JPH0579727B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention is a high-Mn non-staining steel that has become widely used as a substitute for austenitic stainless steel in heavy electrical equipment components such as nuclear power plant components, transformers, and large generator shaft retaining rings. The present invention relates to a method for manufacturing magnetic steel. [Prior Art] High Mn nonmagnetic steel is a steel that has been made nonmagnetic by adding large amounts of C and Mn. This steel has the disadvantage that when subjected to cold working, deformation-induced martensite is generated and the magnetic permeability increases. To prevent this, austenite stabilizing elements such as Mn, Ni, and Cr have been added to this steel. It was added in large quantities. Adding various alloying elements in this manner causes an increase in cost. Water dust treatment is sometimes used as a method to stabilize the austenite structure of steel and reduce magnetic permeability without adding alloying elements such as those mentioned above, but cold working also lowers magnetic permeability. The disadvantage is that it increases. Furthermore, as a conventional means of improving the properties of high-Mn nonmagnetic steel, there has been a method of adding Nb or V, but this is aimed at increasing the strength of the steel through precipitation strengthening. Furthermore, a widely used method has been to reheat non-magnetic steel to 1000°C to 1050°C and treat water dust to dissolve carbides, which have a negative effect on magnetic permeability. The purpose of this is to stabilize the magnetic permeability by solid solution. [Problems to be solved by the invention] As stated above, in the prior art,
It has been extremely difficult to maintain stable magnetic permeability after cold working for low-cost high-Mn nonmagnetic steel. This invention was made to solve the above-mentioned problems, and provides a method for manufacturing high-Mn non-magnetic steel that can inexpensively manufacture high-Mn non-magnetic steel with stable magnetic permeability after cold working. With the goal. [Means for solving the problem] The present invention provides high Mn nonmagnetic steel with Nb or V added singly or in combination at 1150°C to 1250°C.
After heating and hot rolling at 700℃~850℃, 1000℃
By reheating to 1050℃ and water-dust treatment, the processed structure caused by hot rolling is completely recrystallized, and by making the JIS crystal grain size number 7.5 or higher, the High Mn with stable magnetic permeability
A high-quality steel that is characterized by the ability to manufacture non-magnetic steel at low cost.
This is a method for manufacturing Mn nonmagnetic steel. Here, high Mn nonmagnetic steel satisfies the following in terms of weight percentage: C: 0.20% or more, 1.50% or less, Si: 0.80% or less, Mn: 11% or more, 26% or less, and Nb: 0.05% or more. , 0.15% or less, V: 0.30% or more, 0.50% or less, the balance being Fe and S: 0.100
% or less, N: 0.2500% or less, etc. In the present invention, the above-mentioned high Mn nonmagnetic steel has Cr: 5.00%
Below, Ni: 3.00% or less is added to add further non-magnetic stabilization, Mo: 3.00% or less,
Ti: 0.20% or less of one or more types is contained to increase strength, and one or more of the above Cr and Ni and one or more of Mo and Ti are contained to further stabilize nonmagnetism and increase strength. Or to the high Mn non-magnetic steel mentioned above.
Ca: 0.0100% or less is contained to improve machinability. The reason why the components are limited as described above in the present invention will be explained. C: 0.20% or more, 1.50% or less; C is a strong austenite-forming element and at the same time has a significant strengthening effect. However, 0.20
In content less than %, to ensure non-magnetic
Addition of Mn, Ni, etc. is required, resulting in high cost.
