JPH11335787A - Corrosion and weather resistant steel excellent in cold workability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel excellent in cold working, having good corrosion/ weather resistance and not requiring a coating film of plating, etc., at a low cost by incorporating the elements of C, Si, Mn, Cr, N, etc., respectively of a specified quantity. SOLUTION: This steel contains 0.10-<0.35% C, <=0.5% Si, <=0.5% Mn, 4.0-11.0% Cr, 0.04-0.20% N, one kind or two kinds among 0.2-1.0% Mo, 0.05-0.5% V, 0.05-0.5% Nb and the balance Fe with inevitable impurities. C is contained to increase a hardness and wear resistance, Si and Mn is contained as deoxidizer in refining. Cr forms a protective film on a material surface to impart corrosion resistance, softens the material with forming an carbide at the time of tempering/annealing and imparts cold workability. Further, N is included to improve corrosion resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion-resistant and weather-resistant steel which has good cold workability and does not rust under a moderately corrosive environment, but also has a certain level of corrosion resistance in a corrosive environment.

[0002]

2. Description of the Related Art Conventionally, materials for parts used in OA equipment and the like are required to have excellent cold drawing properties in order to improve productivity in processing into a predetermined shape, and to be used in indoor environments. SUS42 is required to have corrosion-resistant and weather-resistant steel that can withstand.
0J2 (C: 0.26 to 0.40%, Si: 1.00%
Hereinafter, Mn: 1.00% or less, P: 0.040% or less,
S: 0.030% or less, Cr: 12.00 to 14.00
%, Balance substantially Fe), SUS410 (C: 0.15
%, Si: 1.00% or less, Mn: 1.00% or less, P: 0.040% or less, S: 0.030% or less, C
r: 11.50 to 13.50%, with the balance being substantially Fe).

Further, SUM12 (C: 0.08-0, 1,
3%, Si: not specified, Mn: 0.60 to 0.90%,
P: 0.040% or less, S: 0.08 to 0.13%, balance substantially Fe), SUM22 (C: 0.13% or less,
Si: Not specified, Mn: 0.70 to 1.00%, P:
Using free-cutting steel such as 0.07 to 0.12%, S: 0.24 to 0.35%, and the balance substantially Fe), and applying Ni plating or Zn plating such as Kanigen plating after cutting. There was also.

[0004] However, these OA equipments only need to be provided with corrosion-resistant and weather-resistant steel that can withstand use in an indoor environment. Was not even appropriate.

[0005] When plating free-cutting steel such as SUM12 and SUM22, the quality tends to vary depending on the thickness of the plating and the presence or absence of defects, so that the reliability of the product is reduced. There was something. In addition, since environmental pollution may be considered, disposal of waste liquid generated during plating production must be taken into consideration, which may lead to a rise in processing costs, and the cost cannot be said to be low. Was.

[0006]

DISCLOSURE OF THE INVENTION The present invention has excellent cold workability required for improving the productivity when working into a predetermined shape, and is sufficient for use in a normal indoor environment. It is an object of the present invention to provide an inexpensive steel that has excellent corrosion resistance and weather resistance and does not require coating such as plating.

[0007]

Means for Solving the Problems To solve the above problems, the present inventor has developed a steel having excellent cold workability and sufficient corrosion resistance and weather resistance for use in a normal indoor environment. We have been studying the manufacturing process, component composition, and heat treatment of inexpensive steel that does not require coating such as plating.In order to obtain the required corrosion resistance, we need to use the amount of Cr that improves corrosion resistance for machine structures. In order to suppress the generation of coarse carbides that impair corrosion resistance by adding N to increase the corrosion resistance and increase the corrosion resistance of steel, the content of C is limited to the amount of solid solution necessary to obtain a desired strength, and the content of Cr is reduced. The content may be limited, and in order to improve the cold workability, the amount of Si and Mn in the annealing structure may be in a range that does not cause hardening of the matrix. Obtained knowledge is obtained without the present invention.

[0008] That is, in order to solve the above-mentioned problems, the corrosion-resistant and weather-resistant steel of the present invention having excellent cold workability includes:
C: 0.10 to less than 0.35%, Si: 0.5% or less,
Mn: 0.5% or less, Cr: 4.0 to 11.0%, and N: 0.04 to 0.20%, with the balance being Fe and unavoidable impurities.

