JPS59501551A - Wear-resistant white cast iron - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Wear-resistant white cast iron Technical field This invention relates to cast iron, and in particular to improved toughness and wear resistance with a significant increase in tensile strength. Concerning cast iron with excellent properties.

More specifically, 5 the present invention maintains desired wear resistance by improving the morphology of carbides. A new white cast iron composition with excellent toughness, ductility and tensile strength while and related to casting and iron manufacturing methods.

Background technology Alloyed white cast iron is a highly wear-resistant material generally formed with a carbon content of L5% or more. is alloyed with another metal (usually chromium) and combined with carbon to form a metal such as MxCy. It is well known that Fe-Cr carbide compounds can be produced. Many In many cases, the inherent wear resistance of unalloyed cast iron is sufficient to meet the intended application. Therefore, they do not bring up the problem to the users. However, forming industrial machinery When cast iron is subjected to special wear, the inherent mechanical properties of the cast iron are significantly reduced from the desired ones. Leave.

It is well known that the wear that cast iron materials undergo can be classified into several types. 1st row In boring (or miso-kiri) wear, coarse abrasive particles penetrate the machined surface of cast iron. to remove metal at high speed. Typical experience of this type of wear 1 e.g. earthmoving equipment , hammer mill operations and show crushers have a detrimental effect on cast iron. It involves severe impact loads that remove metal where it is known to cause damage.

Secondary wear, often referred to as high stress wear (e.g.

(encountered in mining operations), abrasive particles are used to crush moving metal surfaces. It is crushed under use. For castings used in grinding rolls, grinding rolls and mill liners. The stress levels involved in this type of wear process typically occur in This often causes damage to the equipment beyond its capacity.

In the second category of wear, low stress wear or erosion, the cast iron surface of the equipment Although the abrasive action to which the surface is subjected is not a severe stress condition, high wear resistance is required.

Gouge (or gouge) wear associated with severe impact loads has typically been It requires all the sensitivities that it characteristically did not have. High plasticity and toughness Manganese steel meets the harsh impact requirements for materials that are subject to this type of wear. I was able to However, its hardness and wear resistance are generally Extremely high wear rates in high stress abrasive action in extensive grinding processes such as Lumil It was found to be inadequate to prevent the disease. In this high stress action, chromium ・Molybdenum steels and white alloy alloys combine toughness requirements and necessary wear resistance. It can be used in various devices depending on the application. The fifth category includes low stress effects. For wear, chromium with or without molybdenum or nickel is used. Ferrous alloys use a desirable martensitic matrix with dispersed carbides taking into account industry knowledge of the types of metals utilized to meet the requirements of The person skilled in the art is then faced with a dilemma. At least the first two categories For operating equipment subject to wear, optimum wear resistance and wear characteristic of these Requires sufficient toughness to withstand severe shock and stress conditions. Generally hardness and Since toughness is considered to be at the extremes of a range, we The composition also requires some other properties such as Lax<, and both hardness and toughness.

The industry that supplies wear-resistant castings is concerned with the useful life of equipment that utilizes castings to reduce the aforementioned wear. I have always sought to improve lives.

Various alloyed and unalloyed iron-carbon compositions.

Carbon starting with a low content of o, oq% has a high carbon content in the martensitic state. It has no gender. Hypereutectoid steel and white pig iron are It shows insufficient stiffness. Alloying of iron-carbon compositions is carbide (MxCy)k As it increases hardness, it slightly satisfies the requirement for high wear resistance. However, eventually As long as the grain size of the carbide does not decrease even in the volume of , as the volume of the carbide increases, Abrasion resistance increases, but toughness or fracture resistance decreases. Metallurgists believe that there are two main White because the constituent carbides and matrix act virtually independently of each other. I have come to appreciate the complexity of cast iron. Nevertheless, the final properties of the material are Wear and impact conditions result from the interdependence between the two microcomponents.

