KR20150089846A - Spring and method of manufacturing the same - Google Patents

Abstract

The present specification discloses a spring and a manufacturing method thereof. According to the present invention, the spring is composed of 0.52-0.56 wt% of C, 1.50-1.60 wt% of Si, 0.6-0.8 wt% of Mn, 0.01 wt% or less of P, 0.005 wt% or less of S, 0.65-0.75 wt% of Cr, 0.27-0.32 wt% of Ni, 0.01-0.03 wt% of Mo, 0.07-0.10 wt% of V, 0.02-0.03 wt% of Nb, 0.03-0.06 wt% of Ti, 0.27-0.32 wt% of Cu, 0.03-0.05 wt% of Al, 0.0005-0.0025 wt% of B, 0.001 wt% or less of O, 0.005 wt% or less of N, and a remaining amount of Fe and impurities.

Description

[0001] SPRING AND METHOD OF MANUFACTURING THE SAME [0002]

More particularly, the present invention relates to a spring having excellent durability and impact toughness, and a method of manufacturing the spring.

The spring absorbs shocks and vibrations transmitted from the outside to prevent it from being transmitted to other parts.

For example, it effectively absorbs and disperses shocks and vibrations transmitted from the road surface when the vehicle is driven in a vehicle suspension system.

Since these springs must be strong against fatigue, high tensile strength is basically required, and hardness and impact toughness should be excellent.

As a background technique related to the present invention, Korean Patent Registration No. 10-0328087 (published on Apr. 17, 2002) discloses a steel for a high-stress spring having excellent cutting workability and a method for manufacturing a spring using the steel. .

An object of the present invention is to provide a spring having excellent strength, hardness, corrosion resistance and impact toughness, and a method of manufacturing the same.

In order to achieve the above object, the present invention provides a method of manufacturing a spring, comprising: (a) 0.52 to 0.56% of carbon (C), 1.50 to 1.60% of silicon (Si) (P): 0.01% or less, sulfur (S): 0.005% or less, chromium (Cr): 0.65 to 0.75%, nickel (Ni): 0.27 to 0.32%, molybdenum (Mo) 0.02 to 0.03 wt% of vanadium (V), 0.07 to 0.10 wt% of niobium (Nb), 0.03 to 0.06 wt% of titanium (Ti), 0.27 to 0.32 wt% of copper (Cu) (B): 0.005 to 0.0025% by weight, oxygen (O): 0.001% or less, nitrogen (N): 0.005% or less and the balance of iron (Fe) and unavoidable impurities; And (b) post-treating the molded product.

The step (a) may include heating the steel wire to form a spring shape in the hot state, performing a quenching process on the resultant product, and blanching the quenched product.

In addition, the step (b) may include a step of pre-setting the formed product by applying a compressive force, a step of sharpening the surface by shot peening the primary preset product, And a second pre-setting step of applying compression force to the shot-pinned product.

In order to achieve the above object, the spring according to an embodiment of the present invention includes 0.52 to 0.56% of carbon (C), 1.50 to 1.60% of silicon (Si), 0.6 to 0.8% of manganese (Mn) P): not more than 0.01%, sulfur (S): not more than 0.005%, chromium (Cr): 0.65 to 0.75%, nickel (Ni): 0.27 to 0.32%, molybdenum (Mo) : 0.07 to 0.10%, niobium (Nb): 0.02 to 0.03%, titanium (Ti): 0.03 to 0.06%, copper (Cu): 0.27 to 0.32% ) Of 0.0005 to 0.0025% by weight, oxygen (O) of 0.001% or less, nitrogen (N) of 0.005% or less and balance of iron (Fe) and unavoidable impurities, (HRC): 55 or more, and an impact value of 55J or more.

According to the method for manufacturing a spring according to the present invention, it is possible to control an alloy component such as molybdenum, niobium, vanadium, nickel, copper and the like, a spring forming process and a post treatment process control to obtain excellent tensile strength of 2100 MPa or more, excellent hardness, Can be manufactured.

Therefore, the spring according to the present invention is usefully applied to suspension devices of automobiles and the like.

