CN110724880A

CN110724880A - Cr-Ni-Mn series non-magnetic stainless steel and preparation method thereof

Info

Publication number: CN110724880A
Application number: CN201810779213.7A
Authority: CN
Inventors: 邵聪; 郑金桥; 李静媛
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2018-07-16
Filing date: 2018-07-16
Publication date: 2020-01-24

Abstract

The invention discloses Cr-Ni-Mn series non-magnetic stainless steel, which comprises the following components in percentage by mass: c is more than or equal to 0.04 percent and less than or equal to 0.06 percent, Cr is more than or equal to 18.5 percent and less than or equal to 19.5 percent, Ni is more than or equal to 12.0 percent and less than or equal to 14.0 percent, Mn is less than or equal to 1.0 percent, N is more than or equal to 0.15 percent and less than or equal to 0.25 percent, and the balance is Fe and inevitable impurities. The invention also discloses a preparation method of the Cr-Ni-Mn series nonmagnetic stainless steel.

Description

Cr-Ni-Mn series non-magnetic stainless steel and preparation method thereof

Technical Field

The invention relates to the technical field of stainless steel materials, in particular to Cr-Ni-Mn series non-magnetic stainless steel and a preparation method thereof.

Background

The non-magnetic steel is steel without magnetic induction in magnetic field, the structure of the steel is mainly austenite, and the magnetic conductivity mu is less than or equal to 1.29 multiplied by 10^-6H/m, and the relative magnetic permeability mu r is less than or equal to 1.05. The non-magnetic steel has wide application, and is required to be adopted in automatic control systems, precision instruments, telecommunication, motors and many military fields. With the progress of society and the development of economy, the demand for high-performance non-magnetic steel is increasing day by day.

Common austenitic stainless steel, such as types 304 and 316, has a solid solution structure of austenite, a relative permeability of less than 1.05, and belongs to the nonmagnetic category, but after a certain amount of cold deformation processing, the austenitic stainless steel is easy to deform, so that martensite phase transformation is induced. Along with the increase of the cold deformation rate, the relative permeability is greatly improved, so that after the austenitic stainless steel is processed into parts or products, magnetism is generated more or less, and the austenitic stainless steel cannot be applied to the field needing no magnetism.

In the non-magnetic stainless steel having a stable austenite structure, in order to ensure the stability of austenite and the performance of stainless steel, Ni and Mn (or C) are generally added to the non-magnetic stainless steel in sufficient amounts, but if the Ni content is high, the production cost is too high, and if the C or Mn content is high, the corrosion resistance is easily reduced.

Disclosure of Invention

In view of the above, the present invention is directed to a Cr-Ni-Mn based non-magnetic stainless steel and a method for preparing the same, which can improve non-magnetic properties and corrosion resistance of the non-magnetic stainless steel.

The technical scheme of the embodiment of the invention is realized as follows: the embodiment of the invention provides Cr-Ni-Mn series non-magnetic stainless steel, which comprises the following components in percentage by mass: c is more than or equal to 0.04 percent and less than or equal to 0.06 percent, Cr is more than or equal to 18.5 percent and less than or equal to 19.5 percent, Ni is more than or equal to 12.0 percent and less than or equal to 14.0 percent, Mn is less than or equal to 1.0 percent, N is more than or equal to 0.15 percent and less than or equal to 0.25 percent, and the balance is Fe and inevitable impurities.

In the scheme, the mass percent of C is 0.059%; the mass percent of Cr is 19.3%; the mass percent of Ni is 13.2%; the mass percent of Mn is 0.22%; the mass percent of N is 0.21%.

In the scheme, the mass percent of C is 0.043%; the mass percent of Cr is 18.9%; the mass percent of Ni is 12.7%; the mass percent of Mn is 0.31%; the mass percent of N is 0.21%.

In the scheme, the mass percent of C is 0.047%; the mass percent of Cr is 19.1%; the mass percent of Ni is 12.2%; the mass percent of Mn is 0.15%; the mass percent of N is 0.18%.

