CN115254968A - A kind of manufacturing process of 316L seamless stainless steel pipe - Google Patents

Abstract

The invention discloses a manufacturing process of a 316L seamless stainless steel tube, which comprises the following steps of heating a cast ingot bar to 1080-1200 ℃, and then preserving heat to prepare a pierced billet; step two, cold rolling the pierced billet; removing the lubricating oil on the outer surface of the pipe; heating the pipe to 950-1100 ℃, preserving the heat, and spraying the pipe with room temperature water; step five, reducing the diameter of the pipe through a cold drawing die; step six, firstly carrying out rough straightening and then carrying out fine straightening on the pipe; the manufacturing process provided by the invention can enable the size and the straightness of the pipe to meet the technical requirements, and avoid the deformation waves generated on the surface of the pipe; the pipe is reduced by a cold drawing die so as to reach the size required by the process and improve the roundness of the pipe; the combination of the solid solution treatment and the room-temperature water spraying can improve the metallographic structure of the pipe while softening the pipe; the step straightening process can reduce the pressure of the straightening roller on the pipe, and avoid the generation of waves on the surface of the pipe due to large primary straightening deformation.

Description

A kind of manufacturing process of 316L seamless stainless steel pipe

technical field

The invention relates to the technical field of stainless steel pipes for nuclear power, in particular to a manufacturing process of 316L seamless stainless steel pipes.

Background technique

Most of the existing precision pipes for nuclear power are imported, and the dimensional accuracy of similar domestic 316L seamless stainless steel pipes is poor, and the comprehensive performance cannot meet the requirements of precision seamless stainless steel pipes for nuclear power; in order to meet the mechanical performance requirements of pipes, 316L seamless stainless steel must be solidified. Solvent treatment. During the solution treatment process, because the heating uniformity and rapid cooling consistency of each part of the pipe are not completely consistent, the solution treatment will cause deformation, and the roundness and straightness of the inner and outer diameters formed by cold working will deteriorate, so the pipe needs to be mechanically straightened. direct way to improve.

In the prior art, direct straightening of the 316L stainless steel pipe after solution treatment will cause straightening waves on the surface of the pipe, which will seriously affect the tolerance of the inner and outer diameters and cause the pipe to be scrapped. The reason for the wave is that the manufactured 316L stainless steel pipe is a thin-walled pipe, and the solid solution treatment of the finished product will soften the pipe and deteriorate the roundness and straightness of the pipe. Directly straightening the pipe will bear high pressure, so the surface of the pipe will produce deformation waves.

Contents of the invention

The purpose of the present invention is to provide a manufacturing process of 316L seamless stainless steel pipe to solve the problems raised in the above-mentioned background technology.

In order to achieve the above object, the present invention provides the following technical solutions: the manufacturing process includes the following steps: a manufacturing process of 316L seamless stainless steel pipe, step 1, heat the ingot bar to 1080-1200 °C, and then keep it warm. Finally, the bar is prepared into a blank tube;

Step 2, cold-rolling the blank pipe prepared in step 1 to obtain a deformation-hardened pipe;

Step 3, removing the lubricating oil on the inner and outer surfaces of the deformation-hardened pipe in step 2;

Step 4: Heating the deformed and hardened pipe treated in step 3, heating it to 950-1100°C and then keeping it warm, spraying the pipe with room temperature water after the heat preservation is completed, and cleaning the inner and outer surfaces of the pipe with acidic aqueous solution;

Step 5, reducing the diameter of the pipe processed in step 4 through a cold drawing die;

Step 6. Rough straightening and then fine straightening of the pipes processed in step 4, wherein,

The rough straightening operation is as follows: the straightening roller presses down according to 40-60% of the total reduction, so that the straightness of the pipe reaches 2mm/m and then stops;

The detailed straightening operation is as follows: the straightening roller is pressed down according to 40-60% of the total reduction, so that the straightness of the pipe is ≤0.1mm/m, and the target pipe is obtained.

As a preferred technical solution of the present invention, in the above-mentioned step 1, keep warm for 20-60 minutes.

As a preferred technical solution of the present invention, during the cold rolling in the above step 2, the blank tube is sheathed on the mandrel, and the outer wall of the blank tube is in contact with the pressure roller.

As a preferred technical solution of the present invention, the heat preservation time in the above step 4 is 10-30 minutes.

As a preferred technical solution of the present invention, the acidic aqueous solution used in step 4 above is prepared by mixing 5% HF, 25% HNO ₃ and 70% H ₂ O.