1 schematically shows a method of manufacturing a spring according to an embodiment of the present invention.
2 schematically shows a method of manufacturing a spring when hot spring forming is used.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Hereinafter, a spring according to a preferred embodiment of the present invention and a method of manufacturing the same will be described in detail with reference to the accompanying drawings.

spring

The spring according to the present invention is, for example, a coil spring which comprises 0.52 to 0.56% of carbon (C), 1.50 to 1.60% of silicon (Si), 0.6 to 0.8% of manganese (Mn) 0.01% or less of sulfur, 0.005% or less of sulfur, 0.65 to 0.75% of chromium, 0.27 to 0.32% of nickel, 0.01 to 0.03% of molybdenum, 0.10%, niobium (Nb): 0.02-0.03 wt%, titanium: 0.03-0.06%, copper: 0.27-0.32%, aluminum (Al): 0.03-0.05%, boron (B) To 0.0025% by weight, oxygen (O): 0.001% or less, and nitrogen (N): 0.005% or less.

The rest of the alloying components are composed of iron (Fe) and unavoidable impurities generated in the steelmaking process.

Hereinafter, the role and content of each component included in the spring according to the present invention will be described.

Carbon (C)

Carbon (C) contributes to securing the strength of the spring through incineration.

The carbon preferably comprises 0.52 to 0.56% by weight of the total weight of the spring. When the content of carbon is less than 0.52% by weight, the incombustibility is insufficient. On the contrary, when the carbon content exceeds 0.56% by weight, impact toughness is deteriorated.

Silicon (Si)

The role of silicon in the springs is enhanced in the ferrite to enhance the strength of the base material and also to improve fatigue properties and resistance to permanent deformation through stabilization of the epilone carbide precipitates.

Preferably, the silicone is added in an amount of 1.5 to 1.6 wt% of the total weight of the spring. If the addition amount of silicon is less than 1.5% by weight, the effect of adding silicon may be insufficient. On the other hand, when the amount of silicon added exceeds 1.6% by weight, there is a fear of occurrence of permanent deformation resistance saturation and surface decarburization in the heat treatment.

Manganese (Mn)

Manganese (Mn) contributes to securing strength by improving the incombustibility in the manufacture of springs.

The manganese is preferably added in an amount of 0.6 to 0.8% by weight based on the total weight of the spring. If the manganese content is less than 0.6 wt%, the effect of the addition is insufficient. On the other hand, when the amount of manganese added exceeds 0.8% by weight, there is a problem in that the impact toughness is lowered.

Phosphorus (P), sulfur (S)

Phosphorus (P) is segregated at crystal grain boundaries, which causes a decrease in impact toughness. In the present invention, the content of phosphorus is limited to not more than 0.01% by weight of the total weight of the spring.

Sulfur (S) segregates as a low-melting point element to lower the impact toughness and form an emulsion, which has a detrimental effect on the spring characteristics. Therefore, the content of sulfur in the present invention is limited to 0.005% by weight or less.

Chromium (Cr)

Chromium lowers the diffusion rate of carbon to suppress surface decarburization and contributes to securing strength in manufacturing springs through improved ingotability.

The chromium is preferably added in an amount of 0.65 to 0.75% by weight based on the total weight of the spring. When the addition amount of chromium is less than 0.65% by weight, the effect of addition is insufficient. On the other hand, when the addition amount of chromium exceeds 0.75% by weight, the brittleness may increase and the resistance to permanent deformation may deteriorate.

Nickel (Ni)

Nickel (Ni) contributes to strength improvement through the solid solution strengthening effect.

The nickel is preferably added in an amount of 0.27 to 0.32% by weight based on the total weight of the spring. When the addition amount of nickel is less than 0.27% by weight, the effect of the addition is insufficient. On the contrary, when the addition amount of nickel exceeds 0.32 wt%, the fatigue characteristics may be deteriorated.

Molybdenum (Mo)

Molybdenum (Mo) contributes to improvement of strength at room temperature and high temperature, improvement of impact toughness, and also contributes to enhancement of resistance to permanent deformation.

The molybdenum is preferably added in an amount of 0.01 to 0.03% by weight based on the total weight of the spring. If the addition amount of molybdenum is less than 0.01% by weight, the effect of the addition is insufficient. On the other hand, if the amount of molybdenum added exceeds 0.03% by weight, the moldability may be deteriorated in the production of springs.

Vanadium (V), niobium (Nb)

Vanadium (V) and niobium (Nb) contribute to the strength improvement through grain refinement.

