JP2008049353A - Nickel plated stainless steel wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nickel plated stainless steel wire which is satisfactory in lubricity with a tool and is excellent in workability. <P>SOLUTION: An inorganic salt having an action of holding a lubricant is stored in each recessed part (A part) formed on the surface of a plating layer by wire drawing after the application of nickel plating to the stock of a stainless steel wire, thus, by the lubricant holding action of the inorganic salt stored in each recessed part, its lubricity with a tool upon wire drawing and coiling in a poststage is made satisfactory even if the inorganic salt is not hardly stuck to each almost flat part (B part) in the surface other than the recessed parts of the nickel plating layer, so as to improve its workability. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a nickel-plated stainless steel wire.

Stainless steel wire has higher work hardenability than carbon steel wire and poor lubricity with tools, so the workability during wire drawing and spring forming (coiling) is low, and the product dimensions vary. There was a problem that it was easy to grow. For this reason, in the past, many nickel plated with excellent lubricity and improved workability have been used. However, stainless steel wires subjected to such nickel plating are also becoming more demanding for workability. , It is not always enough to meet that demand. On the other hand, in order to further improve the workability, the surface of the nickel plating layer is coated with an inorganic salt such as potassium sulfate (see Patent Document 1), or adheres to the surface of the coating layer of the inorganic salt. A method for adjusting the amount of lubricant to an appropriate range (see Patent Document 2) has been proposed.
Japanese Patent Laid-Open No. 10-118711 JP-A-11-92882

  However, as described in Patent Documents 1 and 2 above, even if the plating layer surface of the nickel-plated stainless steel wire is coated with an inorganic salt, it was present on the surface of the plating layer before processing in the process of wire drawing. Since the unevenness is further reduced, the coated inorganic salt tends to fall off, and it has been difficult to improve the workability by improving the lubricity with the tool when actually drawing or coiling.

  Moreover, although the said patent document 2 has described the appropriate range of the roughness of a stainless steel wire surface (nickel plating surface) and lubricant adhesion amount, the appropriate range of lubricant adhesion amount is not only the surface state of nickel plating. It also changes depending on the processing conditions. Therefore, in the method as described in Patent Document 2, it is necessary to precisely control the lubricant adhesion amount in order to improve the workability, and it is not easy to realize the control.

  An object of the present invention is to provide a nickel-plated stainless steel wire having good lubricity with a tool and excellent workability.

  In order to solve the above problems, the nickel-plated stainless steel wire of the present invention has a recess on the surface of the nickel plating layer, and the recess contains at least one of potassium sulfate, sodium sulfate, or borax. It was set as the structure by which the inorganic salt was hold | maintained.

  That is, an inorganic salt having an action of retaining a lubricant is stored in a concave portion (A portion (dark portion) in FIG. 1) formed on the surface of the plating layer by wire drawing after nickel plating on a stainless steel wire material. As a result, the inorganic salt accumulated in the recesses can be obtained even if almost no inorganic salt adheres to the substantially flat portion (B portion (bright portion) in FIG. 1) of the surface other than the recesses of the nickel plating layer. This lubricant holding action improves the lubricity with the tool during wire drawing and coiling in the subsequent process, and improves the workability.

  Here, the concave portion of the nickel plating layer can be generated by expanding a crack generated in the plating layer by performing wire drawing at a surface reduction rate of about 30 to 40% after nickel plating. And after immersing the stainless steel wire which performed this wire drawing in the aqueous solution containing an inorganic salt, it dries and removes a water | moisture content, and forms the coating layer of an inorganic salt, and is about 40 to 55% after that Finishing to product dimensions by drawing at a reduction rate of. Thereby, even if the inorganic salt on the surface other than the concave portion of the plating layer is almost removed in the subsequent drawing step, the inorganic salt can remain in the concave portion of the plated layer of the product.

  In the above configuration, a coating layer of an inorganic salt containing at least one of potassium sulfate, sodium sulfate, or borax is thinner on the surface of the nickel plating layer than the concave portion than the inorganic salt held in the concave portion. It is desirable to form. This is because the smaller the thickness of the inorganic salt adhering to the surface other than the recesses, the more difficult it is to drop off during processing in the subsequent process, which contributes to the improvement of workability.

  Here, the coating layer of the inorganic salt has a substantially uniform thickness on the surface of the plating layer at the stage formed by immersing the stainless steel wire in the aqueous solution containing the inorganic salt, but the inorganic salt coating layer is formed. Subsequent to the subsequent drawing process, the drawing process is performed with a small area reduction of about 0.1 to 5%, so that only the portion formed on the surface other than the concave portion of the plating layer can be thinned. it can. In addition, the magnitude of the thickness of the inorganic salt coating layer in the recessed part of the plating layer and other than the recessed part can be determined from the result of analyzing the surface of the stainless steel wire by X-ray analysis (thin film XRD analysis) or Auger electron spectroscopy.

