GB2252931A

GB2252931A - Welding rod

Info

Publication number: GB2252931A
Application number: GB9203627A
Authority: GB
Inventors: Kazuo Azuma
Original assignee: TOEI GIKO KK
Current assignee: TOEI GIKO KK
Priority date: 1991-02-20
Filing date: 1992-02-19
Publication date: 1992-08-26
Anticipated expiration: 2012-02-19
Also published as: JP3247958B2; TW205523B; GB2252931B; KR920016184A; KR960010512B1; JPH05169293A; GB9203627D0

Abstract

The present invention relates to a corrosion-resistant, abrasion-resistant welding rod in which Cu, Sb or both are added to an abrasion-resistant welding rod comprised of C, Si, Cr, Mo and/or W in the deposited metal and impurities and Fe in the remainder. The present invention eliminates the need for a chrome plating process while also improving both corrosion resistance and abrasion resistance. Preferred composition for the rod are 0.1-0.4% C, 0.5-1.5% Si, 1.0-7.5% Cr, 0.5-1.5% Mo, 3.0-8.0% W and either 0.2-2.5% Cu, or 0.1 to 1.5% Sb, or 0.3-3.0% Cr and Sb in total.

Description

WELDING ROD The present invention relates a welding rod suitable for cases of build-up welding in locations in which there is the formation of slipping, impact abrasion and corrosion as in the pistons of diesel engines, and in particular to a welding rod that produces a weld having good corrosion and abrasion resistance properties.

Although cast forged steel is normally used for the pistons of, for example, large marine engines, during the course of long-term use, the piston rings begin to slide in the grooves into which they fit resulting in the formation of impact abrasion.

Moreover, when coupled with the production of corrosive acid due to the presence of sulfur dioxide gas, the piston rings become unable to withstand further use. Thus, although repairs become necessary at that point, in the past, welding materials such as DF2A of Japanese Industrial Standard Z3223-1987 (molybdenum steel and chrome molybdenum steel coated arc welding rods) or Japan Industrial Standard Z3251-1981 (hard facing coated arc welding rods) have been used for such repairs, followed by chrome plating.

In the method of the prior art described above, the additional task of hard chrome plating was required following welding thus increasing repair costs. In addition, in the case of present diesel engines which are required to have low fuel consumption and produce a high output, the pressure to which the pistons are subjected is greatly increased. As such, conventional welding materials are unable to withstand long-term use under such conditions thus resulting in a considerable shortening of the service life.

In consideration of the circumstances described above, the present invention provides a welding rod (including diamond) which is able to obtain a level ot performance that is equivalent to that of the prior art with build-up welding alone. The objective of the present invention is thus to provide a corrosionresistant, abrasion-resistant welding rod that is able to achieve a reduction in both repair man-hours and repair costs as well as lengthening of service life.

According to the present invention there is provided a welding rod in which corrosion resistance is improved by the addition of Cu, Sb or both to an abrasion-resistant welding rod comprised of C, Si, Cr, Mo and/or W in the deposited metal and impurities and Fe in the remainder.

In the present invention, corrosion resistance is improved as a result of the addition of Cu, Sb or both, having superior resistance to sulfur.

Moreover, chrome plating processes are no longer required as in the past, thereby allowing a reduction in the number of man-hours required for repairs as well as repair costs.

In addition, the lower limit of hardness (Hv 450) that can be obtained by performance with the present invention, as well as the upper limit of hardness (Hv 600) that is possible with mechanical processing can be obtained from the first layer, thereby lengthening service life.

Some embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a front view of a test piece used in anti-corrosion testing; Fig. 2 is a cross-sectional view along line II-II in Fig. 1; Fig. 3 is a front view of a test piece used in abrasion testing; Fig. 4 is a cross-sectional view along line IV-IV in Fig. 3; Fig. 5 is a schematic drawing of a sliding abrasion test apparatus; Fig. 6 is a graph indicating the results of measurement of cross-sectional hardness; and Fig. 7 is a front view indicating the location of cross-sectional hardness measurement.

The corrosion-resistant, abrasion-resistant welding rod of the present invention can be manufactured by conventional manufacturing methods.

Welding rods 1-19 were manufactured by varying the amounts of various components as indicated in Tables 1 and 2 below. Welding rods 12 and 13 are conventional welding rods. At this point it should be noted that throughout this specification the percentages quoted are percentages by weight.