When such materials are subjected to impact, the carbides turn into powder, and the carbides become continuous. If the crack is relatively large, it will propagate throughout the tissue, often leading to fracture, or Or at least accelerate the wear of the material.

Thus to date, the requirements for good wear resistance and good impact stress absorption Iron-carbon alloys with a carbon content of more than 17% by weight are not recognized. .

Therefore, the main objective of the present invention is to provide a material with high hardness or high wear resistance and excellent toughness. We offer a complete range of white cast iron.

Furthermore, it is an object of the present invention to provide not only the desired wear resistance and toughness but also excellent tensile strength. Our objective is to provide white cast iron with strength.

Another object of the present invention is to provide high wear resistance and near-spherical carbide. An object of the present invention is to provide a cast iron composition having high strength and toughness.

Moreover, the object of the present invention is to reduce the size of carbides smaller than the conventional average value. Provides tough, wear-resistant cast iron that is virtually evenly distributed throughout the nox It is to be.

In addition, 1) the object of the present invention is 2) to have not only spherical particles but also uniformly distributed small average particle diameters. High energy in single-alloy cast iron by introducing boron to produce fine grains It is to provide something of entropy.

Furthermore, it is an object of the present invention to cool a molten cast iron composition to a supercooling temperature below the equilibrium solidification temperature. The average particle size is smaller than the average particle size of conventional cast iron carbides. It is an object of the present invention to provide a cast iron that is entirely made of completely blind spheroidal carbides and has toughness and wear resistance.

Disclosure of invention The present invention consists of iron as the main component, vanadium added or not added singly or cumulatively, titanium, niobium, molybdenum, nickel, copper, tantalum or chromium, or Mixture Q of n et al., 001% to 50% by weight and 20% carbon forming 5 alloy composition ~45% by weight, which was introduced to improve wear resistance, toughness and tensile strength. This is a unique development of alloyed cast iron compositions consisting of 0,001% to 40% by weight. Book The alloy is 1204t: (2200F) - 1316℃ (21100F) range, general Generally solidification within the range of 1238℃ (2260p) to 1260℃ (2500F) Has a point. This freezing point is within 157" of the eutectic temperature of cast iron for a given alloying element. be. Carbide exists in a spherical shape, and the average particle size of carbide in conventional cast iron is It has a particle size of less than U micron, which is small.

In the method of the present invention, o, oo 1% to 50% vanadium, titanium, niobium, Molybdenum, nickel, copper, tantalum, or chromium or mixtures thereof, or Alloyed white cast iron containing 20% to 4.5% carbon forms a molten cast iron composition; Entropy increasing agents such as O,OO1% to lIO% boron in molten cast iron compositions Additives are added and the molten cast iron composition is heated to 12011°C (22007;') to 1 to a subcooling temperature of at least 5F below the equilibrium solidification temperature of 316°C (211007) The molten cast iron composition is cooled and then solidified into flat pieces that are smaller than conventional cast iron. Spherical carbides with a uniform particle size or carbides with an average particle diameter of 4 μ or less are produced.

BEST MODE FOR CARRYING OUT THE INVENTION White cast iron has the desired wear resistance to meet the various wear conditions to which equipment made of cast iron is subjected. It has long been recognized that it has inherent wear properties. However, carbides in single-alloyed cast iron The form of can be changed to retain wear resistance and increase tensile strength. What is more important is that it not only imparts plastic deformability but also significantly improves the It has now been discovered that In conventional cast iron, austenite, pearlite or Excess free carbon found in the martensitic or martensitic matrix A dimensional shape somewhat similar to that of gold or graphite, or plate-shaped or fc, is a rod-shaped carbide. It has been recognized as a form of

In either form, normal total heat extraction from the sand mold.

Assuming that the cross-sectional dimension of the metal is 10 or more fins, one particle is microscopic in size, Usually the average particle size is 10 microns or more.