In addition, if the content exceeds 1.50%, workability and cracking resistance will deteriorate, and carbides will be generated due to the effects of welding heat, resulting in deterioration of toughness and non-magnetism. did. Si: 0.80% or less; Si is a necessary element for melting and refining as a deoxidizing element. However, a content exceeding 0.80% promotes the generation of delta ferrite, etc., and impairs toughness and non-magnetism, so it is set at 0.80% or less. Mn: 11% or more, 26% or less; Mn is an austenite-forming element, and at the same time is an element useful for stabilizing austenite and nonmagnetism. It also increases the solubility of N, which is one of the important strengthening elements. However, if the content is less than 11%, it is necessary to add expensive alloying elements such as Ni and Cr to ensure nonmagnetism. In addition, since a content exceeding 26% would lead to an increase in cost, it was set at 11% or more and 26% or less. Nb: 0.05% or more, 0.15% or less; V: 0.30% or more, 0.50% or less; In the present invention, Nb and V have the effect of controlling crystal grain coarsening during reheating toughness treatment. The magnetic permeability after cold working is stabilized by making the particles finer by adding these elements. However, even if less than 0.05% of Nb or less than 0.30% of V is added, a sufficient crystal grain refinement effect cannot be obtained. Further, even if more than 0.15% of Nb or more than 0.50% of V is added, a more effective crystal grain refining effect cannot be obtained, and ductility and toughness decrease, and furthermore, cost increases. S: 0.100% or less; Adding S is effective in improving the machinability of high-Mn nonmagnetic steel, which is a difficult-to-cut material. However, since S causes a decrease in ductility, it is limited to 0.100% or less. N: 0.2500% or less; N is also one of the important elements for increasing strength. However, if the content exceeds 0.2500%, it causes a decrease in ductility and hot ductility, so it was set to 0.2500% or less. Cr: 5.00% or less; Cr is an important element for stabilizing nonmagnetism,
Since a content exceeding 5.00% leads to a decrease in ductility and an increase in cost, the content was set to 5.00% or less. Ni: 3.00% or less; Ni is effective in stabilizing non-magnetism and improving toughness, but excessive addition causes an increase in cost, so it was set at 3.00% or less. Mo: 3.00% or less; Mo is an important element for increasing strength, but 3.00%
Since a content exceeding 3.0% leads to deterioration of ductility and toughness, the content was set at 3.00% or less. Ti: 0.20% or less; Ti is also an important element for increasing yield strength, but excessive addition expands the precipitation temperature range of carbides, which has a negative effect on magnetic permeability, so it was set at 0.20% or less. Ca: 0.0100% or less; Addition of Ca is effective in improving the machinability of high-Mn nonmagnetic steel, which is a difficult-to-cut material. The amount added is 0.0100%
Sufficient machinability can be obtained even below. Next, in the method of the present invention, the slab is heated to 1150℃~1250℃.
℃, but this is to ensure that the precipitates are sufficiently dissolved in solid solution.If heating temperature is lower than this, Ni, V carbon, nitride, etc. will not be sufficiently dissolved in solid solution, and rolling The effect of refining crystal grains during the subsequent reheating water dust treatment is weakened. Furthermore, the reason why the upper limit was set at 1250°C is that heating at a temperature exceeding this lowers hot workability. After the above heating, the slab is hot rolled, but in the method of the present invention, the hot rolling end temperature is
The temperature was 700℃ or higher and 850℃ or lower. The reason for setting the temperature above 700°C is that if hot rolling is finished at a temperature below 700°C, carbides, etc. will precipitate during rolling, which may cause cracks during rolling, and deformation resistance will increase, making the rolling process difficult. This is because it becomes difficult. On the other hand, if the temperature is below 850℃, there is almost no difference in mechanical and physical properties no matter which temperature hot rolling is finished, but if the hot rolling finish temperature exceeds 850℃ The processed structure cannot be left sufficiently, and sufficiently fine crystal grains cannot be obtained during reheating and water dust treatment.
As a result, it becomes difficult to maintain stable magnetic permeability after cold working. Although it is more advantageous to take a high rolling reduction rate at low temperatures in order to sufficiently preserve the processed structure caused by hot rolling, the conditions of commonly used hot rolling are sufficient for the purpose of the present invention. You can get the following effect. Further, similar results can be obtained whether the cooling conditions after rolling are air cooling, water cooling, or direct water cooling, but in the case of water cooling or direct water cooling, distortion of the steel plate may occur. In addition, the temperature of reheated water after rolling is 1000℃~
The temperature was limited to 1050°C because carbides that adversely affect magnetic permeability cannot be sufficiently dissolved below 1000°C. Furthermore, if water dust treatment is performed at a temperature exceeding 1050°C, crystal grains will become coarser as the water dust treatment temperature increases, making it impossible to obtain stable magnetic permeability after cold working. Using these ingredients and manufacturing methods, the processed structure during hot rolling can be completely recrystallized, and
By setting the JIS grain size number to 7.5 or higher, the magnetic permeability after cold working is stabilized. To completely recrystallize the processed structure during hot rolling,
This is because if the processed structure remains, the magnetic permeability after cold working increases. Furthermore, the reason why the JIS crystal grain size number is set to 7.5 or more is because if it is less than 7.5, a sufficiently low magnetic permeability after cold working cannot be obtained. [Function] The present invention applies high Mn nonmagnetic steel to which Nb and V have been added singly or in combination. After heating to 1150°C to 1250°C and completing hot rolling at 700°C to 850°C,
By reheating to 1050°C and performing a water dust treatment, the processed structure due to hot rolling is completely recrystallized and the JIS grain size number is 7.5 or higher. This allows Nb to be cooled in the atmosphere after hot rolling at any desired temperature, and subjected to reheating and water dust treatment.
