Showing papers on "Weldability published in 1988"

Welding Metallurgy of Stainless Steels

Abstract: Contents: Significance of Constitution Diagrams for the Understanding of Welding Phenomena * Metallurgical Processes During Solidification and Cooling in Stainless Steel Weld Metal * Metallurgical Phenomena in Secondary Crystallization of Stainless Steels and Weld Metals * Precipitation Phenomena in Stainless Steel and Weld Metals * Hot Cracking Resistance During the Welding of Austenitic Stainless Steels * Welding Metallurgy of Ferritic Stainless Chromium Steels with Carbon Contents Below 0.15 per cent * Welding Metallurgy of Low Carbon Chromium-Nickel Martensitic Stainless Steels (Soft Martensitic Steels) * Welding Metallurgy of Duplex Austenitic-Ferritic Stainless Steels * Welding Metallurgy of Austenitic Stainless Steels * General Instructions for the Welding and Post-Weld Surface Treatments of Fabrications and Welded Components Made from Austenitic Stainless Steel * Welding Metallurgy of Heat Resisting Steels * Welding Metallurgy of Austenitic-Ferritic Dissimilar Joints * Appendix: Abbreviations and Short Designations * References * Author Index * Subject Index.

Aluminium nitride in steel

Abstract: Aluminium nitride (AlN) nucleates with difficulty in steel, unless precipitation is enhanced by thermal or mechanical treatments. This important characteristic determines the precipitation kinetics of AlN, and accounts for the wide variations in precipitate morphology achieved following different processing histories. The most significant effect of AlN in steel is on grain size control, which directly influences hardenability, hot ductility, texture development, and mechanical properties. In addition, the accompanying removal of nitrogen from solid solution affects the strain aging characteristics, weldability, mechanical properties, and creep performance. Aluminium nitride also exerts important second order effects through its influence on the precipitation of other alloy nitrides. The precipitation of AlN can cause embrittlement and cracking phenomena in castings, continuously cast products, ingots, and rolled or forged products, However, the basic mechanisms are well understood, and the occurre...

On the weldability, composition, and hardness of pulsed and continuous Nd:YAG laser welds in aluminum alloys 6061,5456, and 5086

Abstract: The effect of Nd:YAG laser welding aluminum alloys 6061, 5456, and 5086 was studied from a perspective of alloying element vaporization, hot cracking susceptibility, and resultant mechanical properties. Both continuous wave and pulsed Nd.YAG laser welds were investigated. It was found that Mg was vaporized during welding, the extent of which was a function of the weld travel speed. Calculations based upon evaporation theory, and assuming a regular solution model, resulted in an estimation of weld pool surface temperatures from 1080 to 1970 K for the continuous wave welds. Pulsed Nd:YAG laser welds were observed to be extremely susceptible to weld metal hot cracking whereas continuous wave Nd:YAG laser welds were crack-free. The hardness of 6061 welds was affected by the Mg vaporization such that base metal strengths could not be achieved by subsequent re-heat treatment to the T6 condition. This loss in hardness was attributed to a reduced ability of the alloy to precipitation harden due to a lower Mg concentration. In the cases of 5456 and 5086, when samples containing welds were processed to the O condition, the weld metal had reduced hardness relative to the base metal. This loss of hardness was also attributed to the loss of Mg in these welds, resulting in reduced solid solution strengthening.

Vibration welding of thermoplastics. Part I: Phenomenology of the welding process

Abstract: In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters in vibration welding are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time. How these parameters affect weld quality, the conditions that result in the best welds, the weldability of dissimilar plastics, and the effect of fillers such as glass are of interest. To address these issues, a research vibration welding machine in which all the parameters can be independently and accurately controlled and monitored was designed and fabricated. The phenomenology of welding, as determined by experiments on the four thermoplastics polycarbonate, poly (butylene terephthalate), polyetherimide, and modified poly (phenylene oxide), is described.

Vibration welding of thermoplastics. Part IV: Strengths of poly(butylene terephthalate), polyetherimide, and modified polyphenylene oxide butt welds

Abstract: In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time or weld penetration.; The effects of these parameters on weld quality were systematically studied by first butt welding thermoplastic specimens under controlled conditions, over a wide range of process parameters, and by then determining the strengths and ductilities of these welds by tensile tests. The three thermoplastics investigated are poly (butylene terephthalate), polyetherimide, and modified polyphenylene oxide. Changes in the weld pressure are shown to have opposite effects on the strengths of polyetherimide and modified polyphenylene oxide welds; Also, the weld frequency is shown to have a significant effect on the weldability of polyetherimide. The weldability data for these three thermoplastics are compared with data for polycarbonate. Under the right conditions, the strengths of butt welds in these materials are shown to equal the strength of the virgin polymer.

