JP2012149330A - Plated steel excellent in corrosion resistance and workability, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plated steel which is excellent in corrosion resistance and workability, particularly excellent in corrosion resistance at a relatively low amount of deposited Ni, and can withstand severe processing such as a processing into a battery can, and to provide a method for manufacturing the same.SOLUTION: The steel is excellent in corrosion resistance and workability and has a Ni-Fe-Mn diffusion layer formed on its surface, wherein a surface layer of the diffusion layer has a Fe concentration of 10-50% and a Mn concentration of 0.01-1%, the diffusion layer contains 5-40 g/mof Ni, and an interface between the diffusion layer and the base steel is substantially a Ni-Fe diffusion plating layer. The steel can be formed by carrying out Ni-Mn alloy plating or Ni-Fe-Mn alloy plating and subsequently carrying out a thermal diffusion treatment.

Description

  TECHNICAL FIELD The present invention relates to a Ni-based plated steel material excellent in corrosion resistance and workability, and in particular, a plated steel material and manufacturing method capable of withstanding severe processing such as a battery can with excellent resistance to corrosion with a relatively low adhesion amount of Ni. About.

  In many cases, Ni plating is applied to steel materials used for electric and electronic appliances, container materials represented by battery cans, daily household electrical appliance members such as binders, and the like from the viewpoint of corrosion resistance, workability, and the like. Ni is stable in various environments and is resistant to various chemicals, is excellent in heat resistance, and has little change in the appearance of its surface. Therefore, various developments other than the above applications are expected.

  In Ni plating, since plating is hard, peeling of the plating during processing tends to be a problem, but heat treatment after Ni plating improves the adhesion by forming a Fe-Ni diffusion layer at the interface between plating and ground iron At the same time, there is known a method of recrystallizing and softening Ni to improve the spreadability of the plating layer, and the workability is greatly improved (Patent Document 1).

  In the above technique, since the surface layer Ni is recrystallized and softened, the slidability and the scratch resistance during processing are insufficient, and as a result, the workability may deteriorate. On the other hand, in patent document 2, the surface layer is hardened by providing the surface layer with the Ni-P alloy layer hardened | cured by heating, and the wrinkle resistance is improved. However, since the Ni—P alloy layer has a lower melting point than Ni, there is a problem that the facility is softened or melted during the heat treatment to contaminate the equipment.

  Patent Document 3 is characterized by having a recrystallized and softened Ni plating layer formed through an Fe-Ni diffusion layer and an Ni-P plating layer that is not hardened by heating on the upper layer. An Ni-plated steel sheet for battery cans is shown, and the scratch resistance can be improved without the above-mentioned problems. However, in this technique, Ni-P plating is performed again after Ni plating and thermal diffusion treatment, the process is complicated, and the adhesion of the Ni-P plating layer may be insufficient depending on processing conditions.

  In any of the technologies described above, the effect of improvement from ordinary Ni plating is insignificant with respect to corrosion resistance. Since Ni is electrically nobler than steel, sacrificial anticorrosive action like zinc-based plating cannot be expected, and iron rust (red rust) generation from the plating pinhole part that inevitably exists may be a problem. is there. In such a case, it is necessary to take an extremely disadvantageous economical measure such as extremely increasing the amount of nickel deposited.

  On the other hand, by controlling the composition and thickness of the Fe—Ni diffusion layer, pinholes are reduced, and the potential difference corrosion between noble Ni and base Fe is also alleviated, so that an effect of improving corrosion resistance can be obtained. Although known (Patent Document 4), it is not sufficient in a more severe corrosive environment.

  In Patent Document 5, it is shown that the Mn plating and the Ni plating are performed in this order, and the corrosion resistance is improved by alloying by thermal diffusion treatment. In the composite plating of the Mn plating and the Ni plating, Processability is insufficient.

