JP2668113B2 - Method for producing high-strength non-magnetic stainless steel material with excellent workability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is for producing a non-magnetic stainless steel material having excellent workability and high strength, which is used in various devices and apparatuses that function by utilizing magnetic properties. Regarding the method. (Prior art and its problems) Cr-Ni austenitic stainless steel represented by SUS304 has good corrosion resistance and workability, and has a non-magnetic austenitic structure in the annealed state, so it can be used as a non-magnetic steel, Used for precision equipment parts. Some parts require strength and are used after cold working. However, since the austenite phase of SUS304 steel is metastable, martensitic transformation occurs during cold working and becomes magnetic. Therefore, for such a purpose, SUS316 in which the austenite phase is more stable is used. However, these Cr-Ni-based austenitic steels were not originally developed as non-magnetic steels, but general steels were merely diverted to non-magnetic applications. For example, SUS316, which has a more stable austenite phase, contains a large amount of expensive Ni and Mo, but although Mo exerts an excellent corrosion resistance effect, it does not contribute to high strength or non-magnetism. High Si content steels include heat resistant steels and stress corrosion cracking steels, and these steel types are based on the fact that Si exhibits excellent effects in oxidation resistance or prevention of stress corrosion cracking. Further, as a steel having excellent scratch resistance, there is a steel of Japanese Examined Patent Publication No. 56-32387, the chemical composition of which is Cr: 12-19%, Ni: 4-12%, Mn7-
12%, Si 3-5%, C: 0.01-0.12%, N: 0.03-0.3%,
In order to secure the austenite structure during annealing, the austenite forming element Ni is contained in an amount directly proportional to the Si content. Furthermore, as a steel with heat resistance and scratch resistance, Japanese Patent Publication Sho 56
-11379 steel, the chemical composition of which is Cr: 13-25%, Ni: 5
~ 15%, Mn: 0.5 ~ 5.5%, Si: 2.5 ~ 5.0%, C: 0.15% or less, N: 0.05 ~ 0.20%, which can be used for sliding members under conditions where lubricant cannot be used. It utilizes the strengthening of the geology of Si and N and the formation of oxide films by Si and its self-healing properties. However, these high Si content austenitic steels are not considered at all in terms of weldability and ensuring non-magnetism in the state hardened by cold working. That is, these steels are prone to high temperature cracking during welding depending on the component system, and become magnetic due to the formation of martensite by cold working, and cannot be used as non-magnetic steels. [Means for solving the problem] The present inventors have investigated the effects of alloy elements, cold working and heat treatment on the hardness, permeability and workability of a multi-year Cr-Ni austenitic stainless steel, and found that Si and N are: It has been found that strength is increased by performing cold working or moderate heat treatment after cold working. Further, it was found that the workability deteriorates by adding Si and N, but the workability comparable to SUS304 can be maintained by adding Cu to this. In other words, by adding Si and N on the basis of Cr-Ni and further adding Cu, we succeeded in developing a high-strength non-magnetic stainless steel with excellent workability and high age hardening after cold working. did. In addition, in the present invention, nonmagnetic means a magnetic permeability of 1.01 or less. [Structure and Action of the Invention] According to the present invention, in% by weight, C: 0.08% or less, Si: 3 to 6%, Mn: 3 to 9%, Ni: 10 to 16%, Cr: 16 to 22% , N: 0.05 to 0.25%, Cu: 3% or less, with the balance being Fe and impurities, A defined by the following formula: A (γ) = Ni + Cu + 0.5Mn + 30 (C + N) -1.3Cr-2.6Si + 