This graphite flake is said to be a source of fracture along the plane of the flake. Ru. Typically, good quality cast iron has a tensile strength of approximately 3500 kg/cl (50,000 kg/cl). 000psi).

Either it has 0% elongation and is extremely brittle, or it has no toughness and cannot undergo any deformation. Appropriately When alloyed, free carbon typically forms plate-like or rod-like intermetallic metal carbides (usually chromium carbide), continuous or discontinuous within the matrix, but again The average particle size is 10 microns or more. Moreover, the carbide particles exhibit a needle shape.

Whatever their shape, they microscopically have an average long dimension of at least 10 microns, which increases the tendency for crack initiation under stress and often reduces the final cause destruction.

In the present invention, the rod-like or plate-like shape of this carbide is changed to a spherical shape that is close to a completely spherical shape. It has been found that not only the desired toughness but also the tensile strength can be significantly increased. It was. This morphological change of cast iron carbides is past non-ductile.

The brittle, non-deformable cast iron has plastic workability, high tensile strength, and excellent wear resistance. I changed it to what I kept.

For example, the cast iron of the present invention bends before breaking, and the stress level it receives causes it to break. It was found that the material was extremely high compared to the conventional well-known cast iron. The cast iron of the present invention is chromium It is desirable to alloy with Q, 001% to 50% vanadium, titanium, Depending on various additives of niobium, tantalum, nickel, molybdenum or copper.

The properties of the resulting cast iron vary.

In general, the cast iron of the present invention has the traditional tensile strength of conventional well-known cast irons of 5 o　Kg. /cl (50,000psi) ~ 1k200 to 9/d (60,000 ps i) 8400 K9/Crd (120,000 ps i) It was found that it has a high tensile strength. The typical elongation of cast iron is 0%. However, the cast iron of the present invention has an elongation of 3%. For example, crushers and crushers for mining.

It also handles significant wear and shock loads, such as pumps delivering fluids containing abrasive solids. A person skilled in the art will immediately understand that the An important advantage will be realized: increased elongation or plastic deformability. in cast iron It is not only desirable to achieve a shape change in carbides that The shape of the cast iron becomes spherical, and the average grain size of conventional cast iron is 10 to 11.1 microns. This is almost as effective as reducing the surface area to a much smaller 4 microns. Carbide particle size This degree of reduction results in high tensile strength values, good wear resistance and increased deformability. The mean free path between individual small spherical particles can be minimized to contribute to . In this way, the present invention not only changes the shape of the carbide into a spherical shape, but also changes the shape of the carbide into a spherical shape. The spherical particles were reduced to an average particle size of less than U microns.

It is well known that cast iron is an alloyed iron-carbon composition. in general, The dividing line between cast iron and steel is the solubility of carbon in iron in the solid state. Recognized. At high levels of carbon, carbon becomes free graphite unless alloyed. It exists in the form of Typically, carbides are formed in cast iron to improve various properties. The alloying element used for this purpose is chromium. However, molybdenum, vanadium aluminum, titanium, copper, nickel, niobium and tantalum can be optionally combined in various combinations. It can be added to chromium or can be substituted for chromium. chrome and When used in combination, these metal elements are usually present in amounts up to about 7%, but are optional. Specifically, vanadium and niobium range from 0001% to 5%, and molybdenum and copper range from 0001% to 5%. 01% to 11%, nickel iQ, OO1% to 7%, titanium and tantalum 00 In the range of 01% to 1I%, in combination with chromium or alone, it is known that It is within the range of 0001% to 0%. Chromium ranges from 7% to 29% A more desirable range is 25% to 28% or 111% to 22%. or 7% to 12% (this range of chromium is the main group of commercial alloys in Nippon Steel). ). The carbon content is desirably 20% or more and approximately 5% or less, and chromium 2 For cast iron with a content of 5% to 28% and 14% to 22%, a range of 20% to 2% , a carbon content of 2% to 35% is desirable for 7% to 12% of chromium.