JP 61-235594 A Japanese Patent Publication No. 5-25958 Japanese Patent No. 4031679 JP-A-6-2104 JP 2009-203497 A

An object of the present invention is to provide a Ni-based plated steel material and a manufacturing method that are excellent in corrosion resistance and workability, have excellent corrosion resistance even at a low adhesion amount, and can withstand severe processing including battery cans.
Another object of the present invention is to obtain a plated steel material excellent in corrosion resistance and workability by one type of plating and one thermal diffusion treatment without using a plurality of types of plating often used in the prior art.

The gist of the present invention is that
(1) A Ni—Fe—Mn diffusion plating layer is formed on the surface of the steel material, and the Fe concentration in the surface layer of the diffusion plating layer is 10% by mass to 50% by mass, and the Mn concentration is 0.01% by mass to 1% by mass. Yes, the Ni content in the diffusion layer is 5 to 40 g / m ² , and the plating at the interface with the base steel material is substantially a Ni—Fe diffusion alloy layer. Plated steel,

(2) Ni-Mn alloy plating or Ni-Fe-Mn alloy plating is applied to the steel material, and then heat diffusion treatment is performed to diffuse Fe in the plating layer to form a Ni-Fe-Mn diffusion plating layer. The method for producing a plated steel material having excellent corrosion resistance and workability as described in (1) above,

(3) The method for producing a plated steel material having excellent corrosion resistance and workability according to (2), wherein the Mn concentration in the plating layer of the Ni-Mn alloy plating is 0.01% to 2% by mass,

(4) The Mn concentration in the plating layer of the Ni—Fe—Mn alloy plating is 0.01% to 2% by mass, and the Fe concentration is 0.1 to 30% by mass. Manufacturing method of plated steel material with excellent corrosion resistance and workability,
It is.

  According to the present invention, a plated steel material excellent in corrosion resistance and workability can be obtained. A low-cost manufacturing method is also provided.

It is a conceptual diagram which shows the example of a plating layer structure (GDS (glow discharge emission spectroscopic analysis)) of the steel material of this invention.

In the steel material of the present invention, a Ni—Fe—Mn diffusion plating layer is formed on the surface, the Fe concentration of the diffusion plating surface layer is 10% by mass to 50% by mass, and the Mn concentration is 0.01% by mass to 1% by mass. The amount of Ni in the diffusion plating layer is 5 to 40 g / m ² , and the plating at the interface with the base steel material is substantially a Ni—Fe diffusion plating layer.

  The diffusion plating layer is a plating layer formed by diffusing Fe in steel to the plating layer by thermal diffusion treatment after plating, and when the element distribution in the depth direction from the surface layer is observed by a technique such as GDS, Characterized by a graded structure with a slowly changing composition. An example of measurement by GDS is shown in FIG. In addition, in the outermost layer obtained by the GDS measurement, a concentrated layer of inevitable contaminants such as C is thinly detected. In FIG. 1, the first measurement data in which C is reduced to 0.1% or less is recorded. It is shown as a plating surface layer of the invention. The diffusion plating surface layer of the present invention is defined as described above, and the component concentration of the diffusion plating surface layer of the present invention is based on the measurement data thus obtained.

  As shown in FIG. 1, the concentration distribution of each component in the steel plating layer of the present invention is such that Ni gradually decreases in concentration from the surface layer toward the steel material, and Fe gradually increases in concentration from the surface layer toward the steel material. is doing. Mn coexists with Ni and Fe in the vicinity of the surface layer, and the maximum value of the concentration may be on the surface layer or a little from the surface layer.

  A feature of the steel material of the present invention is that the Mn concentration is extremely low at the interface with the base steel material, and the Ni-Fe diffusion layer is substantially formed. The reason why the Mn concentration in the vicinity of the interface becomes extremely low is not clear, but the outward diffusion of Fe from the steel into the plating layer in which Ni and Mn coexist is promoted, while the Mn of the plating layer toward the steel It is estimated that inward diffusion is suppressed.