11.8 (gamma) value -10 <a (gamma) satisfies <0, and the value of Ni equivalent = Ni + Cu + 0.6Mn + 9.69 (C + N) + 0.18Cr-0.11Si 2 defined in the Ni equivalent is, after the final annealing A step of smelting steel whose composition is adjusted so as to be in a range above the curve A-A shown in FIG. 1 according to the amount of cold working given, a step of processing into a steel material to be subjected to final annealing, A high-strength non-magnetic stainless steel material with a magnetic permeability of 1.01 or less, consisting of a final annealing step, a cold working step, and if necessary, an aging treatment in the range of 300 to 600 ° C. Production method, is provided. Further, according to the present invention, C: 0.08% or less, Si: 3 to 6%, Mn: 3 to 9%, Ni: 10 to 16%, Cr: 16 to 22%, N: 0.05 to 0.25, by weight. %, Cu: 3% or less, Mo: 3% or less, V: 0.5% or less, Nb: 0.5% or less, Ti: 0.5% or less, and one or more types are contained, and the total of V + Nb + Ti is 0.5%. A (γ) = Ni + Cu + 0.5Mn + 30 (C + N) -1.3Cr-2.6-Si1.3Mo-13 (V + Nb + Ti) +11.8 10 <a (γ) <satisfies 0, and the value of Ni equivalent = Ni + Cu + 0.6Mn + 9.69 (C + N) + 0.18Cr -0.11Si 2 + 0.6Mo + 2.3 (V + Nb + Ti) is defined by the Ni equivalent, final A step of smelting steel whose composition is adjusted so as to be in a range above the curve AA shown in FIG. 1 according to the amount of cold working given after annealing, and processing into a steel material to be subjected to final annealing Process, final annealing process, cold working Degree, optionally further comprising the step of performing an aging treatment in the range of 300 to 600 ° C., the method of producing a high-strength nonmagnetic stainless steel material permeability and excellent workability is 1.01 or less is provided. In the present invention, C is a strong austenite phase stabilizing element similar to N and is an element effective for improving strength. On the other hand, C significantly reduces corrosion resistance and weldability, and a large amount of C is processed. In the case of the present invention, the upper limit of C is 0.08% because it also lowers the property. Si is a useful element that achieves the high strength, which is the main feature of the present invention, and it is necessary to have at least about 3% to achieve its purpose. However, as the Si content increases, the workability decreases significantly. , The steel becomes magnetic after cold working, and the hot workability deteriorates, so the upper limit is 6%. Like Ni, Mn is an element that effectively works to maintain non-magnetism after cold working and increases the solid solubility of N as a strengthening element. Further, Mn is an element that improves workability. About 3% or more is required to exhibit these performances, and in order to maintain non-magnetism after cold working, Ni, Cu
It is necessary to adjust the Mn content with
Has an upper limit of 9% to increase the sensitivity to hot cracking during welding. Ni is a basic component of the austenitic steel and contributes to stabilization of the austenitic phase and is an element imparting workability. About 10% or more is required to maintain non-magnetism after cold working. Further, depending on the content of Si, Cu, Mn,
It is necessary to adjust the equivalent weight. However, a large amount of Ni content is Mn
Similarly to Cu and Cu, the upper limit is set to 16% to increase the sensitivity to hot cracking during welding. Cr is a basic component of stainless steel, and it is necessary to contain about 16% or more in order to obtain good corrosion resistance, but if it is contained in a large amount, a large amount of δ ferrite is generated and hot workability deteriorates. Together with non-magnetic properties,
22% N is an element effective for maintaining the non-magnetic property, which is a main feature of the steel of the present invention, and for obtaining high strength. In order to exhibit these performances, it is necessary to contain about 0.05% or more.
