CN1033844A - High strength grey cast iron with casting bainite - Google Patents

Abstract

The invention provides a kind of as-cast bainite meehanite cast iron and castmethod thereof, belong to field of alloy material.

The present invention selects suitable alloying and inoculation method for use, change stoicheiometry, can under as cast condition, obtain the grey cast iron of bainite structure, and make its salient features obtain to increase substantially, particularly strength property can reach certain degree, and keeps the premium properties of regular gray iron simultaneously.

Description

High strength grey cast iron with casting bainite

The present invention relates to field of alloy material.

Grey cast iron is widely used in machinery, automobile, engineering field, existing grey cast iron as-cast structure is ferrite or perlite, or both mixing+flake graphites, its production is easy, process yield height, cost are low, have a series of good castabilitys and higher mechanical properties, but because the existence of flake graphite makes its mechanical property (particularly strength property) limited; Use the method that breeds and alloying to make it structure refinement (the ball light body of higher dispersity or sorbite+shred shape graphite) more at present and improve strength property, change but essence takes place its metallic matrix, its performance can only arrive certain limit (σ _b=200～400N/mm ², σ _w=450～600N/mm ²); Adopt isothermal quenching technique can change its metallic matrix structure, acquisition has the metallic matrix tissue of bainite structure, its performance is increased substantially, but the power consumption of this method, consuming time, labour intensity is big, though vermicular cast iron and spheroidal graphite cast iron have favorable mechanical (intensity) performance, but its wriggling, nodularization process are numerous and diverse, and particularly the technical requirements of wriggling is very high, and quality is difficult to stable.

World patent does not have to find to have the grey cast iron report that has the bainite matrix under the as cast condition by retrieval.

The objective of the invention is: select suitable alloying and inoculation method for use, change its chemical ingredients, in refinement graphite, do not need numerous and diverse heat treatment process, under as cast condition, obtain to have the grey cast iron of bainite structure, its every performance is increased substantially, keep the premium properties of common graphitic pig iron again simultaneously, and have some advantage of wriggle China ink and spheroidal graphite cast iron concurrently.

Technology contents of the present invention is: high strength grey cast iron with casting bainite, as-cast structure is made up of metallic matrix and shred shape graphite, carbide, its special character is that its metallic matrix is bainite and small portion of residual austenite, and carbide is the upright island carbide of a small amount of arc; Its stoicheiometry is: C3.0～3.3%, and Si1.9～2.4%, Mn0.5～0.9%, S＜0.1%, P＜0.1%, Cr0.2～0.8%, Mo0.2～0.8%, Ni0.5～1.0%, the RE trace, the Ca trace, surplus is Fe.

The characteristics of the castmethod of high strength grey cast iron with casting bainite of the present invention are: foundry technology process and parameter are: raw material go into stove → molten iron change substantially add when clear 1480～1500 ℃ of molten iron of alloy → be superheated to come out of the stove and carry out breeding first time → 1400～1430 ℃ of dried moulds pour into a mould and carry out breeding the second time.

The present invention adopts and repeatedly breeds and Alloying Treatment, has changed Chemical Composition and weave construction, obtains the grey cast iron of as-cast bainite, because the higher comprehensive mechanical performance of bainite makes the main performance index of as-cast bainite cast iron increase substantially (σ _b=402N/mm ², σ _w=804N/mm ²HRC=27), the highest trade mark HT350 graphitic cast iron performance that surpasses new national standard, kept again simultaneously regular gray iron salient features, have some advantage of vermicular cast iron and spheroidal graphite cast iron concurrently, have high strength and good wear-resisting, heat-resisting, corrosion resisting property, saved numerous and diverse thermal treatment, wriggling, nodularization process, thus have that performance is good, the saving of labor, save time, save energy, technology is simple, cost is low advantage.

Accompanying drawing is an as cast condition metallograph of the present invention.

The following describes one embodiment of the present of invention:

Adopt 100KW, 10kg silicon controlled rectifier middle frequency furnace.

Materials are: the Yimen pig iron, Benxi pig iron, carbon steel waste material, 75 ferrosilicon, ferromanganese, ferrochrome, molybdenum-iron, metallic nickel, rare earth, silicocalcium.

Technological process and parameter are:

Raw material go into stove → molten iron change substantially add when clear 1480～1500 ℃ of molten iron of alloy → be superheated to come out of the stove and carry out breeding first time → 1400～1430 ℃ of dried moulds pour into a mould and carry out breeding the second time.

Stoicheiometry is: C3.0～3.3%, and Si1.9～2.4%, Mn0.5～0.9%, S＜0.1%, P＜0.1%, Cr0.2～0.8%, Ni0.5～1.0%, Mo0.2～0.8%, the RE trace, the Ca trace, surplus is Fe.

Mechanical property is measured and is adopted φ 30mm bending resistance sample, and in ShiShimonoseki, Yunnan Province motor vehicle repair four factories, Yunnan Internal Combustion Engine Factory, the test of the light machine in Yunnan Province factory, the result is σ _b=402.73N/mm ², σ _w=804.29N/mm ², HRC=27.

XJG-05 type large-type horizontal metallurgical microscope is adopted in metallurgical analysis, from metallograph (accompanying drawing), can its as-cast structure of clear identification be: bainite+small portion of residual austenite+a small amount of isolated island shape carbide+shred shape graphite.

Claims (2)

1, a kind of high strength grey cast iron with casting bainite, as-cast structure is made up of metallic matrix and shred shape graphite, carbide, it is characterized in that its metallic matrix is bainite and small portion of residual austenite, carbide is a small amount of isolated island shape carbide, and its stoicheiometry is: C3.0～3.3%, Si1.9～2.4%, S＜0.1%, P＜0.1%, Cr0.2～0.8%, Mo0.2～0.8%, Ni0.5～1.0%, Mn0.5～0.9%, RE trace, Ca trace, surplus are Fe.

2, the castmethod of the described high strength grey cast iron with casting bainite of a kind of claim 1 is characterized in that foundry technology process and parameter are:

Raw material go into stove → molten iron change substantially add when clear 1480～1500 ℃ of molten iron of alloy → be superheated to come out of the stove and carry out breeding first time → 1400～1430 ℃ of dried moulds pour into a mould and carry out breeding the second time.

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