  If Mn is present in the Ni—Fe diffusion layer in the vicinity of the interface, the elongation of this layer is lowered, and thus the workability and the corrosion resistance after processing are lowered. The above-mentioned meaning of “substantially” is as follows. Usually, steel materials contain less than a few percent of Mn, and due to the influence of Mn in the steel, it may be observed that Mn is present at the base steel material interface in the GDS analysis technique. Even in this case, if the Mn concentration is less than 0.01%, it can be said to be substantially a Ni—Fe diffusion layer.

  The Fe concentration of the surface layer of the diffusion plating layer needs to be 10% by mass or more and 50% by mass or less, and the Mn concentration needs to be 0.01% by mass or more and 1% by mass or less. If Fe is less than 10% by mass, the slidability is inferior. As a result, the workability is inferior. The Fe concentration in the surface layer of the diffusion plating layer is more preferably 10% by mass to 30% by mass.

  If the Mn of the surface layer of the diffusion plating layer is less than 0.01% by mass, the corrosion resistance is inferior, and if it exceeds 1% by mass, the plating damage during processing increases and the corrosion resistance after processing decreases. The Mn concentration in the surface layer of the diffusion plating layer is more preferably 0.1 to 1% by mass.

Ni content in the diffusion plating layer is required to be 5 to 40 g / m ^2, insufficient corrosion resistance is less than 5 g / m ^2, even beyond 40 g / m ² effect is saturated becomes uneconomical In addition to being contrary to the spirit of the present invention, the adhesion may be lowered depending on the degree of processing, which is not preferable.

  The reason why the corrosion resistance is improved by the structure of the plating layer as described above is not necessarily clear, but the formation of the diffusion layer reduces plating pinholes, and the plating layer is more potential than Ni such as Fe and Mn. It is presumed to be due to the effect that the potential difference corrosion with the base Fe is also mitigated by containing a base metal. Moreover, the corrosion resistance after a process is also improved by the improvement effect of the workability mentioned later.

  The reason why the workability is improved is that the Ni-Fe-Mn diffusion layer has an appropriate hardness, and the effect of improving the slidability of the surface layer, as well as the decrease in elongation is small compared to the plating hardness, It is presumed to be caused by the fact that plating cracks and peeling are less likely to occur. Furthermore, although the interface with the base steel material is substantially a Ni—Fe diffusion layer, the elongation of this layer is large, so that it is presumed to follow severe processing.

  Next, a method for producing the plated steel material of the present invention will be described. In the present invention, Ni—Mn alloy plating or Ni—Fe—Mn alloy plating is applied to the steel material, and then thermal diffusion treatment is performed. That is, it can be manufactured by a simple process comprising a step of applying one type of plating and a subsequent thermal diffusion treatment step.

Ni-Mn alloy plating and Ni-Fe-Mn alloy plating can be performed by using a general Ni plating bath such as a sulfuric acid bath, chloride bath, watt bath, sulfamic acid bath, Mn salt (sulfuric acid Mn, Mn chloride, etc.), or It can obtain by electroplating using the bath which added Fe salt (Ferrous sulfate, ferrous chloride, etc.) in addition to Mn salt. The composition of the plating layer is not only dependent on the plating bath, but also depends on the current density. The higher the current density, the more the Mn concentration of the plating layer tends to increase. It is necessary to adjust the current density in accordance with the target composition, but usually by the 1~100A / dm ² about conditions, it is possible to obtain a plating composition required for the present invention.

  In the case of Ni—Mn alloy plating, the bath concentration and current density are adjusted so that the plating layer Mn concentration is 0.01% by mass to 2% by mass, preferably 0.1% by mass to 1% by mass. In the case of Ni—Fe—Mn alloy plating, the Fe concentration is 0.1 to 2% by mass, preferably 0.1 to 1% by mass, so that the plating layer Mn concentration is 0.1 to 1% by mass. The bath concentration and current density are adjusted to be 30% by mass.