As a preferred technical solution of the present invention, after the pipe in the above step 2 is cold-rolled and shaped, the mechanical cutting method is used to remove the pits, folds and micro-cracks on the inner and outer surfaces of the pipe due to the thermal perforation pipe-making process, and the wall thickness is cut. The amount accounts for 2%-13% of the total wall thickness.

As a preferred technical solution of the present invention, in the above step 1, two-roll and multi-roll cold-rolled pipe mills are used to cold-roll the pipe, and the rolling deformation of the two-roll mill is controlled at 50-70%, and the multi-roll cold-rolled pipe mill The amount of rolling deformation is controlled at 20-40%.

As a preferred technical solution of the present invention, the cold drawing step in the above step five can be lined with mandrel or not lined with mandrel.

As a preferred technical solution of the present invention, in the above step five, a Φ19.80 mm mold with a machining accuracy of ≤0.0005 mm is used to cold-draw the pipe processed in step four.

Compared with prior art, the beneficial effect of the present invention is:

Through the manufacturing process provided by the invention, the size and straightness of the pipe can meet the technical requirements, and deformation waves on the surface of the pipe can be avoided. Among them, the diameter of the pipe is reduced through special cold drawing dies of different sizes to achieve the size required by the process. Due to the high precision of cold drawing die hole processing, cold drawing can improve the roundness of the pipe; the combination of solution treatment and rapid cooling with room temperature water spray can quickly reduce the temperature of the pipe below the intergranular corrosion sensitization temperature, and achieve softening The metallographic structure of the pipe is improved at the same time; the step-by-step straightening process can reduce the pressure of the straightening roller on the pipe, and avoid causing waves on the surface of the pipe due to one-time straightening deformation. At the same time, the first straightening can increase the plastic deformation strength of the pipe by 5%-10%, and can prevent the generation of straightening waves during the second fine straightening.

Detailed ways

In order to enable those skilled in the art to better understand the scheme of the present application, the technical scheme in the embodiment of the present application will be clearly and completely described below. Obviously, the described embodiment is only a part of the embodiment of the present application, rather than Full examples. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without making creative labor achievements shall fall within the scope of protection of this application.

It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other, and the present application will be described in detail below in conjunction with the embodiments.

Example 1

A kind of manufacturing process of 316L seamless stainless steel pipe, described manufacturing process comprises the following steps:

Step 1. Heat the ingot bar to 1080-1200°C and keep it warm for 20-60 minutes. After the heat preservation is over, prepare the bar into a waste tube;

Step 2. Cold rolling the blank pipe prepared in step 1. During cold rolling, the blank pipe is set on the mandrel, and the outer wall of the blank pipe is offset against the pressure roller to obtain a deformed and hardened pipe; the roundness of the mandrel is ≤0.001 mm; the taper of the mandrel outlet is controlled at about 0.01mm, which can take into account that the pipe is easy to separate from the mandrel during the rolling process, and prevents the formation of circular wave marks on the inner diameter; the CASTROL TDN81 internal lubricant with good fluidity is used to make the pipe before rolling A layer of lubricating fluid is evenly attached to the inner wall to avoid the inner diameter of the rolled tube being affected by the different thickness of the mandrel and the inner surface of the tube during the rolling process; two-roll (LG) and multi-roll (LD) cold rolling mills are used Carry out cold rolling on the pipe, the rolling deformation of the two-roll mill is controlled at 50-70%, and the rolling deformation of the multi-roll cold-rolling mill is controlled at 20-40%; the pipe in step 2 is formed by cold rolling and cut by machine The method is to remove the pits, folds and micro-cracks on the inner and outer surfaces of the pipe due to the hot perforation pipe-making process, and the wall thickness cutting amount accounts for 2%-13% of the total wall thickness; through precision-controlled rolling, the last LD cold-rolled pipe The roundness of inner and outer diameters and the deviation of wall thickness are within ±0.005mm, which is within the technical requirements of subsequent processing;

Step 3, removing the lubricating oil on the inner and outer surfaces of the deformation-hardened pipe in step 2;

Step 4. Heat the deformed and hardened pipe treated in step 3. Heat it to 950-1100°C and keep it warm for 10-30 minutes. After the heat preservation is over, spray the pipe with room temperature water and clean the inner and outer surfaces of the pipe with acidic aqueous solution ; The acidic aqueous solution is prepared by mixing 5% HF, 25% HNO ₃ and 70% H ₂ O;

