CN1796591B - Carburized steel wire and its production method - Google Patents

Abstract

Methods are disclosed for processing low carbon steel wire into high carbon steel wire for vehicle tire structures and other applications with improved properties including increased wire strength, corrosion resistance, and rubber adhesion. Low carbon steel wire is carburized to increase the carbon content, resulting in increased strength and corrosion resistance. According to other aspects of the invention, the carburization process may be performed in the presence of a rubber bonding agent that bonds to the steel wire to achieve improved steel-rubber adhesion in a single processing step.

Description

Carburized steel wire and its production method

technical field

The present invention relates to a method for carburizing steel, in particular to a method for increasing the carbon content of low-carbon steel wire used in tire construction in the carburizing process while simultaneously improving the corrosion resistance and rubber adhesion of the steel wire. the

Background technique

The introduction of steel belts in vehicle tires has greatly improved strength, durability and performance. Such belts generally consist of layers of structured steel wires embedded in a rubber compound to form the belt. Due to the high stresses present in the tire, the physical properties of the wires incorporated in the belt, including the ductility, tensile and impact strength of the wires, are strictly controlled in order to produce a belt optimized for use in the tire. In addition to the physical properties of steel wires mentioned above, other physical properties of steel wires used in tires are equally important, including corrosion resistance and the ability to bond with the associated rubber compound. The adhesive properties are especially important to ensure that the steel wires do not separate from the associated rubber in the belt. the

One steel component that affects the physical properties of the steel wire is the carbon content. Typically, steel wires with a high carbon content are used to manufacture the belts of tires. High carbon steel has the advantageous property of high strength which makes it preferred for use in tire applications. "High carbon steel" refers to steel having a carbon content of about 0.6% to 1.5%. The adhesion of steel wire can be improved by introducing adhesion improving agents such as cobalt, copper or brass into the steel wire, however, improving the steel wire by introducing these agents generally involves purchasing more expensive pre-machined steel wire, or The steel wire is subjected to additional processing steps. In order to avoid additional processing of the steel wires, the tire manufacturer may optionally introduce an adhesion improver into the associated rubber instead of the steel wires. While this method improves steel-to-rubber adhesion, it also results in a waste of adhesion-improving agent dispersed in the rubber that does not fully reach the point of contact between the steel wire and the rubber. the

While high carbon steel is preferred for use in tire applications, it is more expensive than comparable low carbon steel. Furthermore, steel wire used in the tire industry is usually produced by drawing the wire to its final diameter. Wires of high carbon steels are generally relatively difficult to draw into properly sized wires compared to mild steels, which results in increased production costs. Furthermore, such filaments currently require separate processing in order to apply coatings or other agents necessary for improved corrosion resistance and rubber adhesion, thereby adding additional processing steps. Tire manufacturers need to bear these additional costs in order to meet tire specifications; however, to produce steel wires with high carbon content, corrosion resistance, and the ability to bond to rubber, it is preferable to start with Increased carbon content as well as corrosion resistance and improved rubber adhesion in a single processing step. In this way, material cost, processing time and number of processing steps can be reduced without sacrificing the benefits of high carbon steel wire processed according to existing methods. the

The present invention solves this problem by proposing a new method and process for the manufacture of high carbon steel wire for useful applications by carburizing low carbon steel wire to increase the carbon content of the wire and during the same process In this method, steel wires are carburized in the presence of appropriate agents for improving corrosion resistance and rubber adhesion. In this way, by means of a process, it is possible to convert cheap low-carbon steel wire into useful, high-carbon, corrosion-resistant steel wire that can be bonded to rubber for a variety of applications. the

Contents of the invention

According to one aspect of the invention, low carbon steel is carburized in the presence of a carburizing agent to produce high carbon steel wire. the

According to another aspect of the invention, a solid carburizing agent is used to carburize low carbon steel wire to form high carbon steel. the

According to yet another aspect of the invention, a liquid carburizing agent is used to carburize low carbon steel wire to form high carbon steel. the

According to another aspect of the invention, a low carbon steel wire is carburized using a gaseous carburizing agent to form a high carbon steel. the

According to another aspect of the invention, low carbon steel wires are carburized in the presence of additives to obtain high carbon steel wires with improved corrosion resistance. the

