JP6454585B2 - Continuous surface treatment method for steel wire - Google Patents

Description

  The present invention relates to a continuous surface treatment method for a steel wire, and more particularly to a method for continuously forming a phosphate coating on the surface of a steel wire.

  Conventionally, for the purpose of improving the dimensional accuracy and mechanical characteristics of a steel wire, a drawing process using a wire drawing die is performed on the steel wire. In order to perform this drawing process smoothly, before the drawing process, a process of removing oxide scale attached to the surface of the steel wire (descaling process), a process of forming a zinc phosphate coating on the surface of the steel wire ( A coating treatment step) and a step of forming a lubricating coating on the zinc phosphate coating (lubricating treatment step). By performing these steps, lubricity is imparted to the surface of the steel wire rod, and the drawing process can be performed smoothly.

  The descaling step is roughly divided into a chemical removal method and a mechanical removal method. However, the chemical removal method uses sulfuric acid and hydrochloric acid, and therefore requires a large amount of waste acid treatment, which is not environmentally preferable. The mechanical removal method is used. Examples of the mechanical removal method include a shot blast method, an air blast method, and a high pressure water jet method.

In the coating treatment step, phosphoric acid composed of a mixed structure of hoplite [Zn ₃ (PO ₄ ) ₂ .4H ₂ O] and phosphophyllite [Zn ₂ Fe (PO ₄ ) ₂ .4H ₂ O] on the surface of the steel wire. A zinc salt coating is formed.

  In the lubrication treatment step, a reactive soap lubrication treatment is performed on the zinc phosphate coating to react the sodium stearate soap component with the phosphate in the zinc phosphate coating to produce zinc stearate (metal soap). ) And sodium stearate (hot water soap).

  The zinc phosphate coating and lubricating coating formed above are excellent in lubricity, rust resistance, and seizure resistance, but further reduce friction during processing, extend mold life, improve processing accuracy, and reduce coating clogging. For the purpose of improving heat resistance and the like, Patent Documents 1 and 2 disclose a technique for forming a phosphate coating containing zinc calcium phosphate. The said phosphoric acid film is formed by immersing a steel wire in the phosphate processing liquid whose weight ratio of the calcium ion with respect to zinc ion is 0.5 or more and 1.5 or less. The zinc calcium phosphate thus formed has a finer crystal structure and better heat resistance than zinc phosphate.

Japanese Patent Laid-Open No. 10-46351 JP-A-10-330953

  In order to form a phosphate coating in a short time, it is effective to increase the total acidity of the phosphating solution, but when the total acidity of the phosphating solution for forming the zinc calcium phosphate is increased, Zinc phosphate was preferentially formed, and it was difficult to form a phosphate coating containing zinc calcium phosphate.

  This invention is made | formed in view of said present condition, The place made into the objective is the continuous surface treatment method of the steel wire which can form the phosphate coating containing a zinc calcium phosphate in a short time. Is to provide.

  In order to achieve the above object, the present inventor has made extensive studies on various factors for forming a phosphate coating containing zinc calcium phosphate. The concentration ratio of calcium ions to zinc ions and the phosphate coating It was confirmed that the total acidity of the treatment solution for forming the glass contributes to the crystal structure and formation rate of the phosphate coating. Based on this, further investigations were made to find the conditions of the treatment liquid capable of forming a phosphate coating containing zinc calcium phosphate, and the present invention described below was completed.

  That is, the steel wire rod continuous surface treatment method of the present invention is a method for continuously treating the surface of a steel wire rod before being cold worked, and includes abrasive particles with respect to the surface of the steel wire rod. Descaling step for removing scale adhered to the surface of the steel wire by spraying the slurry, and surface of the steel wire by immersing the steel wire after the descaling step in a phosphate-containing solution The phosphate treatment solution has a weight ratio of calcium ions to zinc ions of 2 to 9, and a total acidity of 60 pt to 250 pt. It is characterized by that.