  The thickness of the nickel plating layer may be 0.5 to 5 μm, and the depth of the concave portion of the nickel plating layer may be 10 to 100% of the thickness of the nickel plating layer. If the thickness of the plating layer is less than 0.5 μm, the effect of improving workability is small, and if it exceeds 5 μm, the plating layer is easily peeled off, which is not preferable. In addition, if the depth of the concave portion of the plated layer is less than 10% of the thickness of the plated layer, the amount of inorganic salt held in the concave portion is reduced and the effect of improving workability is reduced, which is not preferable.

  Here, the depth of the concave portion of the plating layer can be adjusted by the thickness of the plating layer at the beginning of plating (before the previous drawing process) and the area reduction rate of the entire drawing process. This is because when the initial plating layer thickness is constant, the depth of the recess increases as the area reduction ratio increases. The depth of the recess can be measured by observing the cross section of the stainless steel wire with an optical microscope or an electron microscope, and the nickel elemental analysis is performed from the surface of the stainless steel wire to the depth direction by Auger electron spectroscopy. It can also be determined from the result.

  The width of the concave portion of the nickel plating layer is preferably 0.5 to 20 μm. This is because if the width of the recess is less than 0.5 μm, the area for holding the inorganic salt becomes small, and if it exceeds 20 μm, the action of holding the inorganic salt becomes weak, and in any case, the workability improvement effect becomes small.

  Here, the width of the concave portion of the plated layer can be adjusted by the initial thickness of the plated layer and the area reduction rate, as well as the depth. This is because the recess width increases as the initial plating layer thickness decreases and the area reduction rate increases. Further, by performing the wire drawing with a small area reduction of about 0.1 to 5% after the subsequent wire drawing, the width of the recess can be adjusted with higher accuracy. The recess width can be measured by observing the surface of the stainless steel wire with an optical microscope or an electron microscope.

  Further, when a lubricant is attached to the surface of the nickel plating layer, the amount of the lubricant attached to the surface other than the recess of the nickel plating layer is the lubricant attached to the recess. Is desirable. In this way, it is possible to reduce the amount of lubricant used compared to the conventional method while ensuring lubricity, so the material during wire drawing, which is a problem when there is too much lubricant, or dullness on the surface of the product It is difficult to cause surface property deterioration such as.

  Here, examples of the lubricant include calcium stearate type and sodium stearate type. Note that the amount of lubricant in the plated layer and other than the recessed portion can be determined from the result of analyzing the surface of the stainless steel wire by X-ray analysis (thin film XRD analysis) or Auger electron spectroscopy. .

  As described above, the nickel-plated stainless steel wire of the present invention has a concave portion on the surface of the nickel-plated layer, and an inorganic salt having an action of retaining a lubricant is stored in the concave portion. Good lubricity and excellent workability with tools during wire drawing and coiling in the process.

(Example 1)
Embodiments of the present invention will be described below. The nickel-plated stainless steel wire of Example 1 uses a stainless steel wire having a wire diameter of 3 to 5 mm as a material, and after this material is nickel-plated (Step 1), the former wire drawing (Step 2) is performed. The surface of the plating layer is coated with an inorganic salt (step 3), and finally the subsequent drawing process (step 4) is performed.

  The stainless steel wire used as the material is mass%, carbon: 0.077%, silicon: 0.52%, manganese: 1.27%, phosphorus: 0.025%, nickel: 8.55%, chromium. : 18.58%, molybdenum: 0.02%, the balance consisting of iron and inevitable impurities (SUS304), which has undergone solution treatment.

In the step 1, a nickel plating layer having a thickness of 2 to 20 μm was formed on the surface of the material stainless steel wire under the following plating conditions.
<Plating conditions>
・ Plating solution:
Nickel sulfamate 797 g / l
Nickel bromide 6g / l
Nickel carbonate 25g / l
Boric acid 25g / l
・ Current density: 10 A / dm ²
・ PH: 4
・ Bath temperature: 25 ° C

  In step 2, the stainless steel wire plated with nickel in step 1 was drawn with a normal continuous wire drawing machine at a surface reduction rate of 40%. In the wire drawing, a calcium stearate powder lubricant was used. Thereafter, the lubricant remaining on the surface was removed by dipping in normal hexane to clean the surface.

  In the step 3, the stainless steel wire subjected to the previous wire drawing in the step 2 is immersed in an aqueous solution containing 2% potassium sulfate, and then dried to remove moisture, so that the surface of the nickel plating layer is removed. A coating layer of potassium sulfate was formed.

  In step 4, the stainless steel wire whose surface was coated with potassium sulfate in step 3 was drawn with the same continuous wire drawing machine as in step 2 with a reduction in area of 45%. The same calcium stearate lubricant as in step 2 was also used during the wire drawing.