Alternatively, it is possible to provide stable magnetic permeability after cold working at a lower cost than high-Mn nonmagnetic steel without V addition. Further, Cr, Ni or/and Mo, Ti, and further Ca are added to add nonmagnetism, strength, and machinability to the above functions. [Example] Next, the present invention will be explained with reference to an example. Table 1 shows the chemical composition of each steel plate. (A) to (H) are 18% Mn based, (h) to (L) are 15% Mn based, (M)
-(O) is 12% Mn-based, and (P)-(R) is 23% Mn-based. Table 2 shows the manufacturing method. is based on the manufacturing method of the present invention, and ~ and ~ are based on the conventional manufacturing method. Table 3 shows 18%Mn produced by the production method of
These are the results of measuring the magnetic permeability and JIS grain size number of series non-magnetic steels (A) to (C) after 10% cold tensile processing. Compared to the comparative example, the inventive example has a low magnetic permeability of 1.010 or less (the DIN standard stipulates a magnetic permeability of 1.010 or less), and the JIS particle size number is 7.5 or higher. . In addition, the JIS grain size number for (B) steel in the manufacturing method code and (C) steel in the manufacturing method code is 7.5 or higher, but in these cases, the processed structure due to hot rolling remains. Therefore, a magnetic permeability of less than 1.010 cannot be obtained. Note that no difference was observed between those that were air-cooled after rolling and those that were directly water-cooled. Table 4 shows the products manufactured using the manufacturing method of
These are similar measurement results for 18% Mn-based nonmagnetic steels (A), (D) to (H). In this case as well, the inventive example was 1.010 compared to the comparative example.
% or less, and the JIS grain size number is 7.5 or higher. Table 5 shows 15% Mn-based non-magnetic steel, Table 6 shows 12%
Mn-based non-magnetic steel, Table 7 shows the magnetic permeability and JIS after 10% cold tensile processing of 23% Mn-based non-magnetic steel
This is the measurement result of the particle size number. In both cases, the same trends as in Tables 3 and 4 can be seen. Figure 1 shows steel (A) and (B) manufactured by the manufacturing method of ~.
This is a graph of the magnetic permeability after 10% cold stretching shown in Table 3. [Effects of the Invention] As described above, by limiting the heating temperature, rolling end temperature, and reheating water dust temperature for nonmagnetic steel to which Nb and V are added singly or in combination, the grain size can be reduced. can be miniaturized. This makes it possible to stabilize the magnetic permeability after cold working without increasing costs due to the addition of expensive alloying elements such as Ni and Cr.

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[Table] All others were air cooled after rolling.

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【table】 [Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between water dust treatment temperature and magnetic permeability after 10% cold stretching.

Claims (1)

[Claims] 1. C: 0.20% or more and 1.50% or less, Si: 0.80% or less, Mn: 11% or more and 26% or less, and further Nb: 0.05% or more and 0.15% or less , V: 0.30% or more, 0.50% or less
After heating to ~1250°C and finishing hot rolling at 700°C to 850°C, reheating to 1000°C to 1050°C and water dust treatment completely recrystallizes the processed structure caused by hot rolling. A method for producing a high-Mn nonmagnetic steel with excellent magnetic permeability stability, characterized by making the JIS grain size number 7.5 or higher and stabilizing the magnetic permeability after cold working. 2 By weight, C: 0.20% or more, 1.50% or less, Si: 0.80% or less, Mn: 11% or more, 26% or less, Nb: 0.05% or more, 0.15% or less, V: 0.30% or more, 0.50% or less, contains one or more of the following, further Cr: 5.00% or less,
Contains at least one type of Ni: 3.00% or less, with the balance being Fe
A slab of high Mn non-magnetic steel consisting of and unavoidable impurities is heated to 1150°C to 1250°C, then 700°C to 850°C.
After finishing the hot rolling at 1000°C to 1050°C, the processed structure by hot rolling is completely recrystallized by reheating to 1000°C to 1050°C, and the JIS grain size number is 7.5 or higher. A method for producing high-Mn nonmagnetic steel with excellent magnetic permeability stability, which is characterized by stabilizing magnetic permeability after cold working. 3 By weight, C: 0.20% or more, 1.50% or less, Si: 0.80% or less, Mn: 11% or more, 26% or less, Nb: 0.05% or more, 0.15% or less, V: 0.30% or more, 0.50% or less, contains one or more of the following, further Mo: 3.00% or less,
Contains at least one type of Ti: 0.20% or less, with the balance being Fe
A slab of high Mn non-magnetic steel consisting of and unavoidable impurities is heated to 1150°C to 1250°C, then 700°C to 850°C.