However, if it exceeds 0.25%, a sound steel ingot cannot be obtained, so the upper limit is set. Cu not only imparts the workability, which is the main feature of the steel of the present invention, but also contributes to the stabilization of the austenite phase and maintains the non-magnetism after cold working. However, if contained in a large amount, the sensitivity to hot cracking during welding increases, so the upper limit is set to 3%. Mo is a useful element that contributes to strengthening and stabilization of the austenite phase, but if added in a large amount, the amount of δ ferrite produced increases, and it becomes impossible to maintain non-magnetism, so the upper limit is made 3%. V, Nb and Ti are useful elements contributing to high strength, but when added in a large amount, workability is remarkably reduced, and δ
Since the amount of ferrite generated increases and it becomes impossible to secure non-magnetic properties, the upper limit is 0.5% and the sum of V + Nb + Ti is
0.5% or less. The formulas of A (γ) and Ni equivalent and the numerical range of A (γ) are derived based on experimental results. That is, the stainless steel containing high Si, high Mn, and high Ni is one kind of high alloy steel, and it is necessary to design the composition so as to generate an appropriate amount of δ ferrite in order to prevent hot cracking during welding. Therefore, as a result of various experiments, it was found that the stabilization index A (γ) of the austenite phase was defined as described above, and that the value was 0 or less as described above, and good weldability could be secured. However, the A (γ)
If the value is less than −10, a large amount of δ ferrite is generated, and since this remains in the product material, nonmagnetic properties cannot be secured. Further, the Ni equivalent defined as described above is an index of the stability of the austenite phase against cold working, and as shown in Fig. 1, the Ni equivalent required to secure non-magnetic property after cold rolling. The minimum value of is given by curve A-A in Figure 1 and it can be seen that the more highly cold rolled steel is required to have the higher Ni equivalent value. The steel whose composition is adjusted to satisfy the above conditions is melted, and the melted steel is processed into a shape to be subjected to final annealing. This working method is not particularly limited, and a known hot working method or cold working method can be applied. The final annealing is
What is necessary is just to carry out under conditions where the steel is sufficiently softened, and the annealing conditions adopted for ordinary austenitic stainless steel can be applied. As described above, the present invention provides Cr containing high Si, high N, and high Mn.
-Ni-based austenitic stainless steel contains an appropriate amount of Cu and adjusts the composition as described above to impart workability to the steel and perform high-strength processing by cold working or cold working and aging. And the magnetic permeability after cold working can be suppressed to 1.01 or less. FIG. 2 shows 20Cr-11Ni-2Cu-6Mn-4Si-0.05C of the present invention.
It is a diagram showing the effect of aging temperature (soaking time, 1 hour) on the hardness of -0.17n steel after 60% cold rolling. As can be seen from this figure, the aging treatment is 300-600 ℃. It is desirable to carry out within the range. There is no aging effect in a lower temperature range, and softening occurs in a higher temperature range. [Example] After melting 30 kg of steel having the composition shown in Table 1, 10 mm
Forged to a thickness of 120 mm, subjected to a solution treatment at 1100 ° C for 1 hour, cold-rolled to 3 mm, intermediately annealed at 1050 ° C for 5 minutes, and then cold-rolled to 1.5 mm, and then to 1070 ° C. A final annealing of 2 minutes was performed. The magnetic permeability, tensile properties and Vickers hardness of these annealed materials were measured. Vickers hardness, permeability and bendability after 60% cold rolling of the annealed material, and Vickers hardness after aging treatment of the 60% cold rolled material at 500 ° C for 1 hour. Was measured. The Vickers hardness was measured with a load of 20 kg, and the magnetic permeability was measured under a magnetic field of 1000 Oersted by melting a magnetic balance. Table 2 shows the yield strength, tensile strength, elongation and hardness of each steel in Table 1 after annealing, hardness after 60% cold rolling, permeability and bendability, and at 500 ° C after 60% cold rolling. The hardness after the heat treatment for one hour and the weldability of the annealed material are shown. Here, regarding bendability, the case where a 90 ° butt bend in the L direction was performed and cracks did not occur after bending with R / t = 1, ○,