The vanadium is preferably added in an amount of 0.07 to 0.1% by weight based on the total weight of the spring. If the addition amount of vanadium is less than 0.07% by weight, the effect of the addition is insufficient. On the contrary, when the addition amount of vanadium exceeds 0.1 wt%, the fatigue characteristics of the spring may be deteriorated by the formation of coarse carbonitride.

The niobium is preferably added in an amount of 0.02 to 0.03% by weight based on the total weight of the spring. When the addition amount of niobium is less than 0.02% by weight, the effect of addition thereof is insufficient. On the other hand, when the addition amount of niobium exceeds 0.03% by weight, fatigue characteristics of the spring can be lowered by formation of coarse carbonitride.

Copper (Cu)

Copper (Cu) contributes to securing strength through the solid solution strengthening effect, and copper also plays a role of improving the corrosion resistance of the spring through suppressing generation of pits.

The copper is preferably added in an amount of 0.27 to 0.32 wt% of the total weight of the spring. When the addition amount of copper is less than 0.27% by weight, the effect of the addition is insufficient. On the contrary, when the addition amount of copper exceeds 0.32% by weight, the surface quality of the spring surface can be lowered by surface enrichment.

Titanium (Ti), aluminum (Al)

Titanium (Ti) plays a role in making carbonitride and making crystal grains finer.

The titanium is preferably added in an amount of 0.03 to 0.06% by weight based on the total weight of the spring. If the addition amount of titanium is less than 0.03% by weight, the effect of the addition is insufficient. On the contrary, when the addition amount of titanium exceeds 0.06% by weight, coarse carbonitrides are formed.

Aluminum (Al) acts as a deoxidizing agent and contributes to grain refinement like titanium.

The aluminum is preferably added in an amount of 0.03 to 0.05 wt% of the total weight of the spring. When the addition amount of aluminum is less than 0.03% by weight, the effect of addition is insufficient. On the contrary, when the added amount of aluminum exceeds 0.05% by weight, coarse carbonitride is formed.

Boron (B)

The boron (B) can contribute to improve the incombustibility even when only 0.0005 wt% is added, and addition of boron also enhances the corrosion resistance by densifying the rust formed on the surface. However, when the addition amount of boron exceeds 0.0025% by weight, the carbonitride-based precipitates are coarsened and adversely affect the fatigue characteristics. Therefore, boron is preferably added in an amount of 0.0005 to 0.0025% by weight of the total weight of the spring.

Oxygen (O), nitrogen (N)

Oxygen (O) becomes a nonmetallic inclusion (oxide), which causes the fatigue characteristics of the spring to deteriorate. Therefore, the content of oxygen in the present invention is limited to 0.001 wt% (10 wt ppm) or less of the total weight of the spring.

Nitrogen (N) forms a nitride by bonding with titanium, aluminum or the like to contribute to grain refinement, but if it is contained in large amounts, fatigue characteristics are deteriorated due to coarsening of nitride.

In the present invention, the content of nitrogen is limited to 0.005 wt% (50 wt ppm) or less of the total weight of the spring.

The spring according to the present invention can exhibit a tensile strength of 2100 MPa or more, an elongation of 8% or more, a Rockwell hardness (HRC) of 55 or more, and an impact value of 55 J or more by the above alloy composition and the spring forming process and post- .

How to make spring

Hereinafter, a method of manufacturing a spring according to the present invention will be described.

1 schematically shows a method of manufacturing a spring according to an embodiment of the present invention.

Referring to FIG. 1, a method of manufacturing a spring according to the present invention includes a spring forming step (S110) and a post-processing step (S120).

The spring forming step S110 forms the steel wire having the above-described alloy composition into a spring shape, for example, a coil spring shape. The forming can be carried out by hot forming as in the example shown in Fig.

The post-treatment step S120 is performed to improve the elastic limit of the spring and the surface hardness. This post-processing step may include pre-setting, shot peening as in the example shown in Fig.

2 schematically shows a method of manufacturing a spring when hot spring forming is used.

Referring to FIG. 2, the illustrated spring manufacturing method includes a hot spring forming step S211, a quenching processing step S212, a blanket processing step S213, a first pre-setting step S221, a shot peening step S222, And a second pre-setting step S223.

In the hot spring forming step (S211), the steel wire having the alloy component according to the present invention is heated to a temperature not less than the phase change temperature and formed into a spring shape in the hot state.