  According to the present invention, a phosphate coating can be efficiently formed by using a phosphate-containing solution that satisfies the numerical range of the total acidity. In addition, by satisfying the weight ratio of calcium ions to zinc ions, a phosphate coating having a high zinc calcium phosphate content can be formed in a short time. Since zinc calcium phosphate has a dense crystal structure and excellent heat resistance, forming a phosphate coating with a high content of zinc calcium phosphate on the surface of the steel wire improves processing accuracy and prevents clogging of the coating. Reduction and seizure resistance can be improved.

  In the above configuration, the temperature of the phosphate-containing solution in the coating treatment step is preferably 60 ° C. or higher and 90 ° C. or lower.

  According to this structure, it becomes easy to form a phosphate film having a high content of zinc calcium phosphate.

  In the above configuration, preferably, the phosphate-containing solution has a weight ratio of calcium ions to zinc ions of 3 to 7. With such a weight ratio, the calcium phosphate is easily contained in the phosphate coating.

  In the above configuration, the total acidity of the phosphate-containing solution is preferably 120 pt or more and 200 pt or less. By having such a total acidity, the chemical conversion reaction for forming the phosphate coating is promoted, and the formation time of the phosphate coating can be shortened.

  According to this configuration, the formation rate of the phosphate coating can be further increased, and a phosphate coating containing zinc calcium phosphate can be easily formed.

  The said structure WHEREIN: Preferably it is performed after the said descaling process and before the said film treatment process, and further includes the preheating process which preheats the said steel wire.

  Since the formation of the phosphate coating in the coating treatment process is performed by a chemical conversion reaction, the higher the temperature of the steel wire, the more the reaction is promoted and the phosphate coating tends to be easily formed. For this reason, by preheating the steel wire in the preheating step before the coating treatment step, the formation of the phosphate coating in the subsequent coating treatment step is promoted, and the phosphate coating can be formed in a short time.

  The said structure WHEREIN: It is preferable that the said preheating process heats the said steel wire so that the temperature difference with the temperature of the phosphate containing solution used at the process of forming the said phosphate film may be 30 degrees C or less.

  According to the said structure, when a steel wire passes a process liquid, it can suppress that a process liquid hydrolyzes or changes in quality by the temperature difference of a steel wire and a process liquid, The quality of a process liquid There is an advantage that it is difficult to lower.

  ADVANTAGE OF THE INVENTION According to this invention, the continuous surface treatment method of the steel wire which can form the phosphate film containing a zinc calcium phosphate in a short time can be provided.

It is the figure which showed the process of the continuous surface treatment method which concerns on embodiment of this invention. It is an observation image by the scanning electron microscope of the phosphate film of Example 3. It is an observation image by the scanning electron microscope of the phosphate film of the comparative example 1. It is an observation image by the scanning electron microscope of the phosphate film of the comparative example 2. It is an observation image by the scanning electron microscope of the phosphate film of the comparative example 3.

  Hereinafter, embodiments of the continuous surface treatment method of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the continuous surface treatment method for steel wire according to the present embodiment is applied to a production line 1 (drawing line and forging line) for performing cold working such as wire drawing on a steel wire (steel wire). In order to ensure lubrication between the die 5 and the steel wire during the wire drawing process, a coating treatment process for forming a phosphate coating as a base of the lubricant on the surface of the steel wire And a lubricating treatment step P6 for coating a lubricant containing metal soap or the like so as to cover the phosphate coating.

  Specifically, the steel wire rod continuous surface treatment method of the present embodiment includes a step of unwinding the steel wire rod from the coil of the supply stand 2 (unwinding step P1), and straightening the steel wire rod into a strand by the straightening machine 4. A process (correcting process P2), a process of removing scales adhering to the surface of the steel wire (descaling process P3), a process of heating the steel wire after descaling (preheating process P4), and the heated steel wire The coating process P5 for forming a phosphate coating on the surface of the steel wire by immersing the coating in a coating bath, and the lubrication process for coating the steel wire after coating with a lubricant such as metal soap P6, including a step of drawing a steel wire coated with a lubricant by cold working (drawing step P8), and a step of winding the drawn steel wire with a winder (winding step P9). .

