KR0162964B1 - The manufacturing of hydraulic breaker chisel material - Google Patents

Abstract

The present invention relates to a method for manufacturing a hydraulic breaker chisel material, the chemical composition of carbon: 2.8-3.4wt%, silicon: 2.0-2.5wt%, manganese: 0.3wt% or less, nickel: 1.0-3.0wt%, molybdenum : 0.1-0.3wt%, copper: 0.5-2.0wt%, the remainder is subjected to a predetermined heat treatment process of the spheroidal graphite iron raw material consisting of Fe, the base structure mixed with the upper bainite and residual austenite It has a spherical graphite structure in the middle, so that high strength / toughness and abrasion resistance can be obtained at the same time.

Description

Manufacturing Method of Hydraulic Breaker Chisel Material

1 is an enlarged photograph of a tissue cross section of a conventional hydraulic breaker chisel material 400 times.

2 is an enlarged photograph 400 times the tissue cross section of the material for the hydraulic breaker chisel according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a chisel material for a hydraulic breaker, and more particularly, to a spherical graphite cast iron having strength and abrasion resistance suitable for use as a material for a hydraulic breaker chisel used for crushing rock or soil. It relates to a manufacturing method.

In general, the hydraulic breaker is used for the excavation work is mounted on the arm end of the excavator is to be crushed by the impact force generated by continuously hitting the upper end of the chisel while the piston rod actuated by the hydraulic up and down repeated movement.

At this time, the chisel has the characteristics required for the hydraulic breaker chisel material of heavy construction equipment such as excavators from the piston rod, which can withstand high wear resistance, high strength to withstand high loads during crushing work, and high impact force acting on the chisel during crushing work. Impact resistance is required.

Table 1 shows the chemical constituents of representative practical materials that have been conventionally used to exhibit such characteristics.

In Table 1, prior art material 1 is SCM440-based alloy steel to which a small amount of alloying elements such as Ni, Cr, and Mo is added to increase hardenability by quenching and tempering heat treatment. In order to improve the strength and abrasion resistance, the conventional SCM440 steels have increased the components of C and Si, and Ni, V, and Al are added.

However, the conventional chisel material, as well known, not only breakage easily occurs during rock crushing operation but also low wear resistance has a problem of increasing the economic burden of the user only 3 months or less.

In addition, in recent years, the performance of heavy equipment is also required, and the need for highly tough materials that are more wear-resistant than conventional materials and particularly difficult to break even in rock crushing operations is increasing.

Accordingly, the present invention is to solve the above problems, the hydraulic breaker for chisels having high strength and toughness that can withstand high impact loads, which is required for the chisel material of heavy equipment such as excavators It is an object to provide a method for producing a material.

In order to achieve the above object, the method for producing a high strength, wear resistant material of the present invention comprises preheating spherical graphite iron material at 500-600 ° C. for 2 to 3 hours in a salt bath or in an inert atmosphere, and 900-930 ° C. Austenitic heating in a salt bath or in an inert atmosphere for a predetermined time, followed by rapid cooling to 380-420 ° C. in a salt bath to perform an ostempering constant temperature heat treatment.

In another embodiment of the present invention, the spheroidal graphite iron raw material, carbon: 2.8-3.4wt%, silicon: 2.0-2.5wt%, manganese: 0.3wt% or less, nickel: 1.0-3.0wt%, molybdenum: 0.1 It contains -0.3wt%, and remainder is a spherical graphite cast iron raw material consisting of Fe.

In another embodiment, the chemical composition of the raw material is characterized in that it further comprises 0.5-2.0wt% copper.

At this time, it is preferable to heat-treat using the spherical graphite cast iron raw material of the chemical composition which contained a trace amount of P below 0.03% and S below 0.02% in the said chemical component.

Spheroidal graphite cast iron prepared according to the present invention has a spherical graphite structure in the base structure mixed with the upper bainite and residual austenite, can be obtained simultaneously with high strength, high toughness and wear resistance characteristics used as a hydraulic breaker chisel It is suitable to do.

The following describes a heat treatment process and conditions for producing a high strength wear resistant material of the present invention.

The raw material of spherical graphite iron is heat-treated in the following preheating step, austenite heating step, and austempering step, and the conditions thereof will be described in detail below.

1) Preheating process

Preheating process is necessary to prevent deformation of the product is maintained for 2-3 hours at the temperature of 500-600 ℃ bar temperature is limited to 500-600 ℃ because the growth of the graphite structure occurs above 600 ℃.

The retention time depends on the size and thickness of the product, but is based on 40 minutes per 25mm product thickness.

In addition, during preheating, a salt bath or an inert atmosphere is used to prevent decarburization of the surface.

2) heating process

The heating process is a process of austenite tissue, which is maintained at a temperature of 880-900 ° C. for 2-3 hours or more. If the heating temperature exceeds 930 ° C., coarsening of the base structure occurs, and thus the temperature is 880-900 ° C. Limit to ℃.

The retention time depends on the size and thickness of the product, but is based on 40 minutes per 25mm product thickness.

On the other hand, heating is performed in a salt bath or in an inert atmosphere to prevent decarburization of the surface.

3) Ostempering process

In this step, the austenitic tissue is quenched in a tempering temperature of 380-420 ° C. salt bath, and constant temperature transformation is performed in this temperature range to change the matrix structure from austenite to a dense, tough upper bainite structure. to be.