  And the stainless steel wire which completed the said process 4 has the recessed part by which the crack of the plating layer was extended by the wire drawing process on the surface of a nickel plating layer, and the inorganic salt and potassium stearate type | system | group containing potassium sulfate in this recessed part The lubricant is retained.

Next, a spring forming process test conducted to confirm the effect of the present invention will be described. First, the nickel plating stainless steel wire in which the thickness of the nickel plating layer (plating thickness), the ratio of the recess depth to the thickness of the plating layer (recess depth ratio), and the recess width is different by the steps 1 to 4 described above. 13 types were produced. Next, these stainless steel wires were subjected to spring forming using an automatic coiling device to produce 300 springs having the following specifications. Then, the free length ratio (actual free length / target free length) of the manufactured spring was measured, and the defect rate was determined by assuming that the free length ratio exceeded ± 0.1%.
<Spring specifications>
・ Wire diameter: 1.0mm
・ Coil center diameter: 30.0mm
-Effective number of windings: 9.5
Standard free length: 40.0mm

  The results of the above test are shown in Table 1. From Table 1, it can be seen that the nickel-plated stainless steel wire of Example 1 has a lower defect rate than those of the comparative examples and is excellent in workability under any conditions. That is, by forming a concave portion with an enlarged crack on the surface of the plating layer and storing an inorganic salt having an action of retaining a lubricant in the concave portion, a coiling tool and It was confirmed that the lubricity of the steel improved and the workability improved.

(Example 2)
No. of Example 1 The stainless steel wire produced under the condition No. 4 was further drawn at a surface reduction rate of 1%, and the surface was analyzed by the X-ray analysis method (thin film XRD analysis) under the following conditions.
<X-ray analysis conditions>
・ X-ray used: Cu-Ka
Excitation conditions: 45KV 40mA
・ X-ray incident angle: 0.5 °
・ Measurement range: 2θ = 5-60 °

  As a result of the above analysis, as shown in FIGS. 2 (a) and 2 (b), components of potassium sulfate and calcium stearate were detected in the recesses on the surface of the plating layer (FIG. 2 (a)). It was hardly detected from the surface other than the concave portion (FIG. 2B). And when the same spring shaping | molding processing test as Example 1 was done using this stainless steel wire, No. 1 of Example 1 was obtained. Compared with the four conditions, the defect rate was further reduced by 30%.

(Example 3)
A stainless steel wire that has undergone the same steps 1 and 2 as in Example 1 was immersed in an aqueous solution containing 3% of one of potassium sulfate, sodium sulfate, and borax, and then dried in the same manner as in Example 1 to provide moisture. By removing, a coating layer of potassium sulfate, sodium sulfate or borax was formed on the surface of the nickel plating layer. The stainless steel wires having these three inorganic salt coating layers were each drawn with a calcium stearate-based lubricant at a surface reduction rate of 40%. The nickel plating layer had a thickness of 3 μm and a recess depth ratio. Was 45% and the width of the recess was 5 μm. As a result of performing the same spring molding processing test as in Example 1, the defect rate was 6% for the potassium sulfate coating, 7% for the sodium sulfate coating, and 8% for the borax coating. In the case of salt coating, it was confirmed that the difference in processability improvement effect due to the type of inorganic salt was small.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Schematic diagram of surface micrograph of stainless steel wire (Example 2) drawn after nickel plating a and b are graphs showing the surface analysis results of the concave portion (a) on the surface of the plated layer of the stainless steel wire of Example 2 and the surface (b) other than the concave portion of the plated layer, respectively.

Claims (5)

  The stainless steel wire having a nickel plating layer has a recess on the surface of the nickel plating layer, and the recess holds an inorganic salt containing at least one of potassium sulfate, sodium sulfate, or borax. Characteristic nickel-plated stainless steel wire.   A coating layer of an inorganic salt containing at least one of potassium sulfate, sodium sulfate, or borax is formed on the surface of the nickel plating layer other than the recesses thinner than the inorganic salt held in the recesses. The nickel-plated stainless steel wire according to claim 1.   The thickness of the nickel plating layer is 0.5 to 5 µm, and the depth of the concave portion of the nickel plating layer is 10 to 100% of the thickness of the nickel plating layer. Nickel plated stainless steel wire as described in   The nickel-plated stainless steel wire according to any one of claims 1 to 3, wherein a width of the concave portion of the nickel-plated layer is 0.5 to 20 µm.   Lubricant is attached to the surface of the nickel plating layer, and the amount of lubricant attached to the surface other than the concave portion of the nickel plating layer is less than the lubricant attached to the concave portion. The nickel-plated stainless steel wire according to any one of claims 1 to 4.