In the scheme, the mass ratio of the Cr, Ni and N in the non-magnetic stainless steel is as follows: cr: ni: n is 1-1.054: 0.649-0.757: 0.0081-0.1351.

In the above scheme, the inevitable impurities include P and S, and the mass percentages of P and S in the non-magnetic stainless steel are as follows: p is less than 0.045% and S is less than 0.030%.

In another aspect of the embodiments of the present invention, there is provided a method for preparing a Cr-Ni-Mn series non-magnetic stainless steel, including:

putting pure iron, metal chromium and metal nickel blocks into a vacuum smelting furnace for smelting;

after the molten liquid is formed, adding chromium nitride iron and electrolytic manganese into the liquid for continuous smelting until the chromium nitride iron and the electrolytic manganese are molten to form molten steel;

and pouring the molten steel to prepare the nonmagnetic stainless steel billet.

In the scheme, the particle size of the ferrochromium nitride is 10-20mm or 2-4 mm.

In the scheme, the time for smelting the chromium iron nitride and the electrolytic manganese is 10-11 min.

In the scheme, the pouring temperature is 1500-.

In the scheme, the material of the casting mould used for casting the molten steel is copper or graphite.

In the above scheme, the preparation method further comprises:

carrying out hot forging or hot rolling treatment on the steel billet to prepare a blank with a preset size;

and quenching the blank.

In the above scheme, after the quenching treatment is performed on the blank, the preparation method further includes:

carrying out solution treatment on the blank;

and quenching the blank subjected to the solution treatment.

In the above scheme, the hot forging the steel billet comprises: and (3) putting the billet into a heating furnace, heating to 1100-1200 ℃, preserving heat for 10-20min, and forging into a blank with a preset size.

In the above aspect, the hot rolling the steel slab includes: and (3) placing the steel billet into a heating furnace, heating to 1050-1100 ℃, and rolling into a blank with a preset size after heat preservation for 50-90 min.

In the scheme, the temperature of the solution treatment is 1050-1100 ℃, and the treatment time is 50-90 min.

The embodiment of the invention provides Cr-Ni-Mn series non-magnetic stainless steel and a preparation method thereof, wherein during preparation, ferrochrome nitride is added, so that N element is added into the prepared non-magnetic stainless steel, and the content of Cr, Ni and N element is coordinated, so that on the basis of not increasing the content of Ni element, the as-cast structure is ensured to be fully austenitic, and the content of C, Mn element is greatly reduced, thereby not only improving the non-magnetic property of the non-magnetic stainless steel, but also ensuring the corrosion resistance (the corrosion resistance is not lower than that of common 316 (referred to as type) stainless steel) under the condition of not increasing the production cost, and achieving the aim of coexistence of stable austenitic structure and excellent corrosion resistance.

Drawings

FIG. 1 is a schematic flow chart of a method for preparing a Cr-Ni-Mn series non-magnetic stainless steel according to an embodiment of the present invention;

FIG. 2 is a schematic flow chart of another method for preparing a Cr-Ni-Mn series non-magnetic stainless steel according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples.

In the related art, the stability of austenite and the performance of stainless steel are ensured by adding sufficient amounts of Ni and Mn (or C) elements, and in this case, the production cost and the performance of non-magnetic stainless steel need to be considered.

How to ensure the performance of the non-magnetic stainless steel on the basis of lower cost is a problem to be solved urgently at present.

Based on this, in various embodiments of the invention, ferrochrome nitride is additionally added in the preparation process, N element is added in the prepared non-magnetic stainless steel, and the content of C, Mn element is greatly reduced on the premise of not increasing the content of Ni element by coordinating the content of Cr, Ni and N element, namely ensuring that the as-cast structure is fully austenitic.

In the following description, the minute is simply referred to as min.

The embodiment of the invention provides a preparation method of Cr-Ni-Mn series non-magnetic stainless steel, as shown in figure 1, the preparation method mainly comprises the following steps:

step 101: preparing raw materials according to the mixture ratio.