  As shown in FIG. 1, when the lubricant used in the lubrication step P6 is liquid, a step of drying the lubricant covering the surface of the steel wire (drying step P7) may be included before the wire drawing step P8. Good. In addition, you may abbreviate | omit the preheating process P4 between the descaling process P3 and the film processing process P5 according to a specification.

  Below, the steel wire material surface-treated by the continuous surface treatment method and each process which comprises this continuous surface treatment method are demonstrated.

  The steel wire processed by the continuous surface treatment method of the present embodiment is obtained by rolling steel, stainless steel, or the like into a long linear shape with a hot rolling mill, and has a diameter of 5.0 mm to 55 mm. This steel wire is wound as a coil after rolling. After rolling, in order to adjust the structure and mechanical characteristics of the steel wire, the steel wire may be subjected to heat treatment such as annealing in a batch furnace or a continuous furnace.

<Unwinding process P1>
In the unwinding process P1, the steel wire is unwound in a line form from the coil of the steel wire disposed on the supply stand 2. The supply stand 2 is a facility that supports a coil of a steel wire rod after hot rolling so that its axis is directed in the vertical direction or the horizontal direction. The unwinding of the steel wire is performed by unwinding the steel wire so as to be pulled out toward the upper side of the coil or the downstream side of the production line, or unwinding the steel wire while rotating the coil itself in a horizontal plane.

<Correction process P2>
In the straightening process P2, the curl of the steel wire rod is straightened using the straightening machine 3. The straightening machine 3 includes a plurality of straightening rolls 4, and these straightening rolls 4 perform straightening to eliminate curling of the steel wire rod unwound from the supply stand 2. Specifically, the steel wire wound in a coil shape after hot rolling passes through a plurality of straightening rolls 4 in order to eliminate the curl of the steel wire and straighten the steel wire. Can do.

<Descaling process P3>
In the descaling process P3, the scale adhering to the surface is removed by spraying a slurry containing abrasive particles onto the surface of the steel wire, and the surface of the steel wire is made by adding processing strain to the surface of the steel wire. Activate. Hereinafter, the slurry injection performed in the descaling process P3 may be referred to as “wet blasting”.

  In wet blasting, a slurry, which is a mixture of water and hard particles, is jetted from a plurality of nozzles toward a target with high-pressure air, so that the slurry is made to collide with the surface of the steel wire. This is an operation to remove the oxide scale on the surface. By this operation, the surface of the steel wire is activated by applying processing strain to the surface of the steel wire. Thereby, the chemical conversion reaction in the coating treatment step P5 is promoted, and the phosphate coating can be formed in a short time. Wet blasting has an advantage that dust can be hardly generated because the oxide scale can be efficiently removed by appropriately setting the size of hard particles and the like, and the scattering of particles can be suppressed by water.

  In the descaling process P3, in order to activate the surface of the steel wire while removing the scale, the air pressure of the wet blast, the distance between the nozzle and the steel wire, the shape and material of the abrasive grains, the interval between the plurality of nozzles, the abrasive It is preferable to adjust the grain concentration and the like appropriately.

  The higher the air pressure of wet blasting, the easier it is to remove the scale attached to the surface of the steel wire, and the surface of the steel wire can be activated. From such a viewpoint, the air pressure of wet blasting is preferably 0.2 MPa or more and 0.6 MPa or less. By being 0.2 MPa or more, the scale can be sufficiently removed, and the slurry can be prevented from flowing back into the air flow path.

  The distance between the nozzle and the steel wire during wet blasting is preferably 20 mm or more and 200 mm or less. By setting the distance between the steel wire rod and the nozzle to 20 mm or more, the slurry can be sprayed on the entire surface of the steel wire rod. Moreover, since wet blasting is insufficient in acceleration of abrasive grains by air in the vicinity of the nozzle tip, a sufficient grinding force can be secured by securing an interval of 20 mm or more. When the distance between the steel wire rod and the nozzle is 200 mm or less, it is possible to avoid a reduction in grinding force due to attenuation of wet blasting.

