JPH0317245A - High strength, non-magnetic stainless steel with excellent machinability - Google Patents

Abstract

PURPOSE:To obtain the non-magnetic free cutting stainless steel having low magnetic permeability and high strength and having excellent machinability by adding specified elements for improving strength and elements for improving machinability to an austenitic stainless steel. CONSTITUTION:As a non-magnetic material used for various magnetic devices, an austenitic stainless slab having the compsn. contg., by weight, 0.05 to 0.20% C, <1.00% Si, 0.70 to 2.00% Mn, 8.00 to 11.00% Ni, 17.00 to 20.00% Cr, <3.5% Cu, 0.05 to 0.6% Nb, 0.05 to 0.4% V, 0.1 to 0.32% N, 0.1 to 0.25% S and 0.05 to 0.12% Se is subjected to hot rolling and is worked into wire rod or bar stock, which is used as parts material for various magnetic devices. The non- magnetic austenitic stainless steel having improved strength by the addition of Nb and V to an originally non-magnetic austenitic stainless steel, having improved corrosion resistance and cold workability by the addition of Cu and furthermore having excellent machinability by the addition of S and Se can be obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention has corrosion resistance as an austenitic stainless steel, and is used as various parts such as magnetic devices that exhibit high strength and non-magnetism with excellent machinability. This is related to stainless steel. [Prior Art 1] Conventionally, magnetic devices such as audio devices and magnetic recording devices are equipped with devices for inducing various kinds of magnetic generation. Under the influence of these devices, components that do not require magnetism, such as shafts, receive induced magnetization, generating magnetic noise and deteriorating performance. Therefore, such parts have a permeability μ1.
The required condition is that the value is 01 or less. This kind of low permeability austenite. stainless steel, e.g. SU
Based on S304, about 3% of Cu was added, and Ni.
Products with measures such as slightly increasing Mn have been used. However, in recent years, in terms of weight reduction and friction resistance, even more N,
Those with added Ti and Nb to improve strength are used. However, from the industry, low magnetic permeability (μ
= 1.01 or less), has high strength, and has good machinability. Austenitic and stainless steels are desired.
In order to satisfy these characteristics, Japanese Patent Application Laid-open No. 63-19
Publication No. 9852 is disclosed. [Problems to be Solved by the Invention] However, the above stainless steel has high strength and non-magnetism, that is, low magnetic permeability, and in order to improve workability such as machinability, a predetermined amount of S is added. Although a predetermined amount of N is added to obtain sufficient hardness after wire drawing, there are two problems: expensive Mo is added, and ferrite tends to form, increasing magnetic permeability. Also S,
When elements such as N and Cu are added, hot and cold workability becomes a serious problem. In particular, with regard to hot working, it is an important issue to formulate a steel ingot that has workability that allows it to be manufactured through the steps of blooming and rolling using rolls, and also to formulate a compound that satisfies the above characteristics. To solve these problems, first of all, when manufacturing products, the magnetic permeability is 1.0, assuming a cold working rate of about 50%.
1 or less can be achieved by adding stenite or foamer elements such as Ni, Cu, Mn, etc. However, this increases the cost. Limited by strength and machinability. Therefore, it is most effective to add a fairly large amount of N. Next, as a means of increasing strength, in the case of stainless steel, from a component standpoint, the most effective method is to add interstitial elements such as C and N. However, C is limited in terms of corrosion resistance, and N is used for melting and hot heating. Since there are manufacturing constraints such as cold working, it is necessary to add Nb, V, etc. to increase strength by precipitation of fine carbides and refinement of crystal grains. Furthermore, in imparting machinability, S, SePb. Bi
, Te, and other free-cutting elements may be added alone or in combination, but when high N is added and these free-cutting elements are added,
Hot and cold workability becomes extremely poor, and normal austenitic and stainless steel m (e.g. SUS304, SUS3
It becomes difficult to manufacture using the same process as 03).