In both cases of Ni—Mn alloy plating and Ni—Fe—Mn alloy plating, there is basically no difference in performance as long as the surface layer Fe concentration and Mn concentration are the same as a result of the subsequent thermal diffusion treatment. Ni-Fe-Mn alloy plating is used for steel types that require thermal diffusion treatment at a low temperature in a short time because the annealing conditions are limited depending on the material properties of the steel material, and Ni is used for steel types that require annealing at high temperatures. -Mn alloy plating may be used. In either case, the adhesion amount of the plating layer is set to 5 to 40 g / m ² as the Ni amount.

The thermal diffusion treatment after plating can be performed by a normal heating method, and either a batch heating method or a continuous heating method is used. It is also possible to use both together.
In consideration of the material characteristics of the steel material to be plated, it is preferable to perform the heat diffusion treatment and the annealing treatment at the same time. In normal Ni plating, since the diffusion rate of Fe is rate-limiting, it is sometimes difficult to achieve both heat diffusion treatment and annealing treatment conditions, particularly when the amount of plating adhesion is large. Plating and Ni-Fe-Mn alloy plating tend to have a faster diffusion of Fe in steel than normal Ni plating, and this effect allows normal annealing as described later even when the amount of plating is large. Within the range of conditions corresponding to the conditions, Fe diffuses to the surface layer, and a desirable plated layer structure of the present invention can be obtained. The reason why Fe diffusion is fast in Ni—Mn alloy plating and Ni—Fe—Mn alloy plating is not necessarily clear, but the presence of Mn lowers the activity of Fe in Ni and may increase the activity gradient of Fe. Conceivable. The Mn concentration for obtaining this effect is preferably 0.1% by mass or more.

  When performing the above-described heat diffusion treatment and annealing treatment simultaneously, the heat treatment can be performed in a normal annealing furnace, either batch annealing or continuous annealing may be used, or both may be used in combination. It is. As for the conditions, in batch heating or batch annealing, the steel material temperature is 450 to 650 ° C., preferably 500 to 600 ° C., and the treatment is performed for several hours to several tens of hours, preferably 6 to 24 hours. In continuous heating or continuous annealing, the steel material temperature is 700 to 900 ° C, preferably 700 to 850 ° C, and the soaking time is several seconds to several tens of minutes, usually 10 seconds to 120 seconds.

  The temperature and time may be finely adjusted so that Fe in the steel material and the plating layer are interdiffused to form a diffusion layer having the composition described above. In order to avoid surface oxidation, it is desirable that the atmosphere during the treatment is an atmosphere in which an inert gas such as nitrogen or a reducing gas such as hydrogen is mixed with an inert gas.

  After the thermal diffusion treatment, rolling ordinarily used can be performed as necessary to adjust the shape and surface roughness.

(Examples 1-13 and Comparative Examples 1-3)
Using an ultra-low carbon steel sheet (non-recrystallized steel sheet) added with Nb and Ti as a base plate, Ni-Mn alloy plating is performed under the conditions shown in Table 1 after degreasing and pickling treatment, and various compositions and adhesion amounts of Ni -Mn alloy plating was formed. Thereafter, thermal diffusion treatment was performed. The thermal diffusion treatment was performed in a continuous annealing furnace at various temperatures and times in an N ₂ atmosphere containing 5% H ₂ (dew point −40 ° C.). Table 5 below shows the Ni amount and composition of the Ni—Mn alloy plating, the soaking temperature in the thermal diffusion treatment, and the time conditions.

(Examples 14 to 17 and Comparative Example 4)
Using Nb and Ti composite added ultra-low carbon steel plate (non-recrystallized steel plate) as the original plate, Ni-Fe-Mn alloy plating is performed under the conditions shown in Table 2 after degreasing and pickling treatment, and various compositions and adhesion amounts The Ni—Fe—Mn alloy plating was formed. Thereafter, thermal diffusion treatment was performed. The thermal diffusion treatment was performed in a continuous annealing furnace at various temperatures and times in an N ₂ atmosphere containing 5% H ₂ (dew point −40 ° C.). Table 5 below shows the Ni amount and composition of the Ni—Fe—Mn alloy plating, the soaking temperature in the thermal diffusion treatment, and the time conditions.