  The abrasive concentration of wet blasting is preferably 5% by volume or more and 25% by volume or less. When the abrasive concentration is 5% by volume or more, the processing force does not extremely decrease, and when the abrasive concentration is 25% by volume or less, interference between the abrasive particles can be avoided, and a decrease in processing efficiency can be avoided.

  The plurality of nozzles are respectively disposed at a plurality of positions arranged in the circumferential direction, preferably at three or more positions. Preferably, the plurality of nozzles are arranged at substantially equal angular intervals in a circumferential direction around the axis of the steel wire, and the surface of the steel wire is entirely covered by a plurality of injection regions by the plurality of nozzles. It is arranged so that it can be covered. The positions of the nozzles are preferably distributed in the steel wire conveying direction so that the injection regions of the nozzles do not interfere with each other. Specifically, the plurality of nozzles are staggered along the conveying direction along the axis of the metal wire (the nozzles are alternately distributed to the left and right along the circumferential direction when viewed along the axis of the steel wire. Or) are preferably arranged in a spiral.

  The above-mentioned wet blasting can suppress the impact exerted by the sprayed abrasive on the object, and is less likely to damage the object compared to a water jet having an injection pressure of about 100 MPa. For example, in the water jet, the work-affected layer generated on the surface of the steel wire tends to be thick, and processing defects such as cracking of the steel wire and seizure of the die may occur during cold working. On the other hand, by applying wet blasting using a slurry of water and hard particles to the descaling process P3, the work-affected layer generated on the surface of the steel wire rod can be made thinner compared to the water jet, and polishing. It is possible to reduce the work hardening amount, work hardening depth, and the like of the surface of the steel wire hardened by the collision of the materials. Therefore, in the cold working after the phosphate coating process described later, the possibility of causing processing defects such as cracking of the steel wire and seizure of the die is significantly reduced.

  The abrasive grains used for the above-described wet blasting are preferably grit-like abrasive particles. This grit-like abrasive particle means a grit prescribed as a metal-based abrasive for blasting in JIS Z 0311, and has an angular shape with a ridge angle before use, and has a round surface. It refers to a particle having a proportion of less than ½ of the entire surface of the particle. Therefore, the grit-like abrasive particles are shot processing metal-based abrasives defined in JIS Z 0311, that is, “there is no ridge angle, crushing surface or other sharp surface defects in the state before use, and the major axis has a minor axis. “Spherical particles within 2 times” are greatly different in shape.

  By using such grit-like abrasive particles, a work-affected layer is formed on the surface of the steel wire by fine surface cutting by the corners of the grit-like abrasive particles. This work-affected layer promotes the chemical conversion reaction in the subsequent coating treatment step P5, and can form a phosphate coating in a short time.

  In addition, although the kind of metal used for grit-like abrasive | polishing particle | grains is not ask | required, it is preferable to use the particle | grains whose hardness is higher than the hardness of the steel wire processed from the viewpoint of the processing efficiency of the descaling process P3. Specifically, steel or stainless steel having excellent toughness is preferably used for the grit-like abrasive particles from the viewpoint of preventing residual sticking to the steel wire surface.

<Preheating process P4>
In the preheating process P4, the steel wire is preheated before the coating process P5. By performing the preheating process P4, the time of the film processing process P5 can be shortened. The reason for this is that the coating treatment step P5 forms a phosphoric acid coating by a chemical conversion reaction, so that the higher the treatment temperature of the steel wire, the higher the reaction rate. The preheating process P4 is performed by spraying hot water or steam on the steel wire or heating the steel wire by high frequency induction heating or the like.

  In the preheating step P4, it is preferable to heat the steel wire to a temperature similar to the temperature of the phosphate-containing solution used in the coating treatment step P5. Specifically, the steel wire is heated to 60 ° C or higher and 80 ° C or lower. Is more preferable. When the temperature of the steel wire after the preheating step P4 is 60 ° C. or higher, the formation efficiency of the phosphate coating can be increased. When the temperature of the steel wire after the preheating step P4 is 80 ° C. or less, the temperature increase of the phosphate-containing solution forming the phosphate coating can be suppressed, and the phosphate-containing solution is hydrolyzed. It can be prevented from being altered.

