the prior art, the invention has the beneficial technical effects that:

the method for reducing the cracks of the corrosion-resistant steel for the bridge bearing improves the corrosion resistance and the mechanical property of the material, effectively reduces the crack sensitivity of the corrosion-resistant steel, improves the yield of the bridge bearing, reduces the probability of cracks of the steel for the bridge bearing, and has high economic benefit.

Drawings

The invention is further illustrated in the following description with reference to the drawings.

FIG. 1 is a process flow diagram of the method for reducing cracks in corrosion-resistant steel for a bridge bearing.

Detailed Description

The invention provides a method for reducing corrosion-resistant steel cracks for a bridge bearing, which comprises the following steps:

1) selecting low-phosphorus low-sulfur scrap steel and required alloy materials, and smelting molten steel by adopting an alkaline arc furnace, wherein the molten steel comprises the following elements in parts by weight:

0.08 to 0.15 percent of C; 0.16 to 1.0 percent of Si; 0.5 to 1.6 percent of Mn0; 0.60 to 11.0 percent of Cr0; ni0.30-2.0%; 0.01 to 0.5 percent of Al0; nb0.02-0.05%; 0.01 to 0.03 percent of Ti0.01 percent; p is less than or equal to 0.015 percent; s is less than or equal to 0.015 percent; cu is less than or equal to 0.80 percent; v is less than or equal to 0.06 percent; mo is less than or equal to 0.35 percent; the balance of Fe and inevitable impurities;

2) adding a deoxidizing agent and a rare earth alloy into the steel ladle, and then tapping;

3) pouring molten steel into a casting mould, hammering by using an air impact hammer to remove a riser after a casting is solidified and cooled, wherein the casting mould is a sand casting process model, the riser is set as a necking exothermic riser, and the root of the riser is provided with an easily-cut piece;

4) carrying out heat treatment on the casting: firstly, carrying out normalizing pretreatment, then carrying out quenching and tempering heat treatment, and finally carrying out tempering heat treatment;

5) and (4) performing finished product machining on the casting after the heat treatment is finished, and then assembling the casting into the bridge support.

In one embodiment, the deoxidizer in the step 2) is silicon-calcium-barium, and the addition amount is 2-3 kg/ton of molten steel.

In one embodiment, the amount of the rare earth alloy added in the step 2) is 0.5 to 1.5 kg/ton of molten steel.

In one embodiment, the tapping temperature in step 2) is 1620-.

In one embodiment, the pouring temperature in the step 3) is 1540-1580 DEG C

In one embodiment, the temperature rise rate in the step 4) is 60-80 ℃/h;

in one embodiment, the treatment method of the normalizing pretreatment in the step 4) is as follows: the furnace temperature is kept for 2-4h from normal temperature to 650 ℃, then the furnace is heated to 900-950 ℃ and kept for 4-6h, and then the furnace is cooled to below 500 ℃ and cooled to room temperature.

In one embodiment, the method for quenching and tempering heat treatment in step 4) is as follows: the furnace temperature is raised to 900-950 ℃, the temperature is kept for 4-6h, the furnace is quenched in NaCl solution with the concentration of 5-10 percent and the temperature of 15-35 ℃, and the water outlet temperature of the workpiece is 100-150 ℃.

In one embodiment, the tempering heat treatment in step 4) is performed as follows: the temperature of the furnace is raised to 650-700 ℃, the temperature is kept for 4-7h, and the furnace is cooled to the room temperature by air.

The method for reducing cracks of corrosion-resistant steel for bridge bearings provided by the invention is further described with reference to the following examples.

Example 1

A method for reducing cracks of corrosion-resistant steel for a bridge bearing comprises the following steps:

1) selecting low-phosphorus low-sulfur scrap steel and required alloy materials, and smelting molten steel by adopting an alkaline arc furnace, wherein the molten steel comprises the following elements in parts by weight: 0.085 percent of C; 0.45 percent of Si; 0.92 percent of Mn0; 3.12 percent of Cr3; ni0.52 percent; al0.042%; nb0.036%; 0.025 percent of TiAl; p0.012%; 0.010 percent of S; 0.36 percent of Cu0; v0.04 percent; mo0.21%; the balance of Fe and inevitable impurities;

2) adding 2.0kg of silicon-calcium-barium per ton of molten steel and 1.0kg of rare earth alloy per ton of molten steel into a ladle, and then tapping;

3) the pouring temperature of the molten steel poured into the casting mould is 1560 ℃, after the casting is solidified and cooled for 48 hours, a dead head is removed by hammering by using an air impact hammer, the casting mould is a sand casting process model, the dead head is set as a necking exothermic dead head, and a knock-off strip is arranged at the root of the dead head;

4) carrying out heat treatment on the casting:

normalizing heat treatment: keeping the temperature of the furnace from normal temperature to 650 ℃ at the speed of 60 ℃/h for 2h, then heating the furnace from 650 ℃ to 940 ℃, keeping the temperature for 6h, then cooling the furnace to below 500 ℃, and air-cooling the furnace to the room temperature;

quenching and tempering heat treatment: heating the furnace to 930 ℃ at the speed of 70 ℃/h, preserving the temperature for 5h, quenching in NaCl solution with the concentration of 6% and the temperature of 24 ℃, and ensuring that the water outlet temperature of the workpiece is 120 ℃;

tempering heat treatment: heating the furnace to 680 ℃ at a heating rate of 70 ℃/h, preserving the temperature for 6h, and cooling the furnace to room temperature;

5) and (4) performing finished product machining on the casting after the heat treatment is finished, and then assembling the casting into the bridge support.

Example 2

The difference from example 1 is that: the addition amount of Si, Ca and Ba was 3.0 kg/ton of molten steel.

Example 3

The difference from example 1 is that: the addition amount of the rare earth alloy was 1.5 kg/ton of molten steel.

Example 4

The difference from example 1 is that: the difference from example 1 is that: the Nb content was 0.045%, and the Ti content was 0.03%.

Comparative example 1

The corrosion-resistant steel for the bridge support is prepared by the method disclosed by the publication number CN105624586A entitled "a corrosion-resistant steel for the bridge support suitable for marine environment".

Test example 1

The mechanical properties of the pieces obtained in examples 1 to 4 and comparative example 1 were tested and the results were as follows:

numbering	Rp0.2，MPa	Rm，MPa	A，％	Z，％	Akv(room temperature), J	Akv(-40℃)，J
							Example 1	499	612	21.4	64	135	54
Example 2	503	605	20.6	62	142	66
							Example 3	437	595	23.2	68	137	62
Example 4	452	598	24.0	72	154	71
							Comparative example 1	379	572	18.3	56	117	32

From the above results, it can be seen that the mechanical properties of the workpieces obtained in examples 1 to 4 are significantly better than those of comparative example 1. Then, the workpieces obtained in examples 1 to 4 and comparative example 1 were processed, and magnetic powder flaw detection and ultrasonic flaw detection were performed. The results show that no crack defects were found in the workpieces prepared in examples 1-4, the yield was 100%, and a small amount of fine crack defects were found in the workpieces prepared in comparative example 1.

The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.