Nickel-base superalloy systems

Abstract: Alloy compositions for nickel-base superalloys having the qualities of weldability, castability and forge-ability together with improved high temperature strength and rupture properties are disclosed. The weldability is improved by varying the Al, Ti, Nb and Ta content so as to insure that only the favorable γ" precipitates are formed in the alloy. The high temperature properties of the alloy compositions are optimized by controlling the content of the major alloying elements Co and Cr. Preferably the alloy is substantially free of Fe.

A study of the weldability and weld related microstructure of cabot alloy 214

Abstract: The weldability and weld metal microstructure of Cabot Alloy 214 have been investigated with a variety of experimental and analytical techniques. These include Varestraint hot crack testing, hot ductility testing, pulsed Nd:YAG laser welding, scanning and analytical electron microscopy, electron microprobe analysis, and X-ray diffraction. A heat of Alloy 214 containing intentionally alloyed B (0.003 wt pct) and Zr (0.07 wt pct) was much more sensitive to both fusion zone hot cracking as quantified by the Varestraint test and to simulated heat-affected-zone (HAZ) cracking as quantified by hot ductility testing than a heat of Alloy 214 containing no intentionally added B (0.0002 wt pct) or Zr (0.02 wt pct). Scanning electron microscopy of the high B and Zr alloy showed the presence of dendritically-shaped, Zr-rich constituents in interdendritic regions in the gas-tungsten-arc (GTA) welds. Electron microprobe analysis of these welds revealed a segregation pattern of Cr, Al, Mn, and Zr enrichment in interdendritic regions and Ni and Fe enrichment in dendrite core regions. Analytical electron microscopy revealed the presence of ZrX (X = B, C, N, O), M23C6, andγ′ in the fusion zone of GTA weld specimens,γ′ was also found in the as-received base metal and in the GTA weld HAZ. X-ray diffraction analysis of extractions from the high B and Zr GTA weld metal also indicated the presence of a ZrX-type constituent. The results of this study are in qualitative agreement with earlier work performed on alloys such as NIMONIC 90 and INCONEL 718∗ relative to the detrimental effect of B and Zr additions on fusion zone and HAZ hot cracking susceptibility.

Thinly tin coated steel sheets having excellent rust resistance and weldability

Abstract: Surface treated steel sheets having excellent rust resistance and weldability, suitable for manufacturing various kinds of cans, produced by a process comprising applying 02 to 1 g/m² of tin coating on a surface of a cold rolled steel sheet, applying 001 to 03 g/m² of zinc coating on the tin coating in such an amount that the ratio of the zinc coating amount to the tin coating amount is in a range from 2 to 30 % by weight, and heating the coatings to alloy substantially all of the zinc into the tin coating layer with substantially no non-alloyed zinc left on the tin coating

A comparison of the resistance spot weldability of bare, hot-dipped, galvannealed, and electrogalvanized DQSK sheet steels

Abstract: The spot weldability of various zinc-coated sheet steels was examined using several procedures and criteria

Resistance welding of galvanized steel

Abstract: A coating for improved resistance welding of galvanized steel parts or sheets comprises a binder, and a metal phosphide pigment, preferably a ferrophosphorus pigment, having a particle size of from about 0.1 to about 30 microns. The pigment can also include up to about 40% by weight of an additional metal such as tin, aluminum or lead, which can be combined with the metal phosphide in pigment form or deposited onto the surface of the particles. The coating can be applied to either the faying or non-faying surfaces of the galvanized steel, or to the resistance welding electrode, and may be removed, if desired, after the welding operation. The advantages of the present invention include a significant reduction in welding current and an increase in the weldability lobe width, a restoration of the dynamic resistance beta peak, and an increase in electrode life.