The present invention was made in view of the above-mentioned conventional problems, and has low magnetic permeability and high strength, satisfies the required characteristics of excellent machinability, and has workability that can be manufactured using normal processes. The purpose is to provide low-cost, high-strength, non-magnetic free-cutting stainless steel. [Means and effects for solving the problems 1 The high strength, non-magnetic stainless steel with excellent machinability of the present invention has the following properties: C: 0.05-0.20%, Sf: 1. OO% or less, Mn: 0. 70 ~2. 00%, N
i: 8.00-11.00%, Cr: 17.
00 to 20.00%, Cu: 3, 5% or less, N b
: 0.05 ~ 0.6%, v: 0, 05 ~ 0.4%,
N: 0.1-0.32%, S: 0.1-0.25%S
e: 0.05 to 0.12%, which contains unavoidable impurities resulting from manufacturing, and the remainder is essentially Fe. That is, in the present invention, an ingot is prepared by adjusting the above-mentioned components in an electric furnace or the like, and the ingot is produced through hot rolling, solution treatment, and cold working (drawing, etc.) as a raw material.
The product is manufactured by cutting and has excellent workability, hardness of Hv370 or more, and magnetic permeability μi. It is characterized in that it can be manufactured at a low cost with less than oi and also satisfies good machinability. Therefore, regarding the component adjustment of the present invention, first, in order to make it non-magnetic, the amount of N is added to the maximum of 0.32% or less from the viewpoint of processability, and other properties are taken into account. do,
It was decided to adjust with Ni, Cu, and Mn. Next, regarding strength measures, for the reasons mentioned above, NO. 32%
The following were added, and C was added at a maximum of 0.20% in consideration of corrosion resistance and workability.

Furthermore, precipitation strengthening. Aiming at the combined effect of grain refinement, Nb and V are each added in an amount of 0.05 to 0.6%. 0, 05~0.
Added 4%. Next, it contains a large amount of such N and Nb. In selecting a free-cutting component that imparts machinability to stainless steel containing V and that can be subjected to blooming and cold working using normal manufacturing methods, we investigated SSe, PB, and other composite components. ．． For example, in the case of single S, 0.25% or more is required to satisfy machinability, but in the case of such high nitrogen materials, the workability is extremely poor, and with normal manufacturing methods, the product It is difficult to Also, regarding PB and other composite materials, machinability, workability. It is not possible to simultaneously satisfy corrosion resistance, etc., and the SO. 1 ~ 0.25%,
S e 0. 05~0. By adding 12%, we were able to achieve this objective. Next, the role of each component and component limitations regarding the present invention will be explained in detail below. C: 0.05-0.20% C is extremely important for improving strength, but if it is less than 0.05%, the purpose cannot be achieved, and if it is added in a large amount, corrosion resistance will deteriorate, so the upper limit should be set at 0.05% or less. I kept it at 20%. ΣKunyu' Bu L Ruiou Si is an effective component element as a deoxidizing agent during steel manufacturing, but
If it exceeds 1.00%, ferrite will be more likely to form, so set an upper limit! ．． It was set as 00%. Mn: 0.70 to 2.00% Mn is an element of austenite and former, and at the same time combines with S to form Mn. Creates S pressure material and contributes to machinability. However, if there is too much Mn, it will form a solid solution in the steel, impairing machinability. Therefore, Mn is required for deoxidation and S fixation.
．． The lower limit was set to 70%, and the upper limit was set to 2,00%. Ni: 8.00 to 11.00% Ni is an austenite and former element, and is an important element that controls demagnetization. 00%~11. It was set as 00%. Cr: I7. 00 to 20.00% Cr is one element of ferrite and former, and from the viewpoint of non-magnetic properties it is desirable to keep it low, but it is an element that contributes to improving corrosion resistance, and in order to obtain a sufficient effect, the content should be at least 17.0%.
It is necessary to add 00%. However, if a large amount is added, ferrite will be generated as described above, so the upper limit should be set at 20.
It was set as 00%.

Fresh Nim Yellow 1 Cu is austenite. It is a former element that has the same or higher effect as Ni on demagnetization, and is an effective component element for improving corrosion resistance, reducing work hardening rate, and improving cold workability. However, since it has a negative effect on strength improvement, the upper limit is set at 3.5% or less, taking into account the range that satisfies non-magnetism and the fact that adding too much will reduce hot workability. It was.
Nb: 0.05-0.6% Nb is a strong carbide-forming element and produces fine carbides. Precipitated nitride precipitation and precipitation strengthening are extremely effective in improving strength. However, since it forms a solid solution in the matrix, acts as a ferrite-forming element, and increases deformation resistance, it impairs hot workability and causes wire breakage during wire drawing. The content was set at 0.05 to 0.6%.

V: 0.05-0.4% V is C,! l: combine, VN, Va Cs . VC'!
Which compounds are produced, have a strong precipitation-strengthening effect, and are effective in improving strength. Furthermore, the crystal grains are made finer and the crystal grain coarsening temperature is increased. Therefore, by combined addition with Nb,
A synergistic effect can be expected as a strength improvement measure. This is a major feature of the present invention. In addition, ■ is a small amount of addition,
It has the effect of refining crystal grains and improves hot workability, but when added in large amounts, it increases deformation resistance and deteriorates workability. Therefore, the lower limit was set to 0.05% and the upper limit was set to 0.4%. N: 0.1 to 0.32% N is a strong austenite and former element and is an extremely effective element for making it non-magnetic. It also increases strength in small amounts along with C. However, 0.1
%~0.32%. S: 0. I NO. 25% S is a component element that forms inclusions in MnS and is extremely effective in improving machinability, and at least 0.1% is required to exhibit sufficient machinability. But 0.2
If added in excess of 5%, cracking and the like will occur during wire drawing, so the upper limit was set at 0.25%.