Further, the corrosion resistance of the present invention is excellent in cold workability.
In weathering steel, C: 0.10 to less than 0.35%,
Si: 0.5% or less, Mn: 0.5% or less, Cr: 4.
0-11.0% and N: 0.04-0.20%,
Further, Mo: 0.2 to 1.0% or V: 0.05 to 0.5
% And Nb: one or two of 0.05 to 0.5%, with the balance being Fe and unavoidable impurities.

Next, the reason why the component composition of the corrosion-resistant and weather-resistant steel excellent in cold workability of the present invention is limited as described above will be described. C: 0.10 to less than 0.35% C is an element to be contained in order to increase hardness and improve wear resistance, and if less than 0.10%, there is no effect, and 0.35% or more. In this case, the strength becomes high and cold working becomes difficult, so the content range is 0.10 to 0.35.
Less than%. Si: 0.5% or less, Mn: 0.5% or less Si, Mn is an element to be contained as a deoxidizing agent at the time of melting and refining. , And Mn, so that the ferrite phase is hardened and the cold workability is reduced. In order to further enhance the cold workability, it is preferable that both are set to 0.3% or less.

Cr: 4.0 to 11.0% Cr forms a protective film on the surface of the material to provide corrosion resistance, and also forms carbides during tempering and annealing to soften the material. It is an element to be added to impart cold workability. In order to obtain corrosion resistance to a degree that does not rust in a relatively mild environment, it must be contained at least 4.0%. Is generated, which lowers the cold workability and makes it difficult to secure hardness by leaving undissolved carbides.
11.0%.

N: 0.04 to 0.20% N is an element constituting the skeleton of the present invention to be contained in order to improve corrosion resistance, and it is necessary to contain 0.04% or more in order to obtain the effect. However, if it exceeds 0.20%, the workability is lowered because the nitride does not completely form a solid solution, so the content range is made 0.04 to 0.20%. As elements for improving corrosion resistance, there are Cr, Mo, and the like in addition to N. Utilization of N, which is present in a large amount in the atmosphere, is highly desired from the viewpoint of resource saving. The effect of N is such that adding 0.1% of N corresponds to adding 1% of Cr.

Mo: 0.2 to 1.0% Mo is an element contained together with Cr to improve corrosion resistance. To obtain the effect, it is necessary to contain Mo in an amount of 0.2% or more. When the content exceeds 0%, the cold workability is lowered and the cost is increased. Therefore, the content range is set to 0.2 to 1.0%. V: 0.05-0.5%, Nb: 0.05-0.5% V and Nb both form stable fine carbides,
Element contained to refine crystal grains and improve strength and toughness. To obtain the effect, 0.05%
It is necessary to contain the above, but if it exceeds 0.5%, not only does the cold workability deteriorate, but also the toughness and ductility decrease, so the content range is made 0.05 to 0.5%.

In the present invention, the contents of P, S and O are not limited. However, since all of them are impurities, it is preferable that the content is small, but if P is 0.03% or less, corrosion resistance, tough ductility, etc. Therefore, its content is preferably set to 0.03% or less.
When the content is less than 05%, the effect on hot workability, corrosion resistance and cold workability is small, so the content is 0.005%.
It is preferable to set the following. If O is 0.005% or less, the amount of oxides generated is small and the effect on cold workability, fatigue strength, and toughness and ductility is small. Therefore, the content of O is 0.005% or less. It is preferred that In addition, Ni, which is an impurity mixed from the raw material scrap, becomes difficult to soften and anneal when it becomes large, so it is preferable to set it to 0.6% or less.

The corrosion-resistant and weather-resistant steel excellent in cold workability of the present invention can be manufactured by the same method as an alloy having similar component plasticity, and when used, is usually cooled in an annealed state. It is used while being machined (without heat treatment). Further, the use of the corrosion-resistant and weather-resistant steel having excellent cold workability of the present invention is used in a normal indoor environment, and a component that can be used in a cold-worked state, such as various precision machines. It is a material for manufacturing precision parts such as shafts, rollers, and small screws.

[0016]

The corrosion-resistant and weather-resistant steel of the present invention, which has excellent cold workability, has a higher Cr content for improving the corrosion resistance than the steel for machine structural use and contains N for improving the corrosion resistance, so that the corrosion resistance is improved. I do. In addition, since the content of C is limited to the amount of solid solution necessary to obtain a desired strength and the content of Cr is limited, it is possible to suppress the generation of coarse carbides that degrade corrosion resistance. It can be further improved. Further, since the amounts of Si and Mn are set to 0.5% or less, the matrix hardens and the cold workability does not decrease.

