JPH03226550A - Manufacture of hot-dipped zinc coating or hot-dipped zinc alloy coating steel sheet having high sliding resistance - Google Patents

Abstract

PURPOSE:To manufacture a hot-dipped zinc coating steel sheet having high sliding resistance, at the time of coating a steel sheet with molten zinc, by precoating the surface of the steel sheet with a specified metal or alloy and thereafter regulating the conditions of heating, a hot-dipped zinc coating bath and subsequent reheating. CONSTITUTION:The surface of a steel sheet is precoated with an alloy constituted of two or three kinds among Ni, Fe, Co, Cu, Sn, Zn and P such as Ni-P, Fe-Ni, Ni-Zn, Co-P and Ni-Fe-P by the amt. of 0.1 to 3.0g/m<2>. The above is heated in a heating furnace of <=5% O2 concn. to the temp. range of 430 to 500 deg.C at >=7 deg.C/sec temp. rising rate, is immediately immersed into a hot dipped zinc or hot-dipped zinc alloy coating bath of 430 to 500 deg.C bath temp. having 0.05 to 0.15% effective Al concn. and is hot- dipped. The above is pulled up from the hot dipping bath, is subjected to wiping treatment to regulate the coating weight, is thereafter discharged from a wiping apparatus and is immediately heated at 450 to 550 deg.C for 5 to 40sec, by which the hot-dipped zinc coating or hot-dipped zinc alloy coating steel sheet having high sliding resistance of a hot dipped face can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing zinc or zinc-based alloy hot-dip galvanized steel sheets.

[Conventional technology]

Conventionally, regarding the hot-dip Zn plating method using pre-plating, for example, the hot-dip Zn plating method described in Japanese Patent Publication No. 46-19282 is based on the general CGL method (heating to around 700''C using a non-oxidation furnace and a reduction furnace). (method of activating the steel plate surface by reduction and then hot-dipping)
It is already known as an excellent method for obtaining plated steel sheets with good adhesion and workability at low cost.

[Problem to be solved by the invention]

Recently, excellent surface sliding resistance has become a new requirement for pipe-making materials made from thick hot-dip Zn-coated steel sheets used as building materials, etc., especially from the perspective of preventing slippage during pipe-making. It's here.

However, even with the conventional hot-dip Zn plating method using pre-plating, the sliding resistance of the surface cannot be improved.

Therefore, in order to find a method for obtaining a plated steel sheet with excellent surface sliding resistance while taking advantage of the characteristics of the hot-dip plating method using this pre-plating, the present inventors investigated the pre-treatment heating conditions after pre-plating. As a result of actively considering the balance of hot-dip plating bath conditions, reheating conditions after hot-dip plating, etc.,
By proceeding with appropriate alloying of the plating layer, we succeeded in significantly improving the sliding resistance of the surface of the plating layer.

The present invention provides a method for producing a hot-dip plated steel sheet with excellent surface sliding resistance by controlling the pretreatment heating, plating bath conditions, and reheating conditions after pre-plating as described above.

[Means to solve the problem]

The present inventors first attempted to improve the sliding resistance by promoting alloying during plating by controlling only the heating conditions and bath conditions after pre-plating. As a result, the surface of the steel plate was coated with 0.1% Ni plating, etc.
~3.0g/m'', then heated to 430~500℃ at 7° (:/sec or more) in an atmosphere of 0□4 degrees and 5% or less to make it effective in the bath as it is A j! Concentration 0.05~ 0.15
%, bath m4 If plating is performed by immersion in a zinc or zinc-based alloy bath controlled at 30 to 500°C, the sliding resistance of the surface will be improved compared to when manufactured under one of these conditions. It turns out that it does. Therefore, in order to further increase the effect, we considered combining reheating after plating, and found that a synergistic effect appears only under reheating conditions within the range of the present invention. In other words, N on the surface of the steel plate
i, Fe, Co, Cu, Sn, ZnP selected from the group consisting of 0.1 alone or an alloy of two or three.
~3.0g/m2 After plating, heat to 430-500°C at 7°C/sec or more in an atmosphere with a 02 concentration of 5% or less to obtain an effective pJfj of 4 degrees in the bath, 0.05-0.15%, and a bath temperature of 430. Plating is performed by immersion in a zinc or zinc-based alloy bath controlled at ~500°C, and by heating for 5 to 40 seconds in a temperature range of 450 to 550°C immediately above the wiping after pulling, the adhesion of the plating is improved. However, it was discovered that a plated steel plate with extremely excellent surface sliding resistance could be obtained, and the present invention described below was completed.

That is, the present invention provides Ni, FeCo, and Cu on the surface of the steel plate.
, Sn, Zn, and P alone or in an alloy of two or three of them at 0.1 to 3 Og/m" after plating in an atmosphere with an O2 concentration of 5% or less. 500
℃ heated at 7℃/sec or more to make effective N9 in the bath as it is.
Plating is carried out by immersion in a zinc or zinc-based alloy bath with a temperature of 0.05 to 0.15% and a bath temperature of 430 to 500°C. The gist of this invention is a method for manufacturing a zinc or zinc-based alloy hot-dip galvanized steel sheet with high sliding resistance, which is characterized by heating for ~40 seconds.