Step 5. Reduce the diameter of the pipe processed in step 4 through a cold-drawing die; the specific operation is to use a Φ19.80mm die with a processing accuracy of ≤0.0005mm to cold-draw the pipe processed in step 4, and form a Φ19.82mm cold-rolled pipe The roundness of ≤0.005mm is deteriorated to 0.02mm～0.06mm after step 4 treatment, and the processing accuracy of the cold drawing die hole reaches the roundness ≤0.0005mm. Using the physical properties of metal materials, after the pipe is cold drawn by the Φ19.80mm die, The roundness of the pipe can be restored to ≤0.01mm. Since the outer diameter change of cold drawing is only reduced by 0.02mm, and the wall thickness does not change, the effect of cold drawing micro-shaping on the mechanical properties of the pipe is very small;

Step 6. Rough straightening and then fine straightening of the pipe processed in step 4. The rough straightening operation is as follows: the straightening roller presses down according to 40-60% of the total reduction, so that the straightness of the pipe reaches 2mm/ stop after m;

The detailed straightening operation is as follows: the straightening roller is pressed down according to 40-60% of the total reduction, so that the straightness of the pipe is ≤0.1mm/m to obtain the target pipe.

Example 2

Performance tests were performed on the steel pipes prepared in Example 1, and the results are shown in Table 1 and Table 2, respectively. From the values of roundness tolerance, surface roughness tolerance and straightness tolerance in Table 1, it can be seen that the roundness and straightness of the pipe obtained in Example 1 are good after the straightening operation. Table 2 is the metallographic structure of 316L seamless stainless steel tube.

Table 1 Dimensional tolerance of 316L seamless stainless steel pipe

Table 2 Metallographic structure of 316L seamless stainless steel tube

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solutions of the present invention and Any equivalent replacement or change of the inventive concepts shall fall within the protection scope of the present invention.

Claims (9)

1. A process for manufacturing a 316L seamless stainless steel tube, comprising the steps of:

step one, heating a cast ingot bar to 1080-1200 ℃, preserving heat, and preparing the bar into a pierced billet after heat preservation is finished;

step two, cold rolling the pierced billet prepared in the step one to obtain a deformation hardened pipe;

step three, removing the lubricating oil on the inner surface and the outer surface of the pipe subjected to deformation hardening in the step two;

step four, heating the deformation-hardened pipe processed in the step three to 950-1100 ℃, preserving heat, spraying the pipe with room-temperature water after heat preservation, and cleaning the inner and outer surfaces of the pipe with acidic aqueous solution;

step five, reducing the diameter of the pipe subjected to the treatment in the step four through a cold drawing die;

sixthly, performing rough straightening and then fine straightening on the pipe processed in the fourth step, wherein,

the rough straightening operation is as follows: the straightening roller is pressed down according to 40-60% of the total pressing amount, and the straightening roller is stopped after the straightness of the pipe reaches 2 mm/m;

the fine straightening operation is as follows: and pressing down the straightening roller according to 40-60% of the total pressing down amount to ensure that the straightness of the pipe is less than or equal to 0.1mm/m, thus obtaining the target pipe.

2. The process of claim 1, wherein the first step is performed for 20-60 min.

3. The manufacturing process of a 316L seamless stainless steel tube according to claim 1, wherein during the cold rolling in the second step, the pierced billet is sleeved on the mandrel, and the outer wall of the pierced billet abuts against the press roll.

4. The process of claim 1, wherein the holding time in step four is 10-30 min.

5. The process for manufacturing a 316L seamless stainless steel tube according to claim 1, wherein the acidic aqueous solution used in the fourth step is 5% HF, 25% HNO₃And 70% of H₂And O, mixing and preparing.

6. The manufacturing process of a 316L seamless stainless steel tube according to claim 1, wherein the tube in the second step is subjected to cold rolling and shaping, and then is subjected to mechanical cutting to remove pits, folds and microcracks generated in the tube manufacturing process due to hot perforation on the inner and outer surfaces of the tube, and the wall thickness cutting amount accounts for 2% -13% of the total wall thickness.

7. The process of claim 1, wherein in step one, the tube is cold rolled using two rolls and a multi-roll cold pilger mill, the rolling deformation of the two rolls is controlled to 50-70%, and the rolling deformation of the multi-roll cold pilger mill is controlled to 20-40%.

8. The process of claim 1, wherein the cold drawing step in step five may or may not be core rod lined.

9. A process according to claim 1, wherein in step five the tube obtained from step four is cold drawn using a 19.80mm phi die with machining accuracy less than or equal to 0.0005 mm.