After finishing the hot rolling at 1000°C to 1050°C, the processed structure by hot rolling is completely recrystallized by reheating to 1000°C to 1050°C, and the JIS grain size number is 7.5 or higher. A method for producing high-Mn nonmagnetic steel with excellent magnetic permeability stability, which is characterized by stabilizing magnetic permeability after cold working. 4 By weight, C: 0.20% or more, 1.50% or less, Si: 0.80% or less, Mn: 11% or more, 26% or less, Nb: 0.05% or more, 0.15% or less, V: 0.30% or more, 0.50% or less, Contains one or more of the following, Cr: 5.00% or less, Ni: 3.00
% or less, and further contains one or more of Mo: 3.00% or less, Ti: 0.20% or less, and the balance is
A slab of high Mn non-magnetic steel consisting of Fe and unavoidable impurities is heated to 1150°C to 1250°C and then heated to 700°C to 850°C.
After finishing hot rolling at ℃, reheating to 1000℃~1050℃ and water dust treatment completely recrystallizes the processed structure caused by hot rolling and makes the JIS grain size number 7.5 or higher. , a method for producing high-Mn nonmagnetic steel with excellent permeability stability, which is characterized by stabilizing the magnetic permeability after cold working. 5 By weight, C: 0.20% or more, 1.50% or less, Si: 0.80% or less, Mn: 11% or more, 26% or less, Nb: 0.05% or more, 0.15% or less, V: 0.30% or more, A slab of high-Mn nonmagnetic steel containing at least 0.50% of the following, and further containing at most 0.0100% of Ca, with the balance consisting of Fe and unavoidable impurities, is heated to 1150°C to 1250°C, and then heated to 700°C to 1250°C. 1000 after finishing hot rolling at 850℃
By reheating to 1050°C and performing water dust treatment, the processed structure resulting from hot rolling is completely recrystallized, the JIS grain size number is 7.5 or higher, and the magnetic permeability after cold working is stabilized. A method for manufacturing high-Mn nonmagnetic steel with excellent magnetic permeability stability. 6 By weight, C: 0.20% or more, 1.50% or less, Si: 0.80% or less, Mn: 11% or more, 26% or less, Nb: 0.05% or more, 0.15% or less, V: 0.30% or more, 0.50% or less, Contains one or more of the following, Cr: 5.00% or less, Ni: 3.00
A slab of high Mn nonmagnetic steel containing at least 0.0100% Ca, with the balance consisting of Fe and unavoidable impurities is heated to 1150°C to 1250°C, and then heated to 700°C to 850°C. After finishing hot rolling,
By reheating to 1000°C to 1050°C, the processed structure from hot rolling is completely recrystallized, the JIS grain size number is 7.5 or higher, and the magnetic permeability after cold working is stabilized. A method for producing high-Mn non-magnetic steel with excellent magnetic permeability stability. 7 By weight, C: 0.20% or more, 1.50% or less, Si: 0.80% or less, Mn: 11% or more, 26% or less, Nb: 0.05% or more, 0.15% or less, V: 0.30% or more, 0.50% or less, contains one or more of the following, Mo: 3.00% or less, Ti:
Contains 0.20% or less of one or more types, and further Ca: 0.0100
% or less, with the remainder consisting of Fe and unavoidable impurities.
After heating to 1250°C and completing hot rolling at 700°C to 850°C, reheating to 1000°C to 1050°C is carried out to completely recrystallize the processed structure caused by hot rolling. , and a JIS grain size number of 7.5 or higher to stabilize the magnetic permeability after cold working. 8 By weight, C: 0.20% or more, 1.50% or less, Si: 0.80% or less, Mn: 11% or more, 26% or less, Nb: 0.05% or more, 0.15% or less, V: 0.30% or more, 0.50% or less, Contains one or more of the following, Cr: 5.00% or less, Ni: 3.00
% or more, Mo: 3.00% or less,
Contains at least one type of Ti: 0.20% or less, and further Ca:
A slab of high Mn non-magnetic steel containing 0.0100% or less with the balance consisting of Fe and unavoidable impurities was heated to 1150℃.
After heating to ~1250°C and finishing hot rolling at 700°C to 850°C, reheating to 1000°C to 1050°C and water dust treatment completely recrystallizes the processed structure caused by hot rolling. A method for producing a high-Mn nonmagnetic steel with excellent magnetic permeability stability, characterized by making the JIS grain size number 7.5 or higher and stabilizing the magnetic permeability after cold working.