According to another aspect of the present invention, low carbon steel wires are carburized in the presence of additives to obtain high carbon steel wires with improved rubber adhesion. the

According to another aspect of the invention, the low carbon steel wire is carburized at a temperature of about 1200°C to 1350°C. the

According to another aspect of the present invention, carburized steel wire is rapidly quenched and annealed to produce steel wire that can be used in the manufacture of vehicle tires. the

Other benefits and advantages of the present invention will become apparent to those skilled in the art after reading and understanding the following detailed description. the

Description of drawings

The invention, in certain parts and arrangements of parts, may take certain physical forms, the preferred embodiments of which are described and illustrated in detail in the present specification and in the accompanying drawings which form a part hereof, in which:

Figure 1 depicts the steel wire used for carburizing. the

Figure 2 depicts a cross-section of a steel wire during the carburizing process of the present invention. the

Figure 3 is an image of the microstructure of a steel wire carburized according to the method of the present invention. the

Fig. 4 is another image showing the microstructure of a steel wire carburized according to the method of the present invention. the

Figure 5 is a further image of steel wire carburized according to the method of the present invention. the

Figure 6 depicts a carburized steel wire in a quenching medium. the

Figures 7A-7C show the microstructure of a steel wire carburized according to the method taught in the present invention and in particular in Example 1 below. Fig. 7A is a carburized rolled steel wire. Fig. 7B is the microstructure of the surface area of carburized rolled steel wire. Figure 7C is the microstructure of the carburized steel wire core. the

Figures 8A and 8B show the microstructure of a steel wire carburized according to the method taught in the present invention and in particular in Example 2 below. Figure 8A is a carburized quenched and rolled steel wire. Figure 8B is the microstructure of the surface regions of carburized, quenched, annealed and rolled steel wires. the

Detailed ways

Referring now to the drawings, which are shown for purposes of illustrating preferred embodiments of the invention only and not for purposes of limiting the invention, FIG. 1 depicts a length of steel wire 10 carburized in accordance with the methods described herein. In one embodiment, the length of steel wire 10 shown is a length of mild steel wire. "Low carbon steel wire" means a steel wire having a carbon content of less than about 0.25%. It should be noted that steel wire 10 having any carbon content may be used in accordance with the present invention, including, but not limited to, steel wire having a carbon content of about 0.25% to 0.5%. Although the increase in carbon content obtained by means of carburizing may be correspondingly lower in such higher carbon content steel wires than when using low carbon steel wires, following the methods taught herein, in the presence of corrosion inhibitor 22 or rubber Carburizing process in the presence of mixture 23 can produce other benefits in this wire. the

The wire 10 may have a diameter (d) of about 0.2 millimeters to about 2.0 millimeters, although any diameter wire may be selected with sound engineering judgment. The relatively small diameter (d) of the steel wire 10 allows rapid heating and cooling of the steel wire 10, which increases the speed at which the carburizing process can be performed. The steel wire 10 may be a product of drawing a steel material through a die to reduce the diameter of the steel material. However, the steel wire 10 may be manufactured by any means selected based on sound engineering judgment. While the present invention claims to work on steel wire, it should be noted that the present invention may be practiced on other forms of thin steel material including, without limitation, steel plates having a thickness of about 0.2 mm to about 2.0 mm. the

With continued reference to FIG. 1 , the steel wire 10 may be placed into a container 15 . Vessel 15 may be configured to contain carburizing agent 20 or a carrier medium (not shown) containing carburizing agent 20 . In one embodiment, the support medium can be the same as carburizing agent 20 . The size and material of vessel 15 can be selected based on sound engineering evaluation, and can be fabricated from materials suitable to withstand the temperatures associated with the carburizing process (discussed below). the