Survey of degradation modes of candidate materials for high-level radioactive-waste disposal containers

Abstract: This volume surveys the effects of welding on the degradation modes of three austenitic alloys: Types 304L and 316L stainless steels and Alloy 825. These materials are candidates for the fabrication of containers for the long-term storage of high-level nuclear waste. The metallurgical characteristics of fusion welds are reviewed here and related to potential degradation modes of the containers. Three specific areas are discussed in depth: (1) decreased resistance to corrosion in the forms of preferential corrosion, sensitization, and susceptibility to stress corrosion cracking, (2) hot cracking in the heat-affected zone and the weld zone, and (3) formation of intermetallic phases. The austenitic alloys are ranked as follows in terms of overall weldability: Alloy 825 (best) > Type 316L stainless steel > Type 304L stainless steel (worst). 108 refs., 31 figs., 7 tabs.

Duplex and high alloy stainless steels – corrosion resistance and weldability

Abstract: Conventional 18Cr–8Ni austenitic stainless steels have excellent resistance to corrosion in mildly aggressive environments, good mechanical properties, and are readily weldable. They are therefore used in a wide range of areas, including the food, petrochemical, and pharmaceutical industries. A major disadvantage to the use of austenitic stainless steels however is the drastically reduced resistance to pitting or crevice attack in aqueous environments containing chlorides. Furthermore, at temperatures above 65°C they are susceptible to failure from chloride stress corrosion cracking (SCC). Improvements in pitting or SCC resistance may be achieved by alloying additions, producing the high alloy austenitic stainless steels. Alternative solutions are to employ high Cr and Mo ferritic stainless steels, or the two phase, or duplex, ferritic–austenitic stainless steels. The choice of alloy depends on several factors, such as mechanical properties, economics, and weldability. The last property may be cri...

Manufacture of steel plate coated with fused alloyed zinc by galuanization excellent in spot weldability

Abstract: PURPOSE: To improve the peeling resistance of plating and continuous spot welding characteristic at the time of spot welding by annealing a cold rolled steel plate with a specific composition and subjecting this steel sheet to coating with fuzed zinc in an Al-containing hot dip galvanizing bath and then to alloying treatment by heating so as to specify Fe content in a plating layer. CONSTITUTION: In continuous hot dip galvanizing equipment, a cold rolled steel plate containing ≤0.005% C, 0.005-0.05% Ti, 0.01-0.1% Al, 0.005-0.015% Nb, and 0.0002-0.002% B is annealed at 770-900°C and cooled at ≥10°C/sec cooling rate. Subsequently, the above steel plate is dipped into a hot dip galvanizing bath containing ≥13% Al to undergo galvanizing and is then subjected to alloying treatment by heating, by which Fe content in a plating layer is regulated to 9-12%. By this method, a steel plate coated with fused alloyed zinc by galvanization in which powdering characteristic at the time of press forming is controlled and which has superior continuous spot welding characteristic at the time of spot welding can be obtained. COPYRIGHT: (C)1990,JPO&Japio

Weldability studies in Cr-Mo-V turbine rotor steel

Abstract: This study was undertaken to establish the weldability of a high pressure steam turbine rotor (1.0Cr-1.0Mo-0.25V steel). Characterization of the as-received material and subsequent evaluation of a de-embrittlement procedure suggests that such heat treatment should be carried out prior to welding. But the improvement in toughness experienced by the heat affected zone (HAZ) of welds produced on both as-received and de-embrittled steel coupons suggests that a preweld de-embrittlement treatment is unnecessary. Further, a postweld heat treatment (PWHT) at the optimum temperature was found to improve the impact properties of both the HAZ and the base metal. The welds were automatically made on steel coupons with the welding parameters held constant, controlled by a microprocessor. In terms of short-term mechanical properties, the turbine rotor can be weld repaired. Studies are presently being conducted under simulated service conditions for long-term testing.

High tensile hot rolled steel strip having excellent cold workability and weldability and having >=55kgf/mm2 tensile strength

Abstract: PURPOSE: To manufacture the title steel strip by preparing a hot rolled steel strip contg. specific ratios of C, Si, Mn, Ti, Al, N, P and S and in which the fractional ratio of polygonal ferrite in the final micro structure is specified. CONSTITUTION: A steel material contg., by weight, 0.04 to 0.18% C, 0.05 to 1.00% Si, 0.10 to 0.50% Mn, 0.05 to 0.30% Ti, 0.001 to 0.100% Al, ≤0.0100% N, ≤0.030% P and ≤0.015% S and in which 0.3≤Ti/(C+S+N)<5 and C+Mn/6+Si/24+Cr/5≤0.20% are regulated is heated to about 1100 to 1450°C, is hot- rolled at about ≥1000°C starting temp. of hot rolling, is cooled at about 5 to 100°C/sec cooling speed and is coiled at about 500 to 700°C. By this method, the fractional rate of polygonal ferrite in the final micro structure is regulated to ≥70%, so that the high strength hot rolled steel strip having excellent cold workability and weldability and having ≥55kgf/mm 2 tensile strength can be obtd. COPYRIGHT: (C)1990,JPO&Japio