Se forms an intermetallic compound, and like S, each alone is effective in cutting, but when S and Se are combined, Se
produces composite inclusions with Mn inclusions, which has a remarkable effect on improving cutting. There is a delicate relationship between the addition ratio of Se and S.
In the case of single S, if 0.25% or more is added, the machinability improves, but the workability deteriorates rapidly. Therefore, S is 0.25%
If Se is added to this, SeO. 1
Up to 2%, the machinability is improved and the workability does not deteriorate much. Therefore, 30.1 to 0.25%, S e 0
．． 05~0. Adding it appropriately within the range of 12% will maximize the combined effect of both, and this is the feature of the present invention.

[Example] Steel ingots having the composition shown in Table 1 were hot worked into wire rods and bars. (Left below) The wire rod was rolled to 8mmφ and then cold-worked by 50% to achieve hardness. A magnetic permeability test was conducted. In addition, the bar material was rolled to a diameter of 50 mm and a cutting test was conducted. Figure 1 shows the hot workability of each sample.The test method was to bloom a steel ingot with each section into a 110mm square billet, then sample it at a temperature in the range of 900℃ to 1200℃. A high-temperature, high-speed tensile test was conducted, and the hot workability was evaluated based on the reduction of area. In actual manufacturing, the finishing temperature of hot rolling is 930℃
Therefore, the conditions for hot rolling require a reduction of area of 50% or more (minimum workable value) at 930°C. Applying these conditions to Fig. 1, the present invention material (
A-H) are satisfied, but comparative materials R and S cannot be hot worked. Next, Table 2 shows the magnetic permeability, hardness, and tool life properties of each sample in cutting tests. (Leaving space below) The magnetic permeability and hardness in Table 2 are the values when 50% cold working is performed on a 10 mm wire rod, and the tool life is as follows: Cutting conditions Tool PLO Feed 0. 2"/rev Life judgment without cutting oil This is the result of a cutting test under the conditions of VBs 0. 2mm. However, PIO: A symbol based on the usage selection criteria of JIS, B4053, and P type is mainly for cutting steel materials. }1ll91 or more. The analysis force is over 90''/m. vB:
Wear width of flank face of turning tool. Flank wear. From Table 2, comparative material M has good workability but does not satisfy the magnetic permeability and tool life, while N and P have very poor tool life and O
has insufficient tool life and hardness, and R and S cannot be hot worked as mentioned above. On the other hand, A and B of the present invention materials. C
, E, and G have magnetic permeability. hardness. All characteristics such as tool life and workability were satisfied, and D. Samples F and H have slightly poor workability, but they can be manufactured by controlling the finishing temperature of rolling to a slightly higher temperature. [Effects of the Invention] As explained above, according to the high-strength, non-magnetic free-cutting stainless steel according to the present invention, C: 0.05 to 0.2 in weight%
0%, St: 1.00% or less, Mn: 0.7 ~
2.00%, Ni: 8.00-11.00%,
Cr: 17.00 to 20.00%. Cu: 3.5% or less. Nb: 0, 05NO. 6%, V: 0.05~0
．． 4%. N: [l. 1 to 0.32%, further S: 0.1
~mouth. 25%. and S e : 0. 05 ~0. 1
Contains 2% and unavoidable impurities resulting from manufacturing, and the remainder. Since it is essentially made of Fe, compared to conventional high-strength non-magnetic stainless steel, the combined effect of S and Se provides much better machinability, and the synergistic effect of the combined addition of Nb and In addition to providing a steel with extremely remarkable strength improvement and an extremely low cost without adding Mo, when used in the shafts of actual audio equipment, etc.
Improvements in performance and life as shown in the basic characteristics shown in Table 2 were observed. 4.

[Brief explanation of the drawing]

Figure 1 shows the hot workability of each sample. Special permission Out wish Man Japan Koshuha Steel Co., Ltd.

Claims (1)

[Claims] C: 0.05-0.20% Si: 1.00% or less Mn: 0.70-2.00% Ni: 8.00-11.00% Cr: 17. 00~20.00% Cu: 3.5% or less Nb: 0.05~0.6% V: 0.05~0.4% N: 0.1~0.32% Furthermore, S: 0.1~ 0.25%, Se: 0.05-0.12%, and unavoidable impurities resulting from manufacturing, and the remainder is substantially F.
A high-strength, non-magnetic stainless steel with excellent machinability characterized by being made of E.