  The temperature of the steel wire after the preheating step P4 is preferably 30 ° C. or less with respect to the temperature of the phosphate-containing solution used for forming the phosphate coating in the coating treatment step P5. More preferably, the temperature is 10 ° C. or less. Thus, when the steel wire passes through the phosphate-containing solution due to the small temperature difference between the steel wire after the preheating step P4 and the phosphate-containing solution in the coating treatment step P5, the steel wire and the phosphate-containing material are contained. Due to the temperature difference from the solution, the phosphate-containing solution can be prevented from being hydrolyzed or altered, and there is an advantage that the quality of the phosphate-containing solution is unlikely to deteriorate.

  The heating time in the preheating step P4 is preferably 60 seconds or less. When the heating time in the preheating process P4 is 60 seconds or less, an oxide film that inhibits the formation of the phosphate film in the film treatment process P5 is hardly formed on the surface of the steel wire. This oxide film is likely to occur if the preheating step P4 is performed for a long time when the surface of the steel wire after the descaling step P3 is wet.

<Coating process P5>
In the coating treatment process P5, the steel wire from which the scale has been removed in the descaling process P3 is immersed in a phosphate-containing solution, thereby forming a phosphate coating on the surface of the steel wire. The phosphate coating plays the role of a carrier that draws the lubricant into the die in the cold working such as wire drawing described above, and is formed as an underlayer such as lime soap or metal soap used as the lubricant.

The phosphate-containing solution in the coating treatment step P5 contains phosphate ions, zinc ions, and calcium ions as essential components in order to form a phosphate coating containing zinc calcium phosphate. In the phosphate-containing solution, the weight ratio of calcium ions to zinc ions (hereinafter also referred to as “divalent ion weight ratio”) is 2 or more and 9 or less. When the divalent ion weight ratio is 2 or more, a scholtite [CaZn ₂ (PO ₄ ) ₂ .2H ₂ O] crystal is formed while avoiding the formation of a relatively large crystal such as a whipite or phosphophyllite system. In addition, a phosphate film having fine crystals and excellent heat resistance can be formed as a base for cold working. Such a phosphate coating containing scholtite crystals can reduce mold clogging and improve seizure resistance. When the divalent ion weight ratio is 9 or less, the treatment time can be shortened and a phosphate coating containing zinc calcium phosphate can be easily formed, and the heat resistance is improved. The divalent ion weight ratio is preferably 3 or more and 7 or less. The divalent ion weight ratio can be adjusted by adding a surface conditioner containing zinc ions and / or calcium ions.

  The total acidity of the phosphate-containing solution is preferably 60 pt or more and 250 pt or less. By setting the total acidity to 60 pt or more, the chemical conversion reaction in the coating treatment process P5 is promoted, and the formation time of the phosphate coating can be shortened. In addition, since the total acidity is 250 pt or less, in the water washing treatment after the coating treatment step P5, the contamination of the water washing that tends to occur due to the high concentration of the phosphate-containing solution can be suppressed, and phosphorous having a high concentration can be suppressed. The supply cost of the acid salt-containing solution can be suppressed. The total acidity of the phosphate-containing solution is more preferably 120 pt or more and 200 pt or less, and still more preferably 130 pt or more and 170 pt or less. “Pt” used for the total acidity is a concentration unit of a phosphate-containing solution, and is a titration value of a 0.1 mol / L sodium hydroxide solution necessary for neutralizing 10 ml of the phosphate-containing solution. (Number of mL).

  The phosphate-containing solution in the coating treatment process P5 is preferably immersed in the steel wire while being heated to 60 ° C. or higher and 90 ° C. or lower. A phosphate film can be efficiently formed by being 60 degreeC or more. Moreover, it can prevent that a phosphate containing solution hydrolyzes or changes in quality by being 90 degrees C or less. The temperature of the phosphate-containing solution used in the coating process P5 is preferably heated to the same level as that of the preheating process P4.

