JPS6260854A - Manufacture of screw thread product - Google Patents

Abstract

PURPOSE:To manufacture screw thread product having high precision and superior corrosion resistance, by hot dip coating product to be coated with hot dip zinc coating bath mainly composed of zinc held to a specified temp., then performing thread rolling. CONSTITUTION:One end of a round bar material 10 is forging formed to a hexagonal head part 10A, and the material is dipped and hot dip coated in a hot dip coating bath 12 mainly composed of zinc at 420-500 deg.C low temp. As the bath 12, e.g. that, etc., contg. 0.1-7wt% Al is exemplified. Next, if the screw thread 14 is formed by thread roll forming outer shape of a leg part 10B of the hot dip coated material 10, uniform and thin alloy layer can be maintained on the thread 14 surface. In this way, coated film superior in corrosion resistance is held on surface of the end screw product having good screw thread precision.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing products having threads such as bolts and nuts, and particularly relates to a thread thread having high screw threading accuracy and excellent corrosion resistance. Regarding the production method of Neshiyama products.

[Background technology and matters to be solved]

Generally, when applying corrosion-resistant plating to bolts, etc., threads are formed on the legs of the bolt by cutting, rolling, etc., and then the bolt is immersed in a hot-dip zinc bath to perform the galvanizing. There is.

This zinc plating has excellent corrosion resistance, but because the plating film is uneven and thick, in some cases it may not be possible to thread it into a nut, and the outer shape must be cut to fit the appropriate dimensions. Become.

Electrogalvanizing the bolts is also used as a plating method for mata (lh).This electrogalvanizing has a relatively high precision coating, so there is no need to cut the external shape in post-processing after plating. , it has the disadvantage of inferior corrosion resistance compared to hot-dip galvanizing.

The present invention takes the above-mentioned facts into consideration and provides a method for producing threaded thread products such as bolts that are excellent in corrosion resistance and have high threaded thread precision.

[Summary of the invention]

In the present invention, the product to be plated is coated for 500'
It is characterized in that it is immersed in a molten zinc bath containing zinc as its main component at a temperature lower than C for plating treatment, and then formed into threads by rolling.

In the present invention, the product to be plated includes a material on which threads are to be formed and a thread product on which threads have already been formed. An example of a material on which a thread is to be formed is a round bar material for bolt products in which a hexagonal head is formed at one end by forging.

Since the threaded product of the present invention is not limited to bolts, but also covers screws, nuts, etc., it goes without saying that the material on which threads are to be formed also covers the material for forming screws, nuts, etc. . Therefore, the above-mentioned screw thread products with threads already formed are generically referred to as bolts, screws, and nuts [i]. Moreover, the threaded mountain product is formed by means such as cutting and rolling, and the means for forming it is not limited.

The product to be plated, which is a material on which threads are to be formed or a thread product on which threads have already been formed, is subjected to pretreatments such as degreasing, pickling, and flux treatment as necessary. After these pre-treatments, the product to be plated is subjected to plating treatment by immersing it in a molten zinc bath containing zinc as a main component at a temperature of 420°C or higher and lower than 500°C.

When the temperature of the plating bath is set to 500° C. or higher, the iron-zinc alloy layer formed on the surface of the product to be plated becomes thin and uniform, and no peeling occurs in this iron-zinc alloy layer during rolling forming. However, in order to raise the temperature of the plating bath to a high temperature of 500°C or higher, a heat-resistant container such as a crucible or other ceramic container is required, and a large amount of thermal energy is required to maintain the plating bath at a high temperature. Therefore, there is a disadvantage from a practical point of view. For plating baths at temperatures lower than 500°C, iron containers (steel plates for hot-dip galvanizing) are sufficient. On the other hand, if the temperature of the plating bath is lower than 420°C,
The zinc solidifies and plating is impossible.

In other words, in hot-dip galvanizing whose main component is zinc, 42
The iron-zinc alloy layer formed by the iron of the product to be plated and the zinc of the plating bath in the temperature range of 0° C. or higher and lower than 500° C. must be made as thin and uniform as possible. For this reason, it is better to keep the plating degree as low as possible and the immersion time as short as possible.In this way, when forming threads by rolling on the material to be plated after plating, Alternatively, when modifying the threads of a threaded product as a product to be plated by rolling, it is possible to maintain a uniform plating layer. A more preferable temperature range for a hot-dip plating bath containing zinc as a main component is a temperature lower than 445°C and 425°C or higher, and the immersion time varies depending on the mass of the product to be plated, but is preferably as short as possible.

As a hot-dip plating bath containing zinc as a main component, for example, a zinc-aluminum alloy bath containing 0.1 to 7% aluminum can be used. When an alloy bath containing aluminum is used, the iron-zinc alloy reaction suppressing effect of aluminum makes it difficult to form an iron-zinc alloy layer, and a plating layer with good spreadability can be obtained. When forming threaded threads or when correcting threaded threads by rolling after plating, the plating layer is spread very well.