It is contemplated that the wire 10 may be longer than the container 15 . In this case, the container may have an inlet and an outlet (not shown), whereby the steel wire 10 can enter the container 15 through the inlet and, after processing, exit the container through the outlet. The wire 10 may be provided on a reel located near the inlet. The spool can be rotated so that steel wire 10 is fed substantially continuously from the spool, through the inlet, into the container 15, where it is carburized, and out of the container 15 through the outlet. A second reel may be provided near the exit for receiving the processed wire 10 . Any means for feeding the steel wire 10 through the vessel 15 may be chosen, depending on sound engineering evaluation. The feed rate of steel wire 10 through vessel 15 should be controlled sufficiently so that the carburizing process is carried out in accordance with the present invention. As discussed below, the steel wire 10 may be quenched after the carburizing process, but before being received onto the second spool. the

In the embodiment depicted in FIG. 1 , carburizing agent 20 may be a liquid carburizing agent. However, it should be understood that the carburizing method of the present invention may be performed using a liquid carburizing agent, a solid carburizing agent, or a gaseous carburizing agent. Examples of liquid carburizing agents include petroleum-based oils, salt baths, and synthetic mixtures, which are well known in the art. Examples of solid carburizing agents include carbon black and powdered graphite. Examples of gaseous carburizing agents include methane, propane, ethylene, acetylene, and carbon monoxide. Other solid, liquid, and gaseous carburizing agents can be used in accordance with the methods disclosed herein, are known in the art and can be selected based on sound engineering evaluation. Additionally, as noted above, the carburizing agent 20 may be contained in a carrier medium (not shown), which may be a solid, liquid, or gaseous carrier medium. the

In one embodiment depicted in FIG. 1 , carburizing agent 20 is a liquid carburizing agent. At least a portion of the steel wire 10 may be immersed in the carburizing agent 20. In one embodiment, the steel wire 10 may be fully submerged in the carburizing agent 20 . Steel wire 10 may be maintained in contact with carburizing agent 20 within container 15 by any means selected through sound engineering evaluation. the

Container 15 may contain other reagents than carburizing agent 20 . For example, container 15 may contain more than one carburizing agent 21 . Additionally, container 15 may contain an anti-corrosion agent 22 . "Anti-corrosion agent" means a material known in the art for improving the corrosion resistance of steel wire. Such materials may include, but are not limited to, materials containing chromium, nickel, vanadium, or titanium. The anti-corrosion agent 22 may be selected from a material capable of bonding to the surface of the steel wire 10 or from a material capable of diffusing into the steel wire 10 . Anticorrosion agent 22 may be mixed with a carrier medium that is the same as that of carburizing agent 20 (if present), or a different carrier medium. the

It should be noted that the increased corrosion resistance of the steel wire 10 can result from the carburizing process without the need for the addition of a separate corrosion inhibitor 22 . The carburizing process of the present invention may result in diffusion of carbon from the carburizing agent 20 into the core of the steel wire 10 (shown in FIG. 2 ). This infiltration of carbon into the wire 10 may result in the formation of a layer of carbon-dense cementite (depicted as 37 in FIGS. 3-5 ) starting at the surface of the wire 10 and extending toward the center of the wire 10 . The cementite layer 37 produced by the carburizing process can increase the strength of the steel wire 10 . The cementite layer 37 provides the steel wire 10 with increased corrosion resistance even in the absence of other anti-corrosion agents 22 . Thus, in the absence of other anti-corrosion agents 22, steel wire 10 processed in accordance with the present invention can be expected to have improved corrosion resistance, but by carburizing the steel wire 10 in the presence of other anti-corrosion agents 22 as described above Further improve corrosion resistance. the

The container 15 may also contain a rubber adhesive agent 23 . "Rubber adhesion agent" means a material known in the art for enhancing the adhesion of rubber and rubber-based compounds to steel wire. Such rubber bonding agents 23 may include, but are not limited to, materials comprising cobalt and copper; however, any such agent selected based on sound engineering evaluation may be used. The rubber binding agent 23 may be selected from materials capable of bonding to the surface of the steel wire 10 or from materials capable of diffusing into the steel wire 10 . The rubber bonding agent 23 may be mixed with a carrier medium which is the same as that of the carburizing agent 20 (if any), or a different carrier medium. the

Although FIG. 1 shows a container 15 containing a carburizing agent 20, an anti-corrosion agent 22, and a rubber bonding agent 23, it should be noted that the present invention may be practiced using only the carburizing agent 20, or using the carburizing agent 20 together with the anti-corrosion agent. Reagent 22 and rubber adhesive agent 23 or a mixture of both to implement. the