Those that caused cracks were marked with x. The weldability was evaluated by performing a color check on the annealed material after TIG welding, and those in which cracks were not observed were evaluated as ○ and those in which cracks were observed were evaluated as ×. As is known from Table 2, conventional steel A1 steel (SUS304)
And A2 steel (SUS316) have high ductility of 54.7% and 49.3%, respectively, and have good workability. However, A1 steel cannot secure non-magnetism due to its high magnetic permeability after cold rolling, and A2 steel is insufficient as a high strength material due to its low hardness after cold rolling or after aging treatment. is there. Comparative steel C1 steel is SU
Like S304, its strength level is high, but its magnetic permeability after cold rolling is high. C2 steel has a high hardness after cold rolling and a magnetic permeability of 1.01
The following are non-magnetic, but the A (γ) value is 0 or more, and the weldability is extremely poor. C3 steel has a high content of Si and N, C4 steel has a high content of Si and N, and further contains V, so that it can be strengthened by cold-rolling aging treatment, The magnetic permeability after rolling is 1.01 or less and it is excellent in non-magnetism as well, but the ductility of the annealed material is low at 41 to 43% and the bendability is poor. On the other hand, the B1 to 5 steels of the present invention have high Cu content as well as Si and N contents, and thus have high ductility of 49 to 52%, good bendability, and aged after cold rolling. By performing the treatment, the hardness becomes Hv470 or more, and particularly Hv500 or more for B4 steel and B5 steel. B6 to B15 steels are also Mo, V, Nb and Ti.
Of these steels, one or more of them are included, so that the strength is further enhanced, but the ductility is 46%, the bendability is good, and the workability is still superior to that of the comparative steel. The magnetic permeability is It contains an appropriate amount of Ni, Mn, Cu and N so that the given Ni equivalent is 19.0 or more, and has a magnetic permeability of 1.01 or less even after cold rolling of 60%, and is excellent in non-magnetic properties.
Further, the composition is adjusted so that the A (γ) value given by the above formula is -10 to 0, no high-temperature cracking occurs during welding, an appropriate amount of δ ferrite is formed, and non-magnetism in the annealed material can be secured. It is a thing. [Effect of the Invention] The present invention is excellent in workability, has a sufficiently high strength level after cold working and after aging treatment after cold working, and has a sufficiently stable magnetic permeability after cold working of 1.01 or less. It is intended to provide a non-magnetic stainless steel material having non-magnetic properties, and in particular, to provide a non-magnetic stainless steel material having extremely high practicality as a material for electrical equipment parts and devices requiring workability and high strength. It has become possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the relationship between the minimum Ni equivalent required to maintain non-magnetism and the cold rolling rate in the steel of the present invention. FIG. 2 shows 20Cr-11Ni-2Cu-6Mn-4Si-0.05C- according to the present invention.
FIG. 3 is a diagram showing the effect of aging temperature (soaking time: 1 hour) on the hardness of a 0.17N steel after 60% cold working.

   ────────────────────────────────────────────────── ─── Continuation of front page    (56) References JP-A-50-30727 (JP, A)                 JP-A-54-81118 (JP, A)                 JP-A-58-64356 (JP, A)                 JP-A-59-76824 (JP, A)                 Tokiko Sho 59-53343 (JP, B2)                 Tokiko Sho 51-29858 (JP, B2)