The typical cast iron compositions outlined above generally contain boron in the range of 0001% to 1I% as desired. or 0.01% to 1%, optimally 0.01% to OL1%. The form of carbide can be changed by This boron addition produces spherical carbide grains. However, the alloyed iron-carbon composition is related to the eutectic temperature. If you do, it will be even more expensive.

The freezing point of pure iron is approximately 1558°C (2gooF).

As carbon is added, the freezing point becomes lower. Addition of boron, or boron When alloyed without additives, the solidification temperature depends primarily on the amount of chromium present. 014-1516℃ (2200-21t　OO'p)117), It also depends on the selection of specific alloying elements. More preferably, iron-carbon alloy The solidification temperature of the system is within the range of 1238-1260℃ (2260-2300'/;'') , or approximately 22g0'p (12119°C) ± 10-20'p. I found out. Certain castings containing a given alloying element present in a given amount in accordance with the present invention All iron compositions are formed by their specific alloying elements at 15% of the eutectic temperature of the cast iron system. Solidifies within 'F.

This alloyed cast iron composition and the addition of boron change the morphology of the carbides, making them spherical. It was found that spherical carbide particles can be produced.

This important particle size ○ improves and substantially uniform distribution of spherical carbide particles. In order to obtain, the cast iron composition is equilibrated, pseudo-solidification degree is at least 5F, preferably one is solidified. If pre-cooled 8~lo'1'; or more, the carbide grain size will change to normal average grain size. It was found that the average particle size drastically decreased from 10 microns or more to 11 microns or less. . This goal of 21 turned out to be difficult to achieve. and a thermodynamic solution to the problem. In some cases, increasing the entropy of the cast iron melt increases the disorder and degree of the system. It has been found that the melt can be brought under cooling. High entropy value is liquid-solid system lowers the Gibbs free energy value of . and the phase with the lowest free energy is the most It is stable. The relationship is expressed as G = E + P V T S = H - T S It's so hot.

In the formula, G is the Gibbs free energy, T is the feed temperature, and 3 is the entropy. Ru. Furthermore, the thermodynamic relation H-T! 3→-VP is VP = O if it is a solid. Therefore, H-'r　S (in the formula, S is etrobi and H is heat of fusion.

Therefore, f...'' is the perfect freezing point). Increase in entropy (is system J) If is constant: Is it 4'? This results in a decrease in solid point O.

When boron is added to a cast iron composition, it increases entropy and increases the irregularity within the system. It has been found that the necessary conditions are under cooling conditions. The exact changes that occur are completely understandable. It should be understood that the above explanation is theoretical.

The alloy cast iron composition of the present invention has at least 5FC below the equilibrium solidification temperature and an equilibrium quasi-solidification degree. When cooled to the supercooling range (low), no solidification occurs, which means no supercooling occurs. It's more instantaneous than it is now. Thus, supercooling usually occurs for a long time 7v Avoid crystal or particle growth. Rather, the solidification occurs before the particles grow. Ru. Therefore, a set of fine carbide particles can be formed into rod-like or C, instead of agglomerating into a plate shape, it aggregates in the rapid solidification of the alloy cast iron composition of the present invention. These particles do not have the opportunity to There is no chance for them to aggregate into a plate or rod shape. Rather, the uniformity of the carbide distribution is It is inherent in the melt phase even during the supercooling stage of alloyed cast iron compositions. As a result, the uniformity of carbide distribution is maintained during solidification. Supercooled below the equilibrium solidification temperature The strength, toughness, I- and abrasion resistance of the cast iron composition of the present invention This is the basic condition for 71. This is a considerable reduction in the diameter and cast iron mud l) no. If the entire rice cake is covered with carbide, it also creates a more uniform serving of carbide.