In the coating treatment process P5, the weight of the phosphate coating formed on the surface of the steel wire may be 2.5 g / m ² or more and 7.0 g / m ² or less in terms of a unit area of the surface of the steel wire. preferable. When it is 2.5 g / m ² or more, it is possible to suppress the exposure of the steel wire rod, and when it is 7.0 g / m ² or less, it is possible to suppress mold clogging in the forging process. The weight of the phosphate coating is more preferably 3 g / m ² or more and 6 g / m ² or less, and further preferably 3.5 g / m ² or more and 5.5 g / m ² or less.

<Lubrication treatment process P6>
In the lubricating treatment step P6, the surface of the steel wire coated with the phosphate coating is coated with a lubricant containing limestone soap or the like. As a result, the steel wire can be easily lubricated and cold worked, and the steel wire can be processed smoothly. Since the phosphoric acid coating itself has poor lubricity, the life of the die may be shortened if wire drawing or the like is performed without performing the lubricating treatment step P6.

<Drying process P7>
When the lubricant used in the lubrication treatment step P6 is liquid, it is preferable to dry the lubricant in the drying step P7. The drying in drying process P7 can mention methods, such as spraying hot air with a drier. The drying temperature is preferably set to 60 ° C. or higher and 200 ° C. or lower, and the drying time is preferably 1 second or longer and 60 seconds or shorter.

<Wire drawing process P8>
The steel wire covered with the lubricant as described above is subjected to cold working represented by the wire drawing step P8 by a processing machine (in the wire drawing step P8, a wire drawing machine).

  Next, the effects of the continuous surface treatment method of the present invention will be described in detail by referring to Examples and Comparative Examples.

  In each of the examples and comparative examples, the steel type is SUJ2, and the spheroidizing annealing material (scale adhesion), continuous surface treatment, wire drawing process P8 and forging process are performed in this order on the steel wire having a diameter of φ11.0 mm. It was. In addition, the continuous surface treatment performed the descaling process P3, the preheating process P4, the film processing process P5, the lubrication process P6, and the drying process P7 in this order.

Details of the experimental conditions are as follows.
(1) Scale to be removed by descaling Chemical composition: Fe ₃ O ₄ (60%), Fe ₂ O ₃ (40%)
Thickness: 2μm
(Descaling process P3)
(P3-1) Wet blasting Equipment used: General-purpose wet blasting equipment manufactured by Macau Corporation Abrasive: Steel grit Abrasive grain concentration: 15% to 20%
Air pressure: 0.4-0.6MPa
Wire rod and nozzle angle: around 90 ° Distance between wire rod and nozzle: 90 mm
(P3-2) Acid cleaning (referred to as “Pickling” in Table 1)
Hydrochloric acid (20% by mass, normal temperature, immersion time 10 minutes)
(Preheating process P4)
Heat medium used: Hot water (60 ° C or 80 ° C)
Processing time: 60s
(Coating process P5)
Phosphate-containing solution: manufactured by Nippon Parkerizing Co., Ltd. (Product name: PB-3682X)
The total acidity in the phosphate-containing solution in each example and each comparative example was prepared by diluting the product of the phosphate-containing solution with water. Moreover, the weight ratio of the calcium ion with respect to the zinc ion in the phosphate containing solution in each Example and each comparative example was prepared by adding a surface conditioner (Nippon Parkerizing Co., Ltd. (product name: A4770)).

Total acidity: 30-250 pt
Phosphate-containing solution temperature: 80 ° C
Processing time: 30s or 60s
(Lubrication treatment P6)
Lubricant used: Lime soap (MAC-A20 (Inoue Lime Industry))
Lubricant temperature: 80 ° C
Processing time 10s
(Drying process P7)
Drying temperature: 100 ° C
Drying time: 4s

<Cold processing evaluation>
The workability was evaluated by performing cold working on the steel wires produced in each of the above Examples and Comparative Examples. Specifically, the wire drawing was performed on a steel wire of about 1000 kg with a drawing area reduction rate of 12% (φ11 mm → φ10.3 mm). In the forging process, a steel wire having a weight of about 500 kg was extruded forward at a surface reduction rate of 50%. In wire drawing and forging, “×” indicates that seizure occurred immediately during processing, “△” indicates seizure occurred when processing a steel wire of less than 500 kg, or clogging occurred. The steel wire rods of 500 kg or more that were not seized and clogged with coating were evaluated as “◯”. Table 2 shows the evaluation results of the steel wire rods of the examples and the comparative examples. In Table 2, “−” in the evaluation result of “Forging” in Comparative Example 2 means that the forging could not be evaluated because seizure occurred in the wire drawing.