Here, the raw materials may include pure iron, metallic chromium, metallic nickel block ferrochromium nitride, and electrolytic manganese, wherein the electrolytic manganese may be electrolytic manganese block, electrolytic manganese particles, electrolytic manganese powder, or the like.

In practical application, the ratio of the raw materials can be respectively as follows: 60.36 to 69.67 weight percent of pure iron, 13.64 to 16.58 weight percent of metallic chromium, 12 to 14 weight percent of metallic nickel block, 4.69 to 7.81 weight percent of chromium iron nitride and less than or equal to 1.25 weight percent of electrolytic manganese.

Here, wt% means mass percentage.

Step 102: putting pure iron, metal chromium and metal nickel blocks into a vacuum smelting furnace for smelting.

It should be noted that the pure iron refers to iron with relatively high iron content, such as pure iron with a purity of 99.99%.

In practice, the pure iron may also be referred to as pig iron.

Step 103: after the molten liquid is formed, ferrochrome nitride and electrolytic manganese are added into the liquid for continuous smelting until the ferrochrome nitride and the electrolytic manganese are molten to form molten steel.

In practical application, the yield of the granular ferrochromium nitride is higher than that of the powdery ferrochromium nitride. Wherein the yield is as follows: the percentage of the effective components of the added raw materials blended into the alloy steel, taking the added ferrochrome nitride as an example, under the theoretical calculation condition, the mass percentage of the N element in the prepared non-magnetic stainless steel can reach 0.25%, but because 30% of the N element overflows in the form of nitrogen in the smelting process, the yield of the N element is 70%, and then the mass percentage of the N element actually contained in the prepared non-magnetic stainless steel is 0.25% multiplied by 0.7 which is 0.175%.

Based on this, in one embodiment, the particle size of the ferrochrome nitride may be 10-20mm, and the yield of N element detected is about 70%.

In one embodiment, the grain size of the ferrochromium nitride can be 2-4mm, and the yield of the N element can reach 80% through detection.

When the powdery ferrochromium nitride is used for smelting, the yield is very low and is less than 40 percent. The reasons for this phenomenon are: compared with the granules of the granular chromium iron nitride, the granular chromium iron nitride has smaller granularity and larger specific surface area, thereby leading the reaction speed to be faster in the smelting process and further leading the overflow amount of nitrogen to be increased.

Experiments show that: the shorter the time interval from the complete melting of the ferrochromium nitride and the electrolytic manganese to the pouring of the molten steel after the melting, the higher the yield of the N element; meanwhile, the raw materials are required to be completely melted, and the time for smelting the chromium nitride iron and the electrolytic manganese can be 10min-11 min.

The beneficial effect of stirring on smelting is mainly shown as three points: 1. the temperature distribution of molten steel (the molten steel comprises the liquid in the step 102 and the molten steel in the step 103) is uniform; 2. the formed alloy has uniform distribution of components; 3. improve the metallurgical physical and chemical reaction kinetics condition. Meanwhile, in the embodiment of the invention, as the smelted raw material contains ferrochrome nitride, the nitrogen in the molten steel can be promoted to overflow by stirring, so that the solubility of the N element is reduced. Experiments show that: when the stirring time is increased from 0 to 2min, the content of N element in the prepared non-magnetic stainless steel is reduced from 0.13 wt% to 0.092 wt%; therefore, in the embodiment of the invention, proper stirring is required in the smelting process to ensure the content of the N element in the non-magnetic stainless steel and the uniformity of the components of the non-magnetic stainless steel.

Based on this, in practical application, the induction coil can be used for heating to perform smelting, so that molten steel in the crucible (the molten steel includes the liquid in the step 102 and the molten steel in the step 103) can be stirred in a small range under the action of electromagnetic force during smelting; in addition, the molten steel can be stirred by applying artificial external force. Experiments prove that the nitrogen content in the cast ingot can be obviously improved by reducing stirring before the molten steel is poured.

Step 104: and pouring the molten steel to prepare the nonmagnetic stainless steel billet.

In one embodiment, the pouring temperature may be 1500-.