Aluminum alloy sheet having good weldability, filiform corrosion resistance, formability, and bake-hardenability, and a method for manufacturing the same

Abstract: An aluminum alloy sheet according to the present invention essentially consists of an aluminum alloy containing 0.5 to 1.4% magnesium, 0.6 to 1.5% silicon, and 0.005 to 0.1% titanium, all by weight, and aluminum and inevitable impurities for the remainder, and is adjusted so that the ratio of the silicon content to the magnesium content is 0.65 or more. The average crystal grain size and the electric conductivity of the aluminum alloy sheet are 70 μm or less and 43 to 51% IACS, respectively. The composition of the aluminum alloy is adjusted in this manner, and the crystal grain size and the electric conductivity are restricted within the specific ranges by controlling the manufacturing conditions. Thus, there may be provided an aluminum alloy sheet which is improved in arc-weldability and resistance to filiform corrosion, as well as in formability and bake-hardenability at low temperature.

Production of high ductility and high strength steel sheet with composite structure

Abstract: PURPOSE: To obtain a high strength and high ductility steel sheet with composite structure and ensuring superior spot weldability by specifying the contents of C, Si, Mn, etc., and carrying out properly controlled hot rolling, continuous annealing and cooling. CONSTITUTION: A steel slab consisting of 0.12-0.30% C, 1.5-3.0% Si, 1.1-2.4% Mn, 0.01-0.1% Nb, <0.005% S, 0.01-0.06% sol. Al and the balance Fe with inevitable impurities is hot rolled at a finishing temp. of the Ar 3 point or above. The resulting steel sheet is coiled at ≤600°C, cold rolled and subjected to continuous annealing including holding in the austenite-ferrite two-phase range of the Ac 1 point+30°C-the Ac 3 point for ≥4min. It is slowly cooled to 500-800°C at 5-30°C/sec cooling rate, rapidly cooled to 350-450°C at ≥70°C/sec cooling rate, held at 350-450°C for 1-5min and cooled to room temp. at ≥2°C/sec cooling rate. The composite structure consisting of martensite, bainite, ferrite and retained austenite is formed. COPYRIGHT: (C)1989,JPO&Japio

Production of steel sheet having excellent weatherability and sea water resistance

Abstract: PURPOSE: To obtain a laminated steel sheet having excellent toughness, weldability, etc, by laminating steel sheets each formed by imposing a cladding metal of a limited thickness and compsn on a base metal, via release materials and heating the laminated steel sheets in a limited temp range, then rolling the heated sheets and separating the same to one unit CONSTITUTION:One unit of the steel sheet 2 is formed by imposing the cladding metal 4 having 10mum-2mm thickness and consisting of a steel made of a compsn contg, by weight, 1-40% Cr, 1-35% P aud 05-10% total of C and B, or the steel contg, by weight, of 1 or 2 kinds of 005-5% Cu and 005-5% Ni in addition to said components on the steel base material 3 A steel material 6 is then imposed via the release material 5 on the cladding metal 4 side of one unit of the laminated steel sheet 2 and after the steel sheets are heated for >=30 minutes in the temp range T1-T2 determined by the equations 1, 2 (where C, B, P, Cr are W% of the respective elements in the cladding metal), the steel sheets are rolled and are separated to one unit of the laminated steel sheet The reason for limiting the thickness and compsn of the cladding metal 4 lies in that there is no improvement in the effect of the weatherability and sea water resistance if the contents are out of the limited ranges

High strength cold rolled steel sheet excellent in weldability and workability and its production