With continued reference to FIG. 1 , there is provided a heating device 25 which operates in conjunction with the steel wire 10 for heating the steel wire 10 . The heating device 25 may be an induction heating device or a resistive heating device, although any other device for heating the steel wire 10 to a temperature allowing carburization may be selected with sound engineering judgment. As stated above, the heating device 25 may be an electrical heating device in which electricity is introduced into and passed through the wire 10 as a means of heating the wire 10 . In such an embodiment, one or more electrodes 27, 28, which are connected to different ends of the stylet 10, may be provided. The electrodes 27 , 28 may be connected to a power source for generating electrical current through the stylet 10 . The heating device 25 can also be an oven or a furnace, which can be placed inside the vessel 15 or can be placed outside the vessel 15 . With proper engineering evaluation, any heating device 25 capable of heating the steel wire 10 to a suitable temperature can be selected. the

In one embodiment, the heating device 25 is capable of heating the steel wire 10 to a temperature in excess of about 950°C. In another embodiment, the heating device is capable of heating the steel wire 10 to a temperature of about 1200°C to 1350°C. the

Continuing to refer to FIG. 1 , the steel wire 10 in the container 15 containing the carburizing agent 20 may be heated to a temperature of about 1200° C. to 1350° C. by means of a heating device 25 . Container 15 may also contain one or more anti-corrosion agents 22 and rubber adhesive agents 23, as described above. Anti-corrosion agent 22 or rubber adhesive agent 23 can be added to container 15 when steel wire 10 is heated. Alternatively, anti-corrosion agent 22 or rubber adhesive agent 23 may be added to container 15 before steel wire 10 is heated. In this way it is possible to provide a single processing step for modifying the steel wire 10, wherein the corrosion resistance or rubber adhesion or both of the steel wire 10 are improved in the same heating step used during carburizing. the

As shown in FIGS. 2-5 , heating the steel wire 10 in the presence of the carburizing agent 20 may result in carburization of the steel wire 10 as the carbon of the carburizing agent 20 diffuses through the surface of the steel wire 10 and into the core of the steel wire 10 . Carburizing results in an increase in the carbon content of the steel wire 10, which in turn may result in the conversion of the low carbon steel wire to a high carbon steel wire. The higher temperature (approximately 1200°C-1350°C) reached during the carburizing process can lead to an increased rate of carbon diffusion from the carburizing agent into the steel wire 10, which can lead to a shorter transition from low carbon content to high carbon content. processing time. 3-5 show a cross-section of the steel wire 10 after the carburizing process. The cementite layer 37 is the result of an increased carbon content due to the diffusion of carbon into the steel wire. As mentioned above, the cementite layer 37 is capable of providing corrosion resistance to the steel wire 10 even in the absence of other anti-corrosion agents 22 . The cementite layer 37 also increases the strength of the steel wire 10, with deeper cementite layers 37 being associated with increased strength. Carburization of the steel wire 10 may be allowed to proceed until there is a sufficient cementite layer 37 to provide the steel wire 10 with the required strength. the

When the carburizing process is carried out in the container 15 containing the anti-corrosion agent 22, the anti-corrosion agent 22 or elements thereof may adhere to the surface of the steel wire 10 or diffuse into the steel wire 10 or both, thereby resulting in improved resistance in the steel wire. Corrosive (not shown). In a similar manner, when the carburizing process is carried out in the container 15 containing the rubber-bonding agent 23, the rubber-bonding agent 23 or elements thereof may adhere to the surface of the steel wire 10 or diffuse into the steel wire 10, or both, thereby in An improved bond is created between the steel wire 10 and the rubber compound, which can be used in the steel belt of a tire. It should be noted that sufficient amounts of carburizing agent 20, anti-corrosion agent 22 and rubber bonding agent 23 may be added to container 15 to ensure that these elements are sufficiently absorbed to sufficiently modify steel wire 10 to have the desired level of Strength, corrosion resistance and rubber adhesion. the