Experiments show that when 2-4mm of ferrochrome nitride particles are adopted, the time interval from the complete melting (which can be understood as the end of melting) of ferrochrome nitride and electrolytic manganese to the time before pouring is 12min, the yield of N element is 83.13%.

In an embodiment, the material of the casting mold used for casting the molten steel may be a material with good thermal conductivity, such as copper or graphite. Experiments show that compared with the sample cooled by the casting mold made of graphite, the sample cooled by the casting mold made of copper has the N content increased by 13%. This is because copper has a large thermal conductivity, and therefore the cooling rate of molten steel is high, that is, it is advantageous to increase the cooling rate to increase the yield of N element.

After the steps, the prepared nonmagnetic stainless steel billet is in an oblique cylindrical shape, the minimum diameter is 90mm, and the maximum diameter is 120 mm.

In practical application, the manufactured nonmagnetic stainless steel billet can be further subjected to heat treatment so as to achieve the use purpose.

In one embodiment, the heat treatment comprises hot forging or hot rolling.

Specifically, the step of heat treatment is shown in fig. 2 and comprises:

step 105: and (4) carrying out hot forging or hot rolling treatment on the nonmagnetic stainless steel billet prepared in the step (104) to prepare a blank with a preset size.

The hot forging process may include: and (3) putting the blank into a heating furnace, heating to 1100-1200 ℃, preserving heat for 10-20min, and forging into a blank with a preset size. Although the time of the heat treatment has a certain relationship with the thickness of the ingot, the temperature inside the ingot is sufficiently raised in the temperature rise process in the furnace, so that the temperature difference between the inside and the outside of the ingot having a certain thickness is not so large, and the influence of the thickness of the ingot on the holding time can be ignored. In the embodiment of the invention, the forged blank is a square blank with a preset size of 45mm × 45 mm. It is understood that other shapes, such as circular, polygonal, etc., can be forged according to actual needs, and the preset size can be adjusted according to needs.

The manner of the hot rolling process may include: and putting the steel billet into a heating furnace, heating to 1050-1100 ℃, preserving the temperature for 50-90min, and rolling into a blank with a preset size. In the embodiment of the invention, the billet can be cut into square ingots of 90mm × 90mm before hot rolling, and then hot rolling is performed for 6 times, wherein turning is required for 1, 3 and 5 times, so as to ensure that the hot-rolled billet is a square billet with a preset size of 45mm × 45 mm. It is understood that the plate can be hot-rolled into other shapes, such as a circle, a polygon, etc., according to actual needs, and the preset size can be adjusted according to needs.

Step 106: and quenching the blank.

Here, in the embodiment of the present invention, the quenching treatment method that can be adopted is water quenching. It is understood that other quenching methods, such as oil quenching, may be used according to actual requirements.

Step 107: and carrying out solution treatment on the blank.

Further, in order to obtain a proper grain size and ensure the high-temperature creep resistance of the non-magnetic stainless steel, the blank after hot forging or hot rolling treatment can be subjected to solution treatment, the temperature of the solution treatment can be 1050-.

Step 108: and quenching the blank.

After the solution treatment is completed, a quenching treatment is also required. Here, in the embodiment of the present invention, the quenching treatment method that can be adopted is water quenching. It is understood that other quenching methods, such as oil quenching, may be used according to actual requirements.

By the method, the following components can be prepared: the Cr-Ni-Mn series non-magnetic stainless steel comprises the following components: 0.04 to 0.06 weight percent of C, 18.5 to 19.5 weight percent of Cr, 12.0 to 14.0 weight percent of Ni, less than or equal to 1.0 weight percent of Mn, 0.15 to 0.25 weight percent of N, and the balance of Fe and inevitable impurities.

In addition, in the embodiment of the present invention, the P and S elements are present in the nonmagnetic stainless steel as impurities, that is, the inevitable impurities include P, S element, and P, S elements account for the following mass percentages in the Cr — Ni — Mn based nonmagnetic stainless steel, respectively: p is less than 0.045 wt% and S is less than 0.030 wt%.