specific example A typical cast iron composition containing 272% chromium and 2.011% carbon has a temperature of approximately 12') 9°C. J2++ range of 9℃ (2280F) which is above the eutectic temperature of (2263F) It is an alloy composition that solidifies in a surrounding area. With the addition of 0.17% boron, the alloy solidifies evenly. Supercooled to a temperature slightly below 12116°C (2275F), 5F below crystallinity. can do. Between this equilibrium solidification of 1□A degree and the temperature, the melt is supercooled. There is a liquid (4-1). When further cooled, it becomes mostly spherical with an average r and diameter. 1. The tensile strength of the obtained cast iron produces spherical carbides with a size of 4 microns or less. Strength 8ヰOOKri/m (120,000・Gil,+・　a) in negative Therefore, it has a weight of about 5%. Its L-shaped white cast iron is completely wear-resistant and High wear, high Lj: excellent tensile strength and It has the property of

Similar results were obtained for equilibrium solidification at 1255°C (2287F). 2% carbon, 912% phosphorus, t, 5.1!3% nickel and Obtained with 1 g composition of 0.17% boron. Next, 12119℃ (2280:p) Supercooling to occurs before solidification occurs.

As mentioned above, the purpose of the present invention is to accomplish the following: It is believed to be limited only by the scope of the claims.

Claims (1)