<Crystal structure evaluation>
The appearance of the phosphate coating was evaluated by observing the phosphate coating formed in each Example and each Comparative Example at 200 times using a scanning electron microscope (SEM). 2 to 5 are images observed by a scanning electron microscope of the phosphate coatings of Example 3 and Comparative Examples 1 to 3. FIG.

  From the observation image of FIG. 2, it can be confirmed that in Example 3, a phosphate coating having a fine and uniform granular crystal structure is formed. The composition of this crystal is considered to be zinc calcium phosphate.

  From the observation image of FIG. 3, it can be confirmed that a phosphate film having a fine granular crystal structure is formed in Comparative Example 1, but part of the ground iron is exposed. The reason why the base iron is exposed is thought to be that the phosphate coating was not sufficiently formed due to insufficient reaction of the phosphate-containing solution. The composition of the fine granular crystals is zinc calcium phosphate.

  From the observation image of FIG. 4, it can be confirmed that in Comparative Example 2, a phosphate coating having a mixed structure of coarse plate-like crystals and needle-like crystals is formed. The composition of the needle-like crystals is considered to be zinc phosphate.

  From the observation image of FIG. 5, it is confirmed that in Comparative Example 3, a phosphate film having a non-uniform crystal structure in which coarse plate-like crystals, needle-like crystals and fine granular crystals are mixed is formed. it can. This acicular crystal structure is considered to be zinc phosphate, and the composition of coarse plate-like crystals and fine granular crystals is considered to be a mixed structure of zinc phosphate and zinc calcium phosphate.

  Regarding the appearance evaluation of the phosphate coating of each Example and each Comparative Example, the phosphate coating in which the crystal structure equivalent to Example 3 was confirmed was evaluated as “fine and dense” and equivalent to Comparative Examples 1-3. The phosphate coatings with confirmed crystal structures were evaluated as “fine but exposed to iron”, “coarse”, and “coarse and non-uniform”, respectively. Further, the crystal composition of the phosphate coating was evaluated based on visual observation by the observation image and energy dispersive X-ray analysis (EDS analysis). These evaluation results are shown in Table 2. “Composition” in Table 2 means the main component of the phosphate coating composition. For example, the phosphate coating of Example 1 means that zinc calcium phosphate can be included as a main component, and is not intended to consist solely of zinc calcium phosphate.

<Consideration of evaluation results>
From the comparison of the evaluation results of Examples 1 to 10 and Comparative Examples 1 to 5 shown in Table 2, the weight ratio of calcium ions to zinc ions is 2 or more and 9 or less after descaling the steel wire using wet blasting, In addition, by forming a phosphate film on the surface of the steel wire using a phosphate-containing solution having a total acidity of 60 pt or more and 250 pt or less, phosphoric acid having a fine and fine crystal structure as shown in FIG. A phosphate coating containing zinc calcium could be formed. As a result, it became clear that cold processing (drawing processing and forging processing) can be performed without causing seizure of the phosphate coating and mold clogging, and the effect of the present invention was shown.

  Although Examples 1-6 and Examples 7 and 8 differ in whether or not a preheating step is included, by including a preheating step as in Examples 7 and 8, the wire speed of the steel wire rod in continuous processing can be reduced. Even when the speed was doubled (from 20 m / min to 40 m / min), a phosphate film having a thickness comparable to the phosphate film formed in Examples 1 to 6 could be formed. This revealed that the preheating step can promote the formation of the phosphate coating.

  In the comparative example 1, the chemical conversion reactivity which forms a phosphate film fell remarkably, and the base iron was exposed. As a result, sufficient lubricity during wire drawing could not be ensured, and seizure occurred during wire drawing. The reason why the chemical conversion reactivity for forming the phosphate coating is lowered is considered to be that the weight ratio of calcium ions to zinc ions is too high.