The present invention will be described in further detail with reference to the following application examples.

The following examples use chromium iron nitride with a particle size of 2-4 mm; the time interval from the complete melting of the ferrochromium nitride and the electrolytic manganese to the pouring is 12 min; the stirring mode is that the stirring is carried out by the electromagnetic force of the induction coil, and the stirring is carried out without applying artificial external force; cooling by adopting a casting mold made of copper; the smelted nonmagnetic stainless steel billet is in an oblique cylindrical shape, the minimum diameter is 90mm, and the maximum diameter is 120 mm.

Application embodiment 1

1. Taking 64.78 wt% of pure iron, 15.22 wt% of metal chromium, 13.2 wt% of metal nickel block, 6.56 wt% of chromium nitride and 0.28 wt% of electrolytic manganese, smelting and pouring according to the method described in the

steps

102 and 104, and preparing the nonmagnetic stainless steel billet.

2. And (3) forging the prepared nonmagnetic stainless steel billet according to the hot forging treatment mode in the step 105, wherein the temperature of the billet is increased to 1150 ℃, and the temperature is kept for 15 min. And forging to obtain a square billet with the preset size of 45mm multiplied by 45 mm.

3. And carrying out solid solution treatment on the square billet at 1080 ℃ for 60 min. After the solution treatment is completed, water quenching is performed as in step 106.

The Cr-Ni-Mn series non-magnetic stainless steel prepared in the embodiment comprises the following components in percentage by mass: c is 0.059 wt%; 19.3 wt% of Cr; ni is 13.2 wt%; mn is 0.22 wt%; n was 0.21 wt%, and the balance was Fe and inevitable impurities.

Application example two

1. Taking 64.78 wt% of pure iron, 14.82 wt% of metal chromium, 12.7 wt% of metal nickel block, 6.56 wt% of chromium nitride and 0.39 wt% of electrolytic manganese, smelting and pouring according to the method described in the

steps

102 and 104, and preparing the nonmagnetic stainless steel billet.

2. Cutting the prepared nonmagnetic stainless steel billet into square ingots with the diameter of 90mm multiplied by 90mm, and then carrying out rolling treatment according to the hot rolling treatment mode in the step 105, wherein the temperature of the billet is raised to 1080 ℃ and is kept for 60 min. In the embodiment, the hot rolling is carried out for 6 passes, and the steel turning is required in all the 1 st, 3 rd and 5 th passes. And forging to obtain a square billet with the preset size of 45mm multiplied by 45 mm.

The Cr-Ni-Mn series non-magnetic stainless steel prepared in the embodiment comprises the following components in percentage by mass: c is 0.043 wt%; 18.9 wt% of Cr; ni is 12.7 wt%; mn is 0.31 wt%; n was 0.21 wt%, and the balance was Fe and inevitable impurities.

Application example three

1. 66.39 wt% of pure iron, 15.59 wt% of metallic chromium, 12.2 wt% of metallic nickel block, 5.63 wt% of chromium nitride and 0.19 wt% of electrolytic manganese are taken, and smelting and pouring are carried out according to the method described in the steps 102-104, so as to prepare the nonmagnetic stainless steel billet.

The Cr-Ni-Mn series non-magnetic stainless steel prepared in the embodiment comprises the following components in percentage by mass: c is 0.047 wt%; 19.1 wt% of Cr; ni is 12.2 wt%; mn is 0.15 wt%; n was 0.18 wt%, and the balance was Fe and inevitable impurities.

The chemical composition (wt%) and properties of the Cr-Ni-Mn based non-magnetic stainless steel obtained in the above examples one to three are shown in table 1 below, in which the test solution used for measuring the pitting potential was a 3.5% sodium chloride solution.

