Hypereutectic white iron alloys comprising chromium and nitrogen and articles made therefrom

a technology of white iron alloy and chromium and nitrogen, which is applied in the field of hypereutectic white iron alloy, can solve the problems of affecting the appearance of the article, and affecting the wear resistance of high chromium white iron alloy

Inactive Publication Date: 2016-06-02
RADON ROMAN +1
View PDF2 Cites 4 Cited by
  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The alloy achieves improved wear resistance and fracture toughness, enabling the successful sand casting of large parts like pump components with reduced cracking and increased durability, as demonstrated by the refined microstructure and enhanced hardness and abrasion resistance.

Problems solved by technology

However, in severely abrasive applications the wear resistance of these high chromium white iron alloys is not satisfactory due to a lack of a sufficient “Carbide Volume Fraction” (CVF).
However, hardfacing methods have disadvantages, including a limited thickness of the cladding, distortion of the article to be cladded, and high costs of labor, cladding material and equipment.
Moreover, the cladding usually is susceptible to developing defects such as spalling and cracking due to thermal stresses and contraction, and it shows constraints with respect to thermal hardening.
Further, making (slurry) pump components such as pump casings by common foundry methods from hypereutectic high chromium white iron alloys is virtually impossible due to high scrap and rejection rates.
Pump casings are large and heavy and are not uniform in thickness.
In view thereof, it is virtually impossible for a casting to cool uniformly in a sand mold, which results in stress induced cracking during cooling.
These large primary carbides lower the fracture toughness of a casting, wherefore the casting usually cracks during the manufacturing process or later during application in the work field.
This method has the limitation of a difficult to achieve even distribution of the additive, a particulate material, into a stream of molten metal as the metal is being poured for a casting operation.

Method used

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
View more

Image

Smart Image Click on the blue labels to locate them in the text.
Viewing Examples
Smart Image
  • Hypereutectic white iron alloys comprising chromium and nitrogen and articles made therefrom

Examples

Experimental program
Comparison scheme
Effect test

example 1

Comparative

[0059]An alloy of the following composition was used (in % by weight): C: 4.7, N: 0.03, Cr: 30, Mn: 2.4, Si: 0.45, S<0.06, P<0.06. The alloy was melted in a 30 kg high frequency induction furnace. The initial charge materials were steel scrap, ferroalloy and pig iron. The melt temperature was controlled at 2700° F. After all the charge materials had melted in the furnace, the liquidus temperature of the alloy was determined to be 2538° F. Then the molten alloy was poured at 2600° F. into sand molds with dimensions of 20 mm×20 mm×110 mm to obtain four samples for testing. The castings were cooled to ambient temperature in sand molds. As a result, three of the samples had developed cracks throughout their length of 110 mm. The fourth sample developed surface cracks during Brinell hardness testing.

[0060]The Brinell hardness of the samples was determined (10 mm tungsten ball and load of 3000 kg) to be 600 HB.

[0061]The Carbide Volume Fraction (CVF) of the samples can be calcul...

example 2

[0063]An alloy of the following composition was used (in % by weight): C: 4.4, N: 0.58, Cr: 31, Si: 0.45, Mn: 2.9, S<0.06, P<0.06. The alloy was melted in a 30 kg high frequency induction furnace. The initial charge materials were steel scrap, ferroalloy and pig iron. The melt temperature was controlled at 2780° F., whereafter the melt was nitrided by addition of Fe—Mn-8% N. After all the charge materials had melted in the furnace, the liquidus temperature of the alloy was determined to be 2481° F. Then the molten alloy was poured at 2544° F. into sand molds with dimensions of 20 mm×20 mm×110 mm to obtain four samples for testing. The castings were cooled to ambient temperature in sand molds. As a result, all four samples were free of cracks.

[0064]The Brinell hardness of the samples was determined (10 mm tungsten ball and load of 3000 kg) to be 683 HB.

[0065]The Carbonitride Volume Fraction (CNVF) of the samples can be calculated according to: CNVF=(% C+% N)×12.33+(% Cr+% M)×0.55−15....

example 3

Production on Industrial Scale

[0067]A production melt was made at 10,000 lbs. in an induction furnace, using 3 different alloys. The final alloy compositions were (in % by wt.):

ElementCCrSiMnNiMoVNCuFeEutectic alloy2.817.20.61.20.82.54.40.030.6Bal.CM22CNVF = 28%Hypereutectic4.118.20.51.80.64.05.10.120.5Bal.alloy T 60CNVF = 52%Hypereutectic4.732.10.52.40.60.75.90.680.6Bal.alloy T 70CNVF = 70%

[0068]Two commercial castings, i.e., slurry pump parts: Suction Liner 20 X18 HDMD 46, were cast from each of the above three alloy compositions. Each casting weighed 3500 lbs.

[0069]In particular, the eutectic alloy CM22 was controlled at 2780° F. and, after a melt had formed, Fe-V80% was added. The melt (9000 lbs.) was then cooled to 2600° F. and was cast into two sand molds.

[0070]The hypereutectic alloy T60 was controlled at 2780° F. and, after a melt had formed, Fe-V80% was added. The melt (9000 lbs.) was then nitrided by addition of Fe—Mn-7% N and thereafter cooled to 2650° F. and cast into tw...

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to View More

PUM

PropertyMeasurementUnit
dimensionsaaaaaaaaaa
strengthaaaaaaaaaa
strengthaaaaaaaaaa
Login to View More

Abstract

Disclosed are a hypereutectic white iron alloy and articles such as pump components made therefrom. Besides iron and unavoidable impurities the alloy comprises, in weight percent based on the total weight of the alloy, from 2.5 to 6.5 C, from 0.04 to 1.2 N and from 18 to 58 Cr and, optionally, one or more of Mn, Ni, Co, Cu, Mo, W, V, Mg, Ca, Si, rare earth elements, Nb, Ta, Ti, Zr, Hf, Al, B.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application is a continuation of U.S. application Ser. No. 14 / 279,600, filed May 16, 2014, the entire disclosure of which is expressly incorporated by reference herein.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a hypereutectic white iron alloy that comprises chromium and nitrogen, as well as to articles such as pump components made therefrom (e.g., by sand casting).[0004]2. Discussion of Background Information[0005]High chromium white iron alloys find use as abrasion resistant materials for the manufacture of, for example, casings of industrial pumps, in particular pumps which come into contact with abrasive slurries of minerals. This alloy material has exceptional wear resistance and good toughness with its hypoeutectic and eutectic compositions. For example, high chromium white iron in accordance with the ASTM A532 Class III Type A contains from 23% to 30 wt. % of chromiu...

Claims

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to View More

Application Information

Patent Timeline
no application Login to View More
Patent Type & AuthorityApplications(United States)
IPC IPC(8): C22C38/58C22C38/54C22C38/52C22C38/50C22C38/48C22C38/00C22C38/44C22C38/42C22C38/06C22C38/04C22C38/02C22C38/56C22C38/46
CPCC22C38/58C22C38/56C22C38/54C22C38/52C22C38/50C22C38/48C22C38/001C22C38/44C22C38/42C22C38/06C22C38/04C22C38/02C22C38/002C22C38/46C21C1/08C21C5/5241C21D5/04C22C33/08C22C37/00C22C37/06C22C37/08C22C37/10Y02P10/20Y02P10/25
InventorRADON, ROMANRADON, RAPHAEL
OwnerRADON ROMAN