[ Table 1 # Components of Deposited Metal Used in the Eabodinent (N )

Chemical Components of Deposited Metal (N ) C S I M n P S C r M o W Cu Sb Conventional Welding Rod 12 0.07 0.53 0.83 0.012 0.009 1.27 0.50 Conventional Welding Rod 13 0.23 0.64 1.43 0.014 0.011 1. 50 --- --- . --- Welding Rod 1 0.30 0.89 0.27 0.012 0.008 . 6.30 1.02 4.90 0.50 Welding Rod 2 0.21 0.65 0.30 0.012 0.011 6.38 0.99 0. 0.66 Welding Rod 3 0.35 0.77 0.32 0.013 0.011 6.44 1 11 j 1.11 Welding Rod 4 0.15 1.10 0.44 0.012 0.011 6. 11 2. 11 5.90 0. 61 telding-Rod 5 0.22 0.99 0.29 0.014 0.009 5.99 0.84 5. 11 1.48 Welding Rod 6 0.31 2. 10 0.33 0.012 0.009 6. 19 0.63 ~~~ 0.72 We1ding Rod 7 0. 15 0.81 0.40 0.011 0.009 5.81 ~~~ 5.62 0.70 Welding Rod 8 0.32 0.91 0.25 0.011 0.100 6.30 1.05 4.98 ~~~ 0.30 Welding Rod9 0.21 0.90 0.24 0.012 0.008 1 5. 95 0.80 6.10 ~~~ 1.70 Welding Rod 10 0.30 0.79 0.29 0.012 0.009 6.25 1.10 5. 10 1.35 1.02 Welding Rod 11 0.21 0.99 0.26 0.011 0.10 5.79 0.98 4.95 2.08 1.30 (Table 21 Chemical Components of Deposited Metal Used in Hardness and Abrasion Testing

Cheilcal Components of Deposited Metal (%) Hardness C S i M n P S Cr M o W C u S b Hv Conventional Welding Rod 12 0.07 0.53 0.83 0.012 0.009. 1.27 0.50 --- --- --- 220 Conventional Welding Rod 13 0.23 0.64 1.43 0. 014 0.011 1.50 390 Welding Rod15 0.30 0.89 0.27 0.012 0.008 6.30 1.02 4 90 0.50 0.42 535 Welding Rod 15 0.30 1 0.89 Welding Rod 16 0.49 0 880.88 0.21 0.011 0.010 6.21 0.99 5.30 0.62 --- 630 Welding Rod17 0.06 0.91 0.38 0.012 0.012 5 97 1.10 4 89 0.42 --- 310 Welding Rod 18 0.31 1.00 0.42 0.012 0.009 6.11 0.98 --- 0.70 0.35 540 welding Rod 19 0.29 1.02 0.28 0.013 0.010 6.25 1.05 5.05 1 33 1.02 550 In Table 1 above, welding rods 1 and 2 are examples according to Claim 2, welding rod 8 an example according to Claim 3, and welding rod 10 according to Claim 4. In addition, in Table 2 above, welding rods 15 and 19 are examples according to Claim 4.

The results of testing for the presence of corrosion resistance and weld cracks in the deposited metal formed by welding rods 1-11 and conventional welding rods 12 and 13 above are as indicated in Table 3 below.

[ T a b 1 e 3 ] Presence of Corrosion Resistance and Weld Cracks in Deposited Metal

Corrosion Loss Presence of (mg /cm2) Weld Cracks Conventional Welding Rod 12 295.5 0 Conventional Welding Rod 13 311.2 0 Welding Rod 1 32.1 0 Welding Rod 2 35.2 0 Welding Rod 3 99.8 0 Welding Rod 4 38.2 x Welding Rod 5 30.0 x Welding Rod 6 57.6 x Welding Rod 7 40. 1 0 Welding Rod 8 ~ 36.2 0 Welding Rod 9 30.8 x Welding Rod 10 28.9 0 Welding Rod 117 25.6 x Note: .0. indicates the absence of cracks while x indicates the presence of cracks.

Furthermore, test piece 20 used in anti-corrosion testing was obtained form test piece 21 indicated in Figs. 1 and 2.

In other words, four layers of underlaying layer 23 were composed on base metal 22 so as not to be subjected to the effects of base metal 22. Moreover, 15mm of test layer 24 was built up on top of that to obtain test piece 20 from said built up portion.

In addition, anti-corrosion testing was conducted in compliance with Japan Industrial Standard G0591 (5% Sulfuric Acid Corrosion Testing Method for Stainless Steel), using 75% sulfuric acid for the corrosion fluid at a temperature of 120 C. An immersion test was conducted for 24 hours followed by determination of the amount of corrosion loss.

As is clear from Table 3, it was determined that the corrosion resistance of the deposited metal is remarkably improved in welding rods which contain Cu and/or Sb.

The results of abrasion testing of deposited metal 25 formed with welding rods 15-19 and conventional welding rods 12 and 13 indicated in above-mentioned Table 2 are indicated in Table 4 below.

ETa b 1 e 4) Abrasion Test Results and Mechanical Processability of Deposited Metal

Abrasion Loss Mechanical (mg /cm2) Processability Conventional Welding Rod 12 549.4 0 Conventional Welding Rod 13 321.0 0 Welding Rod 15 99.8 0 Welding Rod 16 78.1 x Welding Rod 17 286.3 0 Welding Rod 18 155.7 0 Welding Rod 19 100.5 0 Note: "0" indicates favorable mechanical processability while wx t indicates poor mechanical processability.

Furthermore, test piece 26 used in abrasion testing was made cutting l.Omm from the surface of soft steel base metal 27 of deposited metal 25 in which two layers were built up on soft steel base metal 27 as indicated in Fig. 3 and Fig. 4. The cut surface of said test piece 26 was then used for the testing surface.