As shown in FIG. 6 , the steel wire 10 can be quenched in a quenching medium 35 when the relevant properties of the steel wire 10 , ie, its carbon content, corrosion resistance and rubber adhesion, are properly enhanced. The quench medium 35 may be any quench medium, which may be selected according to sound engineering judgment and may include an oil quench medium or water. Such media 35 are well known in the art for industrial applications. One purpose of the quenching medium 35 is to rapidly cool the steel wire 10 to a temperature below approximately 200° C. and to preserve the grain structure of the steel wire 10 after the carburizing process. the

The carburizing process of the steel wire 10 may result in a steel wire 10 having an increased carbon content. The carbon content of the steel wire 10 may be increased to the level of high carbon steel wire (as defined above). In one embodiment, the carbon content of steel wire 10 may be increased from about less than 0.25% to about 1.3%. As a result of the methods taught herein, the carbon content of steel wire 10 may be increased up to about 4.3%. Furthermore, by introducing an anti-corrosion agent 22 or a cementite layer 37 and a rubber-adhesive agent 23 on the surface of the steel wire 10 or within the steel wire 23, the steel wire 10 can be improved to have increased corrosion resistance and rubber adhesion sex. the

Although the cementite layer (shown as 37 in FIGS. 3-5 ) of the carburized steel wire 10 may cause the steel wire 10 to have increased strength, the cementite layer 37 in the steel wire 10 may also cause the steel wire 10 to have increased brittleness. Accordingly, the carburized steel wire 10 may undergo an additional tempering process in which the steel wire 10 is tempered or annealed to reduce brittleness due to the carburizing process. The tempering process may include successively heating and then cooling the steel wire 10, wherein the steel wire 10 is heated to a temperature of about 200°C to 400°C, and then cooled to a temperature below about 200°C. The tempering cycle of heating and cooling can be repeated. In one embodiment, the tempering process may be repeated up to three times. Additional processing steps, including further reducing the diameter of the wire 10 by drawing, may be performed on the high carbon steel wire produced in accordance with the present invention. the

While this invention has been shown and described with respect to at least one embodiment, it is obvious that considerable alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. Furthermore, while specific features of the invention may have been described above with respect to only one of several illustrated embodiments, those features may be combined with one or more other features of another embodiment, just as for any given It may be required and advantageous for certain applications. the

A more complete understanding of the various aspects of the invention can be had by reference to the following illustrative examples of high carbon steel wire produced in accordance with the invention. While the following examples have specific steps, materials and equipment that can be used in this method to make high carbon steel wire, those skilled in the art will appreciate that many modifications and substitutions can be made. Accordingly, all such modifications, changes, substitutions and additions are considered to be within the spirit and scope of the present invention as defined by the appended claims. the

Example 1 - Liquid carburizing. the

Carburizing experiments were carried out by heating steel wires in engine oil by means of resistance heating. A 6" long mild steel wire with 0.2% carbon and 2 mm diameter was clamped between two electrodes and submerged in a 12" x 4" x 4" stainless steel vessel. The heating of the steel wire is performed using both direct current and alternating current. After the wire was heated and cooled in the oil, it was removed from the container and the oil was cleaned. Carburized samples were mounted in conductive epoxy mounts, polished, and Nital etched to reveal the microstructure of the processed wire. The microstructure of the processed steel wires was investigated in a Leica optical microscope and a Jeol scanning electron microscope. Figures 3 and 4 show the obtained microstructure consisting of pearlite and mainly cementite. This microstructure is typical for carbon contents close to the eutectic composition of 4.3% carbon. It provides a unique combination of the high strength characteristics of cementite and the ductility of pearlite. In addition, a specific residue deposited at the surface provides improved steel-rubber adhesion. the