In the quenching process step S212, quenching is performed to improve the strength of the resultant product. The quenching treatment may be performed in such a manner that the molded product is heated to 850 to 1000 占 폚, held for 30 seconds to 10 minutes, and cooled at an average cooling rate of 200 占 폚 / sec or more.

In the blooming process step S213, in order to eliminate the increase in brittleness due to the brittle process, the brittle process is performed. The bake processing may be performed by, for example, maintaining the quenched product at 350 to 600 ° C for 1 to 3 hours.

In the first pre-setting step S221, a compressive load is applied to the result of the completion of the quenching / blanket process to cause permanent deformation of a certain portion, thereby increasing the elastic limit of the spring.

In the shot peening step (S222), hard particles are sprayed onto the first pre-set result to remove the oxide film on the surface of the material and to smooth the surface to improve the hardness.

In the second pre-setting step S223, as in the case of the first pre-setting, a compression load is applied to the result of the completion of the shot peening to induce permanent deformation of a certain portion, thereby increasing the elastic limit of the spring.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

1. Manufacture of springs

The steel wire having the alloy composition shown in Table 1 was subjected to hot spring forming at 850 占 폚, holding at 950 占 폚 for 5 minutes, quenching for quenching, bake treatment for maintaining at 400 占 폚 for 2 hours, primary presetting, The springs according to Example 1, Comparative Example 1 and Comparative Example 2 were prepared.

[Table 1]

2. Property evaluation

Tensile test, Rockwell hardness, impact toughness test, and inner pit generation test were carried out on the specimens prepared according to Examples 1 to 2 and Comparative Examples 1 to 2, and the results are shown in Table 2.

[Table 2]

In the case of the spring according to the first and second embodiments which satisfy the alloy composition range according to the present invention, the tensile strength is 2100 MPa or more, the elongation is 8% or more, the Rockwell hardness (HRC) is 55 or more, Respectively.

On the other hand, in the case of the spring according to Comparative Example 1 in which molybdenum was not added, the strength was relatively low and the impact value was less than 55J.

Also, in the case of the spring according to Comparative Example 2 in which molybdenum was excessively added, it was confirmed that a crack occurred in the spring. In addition, in the case of Comparative Example 2, the amount of copper added was relatively low, and as a result, the depth of the pit was relatively large and was vulnerable to corrosion.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. Such changes and modifications are intended to fall within the scope of the present invention unless they depart from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.

Claims (4)

(S): not more than 0.01% of phosphorus (P), not more than 0.01% of phosphorus (P) (Ni): 0.07 to 0.32%, molybdenum (Mo): 0.01 to 0.03%, vanadium (V): 0.07 to 0.10%, niobium (Nb): 0.02 (B): 0.0005 to 0.0025% by weight, oxygen (O): 0.03% by weight, titanium (Ti): 0.03 to 0.06%, copper (Cu): 0.27 to 0.32% : 0.001% or less, nitrogen (N): 0.005% or less, and the remaining iron (Fe) and unavoidable impurities; And
(b) post-processing the formed product.
The method according to claim 1,
The step (a)
Heating the steel wire to form a spring shape in the hot state;
Performing a quenching process on the molded product;
And squeezing the result of the quenching process.
The method according to claim 1,
The step (b)
A first pre-setting step of applying a compressive force to the molded product,
Performing a shot peening of the primary pre-set result to train the surface,
And applying a compressive force to the result of the shot peening to perform second presetting.
(S): not more than 0.005% by weight (% by weight), carbon (C): 0.52 to 0.56%, silicon (Si): 1.50 to 1.60%, manganese 0.65 to 0.75% of chromium (Cr), 0.27 to 0.32% of nickel (Ni), 0.01 to 0.03% of molybdenum (Mo), 0.07 to 0.10% of vanadium (V), 0.02 to 0.03 of niobium (B): 0.0005 to 0.0025%, oxygen (O): 0.001%, titanium (Ti): 0.03 to 0.06%, copper (Cu): 0.27 to 0.32% (N): 0.005% or less and balance of iron (Fe) and unavoidable impurities, characterized by exhibiting a tensile strength of 2100 MPa or more, an elongation of 8% or more, a Rockwell hardness (HRC) of 55 or more, Spring.

Images