KR100344531B1 - Composition for manufacturing bolts/nuts for KP mechanical joint and bolts /nuts thereof - Google Patents

Abstract

The present invention relates to a composition for manufacturing bolts / nuts for KP mechanical joints and bolts / nuts thereof, wherein the carbon content is 0.20% by weight or less, manganese 1.25% by weight, sulfur 0.05% by weight, chromium 0.8% by weight, Nickel 0.25% by weight or more, 0.20% by weight of copper, the remainder is composed of iron, and the composition is used as a bolt / nut for KP mechanical joints to maintain excellent corrosion resistance. It has a superior effect to facilitate machinability and other mechanical properties than nuts.

Description

Composition for manufacturing bolts / nuts for KP mechanical joint and bolts / nuts}

The present invention relates to a composition for manufacturing bolts / nuts for KP mechanical joints and their bolts / nuts, and more particularly, to maintains excellent corrosion resistance and is more machinable than conventional nodular cast iron bolts / nuts. And a composition for manufacturing bolts / nuts for captive mechanical joints which can facilitate the mechanical properties and other bolts / nuts thereof.

In general, a ductile iron pipe is generally used as a pipe used for transporting water such as tap water, industrial water, agricultural water, sewage, etc. under pressure or no pressure by pipe to ground or in the ground.

However, these ductile cast iron pipes have a number of disadvantages in corrosion resistance, workability and economic efficiency such as corrosion and corrosion occurred in the coastal area and wetland piping.

Accordingly, the use of the ductile cast iron pipe is the same, but the pipe is developed to improve the corrosion resistance, workability and economical disadvantages of the current polyethylene pipe for water is currently widely used.

This water polyethylene pipe is piped with parts consisting of KP type polyethylene straight pipe connection and joint, pressure ring, rubber ring, bolt, nut. For pipe work, first, insert the pressure ring and rubber ring at the end of the pipe, insert the pipe to be inserted into the straight pipe connection part, and then close the rubber ring and the pressure wheel to the straight pipe connection part, and then combine the straight pipe connection part and the pressure ring and compress it with a box range. Is complete.

Bolts and nuts used in such piping work is usually made of FCD material. FCD is spheroidal graphite cast iron, which spheroidized graphite by adding a small amount of magnesium (Mg) or cobalt (Co) to cast iron (Fe), and is particularly close to steel.

However, the existing spherical graphite cast iron bolts / nuts (FCD 2 types) have the following problems.

First, the bolts / nuts are sand castings, which have a high frequency of internal and external defects, and are poor in workability due to internal and external defects due to thread accuracy and roughness. In addition, the difference between the lot by the casting technology increases the strength is not constant, there is a problem that the strength is higher than necessary. In addition, it is weak to external force during external impact, side pressure and tension, and is inadequate to temperature change. In addition, the production cost is high, it is uneconomical, there is a problem that the occurrence of defects according to the skill of the operator when assembling the bolt due to excessive generation of the acid of the bolt when tightening the nut.

The present invention has been made in view of the above-described problems of the prior art, and maintains excellent corrosion resistance and bolt / nut for KP mechanical joints that can facilitate the machinability and other mechanical properties than the existing spherical graphite cast iron bolt / nut It is an object to provide a composition for preparation.

It is another object of the present invention to provide a bolt / nut for a KP mechanical joint that can be prepared from the composition.

The above object of the present invention is a cape rice composed of 0.20% by weight of carbon, 1.25% by weight of manganese, 0.05% by weight of sulfur, 0.8% by weight of chromium, 0.25% by weight of nickel and 0.20% by weight of copper. It can be achieved by providing a composition for making bolts / nuts for chemical joints.

Another object of the present invention can be achieved by providing bolt / nuts for KP mechanical joints that can maintain excellent corrosion resistance and can facilitate machinability and other mechanical properties than existing spherical graphite cast iron bolts / nuts.

Hereinafter, although the specific structure and effect of this invention are demonstrated, it is a matter of course that the scope of the present invention also changes the kind and numerical value of the component which comprise the composition for manufacturing the bolt / nut for KP mechanical joint of this invention.

Hereinafter, the structure of the bolt / nut composition for KP mechanical joint of this invention is demonstrated.

Looking at the chemical composition of the bolt / nut composition for the KPK mechanical joint and the bolt / nut of the conventional FCD material as follows.