The spreadability of this plating layer is effective when the aluminum content in the zinc-aluminum alloy bath is 0.1% by weight or more.

However, if the aluminum content in the zinc-aluminum alloy bath is too high, non-plating tends to occur and operation becomes difficult, so the aluminum content in the zinc-aluminum alloy bath should be kept at 7% by weight or less. desirable.

In addition, a zinc-aluminum alloy bath containing 0.2 to 2 weight percent aluminum is used as a hot-dip plating bath mainly containing zinc, and after immersing the product to be plated in this alloy bath and taking it out,
Immediately add it to an alloy bath containing 3-7% by weight of aluminum and 0.5-2% by weight of magnesium? i? It can also be set to R.

It is a well-known fact that adding magnesium to a zinc-aluminum alloy bath increases corrosion resistance, but with current technology it is not possible to directly apply zinc-aluminum alloy plating containing magnesium to the iron substrate of wave plated products. Have difficulty.

Therefore, by applying zinc-aluminum alloy plating to a product made of iron to be plated, and then applying zinc-aluminum alloy plating containing magnesium, it is possible to improve the corrosion resistance by adding magnesium.

In this case, the alloy bath initially used for the product to be plated is a zinc-aluminum alloy bath containing 0.2 to 2% by weight of aluminum. In view of the ductility of the plating layer obtained by this plating process, the amount of aluminum remaining is 0.2% by weight.
Although the above amount is desirable, a small amount of about 0.2 to 2% is sufficient in view of the amount of aluminum contained in the plating bath applied after this plating layer.

Next, the zinc-aluminum alloy bath containing magnesium has an aluminum content of 3 to 7% by weight from the viewpoint of corrosion resistance of the plating layer.
The magnesium content is preferably 0.5% by weight or more in order to further improve the corrosion resistance of the plating layer, but if the magnesium content is too large, the appearance of the plating will be poor (2% by weight). The following should be used.

In addition, in the present invention, the product to be plated is immersed in a hot-dip zinc bath at a temperature of 420°C or higher and lower than 500°C, taken out, and then immediately immersed in a zinc-aluminum alloy bath containing 3 to 7% by weight of aluminum. Good too. Also, the product to be plated is immersed in molten zinc at a temperature of 420°C or higher but lower than 500°C, and after taking it out, it is immediately immersed in an alloy bath containing 3 to 7% by weight of aluminum and 0.5 to 2% by weight of magnesium. You may.

When the product to be plated is thoroughly rinsed in a molten zinc bath and quickly taken out and immersed in a zinc-aluminum alloy bath containing 3 to 7% by weight of aluminum, aluminum diffuses into the iron-zinc alloy layer and the iron-zinc The pure zinc layer on the outside (surface layer side) of the alloy layer is replaced by the zinc-aluminum alloy layer to form an alloy plating film containing aluminum, improving spreadability and corrosion resistance.

Similarly, the product to be plated is immersed in a molten zinc bath, and after being taken out, it is immediately immersed in an alloy bath containing 3 to 7% by weight of aluminum and 0.5 to 2% by weight of magnesium.
The pure zinc layer on the outside (surface layer side) of the iron-zinc alloy layer is replaced by the zinc-aluminum-magnesium alloy layer, and an alloy plating film containing aluminum and magnesium is formed on the plating surface layer, which improves ductility and
Corrosion resistance is improved.

When the plating treatment is performed in two steps as described above, it is desirable to perform the plating treatment immediately after the first step before proceeding to the second step. The reason for this is to prevent the surface layer from being oxidized in the first step, prevent the temperature of the plating layer from decreasing in the first step, and promote diffusion during the plating process in the second step.

In this way, the material on which threads are to be formed as a plated product that has an alloy plating layer with excellent ductility and corrosion resistance can be uniformly formed on both surfaces of the thread even after the threads are formed by rolling. A thin alloy layer can be maintained. In addition, screw thread products are coated with an alloy plating layer with excellent ductility and corrosion resistance, and the alloy plating layer remains uniformly on the surface of the thread. Even if the thickness is somewhat uneven, it can be corrected to a uniform film thickness.

Therefore, it is possible to improve the screw-out accuracy of any screw thread product while maintaining its corrosion resistance.

Thread products with an excellent appearance can be manufactured by electrogalvanizing a thread product on which an alloy plating layer has been formed after forming threads by rolling or modifying threads by rolling. can do.

[Embodiments of the invention]

Example 1 FIG. 1 shows a first embodiment of the present application.

In this embodiment, a round bar material 10 is used and a hexagonal head 10A is formed at one end thereof by forging. Therefore, the portion other than this hexagonal head 10A becomes a leg 10B.
No mountain has yet formed in B.