Example 2 - Solid Carburization. the

4" steel wires with a carbon composition of 0.2% and a diameter of 0.2 to 1.5 mm are packed with carbon black in a ceramic ladle with a lid. They are heated in a tube furnace at a temperature of 950° C. to 1350° C. for 5 to 30 Min. The processed sample was cleaned and a metallographic sample was prepared as discussed above in Example 1. Characterization of the obtained microstructure showed the presence of a cementite layer in the surface region of the steel wire, which for a steel wire having about 1.3% carbon A pro-eutectic steel with a content of 0.5% is typical. This cementite layer increases the corrosion resistance of the steel. The obtained wire is rolled in a wire mill to evaluate the processability of the wire. A true strain of up to 2 , without breaking of the wire. Figure 7A shows the transition section of the rolled wire between the initial wire diameter (non-rolled) and the part (rolled section) with reduced diameter. Figure 7B and 7C show respectively Microstructure of surface layer and wire core. Some carburized wires were quenched with water and then annealed at 600°C for 30 to 120 minutes. The wires in the quenched state were brittle and cracks appeared during wire rolling (Fig. 8A and 8B). Annealing leads to increased ductility of the steel wire, allowing rolling without cracks. The microstructure of the obtained tempered steel wire (i.e. quenched and annealed steel wire) shows a typical spherical pearlite structure in the surface layer. In the steel wire core In , the microstructure remains predominantly ferrite, with some pearlite clusters typical for low carbon steels. 

Claims (10)

1. be used to improve the method for the steel wire that is used for the vehicle tyre structure, described method is characterised in that to have following steps:

One section steel wire is provided, and it has the carbon content that is in first carbon level,

At least the first carburizing agent is provided,

At least the first rubber adhesion reagent is provided, the material that this first rubber adhesion reagent is selected from the material on the surface that is adhered to steel wire or diffuses into steel wire,

At least the first carburizing agent is contacted with described one section steel wire with at least the first rubber adhesion reagent,

Be provided for heating the heating installation of described one section steel wire,

Operationally described heating installation is combined with described one section steel wire,

With described one section steel wire heating to first temperature, wherein said first temperature between 950 ℃ and 1350 ℃ and

The described one section steel wire of heating is in second carbon level up to the carbon content of described one section steel wire under first temperature, and wherein second carbon level is higher than first carbon level.

2. the method for claim 1 it is characterized in that the diameter that described one section steel wire has 0.2 millimeter to 2.0 millimeters, and first carbon level of described one section steel wire is lower than 0.5%.

3. the method for claim 2 it is characterized in that first carbon level of described one section steel wire is lower than 0.25%, and second carbon level of described one section steel wire is higher than 0.6%.

4. the method for claim 3 is characterized in that first temperature is 1200 ℃ to 1350 ℃.

5. the method for claim 4 is characterized in that described at least the first carburizing agent is selected from solid carburizing reagent, liquid carburizing reagent and gas cementation reagent, and

The described at least the first rubber adhesion reagent is selected from the copper bearing rubber adhesion reagent of bag and comprises the rubber adhesion reagent of cobalt.

6. the method for claim 4 is further characterized in that to have the step that described one section steel wire is quenched into second temperature, wherein said second temperature be lower than 200 ℃ and

With described one section steel wire tempered step.

7. the method for claim 1 is further characterized in that to have following steps: provide at least the first anticorrosive reagent and

Before the step of first temperature described at least the first anticorrosive reagent is contacted with described one section steel wire described one section steel wire heating, described anticorrosive reagent is selected from the material on the surface that is adhered to steel wire or diffuses into the material of steel wire.

8. the steel wire that has the rubber adhesion of raising, it is by being characterised in that the method preparation with following steps:

One section steel wire is provided, and it has the carbon content that is in first carbon level, and wherein first carbon level is lower than 0.50%,

At least the first carburizing agent is provided,

At least the first rubber adhesion reagent is provided, the material that this first rubber adhesion reagent is selected from the material on the surface that is adhered to steel wire or diffuses into steel wire,

At least the first carburizing agent is contacted with described steel wire with at least the first rubber adhesion reagent,

Be provided for heating the heating installation of described one section steel wire,

Operationally described heating installation is combined with described one section steel wire,

With described one section steel wire heating to first temperature in steel wire, generating cementite lamella, wherein said first temperature between 1200 ℃ and 1350 ℃,

The described one section steel wire of heating is in second carbon level up to the carbon content of described one section steel wire under first temperature, and wherein said second carbon level is higher than 0.6%,

Described one section steel wire is quenched into is lower than 200 ℃ second temperature.

9. the steel wire of claim 8 is characterized in that first carbon level of described one section steel wire is lower than 0.25%.

10. the steel wire of claim 8 is characterized in that described second carbon level is higher than 1.0%.

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