Claims (1)

(57) [Claims] % By weight, C: 0.08% or less, Si: 3 to 6%, Mn: 3 to 9%, Ni: 10 to 16%, Cr: 16 to 22%, N: 0.05 to 0.25%, Cu: 3% or less And the balance is Fe and impurities, and the A (γ) value defined by the following formula A (γ) = Ni + Cu + 0.5Mn + 30 (C + N) −1.3Cr−2.6Si + 11.8 has a value of −10 <A (γ) < satisfies 0, and the value of Ni equivalent = Ni + Cu + 0.6Mn + 9.69 (C + N) + 0.18Cr-0.11Si 2 Ni eq defined in the first diagram in accordance with the cold working amounts to be applied after the final annealing Permeability, which consists of the steps of smelting the steel whose composition has been adjusted so that it is in the range above the curve A-A shown in, the step of processing into the steel material to be subjected to final annealing, the final annealing step, and the cold working step. A method for producing a high-strength non-magnetic stainless steel material excellent in workability, having a value of 1.01 or less. 2. % By weight, C: 0.08% or less, Si: 3 to 6%, Mn: 3 to 9%, Ni: 10 to 16%, Cr: 16 to 22%, N: 0.05 to 0.25%, Cu: 3% or less Mo: 3% or less, V: 0.5% or less, Nb: 0.5% or less, Ti: 0.5% or less, and one or more types are contained, and the total of V + Nb + Ti is 0.5% or less and the balance Fe and impurities. A (γ) = Ni + Cu + 0.5Mn + 30 (C + N) −1.3Cr−2.6Si−1.3Mo−13 (V + Nb + Ti) +11.8 where A (γ) is −10 <A (γ) < satisfies 0, and Ni value of equivalent = Ni + Cu + 0.6Mn + 9.69 (C + N) + 0.18Cr -0.11Si 2 + 0.6Mo + 2.3 (V + Nb + Ti) is defined by the Ni equivalent, cold applied after final annealing The step of producing a steel whose composition is adjusted so as to be in the range above the curve A-A shown in FIG. 1 according to the working amount, the step of working into the steel material to be subjected to the final annealing, the final annealing step, the cooling It has a magnetic permeability of 1 A method for producing a high-strength non-magnetic stainless steel material having excellent workability of 0.01 or less. 3. % By weight, C: 0.08% or less, Si: 3 to 6%, Mn: 3 to 9%, Ni: 10 to 16%, Cr: 16 to 22%, N: 0.05 to 0.25%, Cu: 3% or less And the balance is Fe and impurities, and the A (γ) value defined by the following formula A (γ) = Ni + Cu + 0.5Mn + 30 (C + N) −1.3Cr−2.6Si + 11.8 has a value of −10 <A (γ) < satisfies 0, and the value of Ni equivalent = Ni + Cu + 0.6Mn + 9.69 (C + N) + 0.18Cr-0.11Si 2 Ni eq defined in the first diagram in accordance with the cold working amounts to be applied after the final annealing The process of smelting the steel whose composition is adjusted so as to be in the range above the curve A-A shown in Fig. 4, the process of processing the steel material to be subjected to final annealing, the final annealing process, the cold working process, 300-600 ℃ A method for producing a high-strength non-magnetic stainless steel material excellent in workability and having a magnetic permeability of 1.01 or less, comprising a step of performing an aging treatment in the range described above. 4. % By weight, C: 0.08% or less, Si: 3 to 6%, Mn: 3 to 9%, Ni: 10 to 16%, Cr: 16 to 22%, N: 0.05 to 0.25%, Cu: 3% Contains: Mo: 3% or less, V: 0.5% or less, Nb: 0.5% or less, Ti: 0.5% or less, and one or more of them are contained. The total of V + Nb + Ti is 0.5% or less and the balance Fe and The value of A (γ) which is composed of impurities and is defined by the following equation A (γ) = Ni + Cu + 0.5Mn + 30 (C + N) -1.3Cr-2.6-Si1.3Mo-13 (V + Nb + Ti) +11.8 is -10 <A (γ) <satisfies 0, and cold values of Ni equivalent = Ni + Cu + 0.6Mn + 9.69 (C + N) + 0.18Cr -0.11Si 2 + 0.6Mo + 2.3 (V + Nb + Ti) is defined by the Ni equivalent is applied after the final annealing A step of producing a steel whose composition is adjusted so as to be in a range above the curve A-A shown in FIG. 1 according to the interworking amount, a step of processing a steel material to be subjected to final annealing, a final annealing step, Cold working process, 300-600 ℃ range Comprising the step of performing an aging treatment, high strength method for producing a non-magnetic stainless steel material permeability and excellent workability is 1.01 or less.