TABLE 1

As can be seen from Table 1, the Cr-Ni-Mn series non-magnetic stainless steel prepared by the embodiment of the invention has extremely low relative permeability, the Mur is less than or equal to 1.003, the austenite structure (without magnetic property) is stable, after 30% of cold deformation, the relative permeability Mur is less than or equal to 1.01, and still maintains excellent non-magnetic property, thereby solving the problem that the non-magnetic property of the non-magnetic stainless steel material is reduced in the subsequent processing (deformation processing, turning or Computer Numerical Control (CNC) processing and the like).

As can be seen from Table 1, the Cr-Ni-Mn series non-magnetic stainless steel prepared by the embodiment of the invention has the electrochemical corrosion pitting potential of about 320mV in a 3.5% sodium chloride solution, the neutral salt spray performance of 1000h and excellent corrosion resistance, and can meet the use requirements of oceans, marshes and other environments with higher requirements on corrosion resistance conditions.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of changes or substitutions within the technical scope of the present invention, and all such changes or substitutions are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. The Cr-Ni-Mn series non-magnetic stainless steel is characterized by comprising the following components in percentage by mass: c is more than or equal to 0.04 percent and less than or equal to 0.06 percent, Cr is more than or equal to 18.5 percent and less than or equal to 19.5 percent, Ni is more than or equal to 12.0 percent and less than or equal to 14.0 percent, Mn is less than or equal to 1.0 percent, N is more than or equal to 0.15 percent and less than or equal to 0.25 percent, and the balance is Fe and inevitable impurities.

2. The nonmagnetic stainless steel according to claim 1, characterized in that the mass percentage of C is 0.059%; the mass percent of Cr is 19.3%; the mass percent of Ni is 13.2%; the mass percent of Mn is 0.22%; the mass percent of N is 0.21%.

3. The nonmagnetic stainless steel of claim 1, wherein the mass percent of C is 0.043%; the mass percent of Cr is 18.9%; the mass percent of Ni is 12.7%; the mass percent of Mn is 0.31%; the mass percent of N is 0.21%.

4. The nonmagnetic stainless steel of claim 1, wherein the mass percent of C is 0.047%; the mass percent of Cr is 19.1%; the mass percent of Ni is 12.2%; the mass percent of Mn is 0.15%; the mass percent of N is 0.18%.

5. The nonmagnetic stainless steel according to claim 1, wherein the nonmagnetic stainless steel contains three elements of Cr, Ni and N in the mass ratio of: cr: ni: n is 1-1.054: 0.649-0.757: 0.0081-0.1351.

6. The nonmagnetic stainless steel according to any one of claims 1 to 5, wherein the inevitable impurities include P and S, and the mass percentages of P and S in the nonmagnetic stainless steel are respectively: p is less than 0.045% and S is less than 0.030%.

7. A preparation method of Cr-Ni-Mn series non-magnetic stainless steel is characterized by comprising the following steps:

and pouring the molten steel to prepare the nonmagnetic stainless steel billet.

8. A method according to claim 7, wherein the particle size of the ferrochromium nitride is 10-20mm or 2-4 mm.

9. The method according to claim 7 or 8, wherein the time for smelting the ferrochrome nitride and the electrolytic manganese is 10-11 min.

10. The method as claimed in claim 7 or 8, wherein the casting temperature is 1500-.

11. The method according to claim 7 or 8, wherein a material of a casting mold used for casting the molten steel is copper or graphite.

12. The method of manufacturing according to claim 7, further comprising:

and quenching the blank.

13. The production method according to claim 12, further comprising, after subjecting the billet to a quenching process:

carrying out solution treatment on the blank;

and quenching the blank subjected to the solution treatment.

14. The method of manufacturing of claim 12, wherein said hot forging said steel blank comprises: and (3) putting the billet into a heating furnace, heating to 1100-1200 ℃, preserving heat for 10-20min, and forging into a blank with a preset size.

15. The method of claim 12, wherein said hot rolling said steel slab comprises: and (3) placing the steel billet into a heating furnace, heating to 1050-1100 ℃, and rolling into a blank with a preset size after heat preservation for 50-90 min.

16. The method as claimed in claim 13, wherein the solution treatment temperature is 1050-1100 ℃, and the treatment time is 50-90 min.