The present invention will be explained in detail below.

Figure 1 shows the O
10” (:/se
A bath in which the temperature was raised at c and the effective N concentration in the bath was changed as it was!
Immersed in a molten Zn bath at 450°C for 3 seconds, pulled up,
The graph shows the change in sliding resistance of the plated surface when reheating was performed for 15 seconds at various temperatures after wiping. Note that the measured values of surface hardness (Vickers hardness) and coefficient of static friction were used as indicators of sliding resistance.

The evaluation criteria are as follows.

Evaluation Surface hardness (HV) Friction coefficient (μ) 5--
---------- 150~250 0.15~0
．． 184---------------------- 120~150
0.14~0.153------ 90~1
20 0.13-0.142----70
~90 0.12~0.131------
Less than 70 Less than 0.12 (*Evaluation of 3 or more passes) From this figure, if plating is performed at an effective Al concentration of 0.15% or less in the plating bath and reheated at 450°C or higher, the sliding resistance will decrease. It is clear that a plated steel sheet with a high value can be obtained (the effective M in the bath refers to the effective M that contributes to the plating layer other than dross etc.). An analysis of the plating layer under these conditions revealed that the Fe ratio was 1 to 8%, that Fe diffused from the substrate to the surface layer of the plating layer and alloying progressed, and that Ni combined with M near the substrate. It was found that some Ni also existed in the alloy layer. The alloy layer was mostly composed of ζ phase (FeZn+) and δ1 phase (FeZn). Although the details are still unclear, the reason for the high sliding resistance is the appropriate alloying of the plating layer and the N in the alloy layer.
It is thought that the presence of i or the formation of a N i -jV compound may act synergistically. The sliding resistance is low when the effective M concentration in the bath exceeds 0.15%.
This seems to be due to the fact that alloying of the plating layer does not progress because it combines with the base iron or Ni to form a strong barrier layer. The lower limit of effective M in the bath is 0.0 from the viewpoint of plating adhesion.
05%. Furthermore, if the reheating temperature is lower than 450°C, the sliding resistance will not improve. This is also due to insufficient alloying of the plating layer. The upper limit of the reheating temperature is set at 550° C. from the viewpoint of adhesion.

In other words, Ni has a “phase (F
It seems to have the effect of suppressing the growth of nickel (e, Z nz+), but when the temperature exceeds 550°C, Ni diffuses to the vicinity of the surface of the plating layer, resulting in "phases developing too much and adhesion deteriorating." It seems that the reheating time is 5 to 40 minutes.
sec. If it is less than 5 sec, alloying of the plating layer will be insufficient, and if it exceeds 40 sec, alloying will progress too much and the r phase will develop too much, resulting in poor plating adhesion. The reheating method is not particularly limited, but a heating furnace or burner heating is preferable.

Further, when the pre-plating heating temperature and bath temperature were similarly investigated, it was found that an effect on sliding resistance appears at temperatures of 430° C. or higher. This seems to be due to the fact that alloying progresses as the temperature rises during the plating reaction in the bath. However, if the temperature is heated to 500℃, the phase will grow too much and the sliding resistance and adhesion will deteriorate.There are no particular restrictions on the pretreatment heating method, but radiation heating in a furnace, electrical heating, etc. Furthermore, although this pretreatment heating temperature and heating rate are one of the key conditions of the present invention, heating at 500°C or lower causes little change in the state of pre-Ni plating after heating, making it difficult to perform hot-dip plating and reheating. The sliding resistance and adhesion of the plated surface afterward were good.5
When the temperature exceeded 00°C, Ni diffused into the steel sheet during heating, and a clear decrease in both performances was observed. The heating rate needs to be 7° (:/sec or more. If this is the case,
If the pretreatment heating atmosphere has an O2 concentration of 5% or less, oxidation of the pre-plating will not proceed much and good plating adhesion can be obtained. It was also confirmed that excellent sliding resistance could be obtained if the Oz concentration was within 5%, even if it was not 2% in this experiment.

Furthermore, similarly good performance was obtained when the plating bath immersion time was in the range of 1 to 10 seconds.

Figure 2 shows that after changing the amount of Ni pre-plating and heating up to 450°C at 10°C/sec in a 0°2% atmosphere,
This figure shows the change in sliding resistance when the plate was plated at 50°C for 3 seconds and then reheated at 450°C for 15 seconds. This is the case when the effective M concentration in the bath is 0.1% and 0.15%. Ni
When the adhesion amount is 0.1 g/m or more, the sliding resistance increases dramatically as the basis weight increases.The mechanism is not clear, but the effective M concentration and pre-Ni amount in the bath are appropriate. It is thought that there is some correlation in the proportion of Ni and that it contributes to the sliding resistance.If the amount of Ni deposited is less than 0.1 g/m'', the sliding resistance and adhesion deteriorate. This is thought to be due to the progress of oxidation of the base steel during the pretreatment heating stage when the Ni adhesion amount is less than 0.1 g/m2, and when the Ni adhesion amount is 0.1 g/m2 or more, 5% Even when heated at 7° C./sec in a 0□ atmosphere, oxidation hardly progresses and good plating adhesion can be obtained. There is no particular restriction on the upper limit of the amount of Ni deposited, but it is set at 3.0 g/m'' from an economical point of view. Similar results were obtained in the atmosphere and reducing atmosphere.As for the type of pre-plating, only Ni pre-plating was explained, but Fe and Co.