As is indicated in Fig. 5, abrasion testing involved the determination of abrasion loss using a sliding abrasion tester in which super hard plate 28 was moved in the manner of a piston while applying load X in the amount of 10kg/cm2 to said super hard plate 28 with two of the above-mentioned test pieces 26.

As is clear from Table 4, it was determined that welding rods 15 and 19, containing C, Cr and W, demonstrate superior abrasion resistance.

Fig. 6 indicates the results of measurement of the cross-sectional hardness of test piece 26 obtained using the same methods as indicated in Fig. 3 and Fig. 4 with a Micro Vickers hardness gauge for above-mentioned welding rods 12, 13, 15, 16, 17, 18 and 19.

Furthermore, the location where measurements of cross-sectional hardness were made is indicated by arrow 29. The O.Omm point is the border between base metal 27 and deposited metal 25, and the 5.5mm point indicates a portion close to the surface.

As is indicated in Fig. 6, it was determined that with the exception of welding rod 17 in which the amount of C is reduced considerably, welding rods 15, 16, 18 and 19 all demonstrate the required hardness in comparison to conventional welding rods 12 and 13.

However, with respect to welding rod 16, which exceeds the suitable level of hardness of Hv450-Hv600 in consideration of mechanical processing, mechanical processability presents a problem as the amount of C exceeds the preferred upper limit.

In each of the previous tests, the desirable component amounts of the corrosion-resistant, abrasionresistant welding rods that were determined are as indicated below.

When the amount of C is 0.1% or less, the required hardness cannot be obtained, and when the amount of C is 0.4% or more, the hardness increases to a point beyond that at which processing is possible. Thus, the suitable range for the component amount of C is 0.10.4%.

Although 0.5% or more of Si is required for obtaining deoxidation and fluidity of the deposited metal, since embrittlement of the deposited metal results when the amount is increased to 1.5% or more, the suitable range for the component amount of Si is 0.5-1.5%.

Although Cr increases corrosion resistance in the presence of Cu and Mo while also improving heat resistance, when present at a level of 1.0% or less, such effects are not obtained. However, since Cr carbides are formed resulting in a reduction of those effects when Cr is present at a level in excess of 7.5%, the suitable range for the component amount of Cr is 1.0-7.5%.

Although Mo demonstrates superior resistance to sulfur and has effects which increase softening resistance due to solution treatment and tempering of the substrate, at a level of 0.5% or less, those effects become difficult to obtain, while at a level in excess of 1.5%, the toughness of the deposited metal is lost.

Thus, the suitable range for the component amount of Mo is 0.5-1.5%.

Although W improves abrasion resistance and increases softening resistance at elevated temperatures, as those effects are not present at a level of 3.0% or less while hot cracking resistance is impaired when the level of W exceeds 8.0%, the suitable range for the component amount of W is 3.0-8.0%.

Although Cu demonstrates superior resistance to sulfur, if present only at a level of 0.2% or less, effects which improve sulfur resistance are not demonstrated. Conversely, if added to a level of 2.5% or more, it brings about high temperature cracking of the deposited metal. Thus, the suitable range for the component amount of Cu is 0.2-2.5%.

Although Sb also demonstrates superior resistance to sulfur, if present only at a level of 0.1% or less, effects which improve sulfur resistance are not demonstrated. Conversely, at a level of 1.5% or more, it brings about high-temperature cracking of the deposited metal in the same manner as Cu. Thus, the suitable range for the component amount of Sb is 0.11.5%.

Moreover, in the case of combined addition of Cu and Sb as in Claim 4, it was confirmed that the suitable amounts for the lower limit and upper limit of the total of the added amount are 0.3% and 3.0%, respectively, as a result of synergistic effects.

The welding rod of the present invention is able to demonstrate superior corrosion resistance and abrasion resistance, is suitable for the build-up welding of portions in which there is formation of slipping, impact abrasion and corrosion as in the pistons of diesel engines in particular, and moreover, is able to achieve a reduction in both repair man-hours and repair costs.

Claims

1. A welding rod in which corrosion resistance is improved by the addition of Cu, Sb or both to an abrasion-resistant welding rod comprised of C, Si, Cr, Mo and/or W in the deposited metal and impurities and Fe in the remainder.

2. A welding rod as claimed in Claim 1 comprising 0.10.4% C, 0.5-1.5% Si, 1.0-7.5% Cr, 0.5-1.5% Mo, 3.0-8.0% W and 0.2-2.5% Cu.

3. A welding rod as claimed in Claim 1 comprising 0.10.4% C, 0.5-1.5% Si, 1.0-7.5% Cr, 0.5-1.5% Mo, 3.0-8.0% W and 0.1-1.5% Sb.

4. A welding rod as claimed in Claim 1 comprising 0.10.4% C, 0.5-1.5% Si, 1.0-7.5% Cr, 0.5-1.5% Mo, 3.0-8.0% W and 0.3-3.0% Cu and Sb in total.

5. A welding rod substantially as hereinbefore described and with reference to Examples 1 to 11 and 15 to 19 of the tables.