(Comparative Example 5)
Using an ultra-low carbon steel plate (non-recrystallized steel plate) added with Nb and Ti as a base plate, Ni plating was performed under the conditions shown in Table 3 after degreasing and pickling treatment. Thereafter, thermal diffusion treatment was performed. The thermal diffusion treatment was performed in a 5% H ₂ -containing N ₂ atmosphere (dew point −40 ° C.) in a continuous annealing furnace. Table 5 shows the Ni amount and the soaking temperature and time conditions in the thermal diffusion treatment.

(Comparative Example 6)
Nb, Ti composite added ultra-low carbon steel plate (non-recrystallized steel plate) as the original plate, after degreasing and pickling treatment,
Mn plating was performed under the conditions shown in Table 4, and Ni plating was subsequently performed under the conditions shown in Table 3. Thereafter, thermal diffusion treatment was performed. The thermal diffusion treatment was performed in a 5% H ₂ -containing N ₂ atmosphere (dew point −40 ° C.) in a continuous annealing furnace. Table 5 below shows the conditions of the amount of Ni and the amount of Mn (the amount of Mn is expressed as Mn / (Ni + Mn)%), the soaking temperature in the thermal diffusion treatment, and the time.

(Evaluation method)
-Product composition calculated | required Mn% of surface layer and Fe% by the depth direction analysis of GDS. Similarly, the Mn concentration at the steel material interface was determined by GDS.
・ Corrosion resistance: A salt spray test of JISZ2371 was conducted for 3 days, and the occurrence of red rust (iron rust) was observed and observed. No occurrence, ◎, area ratio less than 3% ○, less than 20% △, more than 20% × It was evaluated.
-Sliding property: The coefficient of friction was measured by a draw bead test, and less than 0.12 was evaluated as ◎, less than 0.15 was evaluated as ◯, less than 0.2 was evaluated as Δ, and 0.2 or more was evaluated as ×.
-Plating crack: 0T bending process was performed, and the plating crack of the bending outer top part was observed with the optical microscope. The case where there was no crack reaching the base was evaluated as ◎, the case where there was a slight crack but not reaching the base was evaluated as ◯, the case where cracks reaching the base were found △, and the case where the crack reaching the base was remarkable was evaluated as ×. .

  Table 5 shows the plating layer structure and performance evaluation results of each sample. It can be seen that the steel material of the present invention has excellent corrosion resistance and workability.

The steel material of the present invention has excellent corrosion resistance and workability, and is not applied to conventional Ni plating, as well as electric and electronic appliances, container materials represented by battery cans, daily household appliances such as binders, etc. There is a possibility that it can be applied to a wide range of components.
In addition, the steel material of the present invention can be manufactured by only one type of plating and a single thermal diffusion treatment, and is advantageous for cost reduction, and is extremely useful industrially.

Claims (4)

A Ni—Fe—Mn diffusion plating layer is formed on the surface of the steel material, the Fe concentration of the surface layer of the diffusion plating layer is 10% by mass to 50% by mass, the Mn concentration is 0.01% by mass to 1% by mass, Corrosion resistance and workability characterized in that the amount of Ni in the Ni—Fe—Mn diffusion plating layer is 5 to 40 g / m ² and the plating at the interface with the base steel material is substantially a Ni—Fe diffusion layer. Excellent plated steel material.   The steel material is subjected to Ni—Mn alloy plating or Ni—Fe—Mn alloy plating and then subjected to thermal diffusion treatment to diffuse Fe in the plating layer to form a Ni—Fe—Mn diffusion plating layer. The method for producing a plated steel material having excellent corrosion resistance and workability according to claim 1.   The method for producing a plated steel material having excellent corrosion resistance and workability according to claim 2, wherein the Mn concentration in the plating layer of the Ni-Mn alloy plating is 0.01% to 2% by mass.   The corrosion resistance and processing according to claim 2, wherein the Ni-Fe-Mn alloy plating layer has a Mn concentration of 0.01% to 2% by mass and an Fe concentration of 0.1 to 30% by mass. Method for producing plated steel with excellent properties.

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