Single plating of Cu, Sn, Zn, P and N1-P, F
2 such as e-Ni, Ni-Zn, Co-P, N1Fe-P, etc.
Similar results were obtained with elemental or ternary alloy plating. Also, regarding the hot-dip plating bath, only the Zn bath was explained, but Zn-3b, Zn-Mg, Zn-
The present invention can be similarly applied to alloy baths such as 3n.

One of the advantages of this pre-plating method is that it is not particularly limited by the base steel plate. It can also be applied to high alloy high tensile strength materials and low carbon steel plates.

〔Example〕

Table 1 shows examples of the present invention. *marked is comparative material.

A pickling material for hot rolled steel plate 5PHC (1.2 mm) was used as the base, and Ni plating was carried out at a current density of 25 A/d in a sulfuric acid acid bath.
I went with 2. Pretreatment heating is 10℃/s in a 0□2% furnace.
The temperature was raised using EC. Furthermore, after hot dipping for 3 seconds, reheating was performed in a furnace in air. Samples were created under various experimental conditions.

The sliding resistance was evaluated using the 5-point method described above. In addition, plating adhesion was evaluated using a ball impact test.
Evaluation was made using the point system. 10 points indicate no peeling, and 1 point indicates frontal peeling. A score of 6 or more is considered passing.

No. As shown in 1 to 13, Ni pre-plating amount is 0
．． 1~3g/m2, pretreatment heating temperature 430~500℃1
Bath temperature: 430-500°C Effective A/fA degree in 2 baths: 0.05
~0.15%, reheating temperature after plating 450~550℃
The steel sheet of the present invention manufactured within the range of 0.05 to 1.00% is excellent in both sliding resistance and plating adhesion. In comparison, the amount of Ni plating deposited is 0.
If the effective N concentration in the bath is less than 0.05% or more than 0.15% (Nα14)
o, 15.16 Sliding resistance and adhesion are poor. In addition, if the pretreatment heating plate temperature, heating rate, bath temperature, post-plating heating temperature and heating time deviate from the scope of the present invention (No. 17 to
25), both performances deteriorate.

Moreover, Nα26-30 is the case where individual plating other than Ni plating and alloy plating are used as pre-plating. Like Ni plating, these also exhibit excellent sliding resistance.

Furthermore, Nos. 31 to 33 are cases where a Zn alloy bath was used as the plating bath. In this case as well, the plated plate obtained showed excellent performance as in the case of the Zn bath.

Finally, in view of the results of Nos. 1 to 13, in the case of Ni pre-plating, the effective M concentration in the bath is 0.11 to 0.0, as seen in ho, 2, 3, and 9.10. 12%,
It is clear that the sliding resistance is the best when the amount of Ni deposited is in the range of 0.5 to 0.8 g/m2, which is a preferable condition.

〔Effect of the invention〕

As described above, according to the present invention, a zinc or zinc-based alloy hot-dip coated steel sheet with unprecedented sliding resistance and coating adhesion can be manufactured at low cost by using pre-plating, and its industrial significance is extremely high. big.

[Brief explanation of drawings]

Figure 1 shows pre-Ni plating of 0.5g/m" and O2
In an atmosphere with a concentration of 2%, the temperature of the pretreatment heating plate was 450"C.
When the temperature was raised at 0°/sec, plating was performed for 3 seconds at a bath temperature of 450°C and various effective M concentrations in the bath, and the reheating temperature after plating was changed (heating time 15 seconds).
) Figure 2 shows the change in sliding resistance of 0.22% atmosphere after pretreatment heating plate temperature was raised to 450°C at a rate of 10°C/sec, bath temperature was 450°C, plating immersion time was 3 sec, and bath temperature was 450°C. FIG. 4 is a diagram showing changes in sliding resistance with changes in the amount of pre-Ni deposited when manufactured at effective M concentrations of 0.1% and 0.15%. Entertainment - Kaoru Minajo (Utsuko) - Field

Claims (1)

[Claims] Ni, Fe, Co, Cu, Sn, Zn, P on the surface of the steel plate
One type selected from among them alone, or two or three types
After plating the seed with alloy at 0.1~3.0g/m^2, O_2
7℃/s from 430 to 500℃ in an atmosphere with a concentration of 5% or less
Effective Al concentration in the bath is 0.05 after heating above ec.
~0.15%, plating is performed by immersion in a zinc or zinc-based alloy bath whose bath temperature is controlled at 430 to 500°C, and then plating is performed in a temperature range of 450 to 550°C immediately above the wiping after pulling.
A method for manufacturing a zinc or zinc-based alloy hot-dip plated steel sheet with high sliding resistance, the method comprising heating for ~40 seconds.