Abstract: PURPOSE: To obtain a high strength steel sheet having a soft surface layer and a hard central layer and excellent in weldability and workability by cold- rolling a hot rolled Mn-containing steel plate with a specific composition, applying decarburizing annealing to the resulting steel sheet, holding the steel sheet in a specific temp. region, and further controlling cooling conditions. CONSTITUTION: A hot rolled steel plate having a composition containing, by weight, 0.15-0.60% C, 0.50-2.50% Si, 0.50-3.50% Mn, ≤0.040% P, ≤0.010% S, ≤0.10% Al, and ≤0.005% N is pickled and cold-rolled, and the cold rolled steel sheet is subjected to decarburizing. annealing. Subsequently, the above sheet is held in a temp. region between Ac 1 +50°C and Ac 3 +50°C for 10-120sec and then cooled down to 350-500°C at 20-200°C/dec cooling rate. Successively, the above temp. is maintained for 30-300sec, and then the above sheet is cooled down to room temp. at ≥10°C/sec cooling rate. By this method, the high strength cold rolled steel sheet which has a 10vol.% at least, of soft surface layer of ≤0.10% C content and a ≥10vol.% of hard central layer containing retained austenite can be easily manufactured. COPYRIGHT: (C)1990,JPO&Japio

Cold rolled steel sheets having improved spot weldability and method for producing the same

Abstract: An extra-low carbon cold rolled steel sheet useful for use in automobiles and the like having an improved spot weldability is obtained by combinedly adding Ti, Nb and B in predetermined amounts to the extra-low carbon steel so as to control the amount of fine Ti precipitate dispersed in steel to the specified reasonable range. Furthermore, the spot weldability is improved by controlling the production conditions of the extra-low carbon steel sheet to specified reasonable ranges.

Welding corrosion inhibiting coating

Abstract: A corrosive resistant coating composition with improved weldability characteristics which is applied to a metal substrate as a wet film and then heated to dry and initiate curing to provide a protective coating tenaciously bonded to the substrate. The composition has corrosion inhibiting finely divided aluminum or stainless steel, a weldability agent of finely divided nickel, a primary bonding resin, and a vehicle of solvents. Preferably, the composition also has a secondary organic resin and thixotropic, metal suspension and hydroscopic agents.

Method for producing cold rolled steel sheets having improved spot weldability

Abstract: An extra-low carbon cold rolled steel sheet useful for use in automobiles, and the like, having an improved spot weldability is obtained by combining and adding Ti, Nb and B in predetermined amounts to the extra-low carbon steel to control the amount of fine Ti precipitate dispersed in steel to within a specified reasonable range. Furthermore, the spot weldability is improved by controlling the production conditions of the extra-low carbon steel sheet to within specified reasonable ranges.

Laminated steel plate with excellent end face corrosion resistance and weldability

Abstract: PURPOSE: To improve end face corrosion resistance of a laminated steel plate without loss of weldability by pure zinc plating a steel plate of a skin material of a laminated steel plate to adhere to resin or zinc alloy plating and chrome plating in a limited amount. CONSTITUTION: Laminated steel plates adhere by interposing resin between steel plates. Conductive powder is dispersed in the resin, the surface of the steel plate to adhere to a resin layer is zinc plated and chrome plated so that the relationship between the chrome plating amount on the zinc plating and the weight fraction of the alloy component in the zinc placing satisfies the following formula 5≤y≤2000x+100 (0≤x≤0.05), 0≤y≤2000x+100 (0.05≤x≤0.1), 0≤y≤300 (0.1≤x≤0.6), where x is the weight fraction of the alloy component in the zinc alloy plating, and y is treating amount (mg/m 2 ) converted by metal Cr of chrome plating. Thus, the surface to adhere to the resin of the steel plate of the skin material is zinc alloy plated limited in the relationship between the plating amount and the Cr adhering amount and coating-chrome plated, thereby improving the end face corrosion resistance and spot weldability of the steel plate. COPYRIGHT: (C)1989,JPO&Japio

Technology for copper alloy plasma-avc welding on the surface of cast iron

Abstract: The invention presents the method for copper alloy straight polarity-arc welding on cast iron. It provides a kind of new copper alloy powder material to solve the problems of wettability and weldability between cast iron and copper alloy, gives an appropriate technology for arc welding. The new copper alloy powder contains certain amount of elements such as Cr, Mn, Ni, P and Si. This invention has great effect compared with conventional method.