In this case, when the holding temperature of the constant temperature transformation is 380 ° C. or lower, the toughness of the bainite structure is lowered. When the temperature is set to 420 ° C. or higher, a structure called a pearlite is formed, which makes it difficult to secure strength and wear resistance. Limit to 380-420 ° C.

Next, the range and limitation reason of content of the chemical component of this invention and each alloying element are demonstrated.

1) carbon

Carbon is an element that affects the determination of spheroidal graphite by working with silicon. It affects castability, Chilling tendency, size distribution of spheroidal graphite and matrix structure. In thick castings, coarse crystallization of coarse graphite easily occurs, and castability is poor when the content is 2.8 wt% or less, and therefore the range is limited to 3.4 to 2.8 wt%.

2) silicon

Silicon is an element that ferrites the matrix structure of raw materials and promotes the crystallization of spheroidal graphite.In the case of thicker castings such as chisels, the casting rate is lower than 2.0wt% and the cooling rate is slower than 2.5wt%. It is possible to form a glass ferrite that can cause a graphite flotation defect, which is a kind of defect, and its content is limited to 2.0-2.5st%.

3) manganese

Manganese is a carbide-forming element, which forms a compound called MnS to remove sulfur, forming a compound called MnS, which is effective for graphitization. Since it promotes the formation of nit (grain boundry Austenite), the content is lowered as much as possible and limited to within 0.3wt%.

4) sulfur

Sulfur is an element harmful to the production of the spheroidal graphite iron raw material of the present invention, and because of its high affinity with Mg, sulfur is limited to 0.03wt% or less.

5) phosphorus

Phosphorus is a trace element incorporated in raw materials, and when it contains 0.04 wt% or more, it forms a low melting three-way process called Fe-FeC-FeP in a steadite structure, causing hot strength reduction and brittleness. The content is limited to below wt%.

6) copper

Copper improves the hardenability during constant temperature transformation heat treatment, and the effective content range for improving the hardenability of heat treatment is 0.5wt%, and when it is more than 2.0wt%, the tendency of chill is increased during casting, so the content range is 0.5-2.0. Limit to wt%.

7) nickel

As an element having an effective effect in the production of high strength wear-resistant material of the present invention, it improves the curing ability during constant temperature transformation heat treatment, suppresses the formation of carbides and does not cause segregation, the effective range for improving the heat treatment curing ability is 1.0-3.0wt %to be.

8) Molybdenum

Molybdenum improves the hardenability in constant temperature transformation heat treatment, but in the case of thicker castings such as chisel above 0.3wt%, the brittleness of the tissue is increased by grain boundary segregation during casting, so the content range is limited to 0.1-0.3wt%. .

EXAMPLE

The charged material was melted in an electric furnace (high frequency induction furnace), melted at 1520 ° C, melted at 1500 ° C, and spheroidized at this temperature to cast a spherical graphite cast chisel material.

The chemical composition of the raw material is shown in Table 2 below.

In this case, Example 1 includes 1.0 wt% of copper and 1.0 wt% of nickel. In Example 2, it contains 2.0 wt% of nickel, and copper is inevitably mixed in the process. To know the effect.

In Table 2, Examples 1 and 2 each contain a small amount of phosphorus, sulfur, and magnesium, which are inevitably incorporated in the manufacturing process, and in particular, the phosphorus and sulfur have their contents as described in the above reason for limiting the ingredient content. It is limited to 0.04wt% and 0.03wt% or less, respectively, but magnesium is required for spherical graphite, the content is not particularly limited.

The chisel material of the chemical composition was heat-treated under the heat treatment conditions shown in Table 3 to prepare a high-strength, high toughness wear resistant material for the chisel.

The mechanical properties of Examples 1 and 2 thus obtained are shown in Table 4 below in comparison with the conventional examples.

From Table 4, it can be seen that Example 1 containing less copper and less nickel has better tensile strength, yield strength and hardness than Example 2 containing less copper and more nickel, and it is carried out only at elongation. Since Example 2 is high, it can be seen that including copper and containing less nickel improves mechanical cleavage.

In addition, it can be seen that Examples 1 and 2 have high strength and high toughness which are excellent in wear resistance and impact resistance compared to conventional materials.

What has been described above is merely a mere example in all respects, and should not be construed as limited thereto, and all modifications existing within the true spirit and scope of the present invention shall fall within the claims of the present invention.

Claims (2)

Spheroidal graphite cast iron containing carbon: 2.8-3.4wt%, silicon: 2.0-2.5wt%, manganese: 0.3wt% or less, nickel: 1.0-3.0wt%, molybdenum: 0.1-0.3wt% The raw material is preheated in an inert atmosphere at a temperature of 500-600 ° C. for 2 to 3 hours and then austenitic heated at 900-930 ° C. for 3 hours, and then quenched to 380-420 ° C. in a salt bath. A method of manufacturing a material for a hydraulic breaker chisel, characterized in that subjected to constant temperature heat treatment for 3 hours. Carbon: 2.8-3.4wt%, Silicon: 2.0-2.5wt%, Manganese: 0.3wt% or less, Nickel: 1.0-3.0wt%, Molybdenum: 0.1-0.3wt%, Copper: 0.5-2.0wt% The remaining spheroidal graphite cast iron material consisting of Fe is preheated in an inert atmosphere at a temperature of 500-600 ° C. for 2 to 3 hours, and then austenitic heated at a temperature of 900-930 ° C. for 3 hours, and then into a salt bath. Quenching at 380-420 ℃ in a method for producing a hydraulic breaker chisel material, characterized in that subjected to an osmosis constant temperature heat treatment for 3 hours.