Chemical composition (composition) comparison table Chemical composition (%) Remarks C Si Mn P S Cr Cu Ni The present invention AWWA11-8.5 0.20 or less - 1.25 and below - 0.05 or less 0.8 or more 0.2 or more 0.25 or more Cr + Cu + Ni = 1.25 or more FCD 0 species KSD 4302 2.5 or more 2.5 or less 0.4 or less Less than 0.08 0.02 or less - - - Reference 1 to 6 types 2.5 or more - - - 0.02 or less - - - Conventional Bolts (FCD Type 2) [Reference] AWWA: American Water Works Association

The composition of the present invention is represented by the basic components (elements) showing the essential conditions (classification of the article) as shown in Table 1, iron (Fe) is the main component and the maximum content element C, Mn, S, It contains Cr, Ni, and Cu as the minimum content elements, and is a preferred raw material as 0.20 wt% carbon, 1.25 wt% manganese, 0.05 wt% sulfur, 0.8 wt% chromium, 0.25 wt% nickel, 0.20 wt% copper, and 97.25 wt% iron. It is preferable to contain%. Other gas or impurity contents are not indicated because they do not significantly affect their own properties.

Carbon (C) is the most important element of steel and its properties greatly depend on its content. In general, the tensile strength and the strength of iron increase with the increase of carbon amount, but the elongation and torsional strength of iron tend to decrease inversely. In general, the hardening of iron hardens almost proportionally with the increase of the amount of carbon to around 0.8%, but the same does not change.

In general, manganese (Mn) is essentially an element to be quenched, and silicon (Si) is an element that is incorporated in the steelmaking process is usually not noticeable effects.

It is preferable to contain sulfur (S) and phosphorus (P) as little as possible as an element considered to be rather harmful in steel.

Characteristic elements of the present invention are Cr, Cu, Ni, these are the components to emphasize the corrosion resistance and to make the machinability and other mechanical properties easier than conventional FCD bolts.

Hereinafter, the specific configuration of the present invention will be described in more detail with reference to preferred embodiments, but these embodiments are for explaining the present invention, the scope of the present invention is not limited to these embodiments, the order or numerical value of the manufacturing process Of course, it can be changed to those of ordinary skill in the art by the change of.

Example 1 Elemental Composition of Bolts / Nuts for KP Mechanical Joint

0.20% by weight of carbon, 1.25% by weight of manganese, 0.05% by weight of sulfur, 0.8% by weight of chromium, 0.25% by weight of nickel, 0.20% by weight of copper, and 97.25% by weight of iron were mixed as raw materials.

Example 2. Fabrication of KP Mechanical Joint Bolts / Nuts

Using the composition formulated according to the composition ratio of Example 1 to prepare a bolt / nut for KP mechanical joint by a conventional hot forming method.

Example 3 Evaluation of Mechanical Properties of the Product of the Invention

The mechanical properties of the inventive KP mechanical joint bolts / nuts prepared according to Example 2 were compared with those of conventional products to evaluate product characteristics (Table 2 and Table 3).

Ultimate tensile strength is the limit of the initial cross-sectional area of a material to determine the maximum load required to pull a material and is usually a standard for indicating the strength of a material and is measured in kgf / mm ² or N / mm. ² .

Yield strength or yield strength is the value obtained by dividing the original cross section by the load at which a moderate permanent strain (usually 0.2%) is produced in a material where the yield point is not apparent in the tensile test.

Elongation or elongation refers to the rate at which the material stretches during the tensile test of the material.

Hardness means a numerical value representing the degree of mechanical hardness and softness of the object. In this embodiment, the hardness is denoted by HB, which is a BRINELL hardness.

Mechanical property comparison table sign Tensile test Reference Hardness (HB) Remarks Tensile Strength (N / mm ² ) Load capacity (N / mm ² ) Elongation (%) The present invention 370 or more 310 or more More than 20 52-100 FCD Type 2 GCD 450 More than 450 280 or more over 10 143-217 Current bolt

Comparison between the conventional product and the bolt / nut of the present invention ranking Contents FCD The present invention One Appearance (scratches and icing, seams) × ○ 2 Economic feasibility (material / processing) △ ○ 3 Corrosion (corrosion resistance) ○ ○ 4 Machinability and Precision × ○ 5 Production method Death Casting Hot forming 6 Weatherability (Climate Change) △ ○ 7 External Shock (Strike, Seal, etc.) × ○ 8 Productivity (Mass Production) △ ○ 9 Product uniformity (by lot) × ○ [Legend] ○: Good △: Normal ×: Poor

As is apparent from Table 3, the KP mechanical joint bolt / nut of the present invention is significantly improved in appearance, economy, workability, precision, impact resistance, etc., compared to the conventional FCD material bolt / nut. .

As described above, the KP mechanical joint bolt / nut according to the present invention has an excellent effect of improving machinability and other mechanical properties while maintaining almost the same corrosion resistance as conventional FCD material bolts / nuts. The invention is very useful in the piping industry, such as industrial water, agricultural water, sewage.

Claims (2)

For the manufacture of bolts / nuts for KP mechanical joints, characterized in that the remainder consists of iron in a composition of 0.20% carbon, 1.25% manganese, 0.05% sulfur, 0.8% chromium, 0.25% nickel and 0.20% copper. Composition. delete