Refractory steel material for structural purposes

Abstract: PURPOSE: To improve the high temp. strength of the steel material for structural purposes having high weldability and high ductility and toughness by specifying the contents of Nb, V and Ti of a steel having specific compsn. and the total amounts of these elements by a specific inequality. CONSTITUTION: The steel material for structural purposes contains, by weight, 0.05≤C 400 to 500°C, >500 to 600°C and >600 to 650°C. COPYRIGHT: (C)1990,JPO&Japio

A Detailed Examination of Weldability Lobes for a Range of Zinc-Coated Steels

Abstract: The objective of this study was to investigate the weldability of four tyes of coated steels. These materials include: uncoated, hot-dipped galvanized, electro-galvanized and galvannealed steels. «Statistically significant» weldability lobes were evaluated for each material. Dynamic resistant traces were also evaluated

Cold rolled steel sheet excellent in workability and having baking hardenability and hot dip zinc galvanizing steel sheet

Abstract: PURPOSE: To uniformize and refine the steel structure of a hot rolled base material under relatively wide range of conditions and to obtain a steel sheet excellent in workability and having enlarged adjustable range of the amount of baking hardening by increasing Mn content in a dead-soft carbon steel with a specific composition to a value in a specific range. CONSTITUTION: This cold rolled steel sheet has a composition consisting of, by weight, ≤0.0050% C, ≤0.03% Si, 1.50-<3.5% Mn, Ti in an amount represented by an expression, 0.010-0.100% Al, ≤0.15% P, ≤0.0050% N, ≤0.015% S, and the balance Fe. A plated steel sheet is obtained by forming a hot dip zinc galvanizing layer on the surface of the above cold rolled steel sheet. In the above steel sheet, superior workability is provided while obviating the necessity of obedience to strict manufacturing conditions and also the adjustable range of the amount of baking hardening is enlarged. In the above steel sheet, when Mn is added by ≥1.5%, remarkable effects are produced upon the improvement of r-bar value,Δr-value, baking hardenability, etc., but, when Mn content is ≥3.5%, tempering color is liable to occur at the steel sheet surface and deterioration in weldability and increase in refining costs are brought about. COPYRIGHT: (C)1990,JPO&Japio

Composite electrode material and its production

Abstract: PURPOSE:To improve the braze weldability of the titled material to a semiconductor by coating Au or Ag, etc., on both sides of the laminate obtained by alternately laminating an Mo (alloy) sheet and a Cu (alloy) sheet in >=3 layers, and hot-rolling the material to approximate the thermal expansion coefficient to that of the semiconductor. CONSTITUTION:The Mo (alloy) sheet 1 and the Cu (alloy) sheet 2 are alternately laminated in >=3 layers. A coating part 5 consisting of an Au or Ag (alloy) sheet 4 is laminated on the uppermost sheet and lowermost sheet of a laminate 3. The material is then hot-rolled to integrate the laminate 3 and the coating parts 5. The thickness of the obtained coating layer 8 is controlled to 1-50mum.

Weldability and Electrode Wear Characteristics of Hot-Dip Galvanized Steel With and Without a Ferrophos Containing Primer

Abstract: This study examined the effect of primers containing a conductive pigment on the resistance spot weldability of hot-dip galvanized steel. The pigment used was ferrophos, essentially Di-iron phosphide. Basically, two types of tests were used in this work. Current range tests were used to establish the effect these primers have on the effective ranges of weldability. Limited electrode life tests were used to infer the long term performance of the hot-dip galvanized steels with and without this paint

Two-layer plated steel sheet having excellent resistance weldability

Abstract: PURPOSE: To develop the resistance weldability excellent in terms of both of a welding current value and electrode contact resistance by subjecting the surface of a steel sheet to plating to two layers consisting of a ceramics-contg. plating layer dispersed with Zn as a lower layer and a Zn layer as an upper layer. CONSTITUTION: The plating layer dispersed with Zn or Zn alloy contg. ≥1 kinds among the oxides, nitrides and carbides of Al, Si, Cu, Ti, Cr, Mn, Fe, Co, Ni, Zr, Nb, Pb, Ca, and Mg at (0.03+1.5/1,000×y)wt.% in total is formed at 3W200g/m 2 as the lower layer on the surface of the steel sheet. (Here, y is the weight of the plating expressed by g/m 2 ). The Zn or Zn alloy plating layer having <0.03% total concn. of the oxides, nitrides and carbides is formed to 0.3W8g/m 2 as the upper layer thereon. The performances of the lower layer and the upper layer are thereby balanced and the excellent resistance weldability is developed in the two-layer plated steel sheet. Furthermore, the corrosion resistance of the painting in the worked part is improved by incorporating ≥1% Cr into the lower layer. COPYRIGHT: (C)1989,JPO&Japio