Next, this round bar material 10 is hot-dipped with zinc as the main component. The following five types of hot-dip plating containing zinc as the main component were selected.

■Hot-dip galvanizing, 430'C, 30sec immersion■
5XA1-Zn alloy plating, 440'C, 1ain■
After immersion in 1χAffi-Zn alloy bath (440'C, 1m1
n).

5χA1-1χMgZn alloy bath 30secfl After immersion in molten zinc bath (430°C, 30sec).

5χA1-Zn alloy bath soaking After immersion in a molten zinc bath (430°C, 30 seconds).

5χAj! -1χMgZn alloy bath immersion Among these methods, for methods ① and ②, it is preferable to apply a special flux in advance before plating.The flux contains components such as those shown in JP-A-58-136759, as an example. . That is, the flux is made of one or more of chloride, fluoride, or silicofluoride of an alkali metal element or an alkaline earth metal element and zinc chloride, and this flux reliably transfers molten zinc containing aluminum to the round bar material 10. It can be attached.

A round bar material 10 that has been hot-dipped with zinc as its main component has threaded threads 14 formed on the outer shape of its leg portions 10B by rolling.

For those plated using the above methods ① and ②, only slight separation of the plating film was observed.
Items plated using methods ■ and ■ have a plating film! R
I # was not recognized. Furthermore, Neshiyama products that have been electroplated using the methods described in ■ to ■, electrolytically galvanized, and chromate treated take a longer time to develop red rust than conventional Neshiyama products in salt spray tests. It was extended to a large width.

Example 2 A hexagonal head was formed at one end of a round bar material by forging, and threaded ridges were formed in a portion (leg) other than the hexagonal head by rolling. Next, for the bolt with threaded threads,
After plating was performed under the same conditions as in Example 1, a process was performed to correct the threads by rolling. As a result, ■ and ■
Only slight peeling of the plated film was observed on the samples plated using the method (2), and no peeling of the plated film was observed on the samples plated using the methods (2) and (2).

〔Effect of the invention〕

As explained above, in the method for manufacturing Neshiyama products according to the present invention, the product to be plated is plated in a plating bath at a temperature of 420'C or higher but lower than 500°C, so an expensive plating bath made of ceramic or the like is not required. A uniform, continuous, spreadable, corrosion-resistant plating film is formed on the plated product by using less energy, and by rolling after this plating process, it is possible to form threads or threads. During repair, since the plating film has ductility, it is spread uniformly on both surfaces of the thread, so that the corrosion-resistant plating film can be maintained on the surface of the final screw product with good thread accuracy.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a manufacturing procedure showing an embodiment of the method for manufacturing a pile product according to the present invention. 10... Round bar material, 10A... Hexagonal head, 10B... Leg, 12... Molten zinc tank, 14... Screw thread.

Claims (7)

[Claims] (1) 420 plating product to be plated
A method for manufacturing a screw thread product, which comprises plating with a hot-dip zinc bath containing zinc as a main component at a temperature of 0.degree. C. or higher and lower than 500.degree. C., followed by rolling processing. (2) The product to be plated is a material on which a thread is to be formed, and the rolling process is a rolling process for forming a thread.
The thread product manufacturing method described in item 1). (3) The scope of the above-mentioned claims, characterized in that the product to be plated is a threaded product in which a thread has already been formed, and the rolling process is a process for modifying the thread of the threaded product. The thread product manufacturing method described in paragraph (1). (4) The above-mentioned claim characterized in that the hot-dip plating mainly containing zinc is performed by immersing the product to be plated in a zinc-aluminum alloy bath containing 0.1 to 7% by weight of aluminum. The thread product manufacturing method described in paragraph (1). (5) Hot-dip plating with zinc as the main component is performed by immersing the product to be plated in a zinc-aluminum alloy bath containing 0.2 to 2% by weight of aluminum in zinc, and after taking it out, immediately adding 3 to 2% of aluminum to the bath. 7% by weight, magnesium 0.5~
The method for manufacturing a threaded product according to claim 1, characterized in that the method is carried out by immersion in an alloy bath containing 2% by weight. (6) Hot-dip plating with zinc as the main component is carried out by immersing the product to be plated in a molten zinc bath, taking it out, and immediately immersing it in a zinc-aluminum alloy bath containing 3 to 7% by weight of aluminum. A thread product manufacturing method according to claim 1, characterized in that the method is carried out. (7) In hot-dip plating with zinc as the main component, the product to be plated is immersed in a hot-dip zinc bath, and after taking it out, immediately add 3 to 7% by weight of aluminum and 0.5% of magnesium.
The method for manufacturing a threaded product according to claim 1, characterized in that the method is carried out by immersion in an alloy bath containing ~2% by weight.