[0017]

Next, embodiments of the present invention will be described.

Example 1 Ingots having the component compositions shown in Table 1 below were melted in a high-frequency induction furnace and cast into ingots. This ingot is hot-rolled to a diameter of 22 mm.
A round bar was heated at 730 ° C. for 2 hours and then air-cooled for annealing. A test piece was cut out from the round bar that had been subjected to this treatment, and the hardness, the deformation resistance by an upsetting test, and the rolling reduction of crack generation were measured. The results are shown in the column of annealing state in Table 2 below. The deformation resistance was obtained by an upsetting test, and was 6 mm in diameter × 12 m in height.
m is applied to the test piece from above in the height direction, and the rolling reduction is 6
It is at 3%. The cracking reduction rate is a reduction rate when a crack is first seen in a test similar to the deformation resistance.

[0018]

[Table 1]

Further, the annealed round bar is subjected to cold working of 40% by cold drawing to obtain a diameter of 17 m.
m, a test piece was cut out from the wire, and hardness and corrosion resistance were measured. The results are shown in the column of 40% cold working state in Table 2 below. The corrosion resistance is 16 mm in diameter,
Wet a test piece with a length of 105 mm (50 ° C, 98% RH)
(Relative humidity), 4 hrs) and drying (70 ° C., 2 hrs) were repeated four times (4 cycles), and evaluated by the presence or absence of pitting.

[0020]

[Table 2]

From these results, the corrosion-resistant and weather-resistant steel of the present invention having excellent cold workability has a higher C content than the present invention,
Further, as compared with Comparative Example No. 9 having a small Cr and N content, the hardness and the deformation resistance value are small, the crack generation reduction ratio is high, and the corrosion resistance is excellent. Further, according to the present invention, C, Mn
Comparative Example No. 10 with high Cr content and low N content
The hardness and the deformation resistance are smaller than those of the above.
Also, as compared with Comparative Example No. 11, which has a higher C and Cr content and a lower N content than the present invention, the hardness and the deformation resistance are smaller and the crack generation reduction ratio is higher. In addition, the deformation resistance is smaller than that of Comparative Example No. 12 having a higher Cr content and a lower C and N content than the present invention.

[0022]

The corrosion-resistant and weather-resistant steel of the present invention having excellent cold workability has the following excellent effects by adopting the above-mentioned constitution. (1) Cold deformation resistance and crack generation reduction ratio, that is, cold workability are good, and corrosion resistance is excellent even in a required corrosive environment (slow corrosive environment). (2) Since a large amount of N present in the atmosphere is contained to increase the corrosion resistance and the content of Cr as an alloying element is reduced, the cost is low and it is effective from the viewpoint of resource saving.

Claims (4)

[Claims] C. 0.10% by weight (the same applies hereinafter)
Less than 0.35%, Si: 0.5% or less, Mn: 0.5%
Hereinafter, Cr: 4.0 to 11.0% and N: 0.04 to
Corrosion-resistant and weather-resistant steel excellent in cold workability, characterized by containing 0.20%, the balance being Fe and inevitable impurities. 2. C: 0.10 to less than 0.35%, Si:
0.5% or less, Mn: 0.5% or less, Cr: 4.0 to 1
1.0%, N: 0.04 to 0.20% and Mo: 0.2
Corrosion-resistant and weather-resistant steel excellent in cold workability, characterized in that the steel contains about 1.0%, and the balance is Fe and inevitable impurities. 3. C: 0.10 to less than 0.35%, Si:
0.5% or less, Mn: 0.5% or less, Cr: 4.0 to 1
1.0% and N: 0.04 to 0.20%, V: 0.05 to 0.5% and Nb: 0.05 to 0.5%
Corrosion-resistant and weather-resistant steel excellent in cold workability, characterized in that it comprises one or two kinds of the above, and is composed of a balance of Fe and inevitable impurities. 4. C: 0.10 to less than 0.35%, Si:
0.5% or less, Mn: 0.5% or less, Cr: 4.0 to 1
1.0%, N: 0.04 to 0.20% and Mo: 0.2
１．０1.0%, V: 0.05-0.5% and N
b: contains 0.05 to 0.5% of one or two kinds, and the balance F
and corrosion-resistant and weather-resistant steel excellent in cold workability, characterized by comprising e and unavoidable impurities.