  In Comparative Example 2, the phosphate coating containing zinc calcium phosphate was not formed, and the phosphate coating containing zinc phosphate was formed, so that the appearance of the phosphate coating was coarse and less than 500 kg of steel. When the wire was processed, many film clogging occurred. The reason why the phosphate coating containing zinc phosphate is formed in this way is that the ratio of calcium ions to zinc in the phosphate-containing solution is relatively low, and only the zinc phosphate coating is formed during coating treatment, As a result, the film is considered to be relatively coarse.

  In Comparative Example 3, since the phosphate coating containing zinc phosphate and zinc calcium phosphate was formed, the appearance of the phosphate coating was coarse and uneven, and the coating was clogged when processing a steel wire of less than 500 kg. There has occurred. The reason why such a phosphate coating is formed is considered to be due to the insufficient weight of calcium ions in the phosphate-containing solution. Moreover, since the zinc phosphate coating was preferentially formed, it is considered that coating clogging occurred.

  In Comparative Example 4, since the chemical conversion reactivity for forming the phosphate coating was significantly reduced with respect to Example 1 and the ground iron was exposed, the lubricity at the time of wire drawing could not be sufficiently ensured, Seizure occurred during wire drawing. The reason for this is considered to be that the total acidity of the phosphate-containing solution was less than 60 pt.

  In Comparative Example 5, the chemical conversion reactivity for forming the phosphate coating with respect to Example 1 was significantly reduced, and the base iron was exposed, so that sufficient lubricity during wire drawing could not be ensured, Seizure occurred during wire drawing. The reason for this is considered to be that activation of the surface of the steel wire was not sufficient because acid cleaning was used in the descaling process.

  In Comparative Example 6, since the phosphate coating containing zinc phosphate and zinc calcium phosphate was formed, the appearance of the zinc phosphate coating was coarse and uneven, and the coating was clogged when a steel wire of less than 500 kg was processed. There has occurred. The reason why such a phosphate coating was formed is considered to be that the coating of the coating was generated because the zinc phosphate coating was preferentially formed.

1 production line, 2 supply stand, 3 straightening machine, 4 straightening roll, 5 dice.

Claims (6)

A method for continuously treating the surface of a steel wire before being cold worked,
A descaling step of removing scales adhering to the surface of the steel wire by injecting slurry containing abrasive particles by wet blasting at an air pressure of 0.2 MPa to 0.6 MPa with respect to the surface of the steel wire; ,
A coating treatment step of forming a phosphate coating on the surface of the steel wire by immersing the steel wire after the descaling step in a phosphate-containing solution,
The said phosphate containing solution is the continuous surface treatment method of the steel wire material whose weight ratio of the calcium ion with respect to zinc ion is 2-9, and a total acidity is 60 pt or more and 250 pt or less. It is the continuous surface treatment method of the steel wire rod according to claim 1,
The continuous surface treatment method of a steel wire, wherein the temperature of the phosphate-containing solution in the coating treatment step is 60 ° C or higher and 90 ° C or lower. It is the continuous surface treatment method of the steel wire rod according to claim 1 or 2,
The phosphate-containing solution is a continuous surface treatment method for steel wire, wherein a weight ratio of calcium ions to zinc ions is 3 or more and 7 or less. It is the continuous surface treatment method of the steel wire rod as described in any one of Claims 1-3,
The total acidity of the said phosphate containing solution is 120pt or more and 200pt or less, The continuous surface treatment method of the steel wire. It is the continuous surface treatment method of the steel wire rod as described in any one of Claims 1-4,
A continuous surface treatment method for a steel wire, further comprising a preheating step that is performed after the descaling step and before the coating treatment step and preheats the steel wire. It is the continuous surface treatment method of the steel wire rod according to claim 5,
The said preheating process is a continuous surface treatment method of the steel wire which heats the said steel wire so that the temperature difference with the temperature of the phosphate containing solution used at the process of forming the said phosphate film may be 30 degrees C or less.