JPS58204166A - Production of zn-plated steel wire having excellent high temperature characteristic - Google Patents

Abstract

PURPOSE:To produce a Zn-plated steel wire which has excellent high temp. characteristics and can prevent the exfoliation of the plating surely in high-temp. environment by controlling the lead contained in a Zn plating bath to a specific amt. or below and plating the steel wire in said plating bath. CONSTITUTION:A hot-rolled wire rod is subjected to lead patenting then to pickling and lubricating followed by drawing. The drawn wire rod is further subjected to a pretreatment for plating to dip the same in a lead bath, whereafter the wire rod is galvanized. If the Pb contained in the Zn plating bath is controlled to <=150ppm, the Zn-plated steel wire having excellent high temp. characteristics is obtained. Since the Zn-plating layer contains virtually no Pb, Fe and Zn are alloyed thoroughly in the high-temp. environment and are bound securely in one body with the base material Fe without peeling, whereby such Zn-plated steel wire having the excellent high temp. characteristic is obtained. Said Zn-plated steel wire is suitable as a steel cored wire for an overhead wire which is elevated in temp. during transmission of electricity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a Zn-plated steel wire with excellent high-temperature properties.

The so-called copper core aluminum stranded wire (hereinafter referred to as ACSR), which is made by placing multiple high-tensile steel wires twisted together in the center and many aluminum wires twisted together on the outside, is currently used as an overhead power transmission line. However, in ACSR for power transmission, high tensile strength Zn is used as the copper core wire.
It is customary to use plated steel wire.

Generally, power transmission lines generate heat due to the Joule heat of power transmission during use, so Zn-plated steel wires for ACSR are required to have good high-temperature properties. Hitherto, high tensile strength Zn-plated steel wires such as J-Kog SG8587 and JISCello have been used for ACSR.

However, in recent years, the use of ACSR for overhead power transmission lines has tended to be as follows. In other words, in recent years, the demand for electricity has increased rapidly, and in response to this, power transmission lines have been made larger in diameter to increase their power transmission capacity. The temperature rise in ACSR becomes remarkable, and in some cases the temperature of the ACSR copper core used as an overhead wire often reaches nearly 500°C.

Under such recent circumstances, the Zn-plated steel wire, which has been used conventionally, cannot be said to have sufficient high-temperature properties for ACSR. That is, when this type of high-tensile galvanized steel wire is exposed to a relatively high temperature environment of about 400° C., there is a risk that the plating layer will easily peel off.

An object of the present invention is to provide a method for manufacturing a Zn-plated steel wire that has excellent high-temperature properties and can sufficiently withstand use in the above-mentioned high-temperature environments.

Generally, this type of Zn-plated steel wire is produced by first subjecting the hot-rolled wire to lead patenting treatment, then pickling and lubrication, drawing the wire, and then pre-plating treatment by immersing it in a lead bath. After that, hot-dip Zn plating is applied.

The present inventors conducted various experiments and studies in order to find out the factors that affect the high-temperature characteristics of Zn-plated steel wire from among the processing conditions of each treatment in the manufacturing process, and as a result, the Zn-plated steel wire It has been found that the amount of lead (hereinafter referred to as Pb) mixed in the plating bath is closely related to the quality of the high temperature characteristics. In other words, the high-temperature characteristics mentioned here basically mean relatively high temperatures (about 400°C).
This refers to the plating peeling resistance under the environment of
j Under AW, the plating layer is heated and the Fe inside it is heated.
The -z'n alloy layer grows outward one after another (hereinafter referred to as Fe-Zn alloy layering), but at this time, as shown in Figure 1 (4), Fe-Zn is generally grown to a certain extent. As the alloy layering progresses, it reaches a saturated state and no more Fe-Z
No progress in forming an n-alloy layer is observed. Figure 2 (A) is a cross-sectional microphotograph showing the saturated state of this Fe-Zn alloy layer, showing the grown Fe-Zn alloy layer (2) and pure Zn layer (1).
) interfaces appear tightly, as if they were completely separated structurally. Peeling off the plating and [1]
This occurs from the interface between the two. This phenomenon of plating peeling may be related to the amount of PB in the plating bath5.
As the amount of PB decreases, the phenomenon of plating peeling tends to become less likely to occur. In addition, as the amount of P'b decreases, the growth of the Fe-Zn alloy layer is promoted, and finally the first
This is because, as shown by CB) in the figure, the entire layer (leaving the pure Zn layer) changes to the alloy layer (2). FIG. 2(B) is a cross-sectional microphotograph showing the plated layer that has undergone this complete change, and it is clear that the interface as seen in FIG. 1(A) has completely disappeared.