[Claims] 14 Main component element iron and 0.001% to 50% vanadium, titanium, niobium , tantalum, molybdenum, nickel, copper, or chromium, or mixtures thereof . Alloy cast iron composition consisting of one or more of the alloying elements: and 20% to 11.5% carbon. and the composition has a temperature of 15'F or higher than the eutectic temperature of the cast iron formed of the predetermined elements. It has a freezing point of: Alloy cast iron characterized by having the desired wear resistance, toughness 2 and tensile strength -Jk. Composition. 2 @ The alloy mentioned above has temperatures of 120Lt℃ (2200F) and 1516℃ (21I00F). A composition according to claim 1, characterized in that it has a freezing point between. 5. said vanadium, titanium, niobium or tantalum is present in an amount up to 7% The composition according to claim 1, characterized in that: 4. Claim No. 4 characterized in that said chromium is present in an amount of 0.1% to 50%. Composition according to item 1. Up to 57% nickel, 4% molybdenum or up to 4% copper or the like A composition according to claim 1, characterized in that a mixture of: 6. Characterized by the carbon at least partially existing in the form of spherical carbides The composition according to claim 1, 5, 2, 3, 4, or 5. 7 The solidification point of the alloy is approximately 1238°C (2260F) to 1260°C (2500' The composition according to claim 2, characterized in that p). 8. The alloy has a freezing point of about 12119°C (22gO°C). A composition according to claim 7. 9 said carbon is at least partially present in the form of spherical carbides, said vanadium; Titanium, niobium, nickel, copper, molybdenum or tantalum present in amounts up to 7% The freezing point of the alloy is approximately 1258°C (2260F) - 1260°C (2500F). F)? The composition according to claim 1, characterized by: 10 said carbon is present at least partially in the form of spheroidal carbides and said alloy is 12 having a freezing point between 011°C (2200:p) and 1516°C (21100F); The vanadium, titanium, niobium, nickel, copper, molybdenum or tantalum Composition according to claim 1, characterized in that it is present in an amount of up to 7%. silicon, the carbon is present at least partially in the form of spherical carbides, and the chromium is 01 % to 50%. The solidification point of the alloy is about 1238°C (2260'p) to 1260°C (2500F) A composition according to claim 1, characterized in that: 55%, and the boron is O, 1% to 10%. A composition according to scope 1. 1) The chromium is 25% to 28%, and the carbon is 20% to 30%, Claim 1, characterized in that the boron is 01% to 1%. Composition of. 1.11 The carbon is in the form of spherical carbides having an average particle size of 11 microns or less Claims 1 or 6 characterized in that at least in part Compositions as described. 1.5. Q, OO1%~30% vanadium, titanium, niobium, molybdenum , nickel 5 copper, tantalum or chromium or mixtures thereof and 20% to lI Q,　OO]%~40% boron is added to alloy cast iron consisting of 5% carbon and melted. A cast iron composition is completely produced, and the molten cast iron composition is cooled to a supercooling temperature below the equilibrium solidification temperature. 7) The molten cast iron composition is completely solidified to have an average particle size smaller than that of conventional cast iron carbide particles. Spheroidal carbide in cast iron characterized by producing spheroidal carbide with How to form. 〘　The alloy has a temperature of 12011℃ (2200'p) 16. A method according to claim 15, characterized in that it has a freezing point between. 17 The vanadium, titanium, niobium, tantalum, molybdenum, copper or nickel The method according to claim 15, characterized in that Kel is present in an amount of up to 7%. Law. 1g Claim characterized in that said chromium is present in an amount of 01% to 50% The method according to paragraph 15. 19. up to 7% nickel, up to 4% molybdenum, or up to 4% copper or The method according to claim 15, characterized in that: is added a mixture thereof. . 20 The molten cast iron composition is brought to a degree of supercooling at least 5F below the equilibrium solidification temperature. 16. A method according to claim 15, characterized in that it is cooled. 21. By continuing to cool the molten cast iron composition to a supercooling temperature, The composition solidifies into a spherical carbide having an average particle size of about 4 microns or less? formed 16. The method according to claim 15, characterized in that: 22. Bringing the molten cast iron composition to a supercooling temperature that is at least 5 F below the equilibrium solidification temperature. cooling and continuing to cool the molten cast iron composition to a supercooling temperature. The iron composition is solidified to form entirely spherical carbides having an average particle size of about 4 microns or less. 16. The method according to claim 15, characterized in that: 23 The equilibrium freezing point is between 12011℃ (2200F) and 1516℃ (2+10oF) F) as set forth in claim 20, 21 or 22, characterized in that: How to put it on. 211 The equilibrium freezing point is between 1258°C (2260'F') and 1260°C (2so oF) according to claim 20, 21 or 22, Method described. 25 Carbon, iron, vanadium, titanium, and molybdenum. Nickel, ': molten cast iron mixed with tantalum or chromium or mixtures thereof. Does melt casting composition increase the total entropy of coalescence? Producing the molten cast iron composition The material is supercooled to a temperature below the equilibrium solidification temperature of the molten cast iron TL product, and then the conventional cast iron carbonization process is performed. The melting process produces spherical carbides having a total average particle size smaller than the average particle size of the material. It is characterized in that it consists of hardening a cast iron composition by 1□. Cast iron shin 1. A method of supercooling molten cast iron to improve wear resistance and tensile strength. 26. A supercooling temperature that is at least about 5 F lower than the equilibrium solidification temperature of the injection cast iron composition. 26. A method according to claim 25, characterized in that the method is cooled at a temperature of 100%. 27 By continuing to cool the molten cast iron composition to a degree of It takes about 11 minutes to solidify the cast iron composition! Noron (spheroidal carbonized with average particle size of 26. The method of claim 25, further comprising forming an object. 28 Before; 4 self-melting-saving oblique iron l111 at least about 5'F lower than the equilibrium solidification temperature. 〕, % cooling 1 degree, 〇〇, the G melt casting method composition continues to be cooled to a supercooling degree. The molten cast iron composition is solidified by solidifying the molten cast iron composition to have a total average particle size of about 4 microns or less. 26. A method according to claim 25, characterized in that a spherical carbide is formed. 29. The said cast iron mixture by adding 0.001% to 40% boron. Claims 25 and 26, all characterized by increasing the entropy of. The method according to paragraph 27 or paragraph 28. 30 Claim characterized in that the boron is present in an amount of 01% to 0%. The method of paragraph 29. 5L Claim characterized in that said boron is present in an amount of 01% to 01I% The method according to item 1 or item 15.