In this way, the plating layer becomes a 100% Fe-Zn alloy layer,
If the interface disappears, peeling of the plating can be prevented.

That is, the gist of the present invention is that molten Zn of steel wire
In plating, 15% of PB mixed in the Zn plating bath
A method for producing a Zn-plated steel wire, characterized in that the Zn-plated steel wire is controlled to 0 ppm or less.

Figure 3 shows P′b in the ZN plating bath obtained by the experiment.
Fig. 3 shows the F+e-Zn alloy layering ratio (saturated state) of the plating layer of the Zn-plated steel wire. The sample I tried was 5WRE (8
A steel wire with a diameter of 8.2 (114 mm) equivalent to 2B was used in the experiment, which was pretreated by immersion in a lead bath, and then Zn plated (bath temperature: 450'C) using Zn plating baths with various Pb contents (bath temperature: 450' The resulting Zn-plated steel wire was
After heating at 0°C for 1 hour 1. The method used was to investigate the Fe--Zn alloy layering ratio and conduct a plating peeling test using an adhesive tape. In the same figure, ○: peeling of plating, ・: no same,
respectively.

As shown in the figure, when the Pb content is 150 ppm or less, the Fe-Zn alloy layering rate of the plating layer is approximately 100%.
No peeling of the plating was observed at all. This relationship remains almost constant even if the various manufacturing conditions described above are changed, and therefore, in the present invention, Pb in the plating bath is
The content is limited to 150 ppm or less.

In the past, the Zn plating conditions for this type of steel wire were determined with emphasis on the appearance of the plating and the amount of coating, and no consideration was given to preventing the plating from peeling off in a high-temperature environment, which is the objective of the present invention. It wasn't.

Pt in the plating bath is what is brought in as the steel wire moves from the Pb bath used for pretreatment, and generally at least 200 B,...
Usually, about 00 pI)m is mixed in, and good plating peeling resistance cannot be expected with this.

Next, examples of the present invention will be described.

A steel wire having a diameter of 3.11 mm and made of steel whose composition complies with the J Engineering S Hard Steel Wire Standard 5WRH82B was manufactured in the following procedure. That is, using a hot-rolled wire rod with a diameter of 8 UF as the raw material, we went through the usual steps of lead patenting, pickling, lubrication, and wire drawing, and then used the resulting steel wire to undergo a lead bath immersion pre-plating treatment. After that, melting Z was performed under each condition shown in Table 1.
n plating was performed.

Each Zn-plated steel wire was heated at 400° C. for 1 hour, and then a plating peeling test was performed using an adhesive tape. The results are shown in the rightmost column of Table 1.

The table also lists the tensile strength of each plated steel wire.

In the above table, Zn-plated steel wire (1
) to (3), no plating peeling was observed, whereas (4) to (6), in which the amount of Pb in the Zn plating bath was within the range of the present invention (150 ppm or less), all showed no peeling in a high-temperature environment. Peeling of the plating was observed. In terms of tensile strength, values with no significant difference were obtained for both the inventive example and the comparative example.

As is clear from the above description, the method of the present invention can produce a Zn-plated steel wire whose plated layer has good high-temperature properties and can reliably prevent plating peeling in a high-temperature environment.
Moreover, deterioration of other properties inherent to Zn-plated steel wire, etc.
There is no concern that there will be any adverse effects, and therefore, the present invention can effectively contribute to prevention of plating peeling, especially in recent AC3R high-tensile Zn-plated steel wires.

[Brief explanation of drawings]

Figure 1 shows the Fe-Z coating layer of Zn-plated steel wire during heating.
Graph showing two types of changes over time in n alloy layering ratio, Figure 2 IA) u Cross-sectional microphotograph of the plating layer showing the saturation state of the Fe-Zn alloy layering, same figure @ is the same (Fe-Zn alloy layer Figure 3 is a graph showing the relationship between the amount of PB in the Zn plating bath, the Fe-Zn alloy layering ratio, and the presence or absence of plating peeling.
It is.

Claims (1)

[Claims] (1) In Zn plating of steel wire, a patent method 0 characterized by controlling the amount of lead mixed in the Zn